explain xkcd - User contributions [en]

2014: JWST Delays

2020-10-18T21:53:25Z

Redbelly98: Changed "coronavirus panic" to "coronavirus pandemic".

<noinclude>:''"2014", this comic's number, redirects here. For the comic named "2014", see [[1311: 2014]].''</noinclude>
{{comic
| number = 2014
| date = July 2, 2018
| title = JWST Delays
| image = jwst_delays.png
| titletext = Since delays should get less likely closer to the launch, most astronomers in 2018 believed the expansion of the schedule was slowing, but by early 2020 new measurements indicated that it was actually accelerating.
}}

==Explanation==

The {{w|James Webb Space Telescope}} (JWST) is a {{w|space telescope}} created to be the successor of the {{w|Hubble Space Telescope}}.

The telescope has been in development since 1996, but has been plagued by numerous delays and cost overruns. This comic was likely inspired by the most recent [https://nasa.gov/press-release/nasa-completes-webb-telescope-review-commits-to-launch-in-early-2021 delay announcement], which was posted on June 27, 2018. At that time, the JWST was scheduled to launch on March 30, 2021. In July 2020, this was pushed back further to October 31, 2021 due to the coronavirus pandemic.

This comic portrays the launch delays and the new predicted launch years and the times at which those predictions were made. There have been so many delays in this project that you can plot a line of best fit with a surprisingly high degree of accuracy. Randall says optimistically that the line’s slope is less than one (there is less than one year of ''new'' delay per year of elapsed time), implying, of course, that if events continue without further intervention, it will eventually be built, with a predicted date of late 2026.

The title text compares the famous research over the {{w|Accelerating expansion of the universe|universe’s accelerating expansion}} to the apparently ever-delaying schedule and observes that the delay per time does not decrease, although the date gets nearer (which should help to schedule the launch date, as research and unknown parameters are replaced with engineering and exact predictions and measurements).

The Wikipedia article linked above includes a {{w|James Webb Space Telescope#Cost and schedule issues|table}} which provides the data points for the chart:

{| class=wikitable
! width=35 | Year !! Planned launch !! Time left (years)
|-
| 1997 || 2007 || 10
|-
| 1998 || 2007 || 9
|-
| 1999 || 2007 to 2008 || 8-9
|-
| 2000 || 2009 || 9
|-
| 2002 || 2010 || 8
|-
| 2003 || 2011 || 8
|-
| 2005 || 2013 || 8
|-
| 2006 || 2014 || 8
|-
| 2008 || 2014 || 6
|-
| 2010 || 2015 to 2016 || 5-6
|-
| 2011 || 2018 || 7
|-
| 2013 || 2018 || 5
|-
| 2017 || 2019 || 2
|-
|2018 || 2020 || 2
|-
|2018 || 2021 || 3
|-
|2020 || 2021 || 1
|}

==Transcript==
:[Top caption, in the panel:]
:James Webb Space Telescope
:[Subtitle of top caption:]
:Launch Delays

:[There is a positive-quadrant only line graph. The x- axis is labeled 'Current Date' and the y axis is labeled 'Planned Launch Date'. The dates on both of the axes range from 1995 to 2030.]
:[In the graph are 15 points, starting at (1997,2007) and extending at a slope of a little less than one. The most recent one is labeled 'Now: 2021'.]
:[There are two lines on the graph: a red one and a dashed black one. The red one is a regression of the points on the graph. The black one is a line with a slope of one. They intersect at the point (2026,2026), marked by the label 'Late 2026'?]

:[Caption below the panel:]
:Look, at least the slope is less than one.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Astronomy]]
[[Category:Space probes]]
[[Category:Line graphs]]

Talk:2289: Scenario 4

2020-04-14T02:07:22Z

Redbelly98: Don't think the stuff about antiparticles is needed or helpful in explaining this comic.

Should definitely make a note re: this officially-Friday comic releasing late Saturday afternoon (EDT). [[User:TPS|TPS]] ([[User talk:TPS|talk]]) 22:06, 4 April 2020 (UTC)
Or is this actually the april fool comic, except it fooled us by being on a Saturday? [[Special:Contributions/162.158.74.81|162.158.74.81]] 22:12, 4 April 2020 (UTC) Sam
Perhaps more likely because the actual April Fool's comic (due Wednesday) delayed 'til Friday. [[User:TPS|TPS]] ([[User talk:TPS|talk]]) 22:19, 4 April 2020 (UTC)

The title should probably be changed, the xkcd site uses the numeral "4" whereas we're using the word "four."--[[User:GoldNinja|GoldNinja]] ([[User talk:GoldNinja|talk]]) 22:50, 4 April 2020 (UTC)
I accidentaly originally put it under Sequence Four. It shows in the image name.

I hope I fixed it correctly [[User:Bugstomper|Bugstomper]] ([[User talk:Bugstomper|talk]]) 02:17, 5 April 2020 (UTC)

Another instance of a graph with poor labels ("bad stuff"), even without the time travel. [[Special:Contributions/162.158.158.225|162.158.158.225]] 23:54, 4 April 2020 (UTC)

Scenario 1 is almost certainly intended to be a logistic curve. Scenario 2 starts off a bit slower, and it looks like one of the cases where you don't have enough data yet, but _hope_ it'll settle into a logistic. Scenario 3 is probably an exponential. These are the standard three scenarios: good, hopeful, and catastrophic. Then in his usual, now lets just get weird twist, comes the impossible one. I think that's all relevant, but I've been up too long to merge it into the text. [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 23:30, 6 April 2020 (UTC)

The issue of time-traveling COVID-19 problems has already be considered in Onion Public Radio's The Topical. https://www.youtube.com/watch?v=E3GQwOcsChQ Apologies for any poor rule-following as this is my first edit. [[User:RandomEdditMemory|RandomEdditMemory]] ([[User talk:RandomEdditMemory|talk]]) 00:00, 5 April 2020 (UTC)RandomEditMemory

The time travel in this comic is probably a reference to the time offset resulting from the April Fool's comic, but possibly coincidentally the comic showed up here in New Zealand in the morning of the April 5 change to Standard Time when the clocks did turn back an hour. [[User:Bugstomper|Bugstomper]] ([[User talk:Bugstomper|talk]]) 01:55, 5 April 2020 (UTC)
: The time travel is almost certainly not a deliberate reference to the April Fool's comic being late (or to any implementation of DST). Rather, there's 4 graphs, each with an increasingly higher curve. the first tapers off, appearing to be approaching an asymptote, with an ever-decreasing rate of increase -- or even heading to a decrease. The second has a steeper slope for a while, but then does start to taper off. whether it becomes linear, approaches an asymptote, or starts declining off the edge of the graph is not known. The third scenario appears to be an exponential curve. The 3.5 scenario (not shown) would be to have a vertical asymptote, where "bad stuff" shoots off toward infinity as time approaches T. Then the only other thing left to do with a curve is to have it continue back the way it came. Been too long since I was in that level of math, but I'm pretty sure it's problematic if you Y-axis has two values at a point on the X-axis. This isn't showing two different functions converging as time progresses, but rather that a high values of "bad stuff," time goes backward.

From the explanation: "This is another comic in the coronavirus series." But ... is it? It certainly isn't explicitly so. The implicit argument is easy to make, but the fact that it is just "bad stuff" as a function of "time," it could easily be relevant to any number of bad scenarios: velociraptor attacks, Macarena flash mobs, mobile game IAP monetization, nationalistic views in politics, cat-based cheeseburger memes, or so on. It's not much of a stretch to say that the comic is topical to current events (especially given that there are many others in a sequence of implicitly or explicitly CoViD-related comics), but it still is a stretch to _definitely_ say so absent Mr. Munroe actually acknowledging so elsewhere, and then a citation would be needed, right?
:It definitely is. All those graphs (except the fourth, obviously) can be found in real countries' data. South Korea would be an example of scenario 1. The United States would be an example of scenario 3. The virus is on everybody's mind, so there's no way it's a coincidence. (I think labeling [[2283: Exa-Exabyte]] as a coronavirus comic is ''way'' more of a stretch.)

I suggest the mathematical background of the graph 'bending over backwards' should be explained in more detail because the contradiction between what is 'natural' tendency of the graph and what is possible mathematically is what makes for the core of the joke. I mean, let's imagine that the graph is a picture of some tangible object, as a non-mathematically inclined person might do. Let's say, it's a rope. Then after observing it 'bend upwards' more and more with each scenario that gets progressively 'worse', it would be reasonable to conclude that continuing to bend this object even more and 'overbending it' would naturally mean some kind of a catastrophe. In reality, of course, it is impossible just because of the way the graph is being plotted. Each next segment is added as time goes by and placed more to the right because the time is shown to flow right on the horizontal axis. Thus the only way this graph could bend like this is for the next added segment to be in time 'before' the last one. And since it is impossible to travel back in time (citation needed), such a graph is unlikely to be predicting a real scenario. --[[User:SomethingLike|SomethingLike]] ([[User talk:SomethingLike|talk]]) 06:30, 5 April 2020 (UTC)
:There are graphs, however, that have multiple Y-values for single X-values (graph of a square root function, at least for positive values of X, graphs of circles, or the batman equation. Might need an ELI5 why those are okay but the line curving back in time isn't.

You laugh here, but I have in fact seen graphs in corporate presentations which folded back. The presenter (a) didn't understand data analysis, (b) thought Excel was the right tool, and finally (c) decided the graph looked "better" by using the (incompetent) Excel pseudo-curve-smoothing graphics tool.[[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 18:33, 6 April 2020 (UTC)

To me this comic seems a commentary on alocalypse. Some see COVID-19 as the start of a coming apocalypse, and some worst apocalypse scenarios involve either an explosive AI researching things like time travel or ending our timeline as physics knows it, or all of us going back to survival mode on a landscape without any modern infrastructure. [[Special:Contributions/172.69.250.58|172.69.250.58]] 22:03, 5 April 2020 (UTC)

I think that "The only way to make sense of it would be by using the common trope in science fiction of time traveling creating an alternate timeline in which events are different, thus the cases could be 100 in one timeline and 1000 in a different timeline."..etc is utterly wrong creating a new timeline would have two 'forward' lines over a stretch of chart but would not have a single inflection joining a forward over ibto a backwards one. Maybe a (reverse) Z-bend if you include the retrograde (tachyonic?) leg, but then the true alternate timeline (also as per a single line splitting into two forward-going streams at a given ''t'', whether or not that was invoked by time-travellers arriving at that point or 'mundane' quantum superpositioning if alternate outcomes) would not be backwards. (Alternative time-arrow, maybe, but that's more like a continuation of the existence of the usual one, which has no existence beyond the rotation of time into a backwards framing... However that happens - and this graph seems to indicate gradually, like the rate of time goes for +ve to -ve by having less seconds/'second' and passing zero, perhaps by somehow rotating in the imaginary time plane (similar, then, to a spacial one?) in which case there's probably more to worry about than the (presumably unrelated) Bad Stuff. (Darnit, forgot to sign...). [[Special:Contributions/162.158.34.210|162.158.34.210]] 15:49, 6 April 2020 (UTC)

Consider for a moment that each graph is not one line segment, but two. That makes scenario 4 the best possible scenario. [[Special:Contributions/172.68.189.49|172.68.189.49]] 10:51, 7 April 2020 (UTC)

Wouldn't an asymptote best represent a 'non time related' apocalypse? [[User:Vee00101010|Vee00101010]] ([[User talk:Vee00101010|talk]]) 20:47, 8 April 2020 (UTC)

I have trouble seeing how it's useful to include the explanation of antiparticles as backward-in-time-traveling particles. It strikes me as only remotely related, and does not really explain anything about the comic. I think a simple explanation in terms of graphs and functions is appropriate here. -- [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:07, 14 April 2020 (UTC)

2292: Thermometer

2020-04-14T01:27:38Z

Redbelly98: /* Explanation */ Added comment about having Boltzmann's constant printed on thermometer.

{{comic
| number = 2292
| date = April 10, 2020
| title = Thermometer
| image = thermometer.png
| titletext = I hate how many times you have to press it to get to the system normal people use, degrees Rømer.
}}

==Explanation==
{{incomplete|Created by a ROGUE RADIAN. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This comic expresses frustration at the multitude of {{w|temperature}} scales. [[Randall]], as a former engineer, has strong opinions about units, as unit conversion is often a gripe for many engineers. (In a special preface in the UK edition of Randall's book ''What If'', he mentions that one does not appreciate the metric system unless they have had to go through a bunch of scientific papers using really unusual units like "kilocubic feet per second" or "acre-feet".) As elevated body temperature is a symptom of {{w|COVID-19}}, the comic is additionally the 17th in a row concerning the virus.

[[Cueball]] is holding what appears to be a medical thermometer, implying that he's trying to check his {{w|Human body temperature|body temperature}}. He mentions that the thermometer is in Celsius, and asks how to change it. Many thermometers sold in the United States have settings for both Fahrenheit and Celsius, with an option to change between the two. Americans are almost always more familiar with body temperatures in Fahrenheit, so Cueball presumably expects to change to that scale. However, he finds that the thermometer provides measurements in a series of scales that are increasingly unhelpful. Human body temperature in Celsius is 37 °C.

*Degrees {{w|Celsius}} are used in most of the world. The Celsius scale sets 0 degrees to water's freezing point and 100 degrees to water's boiling point. Few Americans have a clear idea of what normal and elevated ranges of human body temperature are in Celsius.
*{{w|Kelvin}} is a unit often used in scientific fields. It is calibrated on the same scale as degrees Celsius, but 0 K is set at {{w|absolute zero}} or -273.15 °C. This is used in scientific or engineering contexts requiring an thermodynamically absolute temperature, such as {{w|Charles's law}}, but almost never in a medical context, making the report of little use.
*The {{w|Rankine scale}} is another absolute scale, with its zero set at absolute zero, but degrees identical to degrees Fahrenheit. While this scale is still occasionally used in some industrial and scientific settings (being more convenient for absolute temperatures in a system including Fahrenheit), it's essentially never used in medicine, and most people have never heard of it.
*Thermodynamically, temperature is the average translational {{w|kinetic energy}} of a group of particles. ''Translational'' kinetic energy means it doesn’t include rotational and vibrational kinetic energy. The relation between a gas’s translational kinetic energy E and its temperature T is
::<math>E=\frac32 k_B T,</math>
:where kB is the {{w|Boltzmann constant}}, 1.380649×10−23 J⋅K-1. So if this thermometer told you a translational kinetic energy measurement in joules, you could get the measured temperature in the Kelvin scale by dividing by the Boltzmann constant and multiplying by 2/3. Somebody who actually wanted to use this measure of temperature might then find it useful to have Boltzmann's constant printed on the thermometer.

Using these last three units for home temperature gauging would be ridiculous, as Kelvin and Rankine measurements of body temperature are unfamiliar to the average user and even those familiar with them would need to do calculations to translate normal body temperature. Kinetic energy is obscure enough that only physicists, engineers and thermodynamicists, a relative handful of the potential buyers, would likely know what it refers to. Those that do could make use of the value printed on the thermometer, but such would add a great deal of unnecessary complexity to what should be a simple and intuitive task.

In the last frame Cueball calls the thermometer the worst. It seems to lack {{w|Fahrenheit}} entirely, frustrating its American consumer base, including Cueball. From a nerd's perspective this would be an extraordinary device, offering even exotic temperature scales. However, a "normal person" would find this thermometer terribly difficult to use for everyday purposes when set on any of the non-Celsius scales, like checking their body temperature or the temperature of food. As an item of consumer electronics, especially one sold in the United States, it would be almost completely useless.

Deliberately lacking Fahrenheit is a jab against the {{w|Imperial system of units}}, and against the similar but distinct system of {{w|United States customary units}}. Although Imperial units and local traditional units are still used for various limited purposes (and/or by older generations) in different countries, most of the world has switched to using the metric system for most purposes going forward, with the US being relatively unusual in the extent to which it still routinely defaults to the US customary units in daily life. Many proponents of the metric system have long pushed for the US to change over, arguing that Imperial and US customary units (and degrees Fahrenheit, specifically) are archaic and obsolete. [[Randall]] has dealt with this conflict in [[1643|other strips]]; as a physics major, he's partial to the metric system, and finds it frustrating to maintain multiple different scales (which is the basis of the conflict in this strip). On the other hand, he recognizes certain intuitive advantages to Imperial and US customary measurements, and recognizes that the forces of social inertia in US society make change difficult.

The title text references an archaic temperature unit, {{w|Rømer scale|Rømer}}, first proposed in 1701. Unlike the other measurements mentioned in this strip, the Rømer scale is no longer used in any context, and only people interested in the history of temperature scales have any idea that it even exists. This is the ultimate form of obscure and outdated temperature measurements.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Cueball stands in the center of the panel holding a thermometer.]
:Cueball: This thermometer is in Celsius. How do you change it?
:Off-panel voice: Long press the button.

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Kelvin
:Cueball: No...

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Degrees Rankine
:Cueball: What.

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Average Translational Kinetic Energy
:Cueball: This is the worst thermometer.
:Off-panel voice: Boltzmann's constant is on the side if you need it.

==Trivia==

In [[1643: Degrees]], Cueball struggles with which temperature unit to use, and ultimately tells his friend the temperature in {{w|radian}}s, which is not a valid temperature scale.

In [[1923: Felsius]], Randall proposes a combined Fahrenheit/Celsius temperature scale called Felsius.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:COVID-19]]
[[Category:Science]]
[[Category:Physics]]

2292: Thermometer

2020-04-14T01:12:03Z

Redbelly98: /* Explanation */

{{comic
| number = 2292
| date = April 10, 2020
| title = Thermometer
| image = thermometer.png
| titletext = I hate how many times you have to press it to get to the system normal people use, degrees Rømer.
}}

==Explanation==
{{incomplete|Created by a ROGUE RADIAN. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This comic expresses frustration at the multitude of {{w|temperature}} scales. [[Randall]], as a former engineer, has strong opinions about units, as unit conversion is often a gripe for many engineers. (In a special preface in the UK edition of Randall's book ''What If'', he mentions that one does not appreciate the metric system unless they have had to go through a bunch of scientific papers using really unusual units like "kilocubic feet per second" or "acre-feet".) As elevated body temperature is a symptom of {{w|COVID-19}}, the comic is additionally the 17th in a row concerning the virus.

[[Cueball]] is holding what appears to be a medical thermometer, implying that he's trying to check his {{w|Human body temperature|body temperature}}. He mentions that the thermometer is in Celsius, and asks how to change it. Many thermometers sold in the United States have settings for both Fahrenheit and Celsius, with an option to change between the two. Americans are almost always more familiar with body temperatures in Fahrenheit, so Cueball presumably expects to change to that scale. However, he finds that the thermometer provides measurements in a series of scales that are increasingly unhelpful. Human body temperature in Celsius is 37 °C.

*Degrees {{w|Celsius}} are used in most of the world. The Celsius scale sets 0 degrees to water's freezing point and 100 degrees to water's boiling point. Few Americans have a clear idea of what normal and elevated ranges of human body temperature are in Celsius.
*{{w|Kelvin}} is a unit often used in scientific fields. It is calibrated on the same scale as degrees Celsius, but 0 K is set at {{w|absolute zero}} or -273.15 °C. This is used in scientific or engineering contexts requiring an thermodynamically absolute temperature, such as {{w|Charles's law}}, but almost never in a medical context, making the report of little use.
*The {{w|Rankine scale}} is another absolute scale, with its zero set at absolute zero, but degrees identical to degrees Fahrenheit. While this scale is still occasionally used in some industrial and scientific settings (being more convenient for absolute temperatures in a system including Fahrenheit), it's essentially never used in medicine, and most people have never heard of it.
*Thermodynamically, temperature is the average translational {{w|kinetic energy}} of a group of particles. ''Translational'' kinetic energy means it doesn’t include rotational and vibrational kinetic energy. The relation between a gas’s translational kinetic energy E and its temperature T is
::<math>E=\frac32 k_B T,</math>
:where kB is the {{w|Boltzmann constant}}, 1.380649×10−23 J⋅K-1. So if this thermometer told you a translational kinetic energy measurement in joules, you could get the measured temperature in the Kelvin scale by dividing by the Boltzmann constant and multiplying by 2/3.

Using these last three units for home temperature gauging would be ridiculous, as Kelvin and Rankine measurements of body temperature are unfamiliar to the average user and even those familiar with them would need to do calculations to translate normal body temperature. Kinetic energy is obscure enough that only physicists, engineers and thermodynamicists, a relative handful of the potential buyers, would likely know what it refers to. Those that do could make use of the value printed on the thermometer, but such would add a great deal of unnecessary complexity to what should be a simple and intuitive task.

In the last frame Cueball calls the thermometer the worst. It seems to lack {{w|Fahrenheit}} entirely, frustrating its American consumer base, including Cueball. From a nerd's perspective this would be an extraordinary device, offering even exotic temperature scales. However, a "normal person" would find this thermometer terribly difficult to use for everyday purposes when set on any of the non-Celsius scales, like checking their body temperature or the temperature of food. As an item of consumer electronics, especially one sold in the United States, it would be almost completely useless.

Deliberately lacking Fahrenheit is a jab against the {{w|Imperial system of units}}, and against the similar but distinct system of {{w|United States customary units}}. Although Imperial units and local traditional units are still used for various limited purposes (and/or by older generations) in different countries, most of the world has switched to using the metric system for most purposes going forward, with the US being relatively unusual in the extent to which it still routinely defaults to the US customary units in daily life. Many proponents of the metric system have long pushed for the US to change over, arguing that Imperial and US customary units (and degrees Fahrenheit, specifically) are archaic and obsolete. [[Randall]] has dealt with this conflict in [[1643|other strips]]; as a physics major, he's partial to the metric system, and finds it frustrating to maintain multiple different scales (which is the basis of the conflict in this strip). On the other hand, he recognizes certain intuitive advantages to Imperial and US customary measurements, and recognizes that the forces of social inertia in US society make change difficult.

The title text references an archaic temperature unit, {{w|Rømer scale|Rømer}}, first proposed in 1701. Unlike the other measurements mentioned in this strip, the Rømer scale is no longer used in any context, and only people interested in the history of temperature scales have any idea that it even exists. This is the ultimate form of obscure and outdated temperature measurements.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Cueball stands in the center of the panel holding a thermometer.]
:Cueball: This thermometer is in Celsius. How do you change it?
:Off-panel voice: Long press the button.

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Kelvin
:Cueball: No...

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Degrees Rankine
:Cueball: What.

:[Cueball presses the button, and the thermometer beeps]
:''Press''
:''Beep''
:Thermometer: Units: Average Translational Kinetic Energy
:Cueball: This is the worst thermometer.
:Off-panel voice: Boltzmann's constant is on the side if you need it.

==Trivia==

In [[1643: Degrees]], Cueball struggles with which temperature unit to use, and ultimately tells his friend the temperature in {{w|radian}}s, which is not a valid temperature scale.

In [[1923: Felsius]], Randall proposes a combined Fahrenheit/Celsius temperature scale called Felsius.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:COVID-19]]
[[Category:Science]]
[[Category:Physics]]

2186: Dark Matter

2019-09-16T00:37:19Z

Redbelly98: /* Explanation */ Changed "atomic nuclei" to "subatomic particles", a more general term. When accelerators have two beams running in opposite directions, they tend to be e.g. protons or electrons and their antiparticles, rather than atomic nuclei.

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly by the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the {{w|Earth}}. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass which causes [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them] while birds, with lower mass, do not. This enrages Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Since the {{w|Figure_of_the_Earth#Volume|Earth's volume}} is 1.083 × 1027 cm3 Megan's figures imply that a {{w|squirrel}} has a mass of about 1.3 lb (1.083 x 5.35 × 1027−25 g = 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams]), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for [[2035: Dark Matter Candidates|the composition of dark matter]]. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this mystery, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were subatomic particles, to detect dark matter particles like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels, and the surrounding city.[https://what-if.xkcd.com/1/]

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]

Talk:2202: Earth-Like Exoplanet

2019-09-14T22:31:55Z

Redbelly98:

I'm assuming this is in reference to exoplanet K2-18b? [[Special:Contributions/108.162.241.52|108.162.241.52]] 18:30, 13 September 2019 (UTC)
: I was thinking the same thing. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 18:41, 13 September 2019 (UTC)
: Note that K2-18b was actually "discovered" way back in 2015 by the Kepler Space Observatory. The recent news was the detection of water vapor in the atmosphere of the planet. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:36, 14 September 2019 (UTC)

I'm seeing the actual comic alt-text as "Fire is actually a potential biosignature, since it means something is filling the atmosphere with an unstable gas like oxygen. If we find a planet covered in flames, it might be an indicator that it supports lifeâ€”or used to, anyway, before the fire." Note the tab before "actually" and the odd characters after "life". But that's not what it has on this site. Is that difference intentional?[[Special:Contributions/172.68.70.70|172.68.70.70]] 19:07, 13 September 2019 (UTC)
: I've noticed a similar difference on other pages. For me, there are glitches in the title text on many XKCD pages, but here they appear as I assume they should. [[User:DanTheTransManWithoutAPlan|DanTheTransManWithoutAPlan]] ([[User talk:DanTheTransManWithoutAPlan|talk]]) 19:23, 13 September 2019 (UTC)
::AFAIS the XKCD-webserver claims incorrectly that the charset of the page is ''windows-1252''. --[[User:DaB.|DaB.]] ([[User talk:DaB.|talk]]) 19:49, 13 September 2019 (UTC)
::: Yes. If you change your browser's encoding to Unicode, it shows up properly -- though the tab before "actually" is still there. --[[User:Aaron of Mpls|Aaron of Mpls]] ([[User talk:Aaron of Mpls|talk]]) 00:24, 14 September 2019 (UTC)

A non-tidally-locked planet (like ours) needs to be firmly in a habitable zone (like ours) to allow the daily and seasonal cycles (like ours) to not send every square foot of the planet well outside any 'reasonable' range of conditions so that there's no possible adaptation possible by life (like ours).

OTOH, a tidally-locked planet probably sustains a belt of habitability upon it somewhere between the most sun-scorched face-centre and the most astronomy(-if-not-''astronomer'')-friendly area of the farside, and it may even let the lifeforms survive more extreme stellar 'seasons' than a swirling planet could, so long as that belt doesn't move so far as to 'lift off' either face, if there exist effective migration paths available for the mobile life and hibernation/aestivation states and hidey-holes for those that are forced/choose to be immobile.

There's the argument about a constant hurricane-force surface wind passing between hot and cold hemispheres, but that assumes a reverse upper flow in atmospheric cells (or a phase-cycle of liquid?) which would promote and reinforce elements of turbulance that might interact with 'surface' features (perhaps subsurface, in waterworld environment) to create areas that are lucuna in the chaos, 'islands' of calm.

Though with many theories of abiogenesis and evolution requiring some form of cycling conditions to filter out the unadaptable and promote the adaptable, so the actual 'interesting' zones are probably in habitable-edges surrounding the habital spots of constancy within the habitable belt upon the habitable-zone planet.

It's a bit moot how all this would work, though, given our knowledge based upon post-facto knowledge of a sample of one life-bearing planet. Hard to know how little or much Earth is typical compared with everyone else. At least until my people come back to rescue me, when I'll have to remember to catch up on the basic classes I've obviously missed. [[Special:Contributions/162.158.34.210|162.158.34.210]] 22:01, 13 September 2019 (UTC)

I thought "between the swinging blades" was just a metaphor - [[Special:Contributions/162.158.214.148|162.158.214.148]] 05:41, 14 September 2019 (UTC)
:it is and should be changed in the explanation. It is all the things mentioned by Megan that are the swinging blades--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:42, 14 September 2019 (UTC)
::But anyone who can give some examples where this sentense is used in the real world? I could not find much using google. Would like it in the explanation, better than what I have done so far. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:25, 14 September 2019 (UTC)
::What came to mind for me is the blade-on-a-pendulum from Poe's short story "The Pit and the Pendulum", except that there were multiple ones that a life form would have to avoid being hit by. Do a google image search on "Pit and the Pendulum" to see what I am talking about. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 22:30, 14 September 2019 (UTC)
:I am not sure it's a metaphor. I thought it was Randall's first (of two) instances of something too ridiculous to actually be observed, the other being the screaming. The other stuff mentioned before the blades are all plausible observations. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 22:30, 14 September 2019 (UTC)

Talk:2202: Earth-Like Exoplanet

2019-09-14T22:30:23Z

Redbelly98: Added comments about swinging blades

I'm assuming this is in reference to exoplanet K2-18b? [[Special:Contributions/108.162.241.52|108.162.241.52]] 18:30, 13 September 2019 (UTC)
: I was thinking the same thing. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 18:41, 13 September 2019 (UTC)
: Note that K2-18b was actually "discovered" way back in 2015 by the Kepler Space Observatory. The recent news was the detection of water vapor in the atmosphere of the planet. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:36, 14 September 2019 (UTC)

I'm seeing the actual comic alt-text as "Fire is actually a potential biosignature, since it means something is filling the atmosphere with an unstable gas like oxygen. If we find a planet covered in flames, it might be an indicator that it supports lifeâ€”or used to, anyway, before the fire." Note the tab before "actually" and the odd characters after "life". But that's not what it has on this site. Is that difference intentional?[[Special:Contributions/172.68.70.70|172.68.70.70]] 19:07, 13 September 2019 (UTC)
: I've noticed a similar difference on other pages. For me, there are glitches in the title text on many XKCD pages, but here they appear as I assume they should. [[User:DanTheTransManWithoutAPlan|DanTheTransManWithoutAPlan]] ([[User talk:DanTheTransManWithoutAPlan|talk]]) 19:23, 13 September 2019 (UTC)
::AFAIS the XKCD-webserver claims incorrectly that the charset of the page is ''windows-1252''. --[[User:DaB.|DaB.]] ([[User talk:DaB.|talk]]) 19:49, 13 September 2019 (UTC)
::: Yes. If you change your browser's encoding to Unicode, it shows up properly -- though the tab before "actually" is still there. --[[User:Aaron of Mpls|Aaron of Mpls]] ([[User talk:Aaron of Mpls|talk]]) 00:24, 14 September 2019 (UTC)

A non-tidally-locked planet (like ours) needs to be firmly in a habitable zone (like ours) to allow the daily and seasonal cycles (like ours) to not send every square foot of the planet well outside any 'reasonable' range of conditions so that there's no possible adaptation possible by life (like ours).

OTOH, a tidally-locked planet probably sustains a belt of habitability upon it somewhere between the most sun-scorched face-centre and the most astronomy(-if-not-''astronomer'')-friendly area of the farside, and it may even let the lifeforms survive more extreme stellar 'seasons' than a swirling planet could, so long as that belt doesn't move so far as to 'lift off' either face, if there exist effective migration paths available for the mobile life and hibernation/aestivation states and hidey-holes for those that are forced/choose to be immobile.

There's the argument about a constant hurricane-force surface wind passing between hot and cold hemispheres, but that assumes a reverse upper flow in atmospheric cells (or a phase-cycle of liquid?) which would promote and reinforce elements of turbulance that might interact with 'surface' features (perhaps subsurface, in waterworld environment) to create areas that are lucuna in the chaos, 'islands' of calm.

Though with many theories of abiogenesis and evolution requiring some form of cycling conditions to filter out the unadaptable and promote the adaptable, so the actual 'interesting' zones are probably in habitable-edges surrounding the habital spots of constancy within the habitable belt upon the habitable-zone planet.

It's a bit moot how all this would work, though, given our knowledge based upon post-facto knowledge of a sample of one life-bearing planet. Hard to know how little or much Earth is typical compared with everyone else. At least until my people come back to rescue me, when I'll have to remember to catch up on the basic classes I've obviously missed. [[Special:Contributions/162.158.34.210|162.158.34.210]] 22:01, 13 September 2019 (UTC)

I thought "between the swinging blades" was just a metaphor - [[Special:Contributions/162.158.214.148|162.158.214.148]] 05:41, 14 September 2019 (UTC)
:it is and should be changed in the explanation. It is all the things mentioned by Megan that are the swinging blades--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:42, 14 September 2019 (UTC)
::But anyone who can give some examples where this sentense is used in the real world? I could not find much using google. Would like it in the explanation, better than what I have done so far. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:25, 14 September 2019 (UTC)
::What came to mind for me is the blade-on-a-pendulum from Poe's short story "The Pit and the Pendulum", except that there were multiple ones that a life form would have to avoid being hit by. Do a google image search on "Pit and the Pendulum" to see what I am talking about. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 22:30, 14 September 2019 (UTC)
:I am not sure it's a metaphor. I thought it was Randall's first (of two) instances of something too ridiculous to be observed, the other being the screaming. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 22:30, 14 September 2019 (UTC)

2066: Ballot Selfies

2018-11-18T02:34:02Z

Redbelly98: /* Explanation */ Added note that this is 1st in a series of 3 comics about the election.

{{comic
| number = 2066
| date = October 31, 2018
| title = Ballot Selfies
| image = ballot_selfies.png
| titletext = There were actually some good reasons for those laws, but IMO they now do more harm than good. Which raises a question: If there's a ballot measure to strike them down, how can I resist the urge to take a picture of my "yes" vote?
}}

==Explanation==
{{incomplete|Any comments about the "more harm than good" mentioned in the title text? Do NOT delete this tag too soon.}}

This comic was published six days prior to the {{w|United States elections, 2018|2018 United States general elections}}, also called {{w|United States midterm election|midterm elections}}, because they happen halfway between two presidential elections, two years before and after. At the time, the [[xkcd]] header still provided a link to [https://www.vote.org/ vote.org], a website that helps US citizens with essential voting issues, like how to register or how to find their polling locations. It is the first of three consecutive comics that deal with this election.

In the United States, "{{w|ballot selfie}}s" refers to the practice of taking a picture of oneself with a completed ballot. These have been declared illegal in many states as it technically violates the practice of a "secret ballot".

Without proof of how a vote was cast, if someone bribed (or even violently coerced) a voter to vote for candidate A, the voter could just vote 'B' and the coercer would be unable to tell whether they voted as instructed. This is at the heart of the concept of "a secret ballot". But if ballot-selfies or other proof-of-vote mechanisms are permitted then the evil-doer can demand verification that the voter did what they were coerced to do - and this jeopardizes the idea of a truly free and fair election.

However, the "secret ballot" principle is not universally valued nor enforced. Some voting machines produce a paper receipt showing the choices the voter made - and many jurisdictions permit use of a postal ballot - there are plenty of other ways to circumvent the law in those places. So the ban on ballot selfies is not entirely justifiable unless those other lines of coercion are also ruled out.

On the other hand, the desire to take and distribute ballot selfies often comes from an excitement in participating in the voting process and the desire to share that excitement in the hopes of encouraging others to vote, and anything that helps get more people to the polls is generally considered to be a good thing. In addition, the law is incredibly difficult to enforce -- there is little way to prevent somebody from photographing their ballot and privately showing this photo to somebody else -- and the practice of enforcing it (i.e. searching for possible photographic devices all together) would make the local government incredibly unpopular. Lastly, voters storing evidence of their votes could be useful to prevent voting fraud performed by the state.

This dual threat/benefit has led some states to explicitly legalize ballot selfies, other states to specifically disallow them and even levy steep financial penalties, while the rest are still debating or ignoring the issue[https://www.vox.com/policy-and-politics/2016/10/25/13389980/ballot-selfie-legal-illegal].

As [[Ponytail]] is aware of this law, she believes she has identified a solution wherein she will make an {{w|oil painting}} of her voting rather than taking a {{w|photograph}}. A painting being more of an artistic endeavor that doesn't have to faithfully record all aspects of the image, it may well be valid both on grounds of {{w|freedom of speech}} as well as not being a verbatim record of her vote - thereby preserving the secrecy of the ballot. Of course, making a painting of her vote may lead to additional problems. If she intends to paint the portrait herself, of herself (i.e. a {{w|self-portrait}}) casting her vote, it would be very difficult and time consuming to attempt to do that, especially without a mirror, which she apparently doesn't have with her and which is generally not standard issue in voting booths. She could also try to recruit someone else to do the painting, not knowing the level of their artistic talent, however, usually only the person casting the vote is allowed in the booth, and they are expected to close the curtain or otherwise ensure no outside person, like the painter, can view the vote casting act.

While [[Hairbun]] and [[White Hat]] are simply standing in line, [[Megan]] can be seen using a mobile phone - potentially checking for optimal Selfie Filters{{Citation needed}}.

In many US states, changes to state law can be made through the {{w|Initiatives and referendums in the United States|initiative and referendum}} process, which can be initiated and pursued by any citizen.

The title text refers to the legality of taking a ballot selfie whilst voting against the law against ballot selfies.

==Transcript==
:[Megan, Ponytail, Cueball, White Hat, and Hairbun are standing in a line with Hairbun in front. All are facing forward to the right except Cueball, who is looking to his left at Ponytail. Megan holds a phone in her hand while Ponytail carries an easel under her left arm and a paintbrush in her right hand.]
:Ponytail: Ballot selfies are illegal in this state, so to immortalize my vote I'm doing an oil painting in the voting booth.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairbun]]
[[Category:Politics]]
[[Category:Elections]]

2067: Challengers

2018-11-18T02:29:41Z

Redbelly98: /* Explanation */ Reworded opening paragraph for clarity (I hope), and added note that this is 2nd in a series of 3 comics about the election.

{{comic
| number = 2067
| date = November 2, 2018
| title = Challengers
| image = challengers.png
| titletext = Use your mouse or fingers to pan + zoom. To edit the map, submit your ballot on November 6th.
}}
To see the full zoomable picture go to the [https://xkcd.com/2067/ original] comic page. On that map, when using a keyboard/mouse, doubleclick zooms in, shift-doubleclick zooms out.

==Explanation==
{{incomplete|We should figure out what source is behind all that 13,339 landmarks in gray, there are 2596 U.S. National Historic Landmarks, but Randall claims those other more than 10,000 are also from Wikipedia. So let's identify that sources. Do NOT delete this tag too soon.}}

[[File:challengers_loading_screen.png|thumb|200px|Loading screen]]
Regarding the {{w|United States elections, 2018|midterm elections}} held in the United States on November 6, 2018, this comic shows probably all challengers, which are candidates running against the current office-holder, as well as those running in open seats where a change of the major party from the previous election could occur. It is the second of three consecutive comics that deal with this election.

[[Randall]] states on top that "The bigger the candidate's name is,"
*the higher the office is in command structure, and
*the better their chances of success as a challenger are
While an office can be subclassified by order from state down to county, the guesses on ''better chances to success'' can be only based on surveys before the elections.

All names provide an indirect link to the first {{w|Google Search}} result on that specific person and position. As common, {{w|Democratic Party (United States)|Democratic}} candidates are shown in blue text, {{w|Republican Party (United States)|Republican}} candidates in red, and independent candidates are in green.

The landmarks shown in gray are essentially links to Wikipedia pages containing coordinates pointing to the US in their body (both visible on the site and hidden in the wiki source) that point to places in the US. If they contain more than one coordinate then the first one is used, for example the {{w|List of the major 3000-meter summits of the United States}} page is shown in Alaska, and the {{w|xkcd}} page is linked near Boston, Massachusetts. This list seems to be auto-generated from a Wikipedia dump made possibly before 2017. There doesn't seem to be any other criteria as the list also contains orphaned wikipedia pages that only contain hidden coordinates in their sources pointing to the US, [https://en.wikipedia.org/wiki/Murder_of_Yangjie_Li for example this one].

Since the map is large there's also a [https://imgs.xkcd.com/comics/challengers.png loading screen] present that can be seen while the map is loading.

There are a total of nine comics embedded into the map at various locations. They are showed when zooming into the map at the appropriate section.

===Attack Ads===
[[File:challengers_subcomic_abernathy_texas.png|thumb|200px|Attack Ads]]

Location: '''Lubbock, Texas'''
: [Black Hat and Cueball are talking.]
: Black Hat: Starting on November 7th, we're going to blanket the airwaves with attack ads.
: Cueball: Isn't the election on November 6th?
: Black Hat: Yeah, the advertising rates go way down after that.
{{w|Attack ads}} are campaign advertising that usually attack the opponents' campaign instead of promoting one's own. The comic also refers to the fact that media outlets usually spike their advertising prices during the campaign, and it becomes cheaper afterwards. However there's usually no point in advertising afterwards for a campaign as the polling has already taken place. This may also be a callback to [[1130: Poll Watching]]. Given the proximity to halloween, this may be a reference to the fact that halloween candy often becomes cheaper after October 31.

Lubbock was the place where some [https://www.texastribune.org/2018/08/03/cruz-orourke-attack-ad-reelection-texas/ attack ads were shown] few months before the election. Texas is also notable as in 2008 during the Democratic Party primary Hillary Clinton [https://www.nytimes.com/2008/03/01/us/politics/01campaign.html started running attack ads] aimed at Barack Obama, who later became President, causing controversy.
 

===Ballot Measures===
[[File:challengers_subcomic_weed_california.png|thumb|350px|Ballot Measures]]

Location: '''Weed, California'''
: [Cueball is holding a piece of paper and talking to Megan.]
: Cueball: Question #1 voids all 2018 ballot measures except itself.
: Cueball: Question #2 retroactively lowers the threshold for passing ballot measures to 5%.
: Cueball: Question #3 requires a re-vote on all failed ballot measures a day later.
: Cueball: Question #4 requires a re-vote on all passed ballot measures a day later.
: Cueball: Question #5 bans those annoying phone scammers, but also says that if an odd number of ballot measures pass, Christmas is canceled.
: Cueball: Question #6 makes a "yes" count as a "no" on odd-numbered ballot measures.
: Cueball: Question #7 does nothing but counts as a ballot measure passing.
: Cueball: Question #8 says that-
: Megan: I'm leaving these all blank and voting against whoever approves ballot measures.

Ballot measures are proposed laws that are approved and rejected by voters. In California, apart from the elections to Congressional and state offices, there will be also be [https://ballotpedia.org/California_2018_ballot_propositions 12 extra propositions] for the voters in this election. Sometimes propositions also include changing how voting should be done in subsequent elections. [https://www.vox.com/2016/6/23/11979522/brexit-ballot There are people] who believe proposals on US ballots are asked in a very convoluted way, and could be made simpler.

In this comic a lot of the proposals sound complex and self-referential as well, therefore Megan just says that she doesn't wish to vote to any of them, and would actually like to ban people creating ballot papers like this. Not voting might also refer to the scenario where people believe none of the choices during an election are good, and instead vote to no-one or deface their ballot papers in protest.

The name of the town chosen, Weed, California, may be a pun on how marijuana is legal in California.
 

===Carlymandering===
[[File:challengers_subcomic_seattle_washington.png|thumb|200px|Carlymandering]]

Location: '''Bellingham, Washington'''
: [Cueball holds a presentation to a group of people including White Hat and Hairbun sitting at an office desk. The presentation shows a map of a district.]
: Cueball: Under my new Carlymandering plan, we'll create five red districts, five blue districts, and one district which contains only Carly Rae Jepsen.
: Hairbun: That seems fair.

This refers to {{w|gerrymandering}}, a tactic used to re-shape voting district boundaries to make sure one candidate prevails over the other. "Carlymandering" is a [[739: Malamanteau|malamanteau]] which combines gerrymandering with {{w|Carly Rae Jepsen}}, a Canadian singer, whose single "{{w|Party for One}}" was released the day before the comic's publication. Although the song is about partying (e.g. going out) alone,{{Citation needed}} the joke is that it could also mean a one-person political party, and she would have a full gerrymandered district to herself.

Jepsen lives in Vancouver, which is just on the other side of the US border in Canada. The comic is placed in Whatcom County, which is notable for {{w|Point Roberts}}, a peninsula which, although part of Washington state, is actually an exclave of the US, as it's surrounded by sea on three sides, and has its only land border with Vancouver to the north. The comic might refer to the fact that Jepsen could solely live in this exclave. However, since she is not a US citizen, she can neither vote nor be elected in US elections.
 

===House===
[[File:challengers_subcomic_washington_dc.png|thumb|100px|House]]

Location: '''Washington, DC'''
: [Cueball is standing in the middle of Washington, DC]
: Cueball: I can see my House from here!

Comic is probably referencing the {{w|White House}}, the residence of the President, located in Washington, DC. This could also refer to the {{w|United States Capitol|Capitol Building}}, the home of the {{w|United States House of Representatives|House of Representatives}}, also located in Washington, DC.
 

===Polls===
[[File:challengers_subcomic_primm_nevada.png|thumb|200px|Polls]]

Location: '''Primm, Nevada'''
: [A group of five people are standing]
: Blondie: Remember: The only poll that counts is the one on Election Day. And the ones that help campaigns allocate resources. And the ones that drive media coverage and the ones that inform us all about what our fellow members of the public believe. And the ones that...

The word "poll" has two distinct meanings in regards to elections -- the place where you go to cast your official vote is called a poll, as are the unofficial surveys done to try to gauge how people are likely to vote.

During campaign there is usually polling done by survey companies to determine each candidate's chances of winning. This comic refers to the fact that often the candidate that is behind in the unofficial polls tells their electorate that these polls don't matter, as they are just surveys and not the actual final result. This is usually to encourage their voter base that it's still worth voting for them. The joke here is that Blondie doesn't finish here but tells the electorate that other polls are actually also important.

Nevada is one of the states where there is [https://thehill.com/homenews/campaign-polls/414083-poll-dems-hold-slim-leads-in-arizona-and-nevada-senate-races only a slim difference] between the candidates based on polls hence the need for each candidate to rally their supporters and make sure everyone is voting.
 

===Punish===
[[File:challengers_subcomic_chadron_nebraska.png|thumb|200px|Punish]]

Location: '''Chadron, Nebraska'''
: [Megan is standing at a podium with her arm raised]
: Megan: If elected, I vow to find and punish the voters responsible.

Often candidates make promises of things they will do when they are elected. Vowing to find and punishing people responsible for a certain action, oftentimes criminals, is also common. However, [https://imgur.com/r/misc/d4jbdEV certain performance artists aside,] these two things are generally not conflated, as they are here, to ludicrous effect.

Putting this comic into Nebraska might refer to the fact that in [https://ballotpedia.org/Nebraska_Death_Penalty_Repeal,_Referendum_426_(2016) 2016 Nebraska voted to repeal the death penalty ban], allowing the reinstatement of the death penalty, also called capital punishment, in the state.
 

===Scholten===
[[File:challengers_subcomic_storm_lake_iowa.png|thumb|300px|Scholten]]

Location: '''Storm Lake, Iowa'''
: Cueball: The midterms are so stressful.
: Megan: I just hope J.D. Scholten wins.
: Cueball: Why?
: Megan: Google Steve King.
: [Cueball looking at his phone]
: Cueball: Yikes.

{{w|United_States_House_of_Representatives_elections_in_Iowa,_2018#District_4|J.D. Scholten}} is a Democratic candidate for Iowa's 4th Congressional District. {{w|Steve King}} is a Republican representative who has stirred controversy due his endorsement of candidates, in other countries, who were members of parties with white supremacist ties, and he has explicitly and frequently stated concern with the American society being destroyed by [https://www.nytimes.com/2017/03/12/us/steve-king-white-nationalism-racism.html "other people's babies"].
 

===Spanberger===
[[File:challengers_subcomic_richmond_virginia.png|thumb|100px|Spanberger]]

Location: '''Richmond, Virginia'''
: [Cueball is holding a sign that says: Abigail Spanberger for Congress]

Abigail Spanberger is a candidate running for Congress in Virginia's 7th district, which includes Richmond. Based on polls she has a chance to beat her opponent, and could be the first Democrat in her district after 50 years of Republican control. Cueball probably tries to encourage people to vote for her on election day.
 

===St Louis===
[[File:challengers_subcomic_saint_louis_missouri.png|thumb|200px|St Louis]]

Location: '''Saint Louis, Missouri'''
: [Two people next to the Gateway Arch are talking]
: Cueball: Ah, Saint Louis. Home of America's largest... Whatever that thing is.

Saint Louis, Missouri is the location of the {{w|Gateway Arch}}, the largest arch in the United States. (It's also one of the most recognizable arches in Saint Louis, according to [[1368: One Of The]].) Since in this comic they are next to the side of the arch, it is possible its sheer size stops them from determining what it is, although they should probably know. An alternate interpretation is that they are baffled by the existence of a giant, seemingly-useless steel arch, and do not know what to refer to it as.

The area surrounding the Arch was known as Jefferson National Expansion Memorial until February 2018, when it was renamed to Gateway Arch National Park.
 

===Title text===
The title text shows the hint that the reader can zoom in and move over all 50 states to reveal details which can't be seen in the overall view. Furthermore [[Randall]] calls on Americans to vote: he requests that people take an active part in the elections to change that picture.

==Transcript==
:[A loading screen appears shortly before the large picture has rendered. We can see an American flag in an oval badge with the text:]
:I voted
:[And beneath a text saying:]
:Loading...

:2018 Midterm
:'''Challengers'''
:The bigger the candidate's name, the higher the office and the better their chances of success.

:[In a frame a zoomable map shows all US-States (Alaska and Hawaii are shown in the left lower corner.) The candidates are shown colored mainly in red and blue at different sizes. Each state has many landmarks shown in gray. There are also many comics embedded into the picture.]

:By Randall Monroe, Kelsey Harris, and Max Goodman

:Landmarks from Wikipedia. Success odds estimated from district voting history, special election
:results, and seat ratings. Thank you to Dailykos Elections for their spreadsheets, shapefiles, election
:ratings, and advice, and to @davidshor, @charlotteeffect, and @thedlcc for additional candidate data.

==Trivia==
*The comic [[Design_of_xkcd.com#Header|header]] had changed to:
:''Find out where to vote: [https://www.vote.org/ Vote.org]''
:''See what's on your ballot: [https://www.ballotready.org/ BallotReady.org]''
:This happened on the day this comic came out, as it up till [http://web.archive.org/web/20181101081612/https://xkcd.com/ the day before], had been a different reminder of the election only with the vote.org link.
*The interactive picture did not work in many browsers when using the link ''[https://www.xkcd.com www.xkcd.com]'', only the short ''[https://xkcd.com xkcd.com]'' worked properly because the page used an absolute link to a file ''[https://xkcd.com/2067/asset/map-data.json map-data.json]'' at the domain ''<nowiki>xkcd.com</nowiki>'' which is not allowed from ''<nowiki>www.xkcd.com</nowiki>'' according to {{w|Cross-origin resource sharing}}. This was later fixed by using a relative link only working inside the called domain.
* The internal comics have a kind of "comic" inside the [https://xkcd.com/2067/asset/map-data.json map-data.json] file that contains all of the details shown on the map. All other locations, including politicians and landmarks inside the map-data.json have a kind of "label"
* There are a total of
** 9 subcomics
** 17,643 labels, including:
*** 13,339 landmarks (gray)
*** 2,845 Democratic candidates (blue)
*** 1,456 Republican candidates (red)
*** 3 independent candidates (green)
* The three independent candidates are:
** Alaska Congress candidate Alyse Galvin
** Texas State House District 101 candidate James Allen
** Alabama State Senate District 10 candidate Craig Ford
* The largest names on the map (based on font size) are:
** Michelle Lujan Grisham, Governor candidate for New Mexico (7.187)
** Beto O'Rourke, Texan US Senate candidate (6.773)
** Matt Rosendale, Montanan US Senate candidate (6.773)
** Gretchen Whitmer, Governor candidate for Michigan (6.48)
* There's a landmark label called "xkcd" near Boston, Massachusetts
* Randall seems to have collected the Wikipedia links from an older copy of Wikipedia, as some links are to old article titles. For example, in Cupertino, California, "Apple Campus 2" is shown instead of "Apple Park", even though that article was moved to its current title in February 2017.
*An overview highlighting some parts:
:<imagemap>
Image:Challengers_Map.png|frame|left|Map of interesting features on the comic (Red X: comic strip, Green X: independent candidate, Blue X: xkcd landmark)
rect 179 176 138 129 [[#Carlymandering|Carlymandering]]
rect 95 279 133 325 [[#Ballot Measures|Ballot Measures]]
rect 171 421 208 467 [[#Polls|Polls]]
rect 392 307 430 352 [[#Punish|Punish]]
rect 403 488 441 533 [[#Attack_Ads|Attack Ads]]
rect 510 307 547 351 [[#Scholten|Scholten]]
rect 593 390 628 434 [[#St_Louis|St Louis]]
rect 803 355 839 394 [[#House|House]]
rect 837 436 799 395 [[#Spanberger|Spanberger]]
rect 877 262 915 309 [[#Trivia|Link to xkcd's wikipage]]
rect 141 597 177 644 [[#Trivia|Independent candidate]]
rect 472 527 511 576 [[#Trivia|Independent candidate]]
rect 672 478 710 525 [[#Trivia|Independent candidate]]
desc top-right
</imagemap>
 

{{comic discussion}}

[[Category:Large drawings]]
[[Category:Interactive comics]]
[[Category:Comics with color]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairbun]]
[[Category:Comics featuring Hairy]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Blondie]]
[[Category:Politics]]
[[Category:Elections]]
[[Category:Maps]]

2073: Kilogram

2018-11-18T02:02:25Z

Redbelly98: Added opening paragraph explaining why units get redefined and a brief statement of what the main joke is.

{{comic
| number = 2073
| date = November 16, 2018
| title = Kilogram
| image = kilogram.png
| titletext = I'm glad to hear they're finally redefining the meter to be exactly three feet.
}}

==Explanation==
{{incomplete|Created by a CONSTANT PLANCK. Links to resources would be good. Do NOT delete this tag too soon.}}

Standard units such as the kilogram, meter, and second are redefined from time to time as measurement technologies improve. These redefinitions are generally done to improve the precision to which the various units can be known or reproduced, without changing their actual value. The joke here is that redefining the kilogram to equal one pound would not only fail to improve on it's precision, but would also significantly change the value of what a kilogram is.

On the day of this comic, the {{w|International Committee for Weights and Measures|International Committee for Weights and Measures}} voted to redefine the {{w|kilogram}} by fixing it to the value of {{w|Planck's Constant}}. This is done by passing a measured current through an electromagnet to exert a force to balance 1 kg. The change will take effect on May 20, 2019, when the platinum cylinder International Prototype Kilogram that defines the unit will be retired. This means that the mass of a kilogram will no longer be calibrated by comparing the relative mass of two physical objects, but by measuring the influence of an electromagnetic field relative to local gravitational forces. By fixing the value of Planck constant to 6.62607015×10-34 kg⋅m2⋅s−1, the kilogram will be defined in terms of the second and the speed of light via the meter.

The previous method of confirming that a kilogram is accurate is to use physical metal weights measuring exactly one kilogram, periodically transporting them around the world to an official weight lab to confirm they still weigh the same. Over time these physical objects have changed very slightly in their mass making them unreliable in the long run -- thus running into the issue that a kilogram did not stay a constant measure of mass. Note that these weights and comparisons are so precise that a fingerprint on one of the weights could throw them off.

In this comic, Black Hat announces that the kilogram has been redefined as equal to one {{w|Pound (mass)|pound}}. Ponytail and Cueball seem to think this makes things simpler, but Megan is rightfully alarmed. The metric system of measurement is the one used by most of the world and is the standard system used in science. It is considered superior to the {{w|United States customary system}} and the {{w|Imperial system}} (both of which the pound is part of). Therefore, redefining the kilogram to be based on the pound would make things much, much worse and outrage supporters of the metric system. More to the point, the pound is still often defined by metal weights, thus running right back into the very same problem they tried to escape from. Also, redefining the kilogram as being a completely different size from before will create a lot of confusion, since now when people read a mass in kilograms they need to work out whether it was written in old kilograms or new (pound-sized) kilograms.

In real life, the pound is officially defined as 0.45359237 kilograms, or less than half a kilogram. This makes defining a kilogram as one pound even more impossible as they are then stuck in a loop, as the pound must weigh less than half of a kilogram, meaning the value of each would be equal to zero.

In addition, the pound also exists as a unit of weight or force (lbf), whereas the kilogram is a unit of mass, thus fixing the kilogram to the pound would make even less practical sense.

The title text continues the joke by saying that the meter has been defined as exactly three feet. The yard, the closest US measurement to the meter, is three feet. However, a meter is about 9 centimeters longer than a yard. As with the pound, the metric system is used to define the yard as it is officially defined as 0.9144 meters.

==Transcript==
:[Black Hat talking to Ponytail, Cueball, and Megan while all stand in a row. Megan's hands are raised emphatically.]
:Black Hat: To end many years of confusion, the International Committee for Weights and Measures has just voted to redefine the kilogram.
:Black Hat: As of next May, it will equal exactly one pound.
:Ponytail: Oh, cool.
:Cueball: That ''does'' make things simpler.
:Megan: '''''No!!'''''

==Trivia==
To further expand on this, the classic definitions of all our various units of time, length, mass, and temperature are based on phenomena that are neither convenient to measure precisely nor in fact consistently reproducible. The duration of an Earth day and year vary unpredictably, the circumference of the Earth varies, the International Prototype Kilogram gains or loses mass any time it is handled (and in fact just sitting there it and its reference copies diverge from each other), and the value of baseline temperatures such as the freezing point of water depend on which isotopes of hydrogen are in the water molecules.

Nevertheless, there really are constants of nature. For example, one of them is ‘''c''’, the speed of light in a vacuum. The expressed value of ''c'' depends on your choice of the unit of distance and the unit of time, but it’s a constant in those units. Now just suppose we all had a reproducible way to define a specific unit of time, which just for fun we call a ‘second’. You might not know the length of a ‘meter’, but if I told you that measured in meters per second the universal constant value of ''c'' is exactly 299792458 meters per second, then I would have fixed the length of a meter to be exactly the distance light travels in a vacuum in 1/299792458 seconds. And in fact this is what the international body responsible for defining our SI units has done.

[https://en.wikipedia.org/wiki/Second#%22Atomic%22_second One second] is defined to be a specific number of periods of the radiation emitted in a certain transition of a cesium 133 atom. The specific number was set in the year 1967, so as to match a previous astronomical standard called [https://en.wikipedia.org/wiki/Second#Fraction_of_an_ephemeris_year Ephemeris Time] to the limit of human measuring ability at the time. The 1967 definition didn’t change the actual duration of a second, but it did make its measurement forever reproducible.

In 1983 the value of ''c'' was fixed to the value noted above. Prior to that it had been measured with respect to existing definitions of a meter, and had to be expressed with a measure of uncertainty. For example in 1973 a team at the US National Bureau of Standards refined ''c'' to 299,792,457.4 m/s ± 1 m/s. But from 1983 onwards, with an exact integer value for ''c'' that is quite close to that Bureau measurement, the length of a meter is now fixed with no plus/minus uncertainty. Furthermore, both the second and the meter match their predecessor definitions for all intents and purposes.

Similar redefinitions of units of mass and of temperature in terms of universal constants have been agreed to, mass with regard to the Planck constant ''h'', and temperature with regard to the Boltzmann constant ''k''. The constants ''h'' and ''k'' had previously been measured quantities, complete with uncertainties. The SI body fixed both of them to exact values, resulting in exact, no-uncertainty values for a kilogram of mass and a kelvin of thermodynamic temperature. As with the second and the meter, these new definitions match their predecessor definitions for all intents and purposes.

To expand on this even further, three additional universal constants that were previously measured and that had uncertainty values have been assigned fixed values, resulting in exact definitions of three corresponding units of measurement without affecting their applicability. Fixing the unit of elementary charge, ''e'', serves to define the unit of electric current, the Ampere. Fixing the unit of luminous efficacy ''Kcd'' serves to define the unit of luminous intensity, the candela. And fixing the Avogadro constant ''NA'' serves to define the unit of amount of substance, the mole.

A very recent Wikipedia article about redefining the SI units of measure in terms of newly fixed values of things taken to be universal constants is {{w|Redefinition of SI base units}}.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Ponytail]]
[[Category:Physics]]

2073: Kilogram

2018-11-18T01:30:17Z

Redbelly98: /* Trivia */ Corrected definition of the second (# of periods, not transitions) & year established (1967, not 1965)

{{comic
| number = 2073
| date = November 16, 2018
| title = Kilogram
| image = kilogram.png
| titletext = I'm glad to hear they're finally redefining the meter to be exactly three feet.
}}

==Explanation==
{{incomplete|Created by a CONSTANT PLANCK. Links to resources would be good. Do NOT delete this tag too soon.}}

On the day of this comic, the {{w|International Committee for Weights and Measures|International Committee for Weights and Measures}} voted to redefine the {{w|kilogram}} by fixing it to the value of {{w|Planck's Constant}}. This is done by passing a measured current through an electromagnet to exert a force to balance 1 kg. The change will take effect on May 20, 2019, when the platinum cylinder International Prototype Kilogram that defines the unit will be retired. This means that the mass of a kilogram will no longer be calibrated by comparing the relative mass of two physical objects, but by measuring the influence of an electromagnetic field relative to local gravitational forces. By fixing the value of Planck constant to 6.62607015×10-34 kg⋅m2⋅s−1, the kilogram will be defined in terms of the second and the speed of light via the meter.

The previous method of confirming that a kilogram is accurate is to use physical metal weights measuring exactly one kilogram, periodically transporting them around the world to an official weight lab to confirm they still weigh the same. Over time these physical objects have changed very slightly in their mass making them unreliable in the long run -- thus running into the issue that a kilogram did not stay a constant measure of mass. Note that these weights and comparisons are so precise that a fingerprint on one of the weights could throw them off.

In this comic, Black Hat announces that the kilogram has been redefined as equal to one {{w|Pound (mass)|pound}}. Ponytail and Cueball seem to think this makes things simpler, but Megan is rightfully alarmed. The metric system of measurement is the one used by most of the world and is the standard system used in science. It is considered superior to the {{w|United States customary system}} and the {{w|Imperial system}} (both of which the pound is part of). Therefore, redefining the kilogram to be based on the pound would make things much, much worse and outrage supporters of the metric system. More to the point, the pound is still often defined by metal weights, thus running right back into the very same problem they tried to escape from. Also, redefining the kilogram as being a completely different size from before will create a lot of confusion, since now when people read a mass in kilograms they need to work out whether it was written in old kilograms or new (pound-sized) kilograms.

In real life, the pound is officially defined as 0.45359237 kilograms, or less than half a kilogram. This makes defining a kilogram as one pound even more impossible as they are then stuck in a loop, as the pound must weigh less than half of a kilogram, meaning the value of each would be equal to zero.

In addition, the pound also exists as a unit of weight or force (lbf), whereas the kilogram is a unit of mass, thus fixing the kilogram to the pound would make even less practical sense.

The title text continues the joke by saying that the meter has been defined as exactly three feet. The yard, the closest US measurement to the meter, is three feet. However, a meter is about 9 centimeters longer than a yard. As with the pound, the metric system is used to define the yard as it is officially defined as 0.9144 meters.

==Transcript==
:[Black Hat talking to Ponytail, Cueball, and Megan while all stand in a row. Megan's hands are raised emphatically.]
:Black Hat: To end many years of confusion, the International Committee for Weights and Measures has just voted to redefine the kilogram.
:Black Hat: As of next May, it will equal exactly one pound.
:Ponytail: Oh, cool.
:Cueball: That ''does'' make things simpler.
:Megan: '''''No!!'''''

==Trivia==
To further expand on this, the classic definitions of all our various units of time, length, mass, and temperature are based on phenomena that are neither convenient to measure precisely nor in fact consistently reproducible. The duration of an Earth day and year vary unpredictably, the circumference of the Earth varies, the International Prototype Kilogram gains or loses mass any time it is handled (and in fact just sitting there it and its reference copies diverge from each other), and the value of baseline temperatures such as the freezing point of water depend on which isotopes of hydrogen are in the water molecules.

Nevertheless, there really are constants of nature. For example, one of them is ‘''c''’, the speed of light in a vacuum. The expressed value of ''c'' depends on your choice of the unit of distance and the unit of time, but it’s a constant in those units. Now just suppose we all had a reproducible way to define a specific unit of time, which just for fun we call a ‘second’. You might not know the length of a ‘meter’, but if I told you that measured in meters per second the universal constant value of ''c'' is exactly 299792458 meters per second, then I would have fixed the length of a meter to be exactly the distance light travels in a vacuum in 1/299792458 seconds. And in fact this is what the international body responsible for defining our SI units has done.

[https://en.wikipedia.org/wiki/Second#%22Atomic%22_second One second] is defined to be a specific number of periods of the radiation emitted in a certain transition of a cesium 133 atom. The specific number was set in the year 1967, so as to match a previous astronomical standard called [https://en.wikipedia.org/wiki/Second#Fraction_of_an_ephemeris_year Ephemeris Time] to the limit of human measuring ability at the time. The 1967 definition didn’t change the actual duration of a second, but it did make its measurement forever reproducible.

In 1983 the value of ''c'' was fixed to the value noted above. Prior to that it had been measured with respect to existing definitions of a meter, and had to be expressed with a measure of uncertainty. For example in 1973 a team at the US National Bureau of Standards refined ''c'' to 299,792,457.4 m/s ± 1 m/s. But from 1983 onwards, with an exact integer value for ''c'' that is quite close to that Bureau measurement, the length of a meter is now fixed with no plus/minus uncertainty. Furthermore, both the second and the meter match their predecessor definitions for all intents and purposes.

Similar redefinitions of units of mass and of temperature in terms of universal constants have been agreed to, mass with regard to the Planck constant ''h'', and temperature with regard to the Boltzmann constant ''k''. The constants ''h'' and ''k'' had previously been measured quantities, complete with uncertainties. The SI body fixed both of them to exact values, resulting in exact, no-uncertainty values for a kilogram of mass and a kelvin of thermodynamic temperature. As with the second and the meter, these new definitions match their predecessor definitions for all intents and purposes.

To expand on this even further, three additional universal constants that were previously measured and that had uncertainty values have been assigned fixed values, resulting in exact definitions of three corresponding units of measurement without affecting their applicability. Fixing the unit of elementary charge, ''e'', serves to define the unit of electric current, the Ampere. Fixing the unit of luminous efficacy ''Kcd'' serves to define the unit of luminous intensity, the candela. And fixing the Avogadro constant ''NA'' serves to define the unit of amount of substance, the mole.

A very recent Wikipedia article about redefining the SI units of measure in terms of newly fixed values of things taken to be universal constants is {{w|Redefinition of SI base units}}.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Ponytail]]
[[Category:Physics]]

Talk:2048: Curve-Fitting

2018-10-13T19:52:16Z

Redbelly98: Why I deleted the "+ c" term in the logarithmic and exponential functions.

House of Cards: Not a real method, but a common consequence of mis-application of statistical methods: a curve can be generated that fits the data extremely well, but immediately becomes absurd as soon as one glances outside the training data sample range, and your analysis comes crashing down "like a house of cards". This is a type of _overfitting_

I'm pretty sure it refers to the TV show house of cards, the dots representing the quality of the series increasing until Netflix renewed it a bit too much {{unsigned ip|172.68.26.65}}
:This was my initial interpretation as well, since you can hypothetically extend a literal house of cards indefinitely.[[Special:Contributions/172.68.58.83|172.68.58.83]] 14:23, 20 September 2018 (UTC)

Could someone familiar with the show expand on this? ''Also a potential reference to the TV show, House of Cards ("WAIT NO, NO, DON'T EXTEND IT!").'' Some context on what that line meant in House of Cards would be helpful. - [[User:CRGreathouse|CRGreathouse]] ([[User talk:CRGreathouse|talk]]) 14:20, 21 September 2018 (UTC)

I'm a little mystified by the alt-text. Cauchy and Lorentz both seem like mathematically capable people. What am I missing? [[Special:Contributions/172.69.62.226|172.69.62.226]] 17:46, 19 September 2018 (UTC)

: Google-Fu reveals that it's a continuous probability distribution. This isn't bad per se, but it is quite visually distinctive and also can be quite...concerning if the data set isn't one where probability should be an issue. [[User:Werhdnt|Werhdnt]] ([[User talk:Werhdnt|talk]]) 18:00, 19 September 2018 (UTC)

:: This is not the issue, but the fact that the moments (such as mean and variance) of the distribution don't exist = converge. See edited explanation. So if you wanted to estimate the parameters of the distribution, taking the sample mean for example will not converge with the number of data points, and is therefore bad to attempt. It is more mathematically alarming than alarmingly mathematical. [[User:GamesAndMath|GamesAndMath]]

:: My own Google-Fu brought me to a page with this information: “The distribution is important in physics as it is the solution to the differential equation describing forced resonance, while in spectroscopy it is the description of the line shape of spectral lines.” (from here: https://www.boost.org/doc/libs/1_53_0/libs/math/doc/sf_and_dist/html/math_toolkit/dist/dist_ref/dists/cauchy_dist.html) [[User:Justinjustin7|Justinjustin7]] ([[User talk:Justinjustin7|talk]]) 18:09, 19 September 2018 (UTC)

:: True, but the "check what field I originally worked in" indicates that there might be something else going on with the meaning. [[Special:Contributions/108.162.237.238|108.162.237.238]] 12:47, 20 September 2018 (UTC)

:: I believe the point of "check what field I originally worked in" is that if somebody wasn't trained in statistics using an exotic distribution is highly suspect and suggest that either they are torturing the data to get desired results or have no idea what they are doing. [[Special:Contributions/108.162.246.11|108.162.246.11]] 05:19, 21 September 2018 (UTC)

To be honest, I'm a bit disappointed. I kinda expected a special comic with such a nice round number.. Been counting down since comic #2000... [[Special:Contributions/162.158.92.184|162.158.92.184]] 18:14, 19 September 2018 (UTC)

Different anon here, I think this is very special and if Randall makes a poster available I will be buying several to give away. Of course, part of my business is experimental data analysis and modeling...and this is a fantastic summary of common errors. {{unsigned ip|162.158.75.22}}

: Agreed. This is a very special comic, and a highly subtle title text. Direct any of your friends who do data analysis here. Sort of the next stage from the classic "correlation is not causation" comic https://xkcd.com/552/ . {{unsigned|GamesAndMath}}

'''Curve-Fitting'''

How fitting works needs to be explained. f(x)=mx+b works fine for single values, but how do we get that red line from the data set? --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:12, 19 September 2018 (UTC)

:Generally, you decide for some error function and then search for parameters where the sum of errors for all data points is minimal. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:07, 19 September 2018 (UTC)

:A typical error function is the square of the difference between the fit and the actual data point, hence "sum of squares" method. There are well-known standard formulas for finding m and b in the case of linear regression. In a linear algebra class, I saw a general method that would work for several of these (any where the fit is y = af(x)+bg(x)+...+ch(x), which includes log, exponential, quadratic, cubic, etc). I wish I could remember it. [[User:Blaisepascal|Blaisepascal]] ([[User talk:Blaisepascal|talk]]) 22:39, 19 September 2018 (UTC)
::I'm still looking for an easy example. Let's say five points (x/y) and then calculating the straight line (without and maybe with the zero-point because this is often the assumed start). Just be simple, everything else derives from that. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:00, 20 September 2018 (UTC)

:I wish we could include the graphics at the top of [https://en.wikipedia.org/wiki/Linear_regression#Introduction] and [https://en.wikipedia.org/wiki/Linear_regression#Interpretation] in the explanation. A lot of people are going to look at this one. [[Special:Contributions/172.68.133.168|172.68.133.168]] 17:51, 20 September 2018 (UTC)
::I've included one picture with a small explanation to the linear regression section. I think that explains it well. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:00, 20 September 2018 (UTC)

The data points do not have error bars, which makes the choice of fit even more ludicrous, in my opinion. If the data are that good, then I don't believe there is a correlation, it's random with some distribution. I might hang this up at work...[[User:Arppix|Arppix]] ([[User talk:Arppix|talk]]) 02:46, 20 September 2018 (UTC)
:And of course in serious science data points have error bars. This makes the fitting even more complicated and should be mentioned at the explanation. Because Randall doesn't use error bars I'm sure he refers to presentations not based on real science. Also this should be mentioned here. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:06, 20 September 2018 (UTC)

I hate to be negative here, as obviously some users have put a lot of effort into explaining the details behind each of the curve-fitting methods, but there's absolutely no explanation for Randall's comments on each method. While someone might learn something about the various methods by reading the explanation, they would not gain any insight on what Randall is saying about each method. In addition, the Connecting Lines explanation totally missed the fact that this isn't really even a curve-fitting method - it's just a feature of graphing software (in this case, Excel) where a smooth line is drawn through each data point from left to right rather than an example of overfitting to the data set. I think we could do better. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 02:53, 21 September 2018 (UTC)
:You're not negative, Randall's comments are missing which I've just added into the incomplete reason. And sure other explanations still need a review. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:32, 21 September 2018 (UTC)

Everyone is missing the deeper trolling here of the fisheries community at large, which shall become blindingly clear here. First, this is cartoon number 2048 (2^11), a highly interesting number. Notably, this is the year all fisheries were projected to be collapsed by Worm et al. (2006) Science 314:787-790, a prediction which gained huge attention in the media and took on a life of its own. The prediction was based on fitting a power curve to some data on collapses in catch trends. Numerous rebuttals followed, one of which pointed out that a linear fit to the data is a better fit, and predicts all fisheries collapsed in 2114 (Jaenike et al. 2007, Science 316:1285a). A list of rebuttals is found here: https://sites.google.com/a/uw.edu/most-cited-fisheries/controversies/2048-projection. Later work by the same author and critics found a different prediction and showed rebuilding of fisheries is likely (Worm et al. 2009 Science 325:578-585). Second, lest you think this is a conspiracy theory, I note that in xkcd cartoon 887, Munroe specifically notes this prediction "The future according to google search results... 2048: "Salt-water fish extinct from overfishing" https://xkcd.com/887/. Third, this kind of model-fitting exercise has long plagued fisheries researchers attempting to predict recruitment from spawning biomass. {{unsigned ip|108.162.246.11}}

"Ad hoc filter: Drawing a bunch of different lines by hand, keeping in only the data points perceived as "good". Also not useful. " – I guess it rather refers to data filtering, where for each point you take several points around and try to calculate some kind of mean, e.g. by rejecting most extreme points, or calculating median (see https://en.wikipedia.org/wiki/Median_filter). So it is an algorithm, not actually drawing lines by hand. Still it is tricky to draw conclusions and you can easily fool yourself with this method. {{unsigned ip|162.158.93.21}}

Anyways, what is the actual regression of the plot? {{unsigned ip|162.158.154.241}}
:This also must be better explained: We don't know what the points represent. The fraction of apples vs. bananas harvested by time, the position of stars in the sky, on a logarithmic scale, linear, or maybe the height of mountains in New Jersey... There are just some dots on paper with no further meaning. Thus everything Randall presents is valid by some means but an actual regression does not exist. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:32, 21 September 2018 (UTC)

Just want to note that the Piecewise models is actually a type of modelling often used in housing economics. It has been used to check if different types of housing are priced according to different rules. [[Special:Contributions/172.68.34.34|172.68.34.34]] 22:05, 21 September 2018 (UTC)

Excel's "smooth lines" are actually splines ([https://blog.splitwise.com/2012/01/31/mystery-solved-the-secret-of-excel-curved-line-interpolation/ third-order Bezier splines, apparently]) so they're not completely without mathematical merit. Still wildly unsuited for extrapolation, but often very well suited to interpolation. [[User:JohnWhoIsNotABot|JohnWhoIsNotABot]] ([[User talk:JohnWhoIsNotABot|talk]]) 21:44, 24 September 2018 (UTC)

'''Specific functions'''

In both the '''logarithmic''' and '''exponential''' functions, I have deleted the term "+ ''c''" that was present in both. Simply put, these functions do not include an additive constant. To include the constant removes a basic property of e.g. exponential functions, which is that the function should grow by the same factor for equal increases in the value of ''x''. (In other words, if the functions doubles when ''x'' changes from 1 to 2, then it should double again when ''x'' changes from 2 to 3, or from 3 to 4, etc.) If this does not happen, the function is not exponential. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 19:52, 13 October 2018 (UTC)

2048: Curve-Fitting

2018-10-13T19:41:31Z

Redbelly98: /* Explanation */ Removed constant "+ c" in log and exponential fits (see comments). Added to explanation of "linear, no slope"

{{comic
| number = 2048
| date = September 19, 2018
| title = Curve-Fitting
| image = curve_fitting.png
| titletext = Cauchy-Lorentz: "Something alarmingly mathematical is happening, and you should probably pause to Google my name and check what field I originally worked in."
}}

==Explanation==

An illustration of several plots of the same data with {{w|Curve fitting|curves fitted}} to the points, paired with conclusions that you might draw about the person who made them. These data, when plotted on an X/Y graph, appear to have a general upward trend, but the data is far too noisy, with too few data points, to clearly suggest any specific growth pattern. In such a case, many different mathematical and statistical models ''could'' be presented as roughly fitting the data, but none of them fits well enough to compellingly represent the data.

When modeling such a problem statistically, much of the work of a data scientist or statistician is knowing which fitting method is most appropriate for the data in question. Here we see various hypothetical scientists or statisticians each applying their own interpretations to the exact same data, and the comic mocks each of them for their various personal biases or other assorted excuses. In general, the researcher will specify the form of an equation for the line to be drawn, and an algorithm will produce the actual line.

Nonetheless scientists work much more seriously on the reliability of their assumptions by giving a value for the {{w|Standard deviation|standard deviation}} represented by the Greek letter sigma σ or the Latin letter s as a measure to quantify the amount of variation of the data points against the presented ''best fit''. If the σ-value isn't good enough an interpretation based on a specific fit wouldn't be accepted by the science community.

Since [[Randall]] gives no hint about the nature of the used data set - same in each graph - any fitting presented doesn't make any sense. The graphs could represent a star map, the votes for the latest elected presidents, or your recent invoices on power consumption. This comic just exaggerates various methods on interpreting data, but without the knowledge of the matter in the background nothing makes any sense.

===Linear===
[[File:Anscombe's quartet 3.svg|thumb|200px|Different data sets result in the same regression.]]
<math>f(x) = mx + b</math>

{{w|Linear regression}} is the most basic form of regression; it tries to find the straight line that best approximates the data. As it's the simplest, most widely taught form of regression, and in general derivable function are locally well approximated by a straight line, it's usually the first and most trivial attempt of fit.

The picture to the right shows how totally different data sets can result into the same line. It's obvious that some more basics about the nature of the data must be used to understand if this simple line really does make sense.

The comment below the graph ''"Hey, I did a regression."'' refers to the fact that this is just the easiest way of fitting data into a curve.

===Quadratic===
<math>f(x) = ax^2 + bx + c</math>

{{w|Polynomial regression|Quadratic fit}} (i.e. fitting a parabola through the data) is the lowest grade polynomial that can be used to fit data through a curved line; if the data exhibits clearly "curved" behavior (or if the experimenter feels that its growth should be more than linear), a parabola is often the first, easiest, stab at fitting the data.

The comment below the graph ''"I wanted a curved line, so I made one with math."'' suggests that a quadratic regression is used when straight lines no longer satisfy the researcher, but he still wants to use simple math expression. Quadratic correlations like this are mathematically valid and one of the simplest kind of curve in math, but this curve doesn't appear to satisfy the data any better than does simple, linear regression.

===Logarithmic===
[[File:Logarithm_plots.png|thumb|200px|Common logarithm functions.]]
<math>f(x) = a\log_b(x)</math>

A {{w|Logarithm|logarithmic}} curve growths slower on higher values, but still grows without bound to infinity rather than approaching a horizontal {{w|asymptote}}. The small ''b'' in the formula represents the base which is in most cases ''{{w|e (mathematical constant)|e}}'', 10, or 2. If the data presumably does approach a horizontal asymptote then this fit isn't an effective method to explain the nature of the data.

The comment below the graph ''"Look, it's tapering off!"'' builds up the impression that the data diminishes while under this fit it's still growing to infinity, only much slower than a linear regression does.

===Exponential===
[[File:Exponential.svg|thumb|200px|Exponential growth (green) compared to other functions.]]
<math>f(x) = a\cdot b^x</math>

An {{w|Exponential growth|exponential curve}}, on the contrary, is typical of a phenomenon whose growth gets rapidly faster and faster - a common case is a process that generates stuff that contributes to the process itself, think bacteria growth or compound interest.

The logarithmic and exponential interpretations could very easily be fudged or engineered by a researcher with an agenda (such as by taking a misleading subset or even outright lying about the regression), which the comic mocks by juxtaposing them side-by-side on the same set of data.

The comment below the graph ''"Look, it's growing uncontrollably!"'' gives an other frivolous statement suggesting something like chaos. Also this even faster growth is well defined and has no asymptote at both axes.

===LOESS===
A {{w|Local regression|LOESS fit}} doesn't use a single formula to fit all the data, but approximates data points locally using different polynomials for each "zone" (weighting differently data points as they get further from it) and patching them together. As it has much more degrees of freedom compared to a single polynomial, it generally "fits better" to any data set, although it is generally impossible to derive any strong, "clean" mathematical correlation from it - it is just a nice smooth line that approximates well the data points, with a good degree of rejection from outliers.

The comment below the graph ''"I'm sophisticated, not like those bumbling polynomial people."'' emphasis this more complicated interpretation but without a simple mathematical description it's not very helpful to find academic descriptions on the underlying matter.

===Linear, No Slope===
<math>f(x) = c</math>

Also known as a constant function, since the function takes on the same (constant) value ''c'' for all values of ''x''. The value of ''c'' can be determined simply by taking the average of the ''y''-values in the data.

Apparently, the person making this line figured out pretty early on that their data analysis was turning into a scatter plot, and wanted to escape their personal stigma of scatter plots by drawing an obviously false regression line on top of it. Alternatively, they were hoping the data would be flat, and are trying to pretend that there's no real trend to the data by drawing a horizontal trend line.

The comment below the graph ''"I'm making a scatter plot but I don't want to."'' is probably done by a student who isn't happy with their choice of field of study.

===Logistic===
[[File:Logistic-curve.svg|thumb|200px|A standard logistic function between the values ''0'' and ''1''.]]
The {{w|Logistic regression|logistic regression}} is taken when a variable can take binary results such as "0" and "1" or "old" and "young".

The curve provides a smooth, S-shaped transition curve between two flat intervals (like "0" and "1").

The comment below the graph ''"I need to connect these two lines, but my first idea didn't have enough math."'' implies the experimenter just wants to find a mathematically-respectable way to link two flat lines.

===Confidence Interval===
Not a type of curve fitting, but a method of depicting the predictive power of a curve.

Providing a confidence interval over the graph shows the uncertainty of the acquired data, thus acknowledging the uncertain results of the experiment, and showing the will not to "cheat" with "easy" regression curves.

The comment below the graph ''"Listen, science is hard. But I'm a serious person doing my best."'' is just an honest statement about this uncertainty.

===Piecewise===
Mapping different curves to different segments of the data. This is a legitimate strategy, but the different segments should be meaningful, such as if they were pulled from different populations.

This kind of fit would arise naturally in a study based on a regression discontinuity design. For instance, if students who score below a certain cutoff must take remedial classes, the line for outcomes of those below the cutoff would reasonably be separate from the one for outcomes above the cutoff; the distance between the end of the two lines could be considered the effect of the treatment, under certain assumptions. This kind of study design is used to investigate causal theories, where mere correlation in observational data is not enough to prove anything. Thus, the associated text would be appropriate; there is a theory, and data that might prove the theory is hard to find.

One notable time this is used is when a researcher studying housing economics is trying to identify housing submarkets. The assumption is that if two proposed markets are truly different, they will be better described using two different regression functions than if one were to be used.

The additional curved lines visible in the graph are the kind of confidence intervals you'd get from a simple OLS regression if the standard assumptions were valid. In the case of two separate regressions, it would be surprising if all those assumptions (that is, i.i.d. Normal residuals around an underlying perfectly-linear function) were in fact valid for each part, especially if the slopes are not equal.

A classical example in physics are the different theories to explain the black body radiation at the end of the 19th century. The {{w|Wien approximation}} was good for small wavelengths while the {{w|Rayleigh–Jeans law}} worked for the larger scales (large wavelength means low frequency and thus low energy.) But there was a gap in the middle which was filled by the {{w|Planck's law}} in 1900.

The comment below the graph ''"I have a theory, and this is the only data I could find."'' is a bit ambiguous because there are many data points ignored. Without an explanation why only a subset of the data is used this isn't a useful interpretation at all. As a matter of fact, with the extra degrees of freedom offered by the piecewise regression, it could indicate that the researcher is trying to fit the data to confirm their theory, rather than building their theory off of the data.

===Connecting lines===
This is often used to smooth gaps in measurements. A simple example is the weather temperature which is often measured in distinct intervals. When the intervals are high enough it's safe to assume that the temperature didn't change that much between them and connecting the data points by lines doesn't distort the real situation in many cases.

The comment below the graph ''"I clicked 'Smooth Lines' in {{w|Microsoft Excel|Excel}}."'' refers to the well known spreadsheet application from {{w|Microsoft Office}}. Like other spreadsheet applications it has the feature to visualize data from a table into a graph by many ways. "Smooth Lines" is a setting meant for use on a {{w|line graph}}, a graph in which one axis represents time; as it simply joins up every point rather than finding a sensible line, it is not suitable for regression.

===Ad-Hoc Filter===
Drawing a bunch of different lines by hand, keeping in only the data points perceived as "good". Not really useful except for marketing purposes.

The comment below the graph ''"I had an idea for how to clean up the data. What do you think?"'' admits that in fact the data is whitewashed and tightly focused to a result the presenter wants to show.

===House of Cards===
Not a real method, but a common consequence of misapplication of statistical methods: a curve can be generated that fits the data extremely well, but immediately becomes absurd as soon as one glances outside the training data sample range, and your analysis comes crashing down "like a house of cards". This is a type of ''overfitting''. In other words, the model may do quite well for (approximately) {{w|Interpolation|interpolating}} between values in the sample range, but not extend at all well to {{w|Extrapolation|extrapolating}} values outside that range.

''Note:'' Exact polynomial fitting, a fit which gives the unique <math>(n-1)</math>th degree polynomial through <math>n</math> points, often display this kind of behaviour.

The comment below the graph ''"As you can see, this model smoothly fits the- wait no no don't extend it AAAAAA!!"'' refers to a curve which fits the data points relatively well within the graph's boundaries, but beyond those bounds fails to match at all.

The name is also a reference to the TV show ''{{w|House of Cards (U.S. TV series)|House of Cards}}'' ("WAIT NO, NO, DON'T EXTEND IT!").

===Cauchy-Lorentz (title text)===
{{w|Cauchy_distribution|Cauchy-Lorentz}} is a continuous probability distribution which does not have an expected value or a defined variance. This means that the law of large numbers does not hold and that estimating e.g. the sample mean will diverge (be all over the place) the more data points you have. Hence very troublesome (mathematically alarming).

Since so many different models can fit this data set at first glance, Randall may be making a point about how if a data set is sufficiently messy, you can read any trend you want into it, and the trend that is chosen may say more about the researcher than about the data. This is a similar sentiment to [[1725: Linear Regression]], which also pokes fun at dubious trend lines on scatterplots.

A brief Google search reveals that Augustin-Louis Cauchy originally worked as a junior engineer in a managerial position. Upon his acceptance to the Académie des Sciences in March 1816, many of his peers expressed outrage. Despite his early work in "mere" engineering, Cauchy is widely regarded as one of the founding influences in the rigorous study of calculus & accompanying proofs.

Alternately, the title-text could be implying that the person who applied the Cauchy-Lorentz curve-fitting method may not be well qualified to the task assigned.

==Transcript==
:'''Curve-Fitting Methods'''
:and the messages they send

:[In a single frame twelve scatter plots with unlabeled x- and y-axes are shown. Each plot consists of the same data-set of approximately thirty points located all over the plot but slightly more distributed around the diagonal. Every plot shows in red a different fitting method which is labeled on top in gray.]

:[The first plot shows a line starting at the left bottom above the x-axis rising towards the points to the right.]
:Linear
:"Hey, I did a regression."

:[The second plot shows a curve falling slightly down and then rising up to the right.]
:Quadratic
:"I wanted a curved line, so I made one with math."

:[At the third plot the curve starts near the left bottom and increases more and more less to the right.]
:Logarithmic
:"Look, it's tapering off!"

:[The fourth plot shows a curve starting near the left bottom and increases more and more steeper towards the right.]
:Exponential
:"Look, it's growing uncontrollably!"

:[The fifth plot uses a fitting to match many points. It starts at the left bottom, increases, then decreases, then rapidly increasing again, and finally reaching a plateau.]
:LOESS
:"I'm sophisticated, not like those bumbling polynomial people."

:[The sixth plot simply shows a line above but parallel to the x-axis.]
:Linear, no slope
:"I'm making a scatter plot but I don't want to."

:[At plot #7 starts at a plateau above the x-axis, then increases, and finally reaches a higher plateau.]
:Logistic
:"I need to connect these two lines, but my first idea didn't have enough Math."

:[Plot #8 shows two red lines embedding most points and the area between is painted as a red shadow.]
:Confidence interval
:"Listen, science is hard. But I'm a serious person doing my best."

:[Plot #9 shows two not connected lines, one at the lower left half, and one higher at the right. Both have smaller curved lines in light red above and below.]
:Piecewise
:"I have a theory, and this is the only data I could find."

:[The plot at the left bottom shows a line connecting all points from left to right, resulting in a curve going many times up and down.]
:Connecting lines
:"I clicked 'Smooth Lines' in Excel."

:[The next to last plot shows a echelon form, connecting a few real and some imaginary points.]
:Ad-Hoc filter
:"I had an idea for how to clean up the data. What do you think?"

:[The last plot shows a wave with increasing peak values. Finally the plot of the wave is continued beyond the x- and y-axis borders.]
:House of Cards
:"As you can see, this model smoothly fits the- ''wait no no don't extend it AAAAAA!!''"

==Trivia==
*This is the comic 2048, or 211. In addition to being the name of a popular app referenced in [[1344: Digits]], this is an extremely round number in binary (100,000,000,0002). [[1000: 1000 Comics]] pointed out that comic 1024 would be a round number, but there were not any comics noting 2048.

*This comic is similar to [[977: Map Projections]] which also uses a scientific method not commonly thought about by the general public to determine specific characteristics of one's personality and approach to science.

*Regressions have been the subject of several previous comics. [[1725: Linear Regression]] was about linear regressions on uncorrelated or poorly correlated data. [[1007: Sustainable]], [[1204: Detail]] and [[1281: Minifigs]] depict linear regressions on data that was actually logistic, leading to bizarre extrapolations. [[605: Extrapolating]] shows a line extrapolating from just two data points.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Scatter plots]]
[[Category:Line graphs]]
[[Category:Math]]
[[Category:Science]]

2046: Trum-

2018-09-16T23:55:05Z

Redbelly98: /* Explanation */ Explicitly say that J.Q. Adams is the son of John Adams.

{{comic
| number = 2046
| date = September 14, 2018
| title = Trum-
| image = trum.png
| titletext = Excited to vote for future presidents Bill Eisenhamper, Amy Forb, Ethan Obample, and Abigail Washingtoast.
}}

==Explanation==
{{incomplete|Please edit the explanation below and only mention here why it isn't complete. Do NOT delete this tag too soon.}}

The {{w|President of the United States}}, at the time when this comic was published, is {{w|Donald Trump}} and he shares the first letters of his surname with {{w|Harry S. Truman}}, who was US President between 1945 and 1953. [[Megan]] notes that both of these presidents' last names start with "T-R-U-M", but she also states that they are not much related.

There were several presidents of the US who even have the exact same last name. For example, {{w|John Adams}} and his son {{w|John Quincy Adams}}, and the more recent father and son {{w|George H. W. Bush}} and {{w|George W. Bush}}. Similarly {{w|Theodore Roosevelt}} and {{w|Franklin Delano Roosevelt}} are 5th cousins. Grandfather and grandson {{w|William Henry Harrison}} and {{w|Benjamin Harrison}} also share a last name. And there are the two [https://www.geni.com/path/Lyndon-B-Johnson-36th-President-of-the-United-States+is+related+to+Andrew-Johnson-17th-President-of-the-USA?from=6000000002045454764&to=361204095530004567| most distantly related] presidents with the same surname, both {{w|Andrew Johnson}} and {{w|Lyndon B. Johnson}} have the last name of Johnson (7 letters), although the shared last name is coincidental, given they do not share any relatives with the name Johnson.

Besides T-R-U-M- and the cases of identical names, the longest common surname prefix is H-A-R (3 letters), shared by William Henry (or Benjamin) H-A-R-rison and Warren Gamaliel H-A-R-ding. (The next longest common surname prefixes are B-U-, shared by James B-U-chanan and George (H.) W. Bush; and C-L-, shared by Grover Cleveland and Bill Clinton.)

The longest common suffix (not counting identical names) is also 4 for I-S-O-N for {{w|James Madison}} and the two Harrison presidents. (It is an interesting fact that the name HARRISON contains both the second-longest common prefix and the longest common suffix among non-identical president surnames.)

The joke is that the matching of those few letters is the least weird thing because Trump's presidency has been plagued with {{w|Presidency of Donald Trump#Ethics|several scandals}}.

The title text lists "absurd" last names that could start with the same letters as other presidents: Bill Eisenhamper, Amy Forb, Ethan Obample, and Abigail Washingtoast. These would refer to {{w|Dwight D. Eisenhower|Dwight D. '''Eisenh'''ower}}, {{w|Gerald Ford|Gerald '''For'''d}}, {{w|Barack Obama|Barack '''Obam'''a}}, and {{w|George Washington|George '''Washingto'''n}}.

==Transcript==
:[Cueball and Megan walking together while talking.]
:Megan: It's pretty weird that we've had two totally unrelated presidents whose last names start with '''''"T-R-U-M-"'''''.
:Cueball: Oh, sure, that's ''definitely'' the weirdest thing about the presidency right now.
:Megan: It's less weird than '''''every other fact'''''. But still weird.
:Cueball: True.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Politics]]

2037: Supreme Court Bracket

2018-09-10T00:49:40Z

Redbelly98: /* Explanation */ Added explanation about Rhode Island being annexed. Added note about possibility of UMass-UConn basketball matchup.

{{comic
| number = 2037
| date = August 24, 2018
| title = Supreme Court Bracket
| image = supreme_court_bracket.png
| titletext = My bracket was busted in the first round; I had Massachusetts v. Connecticut in the final, probably in a case over who gets to annex Rhode Island.
}}

==Explanation==
{{incomplete|Each court case needs its own explanation, preferably a small paragraph instead of a sentence in parentheses. Do NOT delete this tag too soon.}}

The {{w|Supreme Court of the United States}} is the highest federal court of the United States. A {{w|Bracket (tournament)|tournament bracket}} is a tree diagram that represents the series of games played during a knockout tournament. US Supreme Court cases are typically titled as Petitioner versus Respondent. To spoof this, [[Randall]] has put sixteen famous Supreme Court cases into a tournament bracket, as though they were games in the first round of a single-elimination tournament, and that the winners of the 16 listed court cases will somehow file against each other and then again until the final winner is selected. This is similar to college basketball's {{w|NCAA Division I Men's Basketball Tournament|March Madness}}, complete with a ranking bracket. "Sweet 16" in the context of a tournament refers to the stage in a tournament where 16 competitors remain. This comic's concept is thus a word play on "court" (court of law v. basketball court).

The cases are:
====Marbury v. ''Madison'' (winner), 1803====
The case {{w|Marbury v. Madison|Marbury v. Madison}} declared a provision of the {{w|Judiciary Act of 1789}} unconstitutional, thus preventing several late-term appointments by outgoing President {{w|John Adams}} from being seated under incoming President {{w|Thomas Jefferson}}. More importantly, the ruling established the principle of {{w|judicial review}} by which the Supreme Court can overturn, on the basis of unconstitutionality, laws passed by {{w|United States Congress|Congress}} and signed into law by the {{w|President of the United States|President}}. For this reason it is considered the single most important decision in American constitutional law.

====''McCulloch'' (winner) v. Maryland, 1819====
The case {{w|McCulloch v. Maryland|McCulloch v. Maryland}} established a broad interpretation of the "necessary and proper" clause, specifically finding that Congress could incorporate a Bank of the United States because the purpose was to help carry out Congress' explicit powers under Article I, section 8.

====''Gibbons'' (winner) v. Ogden, 1824====
The case {{w|Gibbons v. Ogden|Gibbons v. Ogden}} established that interstate commerce is regulated by the U.S. Congress according to the U.S. Constitution, that interstate navigation is fundamental to interstate commerce, and that therefore the power to regulate interstate navigation in this way rests with the U.S. Congress, not with any state legislature.

On 01 March 1824, the US Supreme Court decided in favor of Thomas Gibbons in his appeal of a case brought against him by Aaron Ogden in an attempt to prevent Gibbons from operating steamboats to transport goods and passengers between New York City, New York and Elizabethtown, New Jersey. The US Supreme Court decision reversed a prior injunction against Gibbons issued by a New York State court deciding that Ogden held exclusive navigational rights by way of having licensed them from two men to whom the New York State Legislature had granted the navigation rights in several acts between 1798 and 1807.

====''Near'' (winner) v. Minnesota, Jan 30, 1930 – Jun 1, 1931====
The case {{w|Near v. Minnesota|Near v. Minnesota}} is a landmark United States Supreme Court decision that found that prior restraints on publication violate freedom of the press as protected under the {{w|First Amendment to the United States Constitution}}, a principle that was applied to free speech generally in subsequent jurisprudence. The Court ruled that a Minnesota law that targeted publishers of "malicious" or "scandalous" newspapers violated the First Amendment to the United States Constitution.

Noteworthy it was later a key precedent in {{w|New York Times Co. v. United States}} (1971), in which the court ruled against the Nixon administration's attempt to enjoin publication of the Pentagon Papers.

====''NLRB'' (winner) v. Jones & Laughlin, 1937====
{{w|NLRB v. Jones & Laughlin Steel Corp.|National Labor Relations Board v Jones & Laughlin Steel Corporation}} was a US labor law case. It declared that the {{w|National Labor Relations Act of 1935}} was constitutional. It effectively preserved the {{w|New Deal}}, which was being pursued by US President {{w|Franklin D. Roosevelt|Roosevelt}} in reaction to the {{w|Great Depression}}. Previous Supreme Court cases, unlike ''NLRB v. Jones & Laughlin'', had invalidated New Deal statutes.

====''Brown'' (winner) v. Board of Education, Dec 9, 1952 – May 17, 1954====
The case {{w|Brown v. Board of Education|Brown v. Board of Education}} the Court declared state laws establishing separate public schools for black and white students to be unconstitutional. It stated that "separate educational facilities are inherently unequal."

This ruling paved the way for the {{w|Civil rights movement|Civil Rights Movement}}. However, the decision did not spell out any sort of method for ending racial segregation in schools, and the Court's second decision in {{w|Brown v. Board of Education#Brown II|Brown II}} only ordered states to desegregate "with all deliberate speed."

====''Gideon'' (winner) v. Wainwright, 1963====
In the case {{w|Gideon v. Wainwright|'''Gideon''' v. Wainwright}} the Supreme Court unanimously ruled that states are required under the {{w|Sixth Amendment to the United States Constitution|Sixth Amendment}} to the U.S. Constitution to provide an attorney or lawyer to defendants in criminal cases who are unable to afford their own attorneys.

====''Griswold'' (winner) v. Connecticut, 1965====
In the case {{w|Griswold v. Connecticut}} (1965), the Court ruled that a statute barring {{w|Birth control|birth control}} to prevent pregnancy, also known as contraception, was unconstitutional, at least in its application to married couples, as there was an implicit right to privacy in the "penumbras" and "emanations" of other constitutional provisions. This ruling was used as precedent in {{w|Eisenstadt v. Baird}} (1972), which extended the right to unmarried couples, and in Roe v. Wade and Lawrence v. Texas (see below).

====''Miranda'' (winner) v. Arizona, 1966====
ToDo:{{w|Miranda v. Arizona|Miranda v. Arizona}}
(required police to inform suspects of their rights)

====''Loving'' (winner) v. Virginia, April 10, 1967 - June 12, 1967====
In {{w|Loving v. Virginia}} the Supreme Court ruled that state laws prohibiting interracial marriage were unconstitutional, and were struck down. This decision was well ahead of public opinion; a Gallup poll (cited by [https://thinkprogress.org/public-support-for-same-sex-marriage-surpasses-support-for-interracial-marriage-in-1991-b29fa01c2cfa/ Think Progress]) conducted the following year showed only 20% in favor. This case was cited as precedent in Obergefell v. Hodges, listed below.

====''Roe'' (winner) v. Wade, January 22, 1973====
In {{w|Roe v. Wade}}, the Supreme Court ruled that a woman's right to privacy, balanced against the state's interest in limiting {{w|abortion}}s, allowed women to undergo abortions in the first and second trimesters and allowed states the right to forbid third-trimester abortions.

====''United States'' (winner) v. Nixon, July 8, 1974 - July 24, 1974====
ToDo: {{w|United States v. Nixon|United States v. Nixon}}
(ordered president Nixon to turn over Watergate tapes)

====''Bush'' (winner) v. Gore, December 12, 2000====
ToDo: {{w|Bush v. Gore|Bush v. Gore}}
(disputed 2000 Presidential election)

====''Lawrence'' (winner) v. Texas, June 26, 2003====
ToDo:{{w|Lawrence v. Texas|Lawrence v. Texas}}
(invalidated sodomy laws and made same-sex sexual activity legal in every U.S. state and territory)

====''Massachusetts'' (winner) v. EPA, April 2, 2007====
ToDo:{{w|Massachusetts v. Environmental Protection Agency|Massachusetts v. EPA}}
(decided that the state of Massachusetts has standing to sue the EPA for not doing enough against global warming)

====''Obergefell'' (winner) v. Hodges, June 26, 2015====
ToDo:{{w|Obergefell v. Hodges|Obergefell v. Hodges}}
(requiring government recognition of same-sex marriage)

The title text refers to a practice of filling out a March Madness bracket, predicting a winner for each game up to the championship. A bracket is "busted" when the result of a game is not as predicted; because future matchups depend on previous results, the whole bracket is worthless at that point. Randall "had Massachusetts v. Connecticut in the final", predicting both parties would win all previous rounds and advance to the final game/case. Because Connecticut lost its first-round case to Griswold, his bracket is busted in the first round.

In the second part of the title text, Randall writes: "I had Massachusetts v. Connecticut in the final, probably in a case over who gets to annex Rhode Island." In fact, there actually was a Supreme Court case ''Massachusetts v. Connecticut'' (summary at [https://supreme.justia.com/cases/federal/us/282/660/ Justia.com], full text at [https://scholar.google.com/scholar_case?case=17012735467934830012&q=Connecticut+v.+Massachusetts&hl=en&as_sdt=2006 Google Scholar]) dealing with water rights on the Connecticut River, which flows between the two states.

Rhode Island is a smaller state that borders both Massachusetts and Connecticut (and no other state), hence the joke about "who gets to annex Rhode Island."

In an actual March Madness bracket, "Massachusetts" and "Connecticut" refer to the basketball teams from the University of Massachusetts and the University of Connecticut. So it is possible that a "Massachusetts v. Connecticut" matchup could occur in the basketball championship as well.

==Transcript==
:[A tournament bracket tree is shown with 16 participants each on the left and right side. From both sides toward the middle the brackets reduce to eight, then four, two, and one line where the latter join to a rectangle in the middle.]

:[Left side:]
:Marbury - Madison
:McCulloch - Maryland
:Gibbons - Ogden
:Near - Minnesota
:NLRB - Jones & Laughlin
:Brown - Board of Education
:Gideon - Wainwright
:Griswold - Connecticut

:[Right side:]
:Miranda - Arizona
:Loving - Virginia
:Roe - Wade
:United States - Nixon
:Bush - Gore
:Lawrence - Texas
:Massachusetts - EPA
:Obergefell - Hodges

:[Caption below the frame:]
:Now that we've finished the round of 32, the Supreme Court will be moving on to the Sweet 16.

{{comic discussion}}

Talk:2034: Equations

2018-09-09T18:33:32Z

Redbelly98:

Is the joke that all of the equations are actually wrong/malformed/meaningless but they sort of look like typical equations for that field? {{unsigned ip|172.68.133.66}}
:Sort of. A bit of dimensional analysis would have helped. ;-) --[[Special:Contributions/162.158.91.221|162.158.91.221]] 07:28, 17 August 2018 (UTC)
:I feel that the joke is that all the equations are very complicated, and use multiple letters and symbols. But the last one "Truly deep Physics Equations" are summed up with just 3 characters and 2 basic operators. [[Special:Contributions/108.162.250.11|108.162.250.11]] 10:56, 19 August 2018 (UTC)

He's nerd sniping us all.. ([[Special:Contributions/162.158.167.120|162.158.167.120]] 03:30, 18 August 2018 (UTC))
: ..and perhaps forcing us to build out symbolic usage which is not generating well for math parsers, wiki, etc. [[Special:Contributions/162.158.186.60|162.158.186.60]] 14:45, 21 August 2018 (UTC)

Should we add a column with examples of similar correct equations from the respective fields? Sebastian --[[Special:Contributions/172.68.110.4|172.68.110.4]] 09:33, 17 August 2018 (UTC)
:That would definitely tidy up my attempts to provide context for Randall's versions. The challenge then is working in explanations for the correct equations as well as arguing over which examples should be used. [[User:Exxi|Exxi]] ([[User talk:Exxi|talk]]) 09:45, 17 August 2018 (UTC)

I don't think the part in parentheses about OH in the Chemistry equation explanation is correct. OH- would mean that it's negatively charged and has nothing to do with unpaired electrons of Oxygen. It would add another horror to the equation, though, as it wouldn't be charge preserving anymore. [[Special:Contributions/162.158.88.230|162.158.88.230]] 09:58, 17 August 2018 (UTC)

"Redshit". Best typo ever. Please keep it. [[Special:Contributions/172.69.54.177|172.69.54.177]] 10:13, 17 August 2018 (UTC)

;Deep physics equations
The transcript is wrong here, the last letter is not a <math>\mu</math>, but a "u" with a cedilla: u̧. The math parser refuses to render it, though. [[Special:Contributions/162.158.88.230|162.158.88.230]] 05:54, 17 August 2018 (UTC)
:Looks like it. But I don't think that letter exists even. --[[Special:Contributions/162.158.91.221|162.158.91.221]] 07:28, 17 August 2018 (UTC)
:Is this equation a sort of nod to a Theory Of Everything which unifies quantum mechanics and gravity... H-hat (a Hamiltonian, which in quantum mechanics describes the total energy of a system, and usually runs in to problems describing large systems - such as the entire universe - where gravity or spacetime curvature effects matter) *minus* u0 (the relativistic mass of the whole system at time zero ie. the big bang) gives 0 (no energy everywhere always). Since mass is energy (e=mc^2) and mass is also the sole cause of gravity the two theories cleanly collapse together when mass is zero, and figuring out how to extend the theory to other less clean points on the mass axis is obviously a job for less profound physics? I've no ideas to explain the cedilla. [[Special:Contributions/141.101.98.28|141.101.98.28]] 08:49, 17 August 2018 (UTC)
:It looks to me a little like a parody of the {{w|Wheeler-DeWitt_equation#Hamiltonian_constraint|Wheeler-DeWitt equation}} which (in theory) describes a wavefunction for the entire Universe. [[User:Exxi|Exxi]] ([[User talk:Exxi|talk]]) 09:06, 17 August 2018 (UTC)一
: I'm just thrilled someone found the right character for it. I spent 20 minutes looking for the right u symbol without any luck at all. {{unsigned ip|172.68.143.132}}
Is this poking fun at equation-filled blackboards in movies and cartoons? {{unsigned ip|172.68.254.42}}
:Doesn't seem like it. These equations actually do look like the kinds of equations you would see in these fields. On blackboards in movies you tend to get equations that are pure nonsense. {{unsigned ip|172.68.143.132}}
I think this may also be a reference to Feynman's unworldliness equation, http://www.feynmanlectures.caltech.edu/II_25.html#Ch25-S6 . [[Special:Contributions/108.162.219.220|108.162.219.220]] 17:02, 17 August 2018 (UTC)

I'd thought the point of the "u" with the cedilla was simply visual (not a reference to an actual parameter). It visually looks like the head of "The Thinker" in profile with the bottom of the "u" being the chin and the cedilla being the curled hand upon which the chin rests. So, the joke would be a twist on the term "deep" where in the cartoon the u+cedilla represents deep thought rather than far away (deep) into space. Monroe likes these little visual puns.[[User:Genejockey33000|Genejockey33000]] ([[User talk:Genejockey33000|talk]]) 14:01, 22 August 2018 (UTC)

;Table layout at the explanation
That oversized table is really bad layout. We've had this discussion many times before - tables should only be used for small contents. Right now I would run into too many edit conflicts but I'll change it to a proper floating text with small headers for each section. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 11:51, 17 August 2018 (UTC)
:Done, looks much more like a real paper... --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 12:58, 17 August 2018 (UTC)

;All number theory equation
The explanation for math doesn't seem entirely correct. You can in fact extend the ring of integers (as well as rational and real numbers) with positive and negative infinity, but it won't be a ring anymore. Specifically, the infinities don't have an additive or multiplicative inverse (but 1/infinity = 0); and addition of positive and negative infinity, as well as the product of 0 and either infinity is undefined. However, these properties are not used in the above equation. What we ''can'' use is that <math>\forall n < \infty: n - \infty= -\infty </math>. We would thus have <math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty}) = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-0) = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)i= \sum_{i=0}^{\infty}i\sum_{\pi=n}^{\infty}-\pi= \sum_{i=0}^{\infty}i\cdot(-\infty)=-\infty</math>. Also, how often does one use e and pi in number theory? --[[User:Ycthiognass|Ycthiognass]] ([[User talk:Ycthiognass|talk]]) 12:11, 17 August 2018 (UTC)
:Pi (or any other number) minus infinite is just absurd. You can use the infinite symbol only as a limit but NOT as number in calculations. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 12:33, 17 August 2018 (UTC)
::It is not absurd. Adding the rules <math>n+\infty=\infty\text{ for }n>-\infty,n-\infty=-\infty\text{ for }n<\infty, \pm n\cdot\infty = \pm\infty\text{ for }n>0, \pm n\cdot(-\infty) = \mp\infty\text{ for }n>0,\frac1{\pm\infty}=0</math> gives you a consistent theory that is especially useful when talking about infinite sums and integrals. Would you say the term <math>n-\sum_{i=1}^\infty i</math> is absurd? --[[User:Ycthiognass|Ycthiognass]] ([[User talk:Ycthiognass|talk]]) 14:35, 17 August 2018 (UTC)
:::Of course it's absurd. It is <math>\infty-\infty \neq 0</math> because it could be everything between <math>\infty</math> and <math>-\infty</math>. {{w|Infinity}} is a concept describing something without any bound... And, as you can't divide by zero you can't do the same for infinity. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 17:24, 17 August 2018 (UTC)
:::One more: It is
::::<math>\sum_{i=1}^\infty a_i = \lim_{n\to\infty} \sum_{i=1}^n a_i.</math>
:::When this limit exists, one says that the series is ''convergent'' or ''summable''. Otherwise it's called ''divergent'' and has no solution like this one:
::::<math>\sum_{i=1}^\infty i</math>
:::Infinite is NO number! --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 17:33, 17 August 2018 (UTC)
::::<math>\infty-\infty</math> is indeterminate, just like 0/0 is in standard arithmetic. That's cool, because we don't need the value of <math>\infty-\infty</math> to calculate the above expression. Have a look at the [https://en.wikipedia.org/wiki/Extended_real_number_line extended real number line]. --[[User:Ycthiognass|Ycthiognass]] ([[User talk:Ycthiognass|talk]]) 06:18, 20 August 2018 (UTC)

Completely separate from the above, it's probably worth noting that i is also a constant, and as such has the same misconception as <math>\pi</math>. Computer scientists are happy using i for loops/summations, but mathematicians prefer using n. Based off that, it's probably another misconception/joke that n is treated as a constant, while known-constants are used as variables. [[Special:Contributions/108.162.246.149|108.162.246.149]] 17:28, 17 August 2018 (UTC)
:There is nothing non-standard about using i as an index variable. Often as part of the series i,j,k. Searching for summation convention will give plenty of examples.
:There are fewer letters than mathematical concepts in need of letters, so most letters are used for multiple purposes. Occasionally this causes difficulty. You can be halfway through a linear algebra problem before you discover you need i for an imaginary number despite already using it as an index. Hilarity ensues. [[Special:Contributions/162.158.74.105|162.158.74.105]] 19:57, 17 August 2018 (UTC)

Is it worth mentioning Euler's identity in the explanation? As a non-mathematician, the presence of e, pi, and i together in one equation looks "Euler's identity-ish" while clearly not being it. [[Special:Contributions/162.158.74.39|162.158.74.39]] 22:20, 19 August 2018 (UTC)

Honestly, seeing e, pi, and i isn't that farfetched, since quite a few applications of number theory to coordinate systems (in the computer-ey sense) take familiar XY coordinates, make them polar, and call them to complex numbers, with a bunch of operations done by multiplying by e to some complex power or other. And wherever waves go, pi goes...
Coming from nothing more than a high-school background, this whole system can be rather jarring, and difficult to understand. I'm just glad I understand enough bits and pieces of number theory to laugh at Randall's joke. [[Special:Contributions/162.158.186.12|162.158.186.12]] 19:41, 1 September 2018 (UTC)
;Chemistry equation
OH should have a charge symbol: OH-. The actual reaction would be:

CH4 + OH- + heat -> CH3- + H2O

The methyl group can dissolve in water, and this is presumably happening in water, so this equation can work, just not the one provided by Randell. Reacting longer alkanes with bases is a way to make soaps, but the methyl group would be too reactive to be used this way. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 13:13, 17 August 2018 (UTC)

;Fluid Dynamics equation
I believe the fraction 8/23 in the Fluid Dynamics equation is a Randallesque reference to the fractional approximation of pi = 22/7. It's probably not a coincidence that you get 8/23 from 22/7 if you invert it and add 1 to both the numerator and denominator. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 15:19, 17 August 2018 (UTC)

:I think that is a bit of a stretch. If Randall wanted to reference the 22/7 approximation, I think he would simply use 22/7 and not 8/23. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:40, 18 August 2018 (UTC)

::It might be a stretch, but maybe Randall wanted to be more clever than just inserting 22/7, since pi really has no place in that equation. I don't see anyone else suggesting any reasonable source for 8/23 in the equation. The current explanation is an even bigger stretch, since it has nothing in common with 8/23 beyond being just another fraction - it seems to suggest he picked two random numbers, 8 and 23, for the fraction! How unsatisfying! But if nobody else agrees, I'm not losing any sleep over it. (Sometimes I wish Randall would chime in to clear things like this up for us. Randall, where are you?) [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:54, 18 August 2018 (UTC)

:Fluid dynamicist here -- strange looking numbers and fractions come from multiplying tensors. 2/3 is a common one, but you also get numbers like 1/7 and 8/27.[[Special:Contributions/108.162.241.166|108.162.241.166]] 07:24, 18 August 2018 (UTC)

I changed a "p" to a Greek "rho". [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:40, 18 August 2018 (UTC)

;Gauge theory equation
<s>I think the transcript is missing a left superscript 0 before the turned xi. [[Special:Contributions/172.68.226.16|172.68.226.16]] 16:50, 17 August 2018 (UTC)</s> Ah no, sorry. False alarm. It's just that Randall writes the xi with a funny tail. The same tail is on the non-turned xi earlier. [[Special:Contributions/172.68.226.10|172.68.226.10]] 16:52, 17 August 2018 (UTC)

If explainxkcd.com is to make XKCD comics more understandable then this explanation is failing that. I assumed from the beginning that the joke was about the equations being wrong, but the description of the joke is making my head hurt. {{unsigned ip|162.158.106.216}}
:Read the first paragraph: "To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them." Nevertheless the rest sometimes does hurt. See below. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:28, 17 August 2018 (UTC)

;All truly deep physics equations
In the description paragraph, the last sentence starting "The principle of least action says allows..." does not scan. If someone can fix this (copy&paste?) error, please delete this comment. [[Special:Contributions/162.158.58.171|162.158.58.171]] 19:33, 17 August 2018 (UTC)
:I edited the sentence slightly to address this issue. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 20:51, 17 August 2018 (UTC)

It looks like there is already a section for this above, "Deep physics equations", or am I missing something? [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:40, 18 August 2018 (UTC)

Note that this comics also emphasizes that Randall is more familiar with physics than with chemistry : while most of the equations here require college-level education to grok, the chemistry one is at the very most high-scool-grade. {{unsigned ip|141.101.69.33}}

Could this be a reference to Feynman's jab at hiding complexity underneath symbol definitions to achieve 'simplicity'? See the Feynman Lectures on Physics, Volume II, Chapter 25, Section 6. [[Special:Contributions/162.158.150.100|162.158.150.100]] 09:19, 19 August 2018 (UTC)WhoIsJack
:Sounds good to me. [[User:Exxi|Exxi]] ([[User talk:Exxi|talk]]) 19:29, 23 August 2018 (UTC)

;Explanations in general
“Nobody knows if Randall references a horse here” - what?! Because the expression lacks an equal sign; doesn’t represent an equality, it might mean Randall is referencing equines, aka horses?! Is this vandalism, an attempt at a joke, or what? This explanation clearly still needs quite a bit of work! [[User:PotatoGod|PotatoGod]] ([[User talk:PotatoGod|talk]]) 20:14, 17 August 2018 (UTC)
:I've put a header on top here. It's not vandalism but every explanation looks still highly unscientific. I've gave real sources to the most topics at the beginning but the following explanations are mostly bad. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:22, 17 August 2018 (UTC)
:I left that joke in as it was added whilst I was editing the rest of it, I don't think it belongs though. I did my best to reference real-life stuff while writing [Gauge, Quantum Gravity and Cosmology] the awfulness of the equations makes it hard to be scientific though. If there are specific issues I can have a shot at improving those sections although it's kinda hard to explain why I find them funny without going deep into the related physics. I'm not convinced it's possible to properly get that across to a non-physicist in a paragraph of explainXKCD. [[User:Exxi|Exxi]] ([[User talk:Exxi|talk]]) 19:29, 23 August 2018 (UTC)

;Kinematics equations
I fixed an error: Randall's Greek "rho" ''ρ'', a common symbol for mass density, was incorrectly shown here as ''p'', the common symbol for momentum. The term with the ''ρ'' is very similar to a term in the Bernoulli equation, and I have changed the explanation to reflect this. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:40, 18 August 2018 (UTC)

;You might be overthinking some of these
For example, I see the first one as Energy = cot + private which would be an Army private resting in a cot to regain their energy.
The second one I see the word Knee, so I'm thinking it's either something about taking an arrow to a knee, or perhaps about the Knights of Ki who regain their power by saying "Ni!"
The fourth one, I see most of the word ANALOGY, so perhaps the trident-shaped thing equals N, and x> = L, and l (or 1) = G, so if you resolve all the way through you get GNL = ANALOGY and I don't have that quite right yet.
SU(2)U(1)xSU(U(2)) makes me think of Phil Collins singing "Su-Su-Sussudio oh oh". --[[Special:Contributions/108.162.245.40|108.162.245.40]] 20:37, 18 August 2018 (UTC)

;Has anyone considered the joke part?
As someone unfamiliar with scientific equations, I took the joke to be that Scientific Equations Are Complicated, until you get to the "truly deep" part, in which case they're pretty simple. As much as I appreciate the description of the equations, is anyone gonna explain whether my take on the joke is plausible? Or what it is if I'm wrong? [[Special:Contributions/108.162.219.214|108.162.219.214]] 15:52, 20 August 2018 (UTC)

;Is there a pun?
Am I the only one seeing a possible pun in SU(2)U(1)xSU(U(2))? I can't figure out the whole thing but SU(U(2)) sure looks like it reads "sue you too".
[[Special:Contributions/24.165.207.66|24.165.207.66]] 23:02, 20 August 2018 (UTC)

;No element symbols exist to form EAT
Although you could write HeAt (Helium-Astatine), I could find no element symbols to form EAT on the right-hand side of the reaction, so it appears to be an invalid expression anyway. (and yes, of course I know Randall is messing with us and you might be expected to read the first "heat" as "temperarature".) --[[User:IByte|IByte]] ([[User talk:IByte|talk]]) 11:17, 4 September 2018 (UTC)
: And Randall wrote HEAT, not HeAt. They are different. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 18:33, 9 September 2018 (UTC)

User talk:Dgbrt

2018-09-04T01:28:37Z

Redbelly98:

See the history for more:
* [[User talk:Dgbrt/2013|2013]]
* [[User talk:Dgbrt/2014|2014]]
* [[User talk:Dgbrt/2015-2017|2015-2017]]

== Create comic page in lieu of DgbrtBOT ==

I could see [http://www.explainxkcd.com/wiki/index.php?title=1969:_Not_Available&action=history here] that the bot seemed to have failed this time (or did RamenChef fail to wait long enough?) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:41, 20 March 2018 (UTC)
:Ah sorry, saw your comment in the [[Talk:1969: Not Available|Discussion]] now. Great if it has been fixed. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:47, 20 March 2018 (UTC)

== ReCAPTCHA ==
ReCAPTCHA v1 has expired, and since no one replied on the admin forum, I asked Kynde, and he told me to come to you. So can you upgrade it to v2? Thanks. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 13:05, 9 April 2018 (UTC)
:Hi [[User:Herobrine|Herobrine]], this is bad. Also email notification doesn't work since a long time. All admins are nonexistent since months and I don't have access the the server. I will check what I can do with the BOT account. But there is not much hope. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 15:00, 9 April 2018 (UTC)
::Oh... ok. But if I remember correctly, I think one of the admins (I think Jeff?) has a twitter account, but I don't have one and I can't ask on twitter. Could you like contact him that way? And maybe tell him to add a few admins to deal with problems like this? Thanks! [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 10:18, 11 April 2018 (UTC)
:::Hi [[User:Herobrine|Herobrine]], I don't have a twitter account too, but I will sign in when things go worse. And this will happen in the future when all admins are still absent because:
:::*The next invoice for the web-service at Cloudflare must be paid.
:::*The name registration at namecheap.com will expire on 2018-08-10.
:::And it seems that there is no advertising here on the left. So we definitely need new admins here to address these and other issues. I would apply for this, but not alone. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 13:07, 11 April 2018 (UTC)

Hello Dgbrt, I saw your message both here and on Wikipedia. Messaging me on my talk page is enough, I'll see it in my feed reader. Unfortunately, I can't do anything about recaptcha as I don't have ssh access to the server. --[[User:SlashMe|SlashMe]] ([[User talk:SlashMe|talk]]) 15:25, 11 April 2018 (UTC)
:Thanks for your reply [[User:SlashMe|SlashMe]]. You don't have ssh access but as an Administrator you are maybe able to send an email to the relevant persons. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 16:09, 11 April 2018 (UTC)
::Unfortunately, I don't have [[User:Jeff|Jeff]]'s email address either. --[[User:SlashMe|SlashMe]] ([[User talk:SlashMe|talk]]) 06:47, 12 April 2018 (UTC)
'''The problem is solved.''' --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:50, 22 May 2018 (UTC)

== I'm here ==

I'm sorry Dgbt (and all my other friendly editors/helpers!)
Let me know what needs to be done and I'll work through it. I'm going to try to be much more proactive and logged in. It's been a busy few months. Please accept my apologies.
The main complication with reCaptcha is that to upgrade to use ReCaptchaNoCaptcha, I'd have to upgrade the wiki. I'm not opposed, it is just a larger work effort than I thought! We are also quite a bit behind! --[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 03:18, 13 April 2018 (UTC)

== A slight technical problem ==

The image size for comics is a bit off, the zoom is weird and there's some space to the right of the screen... Not sure what to do about it, but as an admin now (congratulations, by the way!) you should be able to deal with it. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 13:06, 4 July 2018 (UTC)
:Hi [[User:Herobrine|Herobrine]], what is weird? Please give an example of what's wrong and how it should be. BTW: To be an admin just means more work ;) --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 13:20, 4 July 2018 (UTC)
::It seems that there's only one problem left, rather than the three I mentioned before, but it's still a problem. For example, normally pages should be like this, where there's a sidebar to the left, and the rest is the page you're viewing. But now for comic explanations, there's an empty sidebar on the right side of the screen that shouldn't be there, and the page itself has been squeezed so now it only takes up about 60% of the screen's width. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 01:24, 5 July 2018 (UTC)
:::Sorry for the delay, but it should be fixed now. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 16:38, 10 July 2018 (UTC)

== Unicode issues with the Bot ==

Hi, your bot doesn't handle UTF-8 in the alt-text well, as seen on today's comic [[2038]] :P This is a known problem with the xkcd api, which double-utf-8-encodes everything. I believe I've read your bot is programmed in Perl, so I may be able to help fix this. There is a module on CPAN to fix this automagically, [https://metacpan.org/pod/Encode::DoubleEncodedUTF8 Encode::DoubleEncodedUTF8] [[User:Gir|//gir.st/]] ([[User talk:Gir|talk]]) 13:23, 27 August 2018 (UTC)
:'''E''': I've sent you a PR; https://github.com/dgbrt/explainXKCD_update/pull/3 [[User:Gir|//gir.st/]] ([[User talk:Gir|talk]]) 13:44, 27 August 2018 (UTC)
::I was replying at the same time:
:Thanks, you can find the GitHub link here: [[User:DgbrtBOT]]. The latest changes are a little bit ugly because I've had to find a fast solution on the forced https connection. Nonetheless the unicode issue is well known, until now I simply was too lazy. And reading the warnings at the DoubleEncodedUTF8 module tells me it should be solved in a better way.
:I'm not sure, but my CentOS environment looks good:
:<code>env | grep LANG</code> gives me
:<code>LANG=en_US.UTF-8</code>
:The Perl script already has <code>binmode STDOUT, ':utf8';</code> which was needed so maybe the same for <code>STDIN</code> could help. Any ideas? I have a Wiki at my PC for testing. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:26, 27 August 2018 (UTC)
The problem is solved and the script successfully tested. Thanks for the help. And if Randall reads this: You probably can fool the BOT by using double encoded UTF at the comic name. But I believe the corresponding image URI wouldn't work. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:26, 28 August 2018 (UTC)

== ==

Oops, sorry for forgetting my signature in my comment on "1047: Approximations", and thank you for adding it. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 01:27, 4 September 2018 (UTC)

User talk:Dgbrt

2018-09-04T01:27:06Z

Redbelly98: Apologies / thank you

See the history for more:
* [[User talk:Dgbrt/2013|2013]]
* [[User talk:Dgbrt/2014|2014]]
* [[User talk:Dgbrt/2015-2017|2015-2017]]

== Create comic page in lieu of DgbrtBOT ==

I could see [http://www.explainxkcd.com/wiki/index.php?title=1969:_Not_Available&action=history here] that the bot seemed to have failed this time (or did RamenChef fail to wait long enough?) --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:41, 20 March 2018 (UTC)
:Ah sorry, saw your comment in the [[Talk:1969: Not Available|Discussion]] now. Great if it has been fixed. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:47, 20 March 2018 (UTC)

== ReCAPTCHA ==
ReCAPTCHA v1 has expired, and since no one replied on the admin forum, I asked Kynde, and he told me to come to you. So can you upgrade it to v2? Thanks. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 13:05, 9 April 2018 (UTC)
:Hi [[User:Herobrine|Herobrine]], this is bad. Also email notification doesn't work since a long time. All admins are nonexistent since months and I don't have access the the server. I will check what I can do with the BOT account. But there is not much hope. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 15:00, 9 April 2018 (UTC)
::Oh... ok. But if I remember correctly, I think one of the admins (I think Jeff?) has a twitter account, but I don't have one and I can't ask on twitter. Could you like contact him that way? And maybe tell him to add a few admins to deal with problems like this? Thanks! [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 10:18, 11 April 2018 (UTC)
:::Hi [[User:Herobrine|Herobrine]], I don't have a twitter account too, but I will sign in when things go worse. And this will happen in the future when all admins are still absent because:
:::*The next invoice for the web-service at Cloudflare must be paid.
:::*The name registration at namecheap.com will expire on 2018-08-10.
:::And it seems that there is no advertising here on the left. So we definitely need new admins here to address these and other issues. I would apply for this, but not alone. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 13:07, 11 April 2018 (UTC)

Hello Dgbrt, I saw your message both here and on Wikipedia. Messaging me on my talk page is enough, I'll see it in my feed reader. Unfortunately, I can't do anything about recaptcha as I don't have ssh access to the server. --[[User:SlashMe|SlashMe]] ([[User talk:SlashMe|talk]]) 15:25, 11 April 2018 (UTC)
:Thanks for your reply [[User:SlashMe|SlashMe]]. You don't have ssh access but as an Administrator you are maybe able to send an email to the relevant persons. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 16:09, 11 April 2018 (UTC)
::Unfortunately, I don't have [[User:Jeff|Jeff]]'s email address either. --[[User:SlashMe|SlashMe]] ([[User talk:SlashMe|talk]]) 06:47, 12 April 2018 (UTC)
'''The problem is solved.''' --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:50, 22 May 2018 (UTC)

== I'm here ==

I'm sorry Dgbt (and all my other friendly editors/helpers!)
Let me know what needs to be done and I'll work through it. I'm going to try to be much more proactive and logged in. It's been a busy few months. Please accept my apologies.
The main complication with reCaptcha is that to upgrade to use ReCaptchaNoCaptcha, I'd have to upgrade the wiki. I'm not opposed, it is just a larger work effort than I thought! We are also quite a bit behind! --[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 03:18, 13 April 2018 (UTC)

== A slight technical problem ==

The image size for comics is a bit off, the zoom is weird and there's some space to the right of the screen... Not sure what to do about it, but as an admin now (congratulations, by the way!) you should be able to deal with it. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 13:06, 4 July 2018 (UTC)
:Hi [[User:Herobrine|Herobrine]], what is weird? Please give an example of what's wrong and how it should be. BTW: To be an admin just means more work ;) --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 13:20, 4 July 2018 (UTC)
::It seems that there's only one problem left, rather than the three I mentioned before, but it's still a problem. For example, normally pages should be like this, where there's a sidebar to the left, and the rest is the page you're viewing. But now for comic explanations, there's an empty sidebar on the right side of the screen that shouldn't be there, and the page itself has been squeezed so now it only takes up about 60% of the screen's width. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 01:24, 5 July 2018 (UTC)
:::Sorry for the delay, but it should be fixed now. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 16:38, 10 July 2018 (UTC)

== Unicode issues with the Bot ==

Hi, your bot doesn't handle UTF-8 in the alt-text well, as seen on today's comic [[2038]] :P This is a known problem with the xkcd api, which double-utf-8-encodes everything. I believe I've read your bot is programmed in Perl, so I may be able to help fix this. There is a module on CPAN to fix this automagically, [https://metacpan.org/pod/Encode::DoubleEncodedUTF8 Encode::DoubleEncodedUTF8] [[User:Gir|//gir.st/]] ([[User talk:Gir|talk]]) 13:23, 27 August 2018 (UTC)
:'''E''': I've sent you a PR; https://github.com/dgbrt/explainXKCD_update/pull/3 [[User:Gir|//gir.st/]] ([[User talk:Gir|talk]]) 13:44, 27 August 2018 (UTC)
::I was replying at the same time:
:Thanks, you can find the GitHub link here: [[User:DgbrtBOT]]. The latest changes are a little bit ugly because I've had to find a fast solution on the forced https connection. Nonetheless the unicode issue is well known, until now I simply was too lazy. And reading the warnings at the DoubleEncodedUTF8 module tells me it should be solved in a better way.
:I'm not sure, but my CentOS environment looks good:
:<code>env | grep LANG</code> gives me
:<code>LANG=en_US.UTF-8</code>
:The Perl script already has <code>binmode STDOUT, ':utf8';</code> which was needed so maybe the same for <code>STDIN</code> could help. Any ideas? I have a Wiki at my PC for testing. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:26, 27 August 2018 (UTC)
The problem is solved and the script successfully tested. Thanks for the help. And if Randall reads this: You probably can fool the BOT by using double encoded UTF at the comic name. But I believe the corresponding image URI wouldn't work. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 14:26, 28 August 2018 (UTC)

Oops, sorry for forgetting my signature in my comment on "1047: Approximations", and thank you for adding it. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 01:27, 4 September 2018 (UTC)

1512: Horoscopes

2018-09-03T01:07:19Z

Redbelly98: /* Table of Astrological signs */ Cancer: Oct 28 is a few **days** (not weeks) before Halloween, Oct. 31

{{comic
| number = 1512
| date = April 15, 2015
| title = Horoscopes
| image = horoscopes.png
| titletext = If you live in the Northern hemisphere, anyway. In the southern hemisphere, due to the coriolis effect, babies are born nine months BEFORE they're conceived.
}}
==Explanation==
{{w|Horoscopes}} purport to predict someone's personality or future, based on the position of planets and stars at the time of their birth and at present. Horoscopes commonly group people into twelve groups based on {{w|zodiac signs}}. The names of the horoscope Zodiac signs are based on the names of twelve constellations that were the backdrop for the path of the sun in the ancient times when the rules of settings horoscopes were originally developed. Today, due to precession of the Earth's axis of rotation (and to a lesser degree due to the modern formal definitions of constellations), the Zodiac signs do not correspond fully to the names of actual constellations in the path of the Sun. One's zodiac sign is determined by the position of the sun on their birthday, with each sign representing a specific 30.4 day period (1/12th of a year), starting from the {{w|equinox|First point of Aries}}.

Modern science has found {{w|Astrology and science|no basis for horoscopes}}, which is why the comic jokes about the fact that its horoscopes at least ''may'' be true. Actual horoscopes are typically so vague that they could be true for almost anyone regardless of their sign. Note that this horoscope mainly makes sense for people living in the {{w|northern hemisphere}} (as mentioned in the title text) and it is especially tailored for an audience in the {{w|United States}}, as most cultural references are centered on "Western" or even specific "American" culture, several won't even work in Europe, for example. However, with the principle understood, it is easy to apply local traditions for more accuracy in non-Western cultures.

The 12 category zodiac signs in horoscopes are based on birth dates. The average length of pregnancy, culturally considered to be nine months, is actually given as the 40 weeks (9.2 months) after the last menstrual period. However, what is relevant here is that it is only '''38 weeks after {{w|Fertilisation|conception}}''' (8.75 month). The first two weeks of the 40 week period is before {{w|Ovulation#Ovulation_in_humans|Ovulation}}, and the conception cannot occur before that.

Based on this knowledge [[Randall]] can do some informed guessing about the context of someone's conception (apart from the {{w|Sexual intercourse|obvious}}), depending on the sign. For example, people of the sign {{w|Virgo (astrology)|Virgo}} have been born between August 23 and September 22. This makes it most likely that they are conceived during December the year before. Given contemporary holiday music preferences, Christmas songs were likely to be playing the day they were conceived. This leads to the guess "You may have been conceived while a Christmas song played". See detailed description of all the signs and explanation of the horoscopes in the [[#Table of Astrological signs|table]] below.

Randall phrases his "predictions" as possibilities ("you may have") rather than declarations, acknowledging that it is a guess, and that it, unlike actual horoscopes, doesn't necessarily apply to everyone.

The title text refers to the {{w|Coriolis effect}} which applies to a body that is moving relative to an object that is spinning. Since the Earth is rotating, a force (the Coriolis force) causes moving objects to be deflected to the right in the northern hemisphere and to the left in the {{w|southern hemisphere}}. This effect is the reason that {{w|Coriolis_effect#Meteorology|weather systems}} (most clearly seen for {{w|hurricanes}}) spiral in one direction in the northern hemisphere and in the opposite direction in the southern hemisphere.

There is also a common {{w|Coriolis_effect#Draining_in_bathtubs_and_toilets|misconception}} that the Coriolis force in respect of the Earth affects objects on a much smaller scale, such as the direction water will spiral down a drain in the two hemispheres (see also [[843: Misconceptions]]). In reality, the relative rotational speed of the Earth (one rotation per day) is insufficient to affect anything but large-scale, relatively slow movement, such as {{w|prevailing winds}} and {{w|Ocean current|ocean currents}}.

Randall plays on this type of misconception to make a joke involving reversing the flow of time. So whereas babies are born nine months '''after''' conception in the northern hemisphere (clockwise) the Coriolis effect is the reason why babies are being born nine months '''before''' in the southern hemisphere (counterclockwise). Note that unlike these horoscopes, which are declared to have an "actual basis in fact", it makes no sense for the conception of a baby to happen after its birth{{Citation needed}}.

==Table of Astrological signs==
Here below is a table with data and explanation of the individual horoscopes:
{| class="wikitable"
!{{w|Astrological sign|Astrological sign}} (English name)
!{{w|Birthday}} range
!Expected {{w|Fertilisation|conception}}
!Horoscope prediction
!Explanation
|-
|♈ {{w|Aries (astrology)|Aries}} (The Ram)
|March 21 – April 21
|June 28 – July 28
|You may have been conceived after a 4th of July fireworks show
|In the US the {{w|Independence Day (United States)|Independence Day}} is celebrated on the 4th of July, and this is customarily celebrated with huge fireworks. Fireworks are a common metaphor for the culmination of sex (i.e. the orgasm), and offer a convenient opportunity for social gatherings that might lead to conception.
|-
|♉ {{w|Taurus (astrology)|Taurus}} (The Bull)
|April 20 – May 20
|July 27 – August 27
|You may have been conceived on a hot August day
|In most of the northern hemisphere there are many hot days in {{w|August}}. Hot days can lead to less clothing and more lust.
|-
|♊ {{w|Gemini (astrology)|Gemini}} (The Twins)
|May 21 – June 21
|August 28 – September 28
|You may have been conceived as the leaves began to change
|In the northern part of the northern hemisphere the {{w|autumn}} starts at the end of this time period, so the leaves will begin to change color.
|-
|♋ {{w|Cancer (astrology)|Cancer}} (The Crab)
|June 21 – July 21
|September 28 – October 28
|You may have been conceived by people trying on costumes
|This period ends a few days before {{w|Halloween}}, so it is not unlikely that the people who conceived you (mom and dad) tried on their new costumes when they made you. Roleplay, enhanced with costumes, can be a way to spice up a relationship and can lead to sex and procreation.
|-
|♌ {{w|Leo (astrology)|Leo}} (The Lion)
|July 22 – August 23
|October 29 – November 30
|You may have been conceived during Thanksgiving
|{{w|Thanksgiving}} is celebrated in the US on the fourth Thursday of November.
|-
|♍ {{w|Virgo (astrology)|Virgo}} (The Maiden)
|August 23 – September 22
|November 30 – December 29
|You may have been conceived while a Christmas song played
|It is very common for {{w|Christmas}} songs to be played in the month of December.
|-
|♎ {{w|Libra (astrology)|Libra}} (The Scales)
|September 22 – October 23
|December 29 – January 30
|You may have been conceived after a New Year's Eve party
|Since {{w|New Year's Eve}} always falls on December 31, and since the party goes on into the new year this fits with Libra. As it is very likely that people are together in a way that may lead to conception at this type of parties, there may even be rather more than a 30th part of the people that are Libra that are conceived at such a party.
|-
|♏ {{w|Scorpio (astrology)|Scorpio}} (The Scorpion)
|October 23 – November 22
|January 30 – February 29
|You may have been conceived by people stuck inside after a long winter
|This period is during the coolest part and towards the end of the {{w|winter}} in the northern hemisphere. People may even be forced to stay at home due to snow. When people have nothing else to do [https://www.google.dk/search?q=babies+9+month+after+snowstorm&ie=utf-8&oe=utf-8&gws_rd=cr&ei=qzkuVcjAE4qsswGevoC4CQ many babies are born 9 months later].
|-
|♐ {{w|Sagittarius (astrology)|Sagittarius}} (The Archer)
|November 22 – December 21
|February 29 – March 28
|You may have been conceived during March Madness
|Originally {{w|European_hare#Mating_and_reproduction|March madness}} referred to the early part of the mating season for the {{w|European Hare}}, in which females fight off male suitors. Today, in a US context, this is an {{w|NCAA Men's Division I Basketball Championship|American college Basketball tournament}} that started in 1939 and is mainly held in March. It is even covered on TV under the name {{w|NCAA March Madness (CBS/Turner)|NCAA March Madness}}.
|-
|♑ {{w|Capricorn (astrology)|Capricorn}} (The Goat)
|December 22 – January 19
|March 29 – April 28
|You may have been conceived during a sexy Easter Egg hunt
|{{w|Easter}} falls between {{w|List of dates for Easter#Earliest Easter|March 22}} and {{w|List of dates for Easter#Latest Easter|April 25}} so most {{w|Egg hunt|Easter Egg hunts}}, sexy or not, will fall in the most likely period to conceive Capricorn children. The goal of an Easter egg hunt can be to find as many eggs in a given time, or find a sequence of eggs, each containing a clue to the next. It is not difficult to think of adult variations on these themes. Most Egg hunts do not involve people who should make them sexy! On the other hand, the egg itself, as an Easter symbol, is a symbol of fertility and after the little ones have gone to bed the adults may want to produce more little ones.
|-
|♒ {{w|Aquarius (astrology)|Aquarius}} (The Water Carrier)
|January 20 – February 18
|April 27 – May 25
|You may have been conceived on Mother's Day
|{{w|Mother's Day}} in the USA,and some other countries, is on the second Sunday in May, between 8 and 14 May. The husband of a Mother being celebrated may wish to show his appreciation for her by paying her special private attention, potentially leading to sex and conception.
|-
|♓ {{w|Pisces (astrology)|Pisces}} (The Fish)
|February 19 – March 20
|May 25 – June 27
|You may have been conceived at someone's wedding
|It may have been your own parent's wedding, as the traditional wedding honeymoon typically includes sex (potentially lots of it). However, it is also not uncommon that people meet at weddings, and may even go so far as to risk conceiving a child at someone's {{w|wedding}}. June is widely reported as the [http://www.statista.com/statistics/241231/percentage-of-us-weddings-by-month/ most popular month for weddings in the United States]. The tradition of a June Bride (late spring and beginning of summer in the northern hemisphere) may be an old one and hence explains the reference for Pisces which lies mainly in June. [https://open.abc.net.au/explore/22074 ABC claim] that in the 15th and 16th century, May would have been the month for an "annual bath", and moreover {{w|June}} is named for {{w|Juno (mythology)|Juno}}, goddess of marriage and childbirth.
|}

==Transcript==
:[Above the frame:]
:'''Horoscopes'''
:With an actual basis in fact
:[A list with the name of each astrological sign in the first column (in gray) and a horoscope for each sign in the second column. Here given in table form]
:{| class="wikitable"
! Aries •
| You may have been conceived after a 4th of July fireworks show
|-
! Taurus •
| You may have been conceived on a hot August day
|-
! Gemini •
| You may have been conceived as the leaves began to change
|-
! Cancer •
| You may have been conceived by people trying on costumes
|-
! Leo •
| You may have been conceived during Thanksgiving
|-
! Virgo •
| You may have been conceived while a Christmas song played
|-
! Libra •
| You may have been conceived after a New Year's Eve party
|-
! Scorpio •
| You may have been conceived by people stuck inside after a long winter
|-
! Sagittarius •
| You may have been conceived during March Madness
|-
! Capricorn •
| You may have been conceived during a sexy Easter egg hunt
|-
! Aquarius •
| You may have been conceived on Mother's day
|-
! Pisces •
| You may have been conceived at someone's wedding
|}

{{comic discussion}}
[[Category:Charts]]
[[Category:Sex]]
[[Category:Christmas]]

Talk:1047: Approximations

2018-09-03T00:48:50Z

Redbelly98: World population discussion

The US population estimate is now off by 7 million, although 2018 just started. Even so, in December 2017, it would have been 4 million off. [[User:625571b7-aa66-4f98-ac5c-92464cfb4ed8|625571b7-aa66-4f98-ac5c-92464cfb4ed8]] ([[User talk:625571b7-aa66-4f98-ac5c-92464cfb4ed8|talk]]) 00:54, 19 January 2018 (UTC)

: Off by 7 million out of 7-8 billion means that it's accurate to one part in 1,000. That's consistent with it's location in the chart -- next to other values that are accurate to 1 in 1,000.

The world population estimate is still accurate to within .1 billion. [[Special:Contributions/162.158.63.28|162.158.63.28]] 13:41, 5 May 2017 (UTC)

They're actually quite accurate. I've used these in calculations, and they seem to give close enough answers. '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 14:03, 8 January 2013 (UTC)

I only see a use for the liters in a gallon one. The rest are for trolling or simple amusement. The cosine identity bit our math team in the butt at a competition. It was painful. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 05:27, 17 August 2013 (UTC)

Annoyingly this explanation does not cover 42 properly, it does not say that Douglas Adams got the number 42 from Lewis Carroll, who is more relevant to the page because he was a mathematician named Charles Lutwidge Dodgson. He was obsessed with the number forty-two. The original plate illustrations of Alice in Wonderland drawn by him numbered forty-two. Rule Forty-Two in Alice in Wonderland is "All persons more than a mile high to leave the court", There is also a Code of Honour in the preface of The Hunting of the Snark, an extremely long poem written by him when he was 42 years old, in which rule forty-two is "No one shall speak to the Man at the Helm". The queens in Alice Through the Looking Glass the White Queen announces her age as "one hundred and one, five months and a day", which - if the best possible date is assumed for the action of Through the Looking-Glass - gives a total of 37,044 days. With the further (textually unconfirmed) assumption that both Queens were born on the same day their combined age becomes 74,088 days, which is 42 x 42 x 42. --[[Special:Contributions/139.216.242.254|139.216.242.254]] 02:43, 29 August 2013 (UTC)

:: This explanation covers 42 adequately, and would probably be made slightly worse if such information were added. The very widely known cultural reference is to Adams's interpretation, not Dodgson's original obsession. Adding it would be akin to introducing the MPLM into the explanation for the hijacking of Renaissance artists' names by the TMNT. I definitely concede that it does not cover 42 exhaustively, but I think it can be considered complete and in working order without such an addition. If it really irks you, be bold and add it! --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 00:37, 30 August 2013 (UTC)

"sqrt(2) is not even algebraic in the quotient field of Z[pi]" is not correct. Q is part of the quotient field of Z[pi] and sqrt(2) is algebraic of it. The needed facts are that pi is not algebraic, but the formula implies it is in Q(sqrt(2)). --DrMath 06:47, 7 September 2013 (UTC)

13/15 is a better approximation to sqrt(3)/2 than is e/pi. Continued fraction approximations are great! --DrMath 07:23, 7 September 2013 (UTC)

How could he forget 1 gallon ≈ 0.1337 ft³?! [[Special:Contributions/67.188.195.182|67.188.195.182]] 00:51, 8 September 2013 (UTC)

Worth mentioning that Wolfram Alpha now officially recognizes the [http://www.wolframalpha.com/input/?i=e%5E-%28%281%2B8%5E%281%2F%28e-1%29%29%29%5E%281%2Fpi%29%29 White House switchboard constant] and the [http://www.wolframalpha.com/input/?i=%287%5E%28e-1%2Fe%29-9%29*pi%5E2 Jenny constant]. [[Special:Contributions/86.164.243.91|86.164.243.91]] 18:28, 8 October 2013 (UTC)

Maybe we should add the [Extension:LaTeXSVG LaTeX extension] to make it easier to transcribe these equations. -- [[Special:Contributions/108.162.219.220|108.162.219.220]] 23:02, 16 December 2013 (UTC)

;Protip - Does anyone see the correct equation?
Maybe this is just an other Wolfram Alpha error, like we recently have had here: [[1292: Pi vs. Tau]]. All equations still look invalid to me.
*''√2 = 3/5 + π/(7-π)'': is impossible because √2 is an irrational number and no equation can match.
*''cos(π/7) + cos(3π/7) + cos(5π/7) = 1/2'': could only match if ''cos(x) + cos(3x) + cos(5x) = 1/2'' would be valid, because ''π/7'' is also an irrational number.
*''γ = e/34 + e/5 or γ = e/54 + e/5'': would mean that a sum of two irrational numbers do fit to the Gamma Constant. Impossible.
*''√5 = 13 + 4π / 24 - 4π'': √5 and π are irrational numbers, there is no way to match them in any equation like this.
*''Σ 1/nn = ln(3)e'': doesn't make any sense either.
Maybe [[:Category:Comics featuring Miss Lenhart|Miss Lenhart]] can help.
--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:41, 17 December 2013 (UTC)

cos(π/7) + cos(3π/7) + cos(5π/7) = 1/2 is exactly correct.

Let a=π/7, b=3π/7, and c=5π/7, then
(cosa+cosb+cosc)⋅2sina=2cosasina+2cosbsina+2coscsina=sin2a+sin(b+a)−sin(b−a)+sin(c+a)−sin(c−a)=sin(2π/7)+sin(4π/7)−sin(2π/7)+sin(6π/7)−sin(4π/7)=sin(6π/7)=sin(π/7)=sina

Hence, cos(π/7) + cos(3π/7) + cos(5π/7) = sin(π/7) / 2sin(π/7) = 1/2
[[Special:Contributions/108.162.216.74|108.162.216.74]] 01:57, 16 January 2014 (UTC)

:What is this: sin(6π/7)=sin(π/7) ? A new math is born... --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:49, 16 January 2014 (UTC)

::Actually it does. My proof is geometric: the sines of two supplementary angles (angle a + angle b = π (in radians)) are equivalent because they necessarily have the same x height in a Cartesian plane. Look on a unit circle, or even a sine function. Also, Calculus and most other mathematics use radians over degrees because they make the functions simpler and eliminate irrationality when a trig function shows up, but physics uses degrees because it's easier to understand and taught first. Anonymous 01:27, 13 February 2014 (UTC)
::As an aside, just how far along in math are you? Radian measure is taught in high school (at least the good ones). Anonymous 13:24, 13 February 2014 (UTC)
:::Sure, I was wrong at my last statement. sin(6π/7)=sin(π/7) is correct by using the radian measure. But just change π/7 to π/77 would give a very different result on that formular here. I still can't figure out why PI divided by the number 7 should be that unique, PI divided by 77 should be the same. My fault is: I still can't find the Nerd Sniping here. And we all do know that Randall did use wrong WolframAlpha results here. According to the last question: I'm very well on Math, that's because I want to understand this. This is like 0.999=1. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 22:01, 13 February 2014 (UTC)
::::Ah, I see. I think it has to do with the way e^i*π breaks down, as one of the answers shown in the corresponding link explains, but other answers rely on various angle identities (including the supplementary sines one in the proof above). Anonymous 03:10, 14 February 2014 (UTC) (PS, have you checked [[545]] lately? I answered your question there, too)
:::::As per the derivation from january 16 , you can use any a,b,c that satisfies this set of equations: 2 a = b - a, a + b = c- a, c + a = π - a. This is due to the fact that sin(x) = sin(π-x), and what was derived the 16th. [[Special:Contributions/173.245.53.199|173.245.53.199]] 12:38, 21 February 2014 (UTC)
:::: Dgbrt: If not convinced by the proofs linked to in the "explanation" part, you might want to try this: [http://www.wolframalpha.com/input/?i=sum_%28k%3D0%29%5E38+cos%281%2F77+%282+k%2B1%29+pi%29]. I'm sure you'll find inspiration for similar formulas using PI over [any odd integer]. Your assumption that Randall used WolframAlpha for this very identity is probably wrong. This is a very well-known formula that appears in many high school books, and I am pretty sure it is part of Randall's culture. And this has nothing to do with 1=1. As for your original post,
::::*√2 = (√2-1)/((4-2)π/2-π)+1 : Is this what you call "matching an equation" to √2?
::::*So what you mean is that if an equation is true for an irrational number, then it must be for any real number? Like, (√2)^2 = 2, but because √2 is irrational, then x^2=2 (for all x?)
::::*This one's a bit tough. You will probably agree that γ-√2 is irrational. And so is √2. What about their sum?
::::*Well, maybe it doesn't to you. But is Σ n-2 = π^2/6 any better? Well, this one is true (using Fourier's expansion of the rectangular function).
::::Finally,
::::*√2 = 3/5 + π/(7-π) is false because it would imply that π is an algebraic number
::::*cos(π/7) + cos(3π/7) + cos(5π/7) = 1/2 is true, and proven by many
::::*γ = e/34 + e/5 seems false. But there doesn't seem to be a quick way to disprove.
::::*Σ 1/nn = ln(3)e seems false, but I can't see why. [[Special:Contributions/108.162.210.234|108.162.210.234]] 09:15, 11 May 2014 (UTC)
::Dgbrt, yes, sin(6π/7)=sin(π/7). Simple proof: sin(6π/7)=sin(π-π/7)=sin(π)cos(-π/7)+cos(π)sin(-π/7)=0*cos(-π/7)+(-1)*(-sin(π/7))=0+sin(π/7)=sin(π/7) [[Special:Contributions/108.162.215.89|108.162.215.89]] 02:34, 20 May 2014 (UTC)
;So, still incomplete?

Where's our (in)complete judge? [[Special:Contributions/199.27.128.186|199.27.128.186]] 19:21, 18 December 2013 (UTC)
:The protip is still a mystery. I'm calling for help a few lines above. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:16, 18 December 2013 (UTC)
::The cosine one, in radians, is correct [[Special:Contributions/141.101.88.225|141.101.88.225]] 12:54, 28 April 2014 (UTC)

The 'Seconds in a year' ones remind me of one of my favorite quotes: "How many seconds are there in a year? If I tell you there are 3.155 x 10^7, you won't even try to remember it. On the other hand, who could forget that, to within half a percent, pi seconds is a nanocentury" -- Tom Duff, Bell Labs. [[User:Beolach|Beolach]] ([[User talk:Beolach|talk]]) 19:14, 17 April 2014 (UTC)
:Please do not change former discussions. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 23:57, 17 April 2014 (UTC)

;cos(pi/7) + cos(3pi/7) + cos(5pi/7) = 1/2 ???
Why the hell the divider seven makes the difference?
*cos(pi) + cos(3*pi) + cos(5*pi) = -3
*cos(pi/8) + cos(3*pi/8) + cos(5*pi/8) = 0.92387953251128675612818318939678828682241662586364...
So why the "magic" prime number seven produces this exact result? I know radians and π/7 is just a small part of a circle which is 2π. One prove claims that sin(6π/7) equals to sin(π/7); my best calculator can't show a difference. Of course sin(6π) equals to sin(π), in radians, BUT sin(6π/8) is NOT equal to sin(π/8). So if the number 7 plays a magic rule here this would be "one of the", no... the BIGGEST mystery in mathematics forever. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 23:03, 16 May 2014 (UTC)
:Dgbrt, please see my answer from 11 May 2014 up there. Any odd integer will do, as long as you sum enough of cos(pi/[thing]).
:*Let's try with 5 : cos(pi/5) + cos (3pi/5) = 1/2.
:*With 9 : cos(pi/9)+ cos(3pi/9) + cos (5pi/9) + cos(7pi/9) = 1/2
: No big mystery around here. Just a beautiful formula :) I think there are similar formulas with cosines and even integers. I'll post them here if I have time. [[User:Varal7|Varal7]] ([[User talk:Varal7|talk]]) 09:56, 17 May 2014 (UTC)

::You mixing up to different equations and even not prove them. If there is any prove to a mathematician I would accept and include a proper explain for non math people here. We still have to find a prove. And I do not trust my calculators, we just have to explain why even cos(pi/5) + cos (3pi/5) is also nearly the same. This issue is still not explained. So please give us a explain. And a PROTIP: This does not work with Integers, PI is infinite--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 17:55, 17 May 2014 (UTC)

:::Okay. If I understood what you said.
:::* I mix up different topics. -> True. From now on, we'll just focus on the cosine one.
:::* You ask for a proof/explanation. -> My opinion is those are two different requests. Maybe that's why you use the distinction between math people/not math people. For a proof, please read further. What I exposed above are just other "fun experiments" we could do. e.g : [http://www.wolframalpha.com/input/?i=cos%28pi%2F11%29%2Bcos+%283pi%2F11%29+%2B+cos+%285pi%2F11%29+%2B+cos+%287pi%2F11%29%2Bcos+%289pi%2F11%29].
:::* You do not trust your calculators -> Great. I don't either. (Well more accurately, I trust mine to 10^-8, so I would definitely not use it to prove any of the discussed equations in PROTIP). That's why we'll prove the formulas we assert.
:::* "This does not work with integers" -> Well, I got myself misunderstood. It would probably have been better if I had said: the following formula is true for all integer n. sum_{k=0}^{n-1}{cos((2k+1)*pi/(2n+1)). But It's harder to read, so just say. Choose any odd integer, say N=2n+1. Then start the following sum. cos(pi/N) + cos(3pi/N) + … and stop when the numerator is cos((N-2)pi/N). Then the result is 1/2. And that's what we'll prove, a few lines down from here.
:::*"Pi is infinite" -> That's a common misconception. What you mean is, Pi is irrational. (Fun fact: Pi is a transcendental number. Quite difficult theorem. Lindeman proved it in 1882. Hence, if we identify the real number x with the Q-vector space Q[x], it would make sense to say that "x is infinite" because, the Q-vector space Q[x] is indeed of infinite dimension. But then, that's not what mathematicians do). I think Vi Hart made a video where she addresses this issue (or was it someone else?). Anyway, I might come to that point some other time in the future.
:::Okay, so now let's first prove the protip formula. Well first, here is the link that the explainxkcd wiki points to: [http://math.stackexchange.com/questions/140388/how-can-one-prove-cos-pi-7-cos3-pi-7-cos5-pi-7-1-2]. Most of them are correct. Some are more ugly than others. I'll adapt the last one.
::: We need a [http://en.wikipedia.org/wiki/Complex_number complex numbers]. (I choosed this because I think explainxkcd readers are fine with this. See comic [http://explainxkcd.com/179/ 179]). I will be using dots to show the steps of my proof. Please allow me an extra level of indent for clarity's sake.
:::'''Proof'''
:::: *Let z be a primitive 14-th [http://en.wikipedia.org/wiki/Root_of_unity root of unity] (the reader doesn't need to understand the 3 last words). Just say z = exp(i*pi/7) = cos(pi/7) + i sin(pi/7). Using [http://en.wikipedia.org/wiki/Euler%27s_formula Euler's formula].
:::: *We have z^14-1 = (exp(i*pi/7))^14-1 = exp(i*2pi) - 1 = 0. Using exponential law for integer powers, as seen in this article: [http://en.wikipedia.org/wiki/De_Moivre%27s_formula De Moivre's formula].
:::: *Now let's factor: z^14-1 = (z^7-1)(z^7+1) = (z^7-1)(z+1)(z^6-z^5+z^4-z^3+z^2-z+1) = (z^7-1)(z+1)*Phi_14(z). where Phi_14(X)= X^6-X^5+X^4-X^3+X^2-X+1, (see [http://en.wikipedia.org/wiki/Cyclotomic_polynomial cycltomic polynomial]). Now, because z^7-1 = (exp(i*pi/7))^7-1 = exp(i*pi)-1 = -2. And because z is not -1, the two first factors are not 0 so, Phi_14(z) = 0, which is already a pretty awesome equality.
:::: *Note that exp(i*pi/7)*exp(i*6pi/7)= exp(i*pi)=-1. So the inverse of z is -exp(i*6pi/7). But we also know that it is exp(-i*pi/7). Well. That was just a fancy way to prove that exp(-i*pi/7) = - exp(i*6pi/7). Good enough. The same holds for exp(-i*3pi/7) = exp(i*14pi/7)*exp(-i*3pi/7)=exp(i*11pi/7)=exp(i*7pi/7)*exp(i*4pi/7)=-exp(i*4pi/7). And the exact same calculation shows that exp(-i*5pi/7)=-exp(i*2pi/7). Alright.
:::: *Now, use that for any x, we have cos(x) = (exp(ix)+exp(-ix))/2. See [http://en.wikipedia.org/wiki/Euler%27s_formula#Relationship_to_trigonometry here]. Let's calculate twice the sum of the left hand side. 2(cos(pi/7)+cos(3pi/7)+cos(5pi/7))= exp(i*pi/7) + expi(-i*pi/7) + exp(3pi/7) + exp(-3pi/7) + exp(5pi/7) +exp(-5pi/7) = exp(i*pi/7)-exp(i*2pi/7)+exp(i*3pi/7)-exp(i*4pi/7)+exp(i*5pi/7)-exp(i*6pi/7) = -Phi_14(z) +1 = 1.
:::: * So dividing both sides by 2, we get what we want. Pfew.
::: '''Why is 7 so special? Well it isn't.''' Let's prove it for 9.
::::* Let z = exp(i*pi/9) = cos(pi/9) + i sin(pi/9). We have z^18-1 = 0, and z^9-1 and z+1 are not 0, so using the same factorisation, Phi_18(z) = z^8-z^7+z^6-z^5+z^4-z^3+z^2-z+1 = 0.
::::* Hence, the conclusion follow from: 2(cos(pi/9) + cos(3pi/9) + cos(5pi/9) + cos(7pi/9)) = exp(i*pi/9) + exp(-i*pi/9) + exp(i*3pi/9) + exp(-i*3pi/9) + exp(i*5pi/9) + exp(-i*5pi/9) + exp(i*7pi/9) + exp(-i*7pi/9) = -Phi_18(z)+1 = 1.
::: Well, well. I hope you kinda see the pattern. Dgbrt, I know you hate typos, and I'm pretty sure that in this long text lay many of them. So I apologize, and I will correct them later. The following paragraph was posted after I started my text but before I finished mine. It wasn't signed so I will just leave it down there. It's another valid straightforward proof. Oh. And Friendly TIP: Don't say protip when you're not pro. [[User:Varal7|Varal7]] ([[User talk:Varal7|talk]]) 21:50, 17 May 2014 (UTC)

The valid identity cos(pi/7)+cos(3pi/7)+cos(5pi/7)=1/2 was correctly proved by the writer at 108.162.216.74 above. For a different proof, consider the complex number z = cos(pi/7)+i sin(pi/7) corresponding to rotation of the complex plane by pi/7 radians, i.e., 1/14th of a full rotation. It satisfies z^{14} -1 = 0 (z to the fourteenth is one). Dividing by z-1 gives z^{13} + z^{12} + ... + z + 1 = 0. The same argument, starting with z^2 corresponding to 1/7th of a full rotation, gives z^{12} + z^{10} + ... z^2 + 1 = 0. Taking the difference, we get z^{13} + z^{11} + ... + z^3 + z = 0. Looking only at the real parts, we get cos(13pi/7) + cos(11pi/7) + cos(9pi/7) + cos(7pi/7) + cos(5pi/7) + cos(3pi/7) + cos(pi/7) = 0. Here cos(13pi/7) = cos(pi/7), cos(11pi/7) = cos(3pi/7) and cos(9pi/7) = cos(5pi/7), since cos is even and 2pi-periodic. Finally cos(7pi/7) = -1, so 2(cos(pi/7) + cos(3pi/7) + cos(5pi/7)) - 1 = 0, which you can rewrite as the desired identity. All of this can be clearly visualized using a regular 14-gon, so a proof with pictures is possible. {{unsigned ip|141.101.81.216}}

;99 is sexual reference?

In first explanation it says: "99^8 and 69^8 are sexual references". 69 I understand, but what would 99 refer too?
--[[Special:Contributions/173.245.53.167|173.245.53.167]] 17:38, 18 May 2014 (UTC)
: see [[487: Numerical Sex Positions]][[Special:Contributions/141.101.70.181|141.101.70.181]] 15:33, 20 July 2014 (UTC)

I'd add pi = (9^2 + (19^2)/22)^(1/4) [[Special:Contributions/198.41.230.73|198.41.230.73]] 02:41, 13 May 2015 (UTC)

User:Redbelly98

2018-08-21T02:02:01Z

Redbelly98: Punctuation, minor tweaks to wording.

Happy to help out with the physics comics where I can, but can't help much with the IT/programming ones.

Joined Explain xkcd in July 2018. I had discovered Explain xkcd a few years earlier, looking for an explanation of the game 2048 mentioned in [https://www.explainxkcd.com/wiki/index.php/1344:_Digits this comic].

2034: Equations

2018-08-19T14:39:12Z

Redbelly98: /* Technical Explanations */ In correct kinematics formula, changed u to v0 -- to more closely resemble K0 term from formula shown in comic.

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them. In many disciplines, the mathematical description of a large area is summed up in a small number of equations, such as Maxwell's equations for electromagnetism. In similar fashion, the equations here purport to encompass the whole of their given field.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All kinematics equations
Kinematics is the study of the motion of objects. More specifically, it describes how the location, velocity, and acceleration of an object vary over time. The equation shown contains two of these standard kinematic variables, velocity ''v'' and time ''t'', in addition to several quantities (''E'', ''K0'', and ''ρ'') that are completely unrelated to kinematics.

;All number theory equations
Number theory is a branch of mathematics concerned primarily with the study of integers. However, the equation shown contains the non-integer number ''e'' (approximately equal to 2.718...), and uses the Greek letter ''π'' as an integer, even though ''π'' is almost exclusively used in mathematics to denote the well-known, ''non''-integer number 3.14159.... It also treats ''π'' as a variable component in a summation, rather than as a constant.

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction. While the H in "HEAT" is the chemical symbol of the element hydrogen, none of the letters E, A, or T are symbols of any actual elements.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared".

The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case multiplying by <math>t</math> would be wrong. Alternatively, the term is similar to <math>k_B T</math> (sometimes written as ''kT''), a term that often appears in {{w|Statistical_mechanics|statistical mechanics}} equations, where ''kB'' (or ''k'') is {{w|Boltzmann_constant|the Boltzmann constant}}, and ''T'' is the {{w|Thermodynamic_temperature|absolute temperature}}. In this latter case, the term would have units of energy, consistent with the left side of the equation.

The second term looks similar to the kinetic energy term <math> \frac{1}{2}\rho v^2 </math> in [http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html the Bernoulli equation] for fluids. (More properly, this is the kinetic energy ''density'' in the fluid).

The whole equation appears to be a play on the kinematics formula: <math>s = v_0t + \frac{1}{2}\ at^2</math>, where distance travelled (''s'') by a constantly accelerating object is determined by initial velocity (''v0''), time (''t''), and acceleration (''a'')

Kinematics is often one of the first topics covered in an introductory physics course, both at the high school and freshman college levels. As such, mixing in material from more advanced topics like statistical mechanics and the Bernoulli equation, even if done correctly, would be very confusing for a typical student learning kinematics.

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily studying the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: the sum for all i from 0 to infinity, the sum for all pi from 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamics equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is often just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanics equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Since the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is the identity or is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} represents a chemical reaction as a formula, with the reactant entities on the left-hand side, and the product entities on the right-hand side. The number of each element on the left side must match those on the right side. The energy produced or absorbed in this process is not included in that formula.

This is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse, zebra, donkey or other equine here.

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, this is similar to the mistake of messing up units, for instance setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how the equation varies with the shape of the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this is more or less what we observe) while a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamics equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

2034: Equations

2018-08-19T00:50:02Z

Redbelly98: /* Simplified Explanations */ Added simplified explanations for kinematics and number theory. Added note that E, A, T are not chemical symbols.

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them. In many disciplines, the mathematical description of a large area is summed up in a small number of equations, such as Maxwell's equations for electromagnetism. In similar fashion, the equations here purport to encompass the whole of their given field.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All kinematics equations
Kinematics is the study of the motion of objects. More specifically, it describes how the location, velocity, and acceleration of an object vary over time. The equation shown contains two of these standard kinematic variables, velocity ''v'' and time ''t'', in addition to several quantities (''E'', ''K0'', and ''ρ'') that are completely unrelated to kinematics.

;All number theory equations
Number theory is a branch of mathematics concerned primarily with the study of integers. However, the equation shown contains the non-integer number ''e'' (approximately equal to 2.718...), and uses the Greek letter ''π'' as an integer, even though ''π'' is almost exclusively used in mathematics to denote the well-known, ''non''-integer number 3.14159....

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction. While the H in "HEAT" is the chemical symbol of the element hydrogen, none of the letters E, A, or T are symbols of any actual elements.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared".

The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case multiplying by <math>t</math> would be wrong. Alternatively, the term is similar to <math>k_B T</math> (sometimes written as ''kT''), a term that often appears in {{w|Statistical_mechanics|statistical mechanics}} equations, where ''kB'' (or ''k'') is {{w|Boltzmann_constant|the Boltzmann constant}}, and ''T'' is the {{w|Thermodynamic_temperature|absolute temperature}}. In this latter case, the term would have units of energy, consistent with the left side of the equation.

The second term looks similar to the kinetic energy term <math> \frac{1}{2}\rho v^2 </math> in [http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html the Bernoulli equation] for fluids (or, more properly, the kinetic energy ''density'' in the fluid).

The whole equation appears to be a play on the kinematics formula: <math>s = ut + \frac{1}{2}\ at^2</math>, where distance travelled (''s'') by a constantly accelerating object is determined by initial velocity (''u''), time (''t''), and acceleration (''a'')

Kinematics is often one of the first topics covered in an introductory physics course, both at the high school and freshman college levels. As such, mixing in material from more advanced topics like statistical mechanics and the Bernoulli equation, even if done correctly, would be very confusing for a typical student learning kinematics.

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily studying the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: the sum for all i from 0 to infinity, the sum for all pi from 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is often just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Since the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} represents a chemical reaction as a formula, with the reactant entities on the left-hand side, and the product entities on the right-hand side. The number of each element on the left side must match those on the right side. The energy produced or absorbed in this process is not included in that formula.

This is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse, zebra, donkey or other equine here.

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, this is similar to the mistake of messing up units, for instance setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how the equation varies with the shape of the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this is more or less what we observe) while a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamics equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

2034: Equations

2018-08-18T01:41:15Z

Redbelly98: /* Technical Explanations */ Kinematics: added "kB T" from statistical mechanics as possible rationale for "K0 t" term.

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared".

The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case so multiplying by <math>t</math> would be wrong. Alternatively, the term is similar to <math>k_B T</math> (sometimes written as ''kT''), a term that often appears in {{w|Statistical_mechanics|statistical mechanics}} equations, where ''kB'' (or ''k'') is {{w|Boltzmann_constant|the Boltzmann constant}}, and ''T'' is the {{w|Thermodynamic_temperature|absolute temperature}}. In this latter case, the term would have units of energy, consistent with the left side of the equation.

The second term looks similar to the kinetic energy term <math> \frac{1}{2}\rho v^2 </math> in [http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html the Bernoulli equation] for fluids (or, more properly, the kinetic energy ''density'' in the fluid).

The whole equation appears to be a play on the kinematics formula: <math>s = ut + \frac{1}{2}\ at^2</math>, where distance travelled (''s'') by a constantly accelerating object is determined by initial velocity (''u''), time (''t''), and acceleration (''a'')

Kinematics is often one of the first topics covered in an introductory physics course, both at the high school and freshman college levels. As such, mixing in material from more advanced topics like statistical mechanics and the Bernoulli equation, even if done correctly, would be very confusing for a typical student learning kinematics.

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily to the study the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: for all i in 0 to infinity, for all pi in 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is often just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes the nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Seeing as the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side. The number of each element on the left side must match them on the right side, the equation is balanced. The energy produced or absorbed in this process is not included in that formula.

This here is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. To deliver the punchline while maintaining proper stoichiometry, <math>\mathrm{OH}</math> (which should be <math>\mathrm{OH}^-</math>, since the oxygen keeps a free electron when it combines with a single hydrogen) is shown instead of <math>\mathrm{O}_2</math>. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse here (equidae)

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, it is a similar mistake messing up units and setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how what shape the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this more or less what we observe) whilst a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamics equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

Talk:2034: Equations

2018-08-18T00:40:51Z

Redbelly98: Added "kinematics equations" section.

2034: Equations

2018-08-18T00:23:24Z

Redbelly98: /* Technical Explanations */ Change to kinematics: 2nd term looks like term from Bernoulli equation. Previous explanation compared it to kinetic energy and mis-stated density "rho" as momentum "p". "accelerating" refers to an object, not environment.

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared". The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case so multiplying by <math>t</math> would be wrong. The second term looks similar to the kinetic energy term <math>\frac{1}{2}\rho v^2</math> in [http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html the Bernoulli equation] for fluids (or, more properly, the kinetic energy ''density'' in the fluid). The whole equation appears to be a play on the forumula: <math>s = ut + \frac{1}{2}\ at^2</math>, where distance travelled (''s'') by a constantly accelerating object is determined by initial velocity (''u''), time (''t''), and acceleration (''a'')

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily to the study the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: for all i in 0 to infinity, for all pi in 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is actually just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes the nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Seeing as the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side. The number of each element on the left side must match them on the right side, the equation is balanced. The energy produced or absorbed in this process is not included in that formula.

This here is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. To deliver the punchline while maintaining proper stoichiometry, <math>\mathrm{OH}</math> (which should be <math>\mathrm{OH}^-</math>, since the oxygen keeps a free electron when it combines with a single hydrogen) is shown instead of <math>\mathrm{O}_2</math>. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse here (equidae)

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, it is a similar mistake messing up units and setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how what shape the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this more or less what we observe) whilst a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamics equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

2034: Equations

2018-08-18T00:00:15Z

Redbelly98: /* Transcript */ Added "s" to make "dynamics" plural in "fluid dynamics equations"

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared". The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case so multiplying by <math>t</math> would be wrong. The second term looks similar to the traditional kinetic energy formula <math>\frac{1}{2}mv^2</math> but with momentum instead of the mass. This appears to be a play on the forumula: <math>s = ut + \frac{1}{2}\ at^2</math> where distance travelled (s) in a constantly accelerating environment, is determined by initial velocity (u), time (t) and acceleration (a)

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily to the study the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: for all i in 0 to infinity, for all pi in 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is actually just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes the nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Seeing as the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side. The number of each element on the left side must match them on the right side, the equation is balanced. The energy produced or absorbed in this process is not included in that formula.

This here is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. To deliver the punchline while maintaining proper stoichiometry, <math>\mathrm{OH}</math> (which should be <math>\mathrm{OH}^-</math>, since the oxygen keeps a free electron when it combines with a single hydrogen) is shown instead of <math>\mathrm{O}_2</math>. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse here (equidae)

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, it is a similar mistake messing up units and setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how what shape the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this more or less what we observe) whilst a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamics equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

2034: Equations

2018-08-17T23:58:31Z

Redbelly98: /* Transcript */ Should be "rho", not "p", in kinematics and fluid dynamics equations.

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them.

==Simplified Explanations==
{{incomplete|Created by a mere human. Do NOT delete this tag too soon.}}

;All chemistry equations
This shows a parody of the common example chemistry equation of burning Methane and Oxygen (with added heat), to form water and carbon dioxide. However in this form "HEAT" is an actual molecule, rather than simply indicating the presence of heat to start the reaction. Thus the equation is modified to incorporate the fictional "HEAT" into the reaction.

TODO: other simplified explanations.

==Technical Explanations==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared". The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case so multiplying by <math>t</math> would be wrong. The second term looks similar to the traditional kinetic energy formula <math>\frac{1}{2}mv^2</math> but with momentum instead of the mass. This appears to be a play on the forumula: <math>s = ut + \frac{1}{2}\ at^2</math> where distance travelled (s) in a constantly accelerating environment, is determined by initial velocity (u), time (t) and acceleration (a)

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily to the study the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: for all i in 0 to infinity, for all pi in 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is actually just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

The title text stating that the electromagnetism equation is the same as the fluid dynamics equation, but with the arbitrary 8 and 23 replaced with the permittivity and permeability of free space is likely because electromagnetism equations often have relations to fluid dynamics, and because those two constants appear in the vast majority of electromagnetism equations.

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes the nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Seeing as the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side. The number of each element on the left side must match them on the right side, the equation is balanced. The energy produced or absorbed in this process is not included in that formula.

This here is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. To deliver the punchline while maintaining proper stoichiometry, <math>\mathrm{OH}</math> (which should be <math>\mathrm{OH}^-</math>, since the oxygen keeps a free electron when it combines with a single hydrogen) is shown instead of <math>\mathrm{O}_2</math>. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to expressions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse here (equidae)

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, it is a similar mistake messing up units and setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how what shape the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this more or less what we observe) whilst a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic marking indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The "principle of least action" allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. Below each equation there are labels:]

:E = K0t + 1/2 ρvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ ρ = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamic equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ʒ̆) ψ(0a)
:All gauge theory equations

:[There is a brace linking the three cases together.]
:H(t) + Ω + G⋅Λ ...
:... > 0 (Hubble model)
:... = 0 (Flat sphere model)
:... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

Talk:2027: Lightning Distance

2018-08-07T01:05:44Z

Redbelly98:

Calculations I used:

<math>t_1=\frac{s}{v_1}</math>

<math>t_2=\frac{s}{v_2}</math>

Substract:

<math>t_1-t_2=\Delta t=\frac{s}{v_1}-\frac{s}{v_2}=\frac{sv_2-sv_1}{v_1v_2}=s\frac{v_2-v_1}{v_1v_2}=s\frac{\Delta v}{v_1v_2}</math>

Therefore

<math>s=\Delta t\frac{v_1v_2}{\Delta v}</math>

I evaluated <math>\frac{v_1v_2}{\Delta v}</math> and it came to be 13.6 billion. Can someone verify it's correct? [[Special:Contributions/172.68.51.112|172.68.51.112]] 13:08, 1 August 2018 (UTC)

:The comic begins with the question "how many miles away", so converting to kilometers isn't the right calculation.[[Special:Contributions/172.69.71.24|172.69.71.24]] 17:06, 1 August 2018 (UTC)

I used refractive index for visible light of 1.000277 (air at STP as opposed to 0C 1atm) and arrived at around 7.9 billion instead. Refractive index of 1.000337 is then required for the radio waves for the comic to be correct. [[Special:Contributions/172.68.11.221|172.68.11.221]] 13:46, 1 August 2018 (UTC)

:Do you mean 7.9 billion to convert to miles or to kilometers? Because my 13.6 bilion is to kilometers.

::I'm sure the actual comic is referring to miles and 5 billion was picked to match with the "divide by five" rule for miles. [[Special:Contributions/172.69.70.131|172.69.70.131]] 13:59, 1 August 2018 (UTC)

:::I did mean kilometers. If we use miles, 1.000314 fits almost precisely! (5.04 billion) [[Special:Contributions/172.68.11.17|172.68.11.17]] 14:42, 1 August 2018 (UTC)

If you can count several seconds, as is suggested in the comic, the flash is still billions of miles away, the widest possible distance between Earth and Neptune is about 5 billion km. Sebastian --[[Special:Contributions/172.68.110.40|172.68.110.40]] 14:51, 1 August 2018 (UTC)

:Not to mention that there's not a lot of air within a few billion miles of earth, so the dispersion will be much lower for all but the last 100-ish miles, AFAIK.[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:12, 1 August 2018 (UTC)

::Also, while Jupiter has {{w|Great Red Spot|VERY gigantic storms}}, they are still too small to see the lightning from them from Earth. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 23:17, 1 August 2018 (UTC)

Do you really need to know the spectrum of the flash? If we assume that a flash contains UV and X-ray radiation and that the visible light is generated at the same time as the UV or X-ray radiation then you only need to know the refractive index of light/UV/X-ray in air under the same temperature conditions and not the exact spectrum. [[User:Condor70|Condor70]] ([[User talk:Condor70|talk]])

:I initially made the mistake of thinking this referred to time difference between visible and UV/X-ray, but it specifically says "brightness." If you want to compare the brightness at a distance to the brightness at the source you'll need to know the brightness at the source, i.e. the spectrum of the flash itself. With this technique you don't need to know the dispersion "only" the relative attenuation, but I suspect that would be a more error-prone measurement.[[Special:Contributions/172.68.54.142|172.68.54.142]] 18:54, 1 August 2018 (UTC)

I understand the joke Randall was going for, but have a problem with the wording. "Count the number of seconds" won't work for fractions of anything. "Measure" would work, but spoils the gag a bit. Counting numbers are integers; counting the seconds between the visible and radio frequency flashes will give you zero. [[Special:Contributions/172.69.71.24|172.69.71.24]] 17:00, 1 August 2018 (UTC)

:You're certainly correct, but the joke works (for me at least) by its comparison to the standard rule of counting seconds, and humans are not generally precise enough to resolve better than one second. By keeping Megan's wording as close to the customary rule as possible I think it optimizes the humor. That "Billion" at the end is the whole joke for me, the replacement of "sound" with "radio wave" can be glossed-over on first reading, until you get to the unexpected extra 9 orders of magnitude in the conversion.[[Special:Contributions/172.68.54.142|172.68.54.142]] 18:54, 1 August 2018 (UTC)
::No, they would've been correct if she'd said "count the number of seconds" but she said "'''count the seconds'''".It's part of the joke, because it's correct, just completely impractical, because you'd be "counting" something like 10^(-10) seconds--[[Special:Contributions/172.68.132.47|172.68.132.47]] 07:23, 5 August 2018 (UTC)

::Just realized I also glossed-over the replacement of "divide" with "multiply." The brain is a funny thing.[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:07, 1 August 2018 (UTC)

:I took the "count the number of seconds" to be part of the joke, or rather Randall setting us up for the joke. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:18, 6 August 2018 (UTC)

Do these account for the air pressure variability common in most thunderstorms?

I think explanation and transcript are pretty complete now. [[Special:Contributions/172.68.51.112|172.68.51.112]] 20:58, 1 August 2018 (UTC)

:There is the additional problem that a flash is no instantaneous, but progresses at a fraction of the speed of light. Who says that radio waves and light at different wavelenghts or xrays have their maximum at the same moment? ;-) --[[Special:Contributions/162.158.91.59|162.158.91.59]] 08:05, 2 August 2018 (UTC)

:: I added a few words about the problem that a flash is not instantaneous and removed the 'incomplete' tag. Hope that's OK. [[User:Chrisahn|Chrisahn]] ([[User talk:Chrisahn|talk]]) 19:41, 2 August 2018 (UTC)

Here's a variation of the calculation above that simplifies numeric evaluation:

The {{w|refractive index}} is defined as <math>n=\frac{c}{v}</math>, so <math>v=\frac{c}{n}</math> and thus <math>t=\frac{s}{v}=\frac{s\,n}{c}</math>.

<math>t_1=\frac{s\,n_1}{c}</math>

<math>t_2=\frac{s\,n_2}{c}</math>

Subtract:

<math>t_1-t_2=\Delta t=\frac{s\,n_1}{c}-\frac{s\,n_2}{c}=s\frac{n_1-n_2}{c}=s\frac{\Delta n}{c}</math>

Therefore

<math>s=\Delta t\frac{c}{\Delta n}</math>

and the factor we want to calculate is

<math>\frac{c}{\Delta n}</math>

With the numbers given in the sources in the main text:

<math>n_1=1.000315</math>

<math>n_2=1.000277</math>

<math>\Delta n=n_1-n_2=0.000038</math>

For kilometers: <math>\frac{c}{\Delta n}\approx\frac{300,000\,km/s}{0.000038}\approx7.9\cdot10^9\,km/s</math>

For miles: <math>\frac{c}{\Delta n}\approx\frac{186,000\,mi/s}{0.000038}\approx4.9\cdot10^9\,mi/s</math>

[[User:Chrisahn|Chrisahn]] ([[User talk:Chrisahn|talk]]) 18:28, 2 August 2018 (UTC)

:Nice one. I didn't think to use the refractive indicies directly. [[Special:Contributions/172.68.51.118|172.68.51.118]] 22:22, 2 August 2018 (UTC)

:Agreed, nice clear analysis by Chrisahn. I'd like to suggest a couple of corrections regarding the index values:
:* ''n'' for air at 0 C, 1 atm, is closer to 1.000292, according to both {{w|List_of_refractive_indices|the Wikipedia link}} and also the "Simple Shop-floor Formula" given by NIST at [https://emtoolbox.nist.gov/wavelength/documentation.asp the bottom of this site]. This would give a <math>{\Delta n}</math> of 0.000023, and a time-to-distance conversion value of <math>\frac{c}{\Delta n} \approx 7.9\cdot10^9</math> mi/s.
:* Thunderstorms rarely occur at 0 C. Using values for 30 C (86 F) instead, we have 1.000261 for air (from the simple NIST formula) and 1.000429 for radio waves (from Table 1, p. 8 of [https://www.fig.net/resources/proceedings/fig_proceedings/fig_2002/Js28/JS28_rueger.pdf the Rueger paper]). This gives a <math>{\Delta n}</math> of 0.000168, and a time-to-distance conversion value of <math>\frac{c}{\Delta n} \approx 1.1\cdot10^9</math> mi/s.
:This suggests that the conversion value is the desired 5 billion for ''some'' temperature between 0 and 30 C. Linear interpolation of the above suggests this temperature is about 13 C or 55 F [EDIT: See note after this comment]. More to the point, the conversion value varies too strongly with temperature for there to be a simple rule. That being said, I do like that the 5 billion figure ties in nicely with the familiar (in USA) ''divide by 5'' rule. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:18, 6 August 2018 (UTC)

::NOTE: Please ignore the linearly interpolated "13 C" above. It turns out ''n'' for radio waves is a highly nonlinear function of temperature. Plus the 1/Δ''n'' dependence -- where Δ''n'' changes by a factor of 7 or 8 -- makes the nonlinearity even worse. --[[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 01:05, 7 August 2018 (UTC)

== Assumptions on the medium properties sound? ==

Refractive index of *dry* air might be pretty close to 1 for both light and RF EM waves, but:

Let's assume that the air is humid, if not even full of water drops. After all, lightning.

Let's further assume that an air/water mixture or solution has electromagnetic properties between these two materials.

In water, refractive index for light is about <math>n_{\text{water, optical}}=1.33 n_{\text{air, optical}}</math>, (as easily demonstrated by the optical refractive effects); for RF, we typically use values of <math>\frac{n_{\text{water, RF}}^2}{\mu_r}=\epsilon\approx 80</math>. So, <math>n_{\text{water, RF}}\approx \sqrt{80}n_{\text{air, RF}}</math>.

Let's assume a 10⁻³ "EM-effective" water content in the comic air.

That would lead to <math>\frac{v_{\text{opt.}}}{v_{\text{RF}}} = \frac{\frac34}{\sqrt{80}^{-1}}= \frac34\sqrt{80}=6.7</math>.

:While the humidity (amount of water vapor) is certainly higher during the rain, I don't think that would count as a proper "water-air mixture". Wikipedia says that "Violent rain" is above 5 cm/h. If you divide it by 3600 (to get cm/s), and then imagine stretching that all the way to the cloud, you'll find out there's not that much water at given moment in the air. [[Special:Contributions/172.68.51.112|172.68.51.112]] 19:12, 1 August 2018 (UTC)

::Great point. To finish the calculation let's use a typical terminal velocity for a large raindrop (it's a big storm, I'm sure) of 9m/s. 0.05 m/hr / 3600 s/hr / 9 m/s = 0.00015% water by volume. Sure seems like more than that when I have to drive through it! Then it seems more like [http://what-if.xkcd.com/12/].[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:32, 1 August 2018 (UTC)

<code>we can't detect radiation outside the visible spectrum without very specialized instruments</code> Something that I think was overlooked in the explanation is that while humans can't *directly* sense radio waves, there are devices called "radios" which at one point in time were fairly commonly owned by humans, whose whole purpose is to detect encoded radio waves and convert them into sounds which humans can sense. I.e. you hear static during an electrical storm. So you could listen for the static and compare that to the flash... if you were fast enough. [[Special:Contributions/172.68.54.64|172.68.54.64]] 14:22, 3 August 2018 (UTC) (newbie)

:But radios ARE specialized equipment. [[Special:Contributions/172.68.51.52|172.68.51.52]] 10:35, 4 August 2018 (UTC)

::Ehh... I see your point, but I'm not sure I'm *really* convinced. In my mind, a Gamma Ray Spectrometer is specialized equipment. People don't normally have them in their house or car. Radios are (or, at least, *were*) very common. But you're right, it says specialized instrument, not "rare" instrument. I'm not changing the explanation, just wanted to point out for those geeky enough to read the comments that for normal people, *detecting* the radio wave output lightning is doable without buying extra equipment one doesn't normally have in the home. Detecting the difference between the flash and the static on the radio is where it gets impractical. [[Special:Contributions/172.68.54.64|172.68.54.64]] 15:01, 6 August 2018 (UTC) (newbie)

== Whoops! ==

I always thought it was 1 second per mile. I didn't know about the 'divide by 5" part. [[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 01:23, 5 August 2018 (UTC)

:Storms just became 5 times more scary for you :) [[Special:Contributions/188.114.103.95|188.114.103.95]] 12:12, 6 August 2018 (UTC)

Talk:964: Dorm Poster

2018-08-07T00:18:00Z

Redbelly98:

I just noticed that he has the same poster, he (cueball) just turned it upside-down and drew a lens on it. [[Special:Contributions/66.217.162.41|66.217.162.41]] 02:53, 6 January 2013 (UTC)
:The poster is '''''not''''' the same poster turned upside-down. If you look at the rainbow, the rainbow still matches up with the original poster on the left, meaning that if you turned the poster on the right "right-side up", the rainbow would be upside-down when compared to the one on the left.--[[Special:Contributions/108.162.238.155|108.162.238.155]] 06:56, 28 August 2014 (UTC)

Note also that cueball's side of the room is an inverse of the left side of the room in other ways. The left bed has linens, the right does not, the left side of the room is messy, the right is not, the person on the left is sitting at a desktop, cueball is standing at a laptop and so on.
: Given that in the first panel the guy is looking at a piece of paper with the room number, and that the right side isn't just clean, it's devoid of any items save the desk and the bed (sans linen), I'd say it's likely the second guy has just moved in, and hasn't had a chance to cause a mess.-Pennpenn [[Special:Contributions/108.162.250.162|108.162.250.162]] 02:37, 19 November 2015 (UTC)
:: Possibly, but it might also be that he's an ultra-minimalist obsessed with purity - he's working on his laptop before even finding a chair - and has created this new poster to purify the light and get rid of all those messy colors.[[Special:Contributions/141.101.107.42|141.101.107.42]] 17:37, 26 September 2017 (UTC)

Also worth mentioning that this album cover is a very popular - to the point of cliche - poster to have in a student dorm. [[Special:Contributions/31.221.45.4|31.221.45.4]] 14:26, 15 March 2013 (UTC)Chris C

Did anyone notice that the room number is 117? Does Randall play Halo? Or is that just a coincidence?
[[User:NinjaWolf064|You just lost the game. NinjaWolf064]] ([[User talk:NinjaWolf064|talk]]) 05:50, 2 June 2017 (UTC)

The original vinyl sleeve actually looks like those two posters but backwards. The back of the jacket is split light being recombined by a prism and shot at an upwards angle into the prism on the front cover, where it is split again. Demonstrated here: http://mobile.collectorsfrenzy.com/gallery/230925609565.jpg [[Special:Contributions/68.170.77.75|68.170.77.75]] 20:25, 21 April 2013 (UTC)

Also, the other figure in the dorm seems to be the "total douchebag" with a goatee and glasses from http://www.xkcd.com/796/. I think this is his only other appearance, does this say something about Randall's view of Pink Floyd and their fans? {{unsigned ip|141.101.99.165}}
: That goatee/glasses figure is also a psychologist in http://www.xkcd.com/435/ and a person riding the escalator in http://www.xkcd.com/954/. [[Special:Contributions/108.162.246.211|108.162.246.211]] 06:07, 13 July 2014 (UTC)
[Cueball finds home.]

[View into the dorm room. Cueball II lives there.]

[Cueball sees his life unfolding.]

[Cueball fetches his clobber.]

[Cueball returns.]

[View into the dorm room. Cueball / Cueball : Ying / Ying. All is harmony.]

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 21:07, 22 January 2015 (UTC)

The second prism is dispersing (un-dispersing?) light the wrong way, in that it is bending red light through a larger angle than purple. The first prism has it correct. As I'm kind of new here, appreciate any thoughts on whether this sort of thing belongs in the explanation, or trivia section, or it's fine just keeping it to the comments section. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:18, 7 August 2018 (UTC)

Talk:2027: Lightning Distance

2018-08-06T02:18:05Z

Redbelly98:

Calculations I used:

<math>t_1=\frac{s}{v_1}</math>

<math>t_2=\frac{s}{v_2}</math>

Substract:

<math>t_1-t_2=\Delta t=\frac{s}{v_1}-\frac{s}{v_2}=\frac{sv_2-sv_1}{v_1v_2}=s\frac{v_2-v_1}{v_1v_2}=s\frac{\Delta v}{v_1v_2}</math>

Therefore

<math>s=\Delta t\frac{v_1v_2}{\Delta v}</math>

I evaluated <math>\frac{v_1v_2}{\Delta v}</math> and it came to be 13.6 billion. Can someone verify it's correct? [[Special:Contributions/172.68.51.112|172.68.51.112]] 13:08, 1 August 2018 (UTC)

:The comic begins with the question "how many miles away", so converting to kilometers isn't the right calculation.[[Special:Contributions/172.69.71.24|172.69.71.24]] 17:06, 1 August 2018 (UTC)

I used refractive index for visible light of 1.000277 (air at STP as opposed to 0C 1atm) and arrived at around 7.9 billion instead. Refractive index of 1.000337 is then required for the radio waves for the comic to be correct. [[Special:Contributions/172.68.11.221|172.68.11.221]] 13:46, 1 August 2018 (UTC)

:Do you mean 7.9 billion to convert to miles or to kilometers? Because my 13.6 bilion is to kilometers.

::I'm sure the actual comic is referring to miles and 5 billion was picked to match with the "divide by five" rule for miles. [[Special:Contributions/172.69.70.131|172.69.70.131]] 13:59, 1 August 2018 (UTC)

:::I did mean kilometers. If we use miles, 1.000314 fits almost precisely! (5.04 billion) [[Special:Contributions/172.68.11.17|172.68.11.17]] 14:42, 1 August 2018 (UTC)

If you can count several seconds, as is suggested in the comic, the flash is still billions of miles away, the widest possible distance between Earth and Neptune is about 5 billion km. Sebastian --[[Special:Contributions/172.68.110.40|172.68.110.40]] 14:51, 1 August 2018 (UTC)

:Not to mention that there's not a lot of air within a few billion miles of earth, so the dispersion will be much lower for all but the last 100-ish miles, AFAIK.[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:12, 1 August 2018 (UTC)

::Also, while Jupiter has {{w|Great Red Spot|VERY gigantic storms}}, they are still too small to see the lightning from them from Earth. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 23:17, 1 August 2018 (UTC)

Do you really need to know the spectrum of the flash? If we assume that a flash contains UV and X-ray radiation and that the visible light is generated at the same time as the UV or X-ray radiation then you only need to know the refractive index of light/UV/X-ray in air under the same temperature conditions and not the exact spectrum. [[User:Condor70|Condor70]] ([[User talk:Condor70|talk]])

:I initially made the mistake of thinking this referred to time difference between visible and UV/X-ray, but it specifically says "brightness." If you want to compare the brightness at a distance to the brightness at the source you'll need to know the brightness at the source, i.e. the spectrum of the flash itself. With this technique you don't need to know the dispersion "only" the relative attenuation, but I suspect that would be a more error-prone measurement.[[Special:Contributions/172.68.54.142|172.68.54.142]] 18:54, 1 August 2018 (UTC)

I understand the joke Randall was going for, but have a problem with the wording. "Count the number of seconds" won't work for fractions of anything. "Measure" would work, but spoils the gag a bit. Counting numbers are integers; counting the seconds between the visible and radio frequency flashes will give you zero. [[Special:Contributions/172.69.71.24|172.69.71.24]] 17:00, 1 August 2018 (UTC)

:You're certainly correct, but the joke works (for me at least) by its comparison to the standard rule of counting seconds, and humans are not generally precise enough to resolve better than one second. By keeping Megan's wording as close to the customary rule as possible I think it optimizes the humor. That "Billion" at the end is the whole joke for me, the replacement of "sound" with "radio wave" can be glossed-over on first reading, until you get to the unexpected extra 9 orders of magnitude in the conversion.[[Special:Contributions/172.68.54.142|172.68.54.142]] 18:54, 1 August 2018 (UTC)
::No, they would've been correct if she'd said "count the number of seconds" but she said "'''count the seconds'''".It's part of the joke, because it's correct, just completely impractical, because you'd be "counting" something like 10^(-10) seconds--[[Special:Contributions/172.68.132.47|172.68.132.47]] 07:23, 5 August 2018 (UTC)

::Just realized I also glossed-over the replacement of "divide" with "multiply." The brain is a funny thing.[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:07, 1 August 2018 (UTC)

:I took the "count the number of seconds" to be part of the joke, or rather Randall setting us up for the joke. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:18, 6 August 2018 (UTC)

Do these account for the air pressure variability common in most thunderstorms?

I think explanation and transcript are pretty complete now. [[Special:Contributions/172.68.51.112|172.68.51.112]] 20:58, 1 August 2018 (UTC)

:There is the additional problem that a flash is no instantaneous, but progresses at a fraction of the speed of light. Who says that radio waves and light at different wavelenghts or xrays have their maximum at the same moment? ;-) --[[Special:Contributions/162.158.91.59|162.158.91.59]] 08:05, 2 August 2018 (UTC)

:: I added a few words about the problem that a flash is not instantaneous and removed the 'incomplete' tag. Hope that's OK. [[User:Chrisahn|Chrisahn]] ([[User talk:Chrisahn|talk]]) 19:41, 2 August 2018 (UTC)

Here's a variation of the calculation above that simplifies numeric evaluation:

The {{w|refractive index}} is defined as <math>n=\frac{c}{v}</math>, so <math>v=\frac{c}{n}</math> and thus <math>t=\frac{s}{v}=\frac{s\,n}{c}</math>.

<math>t_1=\frac{s\,n_1}{c}</math>

<math>t_2=\frac{s\,n_2}{c}</math>

Subtract:

<math>t_1-t_2=\Delta t=\frac{s\,n_1}{c}-\frac{s\,n_2}{c}=s\frac{n_1-n_2}{c}=s\frac{\Delta n}{c}</math>

Therefore

<math>s=\Delta t\frac{c}{\Delta n}</math>

and the factor we want to calculate is

<math>\frac{c}{\Delta n}</math>

With the numbers given in the sources in the main text:

<math>n_1=1.000315</math>

<math>n_2=1.000277</math>

<math>\Delta n=n_1-n_2=0.000038</math>

For kilometers: <math>\frac{c}{\Delta n}\approx\frac{300,000\,km/s}{0.000038}\approx7.9\cdot10^9\,km/s</math>

For miles: <math>\frac{c}{\Delta n}\approx\frac{186,000\,mi/s}{0.000038}\approx4.9\cdot10^9\,mi/s</math>

[[User:Chrisahn|Chrisahn]] ([[User talk:Chrisahn|talk]]) 18:28, 2 August 2018 (UTC)

:Nice one. I didn't think to use the refractive indicies directly. [[Special:Contributions/172.68.51.118|172.68.51.118]] 22:22, 2 August 2018 (UTC)

:Agreed, nice clear analysis by Chrisahn. I'd like to suggest a couple of corrections regarding the index values:
:* ''n'' for air at 0 C, 1 atm, is closer to 1.000292, according to both {{w|List_of_refractive_indices|the Wikipedia link}} and also the "Simple Shop-floor Formula" given by NIST at [https://emtoolbox.nist.gov/wavelength/documentation.asp the bottom of this site]. This would give a <math>{\Delta n}</math> of 0.000023, and a time-to-distance conversion value of <math>\frac{c}{\Delta n} \approx 7.9\cdot10^9</math> mi/s.
:* Thunderstorms rarely occur at 0 C. Using values for 30 C (86 F) instead, we have 1.000261 for air (from the simple NIST formula) and 1.000429 for radio waves (from Table 1, p. 8 of [https://www.fig.net/resources/proceedings/fig_proceedings/fig_2002/Js28/JS28_rueger.pdf the Rueger paper]). This gives a <math>{\Delta n}</math> of 0.000168, and a time-to-distance conversion value of <math>\frac{c}{\Delta n} \approx 1.1\cdot10^9</math> mi/s.
:This suggests that the conversion value is the desired 5 billion for ''some'' temperature between 0 and 30 C. Linear interpolation of the above suggests this temperature is about 13 C or 55 F. More to the point, the conversion value varies too strongly with temperature for there to be a simple rule. That being said, I do like that the 5 billion figure ties in nicely with the familiar (in USA) ''divide by 5'' rule. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:18, 6 August 2018 (UTC)

== Assumptions on the medium properties sound? ==

Refractive index of *dry* air might be pretty close to 1 for both light and RF EM waves, but:

Let's assume that the air is humid, if not even full of water drops. After all, lightning.

Let's further assume that an air/water mixture or solution has electromagnetic properties between these two materials.

In water, refractive index for light is about <math>n_{\text{water, optical}}=1.33 n_{\text{air, optical}}</math>, (as easily demonstrated by the optical refractive effects); for RF, we typically use values of <math>\frac{n_{\text{water, RF}}^2}{\mu_r}=\epsilon\approx 80</math>. So, <math>n_{\text{water, RF}}\approx \sqrt{80}n_{\text{air, RF}}</math>.

Let's assume a 10⁻³ "EM-effective" water content in the comic air.

That would lead to <math>\frac{v_{\text{opt.}}}{v_{\text{RF}}} = \frac{\frac34}{\sqrt{80}^{-1}}= \frac34\sqrt{80}=6.7</math>.

:While the humidity (amount of water vapor) is certainly higher during the rain, I don't think that would count as a proper "water-air mixture". Wikipedia says that "Violent rain" is above 5 cm/h. If you divide it by 3600 (to get cm/s), and then imagine stretching that all the way to the cloud, you'll find out there's not that much water at given moment in the air. [[Special:Contributions/172.68.51.112|172.68.51.112]] 19:12, 1 August 2018 (UTC)

::Great point. To finish the calculation let's use a typical terminal velocity for a large raindrop (it's a big storm, I'm sure) of 9m/s. 0.05 m/hr / 3600 s/hr / 9 m/s = 0.00015% water by volume. Sure seems like more than that when I have to drive through it! Then it seems more like [http://what-if.xkcd.com/12/].[[Special:Contributions/172.68.54.142|172.68.54.142]] 20:32, 1 August 2018 (UTC)

<code>we can't detect radiation outside the visible spectrum without very specialized instruments</code> Something that I think was overlooked in the explanation is that while humans can't *directly* sense radio waves, there are devices called "radios" which at one point in time were fairly commonly owned by humans, whose whole purpose is to detect encoded radio waves and convert them into sounds which humans can sense. I.e. you hear static during an electrical storm. So you could listen for the static and compare that to the flash... if you were fast enough. [[Special:Contributions/172.68.54.64|172.68.54.64]] 14:22, 3 August 2018 (UTC) (newbie)

:But radios ARE specialized equipment. [[Special:Contributions/172.68.51.52|172.68.51.52]] 10:35, 4 August 2018 (UTC)

== Whoops! ==

I always thought it was 1 second per mile. I didn't know about the 'divide by 5" part. [[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 01:23, 5 August 2018 (UTC)

Category talk:Checkered paper

2018-08-04T20:40:03Z

Redbelly98:

I've never heard it called "checked paper" before, usually I call it "graph paper" or sometimes "grid paper" {{unsigned ip|‎173.245.56.180}}
:I also call it graph paper. As Randall and I are both from the USA, this may be relevant to how he thinks of it. [[User:Momerath|Momerath]] ([[User talk:Momerath|talk]]) 17:09, 18 June 2018 (UTC)
::First it's not "checked paper" but "checkered paper" and a chess board is checkered. A "graph paper" or "grid paper" is finer, e.g. in millimeters. And Randall's first comics were drawn in a students' note-block with small squares -- or simply "checkered paper". --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 17:40, 18 June 2018 (UTC)
:::In the USA (where I am from), we call it "graph paper" regardless of the fineness of the grid. I too never heard the term "checkered paper". I have added the description "coarse-grid graph paper" to the main article. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 20:40, 4 August 2018 (UTC)

Category:Checkered paper

2018-08-04T20:35:49Z

Redbelly98: Added "coarse-grid graph paper" to description of "checkered paper".

Many of the first comics were simply sketches drawn by [[Randall]] on the paper he had at hand, (sometimes during a [[7:_Girl_sleeping_(Sketch_--_11th_grade_Spanish_class)|class]] or a [[24: Godel, Escher, Kurt Halsey|lecture]]). They then scanned in later, (sometimes much later), and posted on [[LiveJournal]].

Several of these sketched were drawn on '''checkered paper''' (coarse-grid graph paper) and they are the one listed here below:
 If the only color in the comic comes from the blue grid on the checkered paper, then the comic is not considered to be [[:Category:Comics with color|colored]]!

*No comics drawn on such paper have been released after [[:Category:First day on xkcd|the first day]] on [[xkcd]] when the web site opened on Sunday the 1st of January 2006.
**Of those comics [[44: Love]] from October 19th, 2005 is the one with the highest number released on xkcd.
***But it was an early comic which just got the highest number when all the comics transfer from [[LiveJournal]] to xkcd got a new and different number.
**The last comic on such paper release on LiveJournal was [[39: Bowl]] released on December 5th, 2005.
***35 out of the [[:Category:Comics posted on livejournal|first 41 LiveJournal comics]] came out on such paper.
**The last comic on such paper was, however, by release-date, [[12: Poisson]] which have the release date December 22nd, 2005.
***It was never released on LiveJournal. It was first released to the public on the opening day of xkcd.
***It came out along with [[5: Blown apart]], the latter also drawn on this paper and not released previously on LiveJournal.
**The exception to the above is [[36: Scientists]].
***It was, because of a mistake, first released at some [[:Category:No_date|unknown date]] later in 2006, but with this low number.
***It was never before released on LiveJournal.
***That would make this the last to come out on xkcd on this type of paper.
*In 2012, Randall revived the blue grid as a background image for ''[[what if?]]''.

[[Category:Distinctive comics]]

Talk:453: Upcoming Hurricanes

2018-07-31T23:49:30Z

Redbelly98:

I wonder, is there a reason why Randall chose cos(x) over sin(x)? Is there a y-axis somewhere on the map? Not that it matters; just curious... [[User:Bobidou23|Bobidou23]] ([[User talk:Bobidou23|talk]]) 23:24, 22 September 2012 (UTC)
:''cos(x)'', ''sin(x)'', they're the same thing, plus or minus pi/4... -- [[User:IronyChef|IronyChef]] ([[User talk:IronyChef|talk]]) 02:57, 23 September 2012 (UTC)
Something seems off about this explanation. Like reading a blog. [[Special:Contributions/76.122.5.96|76.122.5.96]] 05:14, 28 October 2012 (UTC)

:If something is less than satisfactory, you are fully welcome (and even encouraged) to edit the explanation to be better. [[User:Lcarsos|lcarsos]] ([[User talk:Lcarsos|talk]]) 06:37, 28 October 2012 (UTC)

Whoever said hurricanes cannot form within 5 degrees of the equator was wrong... It is not likely but it is possible. http://en.wikipedia.org/wiki/Cyclone_Agni http://en.wikipedia.org/wiki/Typhoon_Vamei [[Special:Contributions/152.2.128.198|152.2.128.198]] 14:36, 5 November 2012 (UTC)

This title-text seems strangely prophetic after Tropical Storm Sandy in 2012. {{unsigned|107.204.46.198}}
:Yes, I agree. [[User:David1217|David1217]] ([[User talk:David1217|talk]]) 17:18, 19 January 2013 (UTC)
::There is more to win from predicting something that is going to happen than there is to lose from predicting something that doesn't happen. [[User:Tharkon|Tharkon]] ([[User talk:Tharkon|talk]]) 19:30, 1 December 2013 (UTC)

Has anyone any idea what the "&" symbol is about in Hurricane Where-The-Hell-Is-Bermuda? [[Special:Contributions/141.101.97.215|141.101.97.215]] 12:32, 13 May 2014 (UTC)

Regarding Hurricane cos(x):
*If {{w|Equator}} is the x-axis and the y-axis goes through the {{w|Prime meridian}} of {{w|Prime meridian (Greenwich)|Greenwich}} it would be possible to say if this was a true cosine function hurricane.
*A cosine would be 1 (the maximum value) at x=0 (i.e. the maximum value would occur under {{w|Greenwich}}), whereas a sine would be 0 at x=0.
*If it had been a basic cos(x) without any constants added, then it should have been centered along the equator instead of as it is - ranging from about 5.5° to 9.5° north {{w|latitude}}.
*But if the formula was of the form a*cos(b*x)+c with a, b and c given constant, the wave could move to the center of this range with c=7.5°. With the constant a=2° the wave would move between the max and minimum of the range, and then b could be chosen to make the wave length fit with the path shown in the map.

--{{unsigned|Kynde}}

:There is no reason to assume the axes are on the meridian and equator. [[User:Tharkon|Tharkon]] ([[User talk:Tharkon|talk]]) 02:41, 7 September 2014 (UTC)

::Disclaimer: I know I'm pretty late to the whole "cos(''x'')" discussion, but here are my 2 cents.
::*Probably no great surprise that Randall wrote "cos" while drawing a sine function. Assuming he did not have any special reason to prefer one over the other, there was a 50/50 chance of him writing "cos" rather than "sin" to label the curve, and a 50/50 chance of him drawing a sine rather than a cosine function -- taking the leftmost point as the origin and not considering other, arbitrary phase offsets. And, finally, there was a 50/50 chance that the choice of label would not agree with the curve drawn.
::*Observation: The letters in "cos" all have the nice feature that, if written in uppercase as is Randall's usual style, they are indistinguishable from lowercase, which is the usual style for trig functions appearing in textbooks and scientific journals. Not so with "sin". So, probably by accident, using "cos" allowed Randall to write in his usual style while still having a function label in the style people are used to seeing in print.
:::Incidentally, Randall has used both lowercase (see #184) and uppercase (#1047, 3rd row below "World Population" table entry) to write "sin".
:: [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 23:49, 31 July 2018 (UTC)

The details for Hurricane cos(x) mentions a trivia section, which is not present in this article. [[User:SuperSupermario24|Just some random derp]] 17:41, 21 June 2015 (UTC)
:I was about to post the same comment but then I decided to read these first. [[Special:Contributions/108.162.237.158|108.162.237.158]] 07:52, 25 June 2015 (UTC)

Is it just me or is long island missing from the map?? --[[User:Effy|Effy]] ([[User talk:Effy|talk]]) 10:15, 2 April 2017 (UTC)

Talk:2014: JWST Delays

2018-07-29T19:55:19Z

Redbelly98:

Haha - I made this same graph 2 weeks ago! [[User:Cosmogoblin|Cosmogoblin]] ([[User talk:Cosmogoblin|talk]]) 17:39, 2 July 2018 (UTC)

Suggest the last sentence be made more general: "The title text refers to a fundamental question of the Big Bang Theory; will the universe expand forever, or will is collapse back on itself? The likely answer to this question has changed over the decades as new measurements have been made, and new theories such as dark matter and dark energy developed to explain the new measurements. Apparently, and for an analogous reason, between 2018 and 2020 the likely answer to the fundamental JWST question will change." [[User:GODZILLA|GODZILLA]] ([[User talk:GODZILLA|talk]]) 17:58, 2 July 2018 (UTC)
:I agree to the current sentence saying "and compares the universe’s accelerating expansion to the apparently ever-delaying schedule" but were the hell comes the conclusion that "the JWST will have enough delays to fill a universe"? This does not make any sense. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:59, 3 July 2018 (UTC)

Does today's prediction of 2026 count? If that is included in the data set, it would then skew the best-fit line to be steeper. If a new prediction is made using that new best-fit line, that would further skew the line, and so on, causing the acceleration the title text anticipates between 2018 and 2020.[[Special:Contributions/162.158.63.88|162.158.63.88]] 20:10, 2 July 2018 (UTC)

> Until the slope of the line becomes more than one and the prediction goes to the past, right? [[Special:Contributions/108.162.216.16|108.162.216.16]] 21:55, 2 July 2018 (UTC)

:No, it doesn't count, because it's just '''prediction''', while the data set is of (official) '''planned launch dates'''. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:06, 2 July 2018 (UTC)

:The Wikipedia data (taking the midpoint for ranges) fits a linear function with slope 0.660618 and intercept 687.739. This implies convergence at 2026.45, which is why Randall is predicting late 2026 for the actual launch. [[Special:Contributions/172.69.22.56|172.69.22.56]] 15:04, 10 July 2018 (UTC)

[[wikipedia:Heinz von Foerster#Doomsday equation|Von Foersters's doomsday]] is Friday 13th of November 2026. (cue Twilight Zone intro) [[Special:Contributions/162.158.89.175|162.158.89.175]] 21:20, 2 July 2018 (UTC)

Why does he keep saying it's 2021? Is he trying to skip Trump's term or what? --[[Special:Contributions/172.68.211.10|172.68.211.10]] 00:30, 3 July 2018 (UTC)
Why do you think that Trump will get only 1 term?[[Special:Contributions/141.101.76.70|141.101.76.70]] 17:10, 3 July 2018 (UTC)

This is the same chart for the new airport in Berlin. Sadly its slope is not less than one, it is indeed accelerating... 
2006     2011 
2010     2012 
2012     2013 
2013     2014 
2014     2016 
2015     2018 
2016     2018 
2017     2022 
[[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 07:57, 3 July 2018 (UTC)
:[https://de.wikipedia.org/wiki/Bau_des_Flughafens_Berlin_Brandenburg#cite_ref-136] says that the planned launch date from December 2017 is in October 2020 (not 2022). That would make the slope slightly less than 1 (unless you ignore the 2016->2011 data point, as outlier) --[[Special:Contributions/162.158.91.35|162.158.91.35]] 09:27, 4 July 2018 (UTC)
::There was a 2022 prediction earlier in 2017, I took the maximum value for each year. And honestly, 2202 sounds more reasonable than 2020 for me. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 14:39, 4 July 2018 (UTC)

I feel a quadratic regression would be needed to determine acceleration / deceleration [[Special:Contributions/172.68.59.24|172.68.59.24]] 13:54, 3 July 2018 (UTC)

: If you plot out the least-squares fit as it changes over time (i.e. repeat Randall's graph as each new data point was added), it fits a quadratic quite well. And converges to a 2025 date.

I wonder what this chart would look like for new york's 2nd avenue subway.
[[Special:Contributions/162.158.75.130|162.158.75.130]] 17:36, 3 July 2018 (UTC)

At least there _is_ a slope. How about Trump's wall? [[Special:Contributions/173.245.52.151|173.245.52.151]] 00:52, 4 July 2018 (UTC)

Two more lines are coming together... the year and the XKCD index. 2018 should happen next week. [[User:IonFreeman|IonFreeman]] ([[User talk:IonFreeman|talk]]) 14:22, 5 July 2018 (UTC)

The last three data points have a slope greater than one. Just sayin'. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 19:55, 29 July 2018 (UTC)

User:Redbelly98

2018-07-29T19:44:55Z

Redbelly98:

Happy to help out with the physics comics, but can't help much with the programming/IT ones.

Joined Explain xkcd in July 2018. I discovered Explain xkcd, a few years earlier, looking for an explanation of the game 2048 mentioned in [https://www.explainxkcd.com/wiki/index.php/1344:_Digits this comic].

User:Redbelly98

2018-07-29T19:44:36Z

Redbelly98:

Talk:2009: Hertzsprung-Russell Diagram

2018-07-27T23:02:37Z

Redbelly98:

How the heck is a lava cake more luminous than a campfire? {{unsigned ip|108.162.219.28}}
:It's Lava '''Lake''', as in a large puddle of lava.[[User:Cgrimes85|Cgrimes85]] ([[User talk:Cgrimes85|talk]]) 15:45, 20 June 2018 (UTC)
:: Now the real question is, Why isn't lava cake included on the diagram?!?! [[User:Veleek|Veleek]] ([[User talk:Veleek|talk]]) 23:54, 20 June 2018 (UTC)
::: It would be to the left and below the astronomer. While it is hotter (at least when it comes out of the oven), the cake is a better insulator than the human, so doesn't dump as much heat, even though it is hotter. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 13:15, 22 June 2018 (UTC)
:This is the best misreading that I've seen in a while! [[User:Quantum7|Quantum7]] ([[User talk:Quantum7|talk]]) 07:56, 21 June 2018 (UTC)

As it's a logarithmic scale, is it more correct to say the plot been expanded to 1 on both axes? [[User:Cgrimes85|Cgrimes85]] ([[User talk:Cgrimes85|talk]]) 15:47, 20 June 2018 (UTC)

It seems Randall thinks an astronomer is about as bright as a light bulb, probably due to the Hertzsprung-Russell diagram itself! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 15:52, 20 June 2018 (UTC)
:A daily food consumption of average human is about 100W when spread out over 24 hours {{unsigned ip|172.68.245.169}}
::It might actually be about that bright, but in the infrared spectrum. http://elte.prompt.hu/sites/default/files/tananyagok/InfraredAstronomy/ch01s04.html [[Special:Contributions/108.162.246.89|108.162.246.89]] 20:54, 20 June 2018 (UTC)
:But they are no where near as hot!
[[Special:Contributions/172.69.198.10|172.69.198.10]] 20:57, 20 June 2018 (UTC)
::You seem to overestimate the attractiveness of most lightbulbs. I've only seen a few that I would consider really hot. {{unsigned ip|162.158.107.37}}
:::And size; Remember that this type of chart is for comparing total luminosity to surface temperature, & although light bulbs get hot, they're usually nowhere near the surface area of an astronomer.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

While wattage is used as an informal proxy for bulb brightness, there is not a 1-to-1 relationship between power consumption and light output. Incandescent bulbs in the United States were commonly labeled with both watts consumed and lumens output to aid consumers in choosing efficient bulbs. {{unsigned ip|172.69.90.40}}
:"Were"? When? These days the lamp itself usually only states volts & watts, & you're lucky if even the box states lumens. My personal least-favorite is "60w equivalent" with no color temperature & no luminosity listed.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

{{w|Ivanpah Solar Power Facility|Ivanpah}} doesn't have a salt tank. Presumably he meant the boiler, and/or was confusing it with {{w|Crescent Dunes Solar Energy Project|Crescent Dunes}}.
[[User:Wwoods|Wwoods]] ([[User talk:Wwoods|talk]]) 17:29, 20 June 2018 (UTC)
:Thank you! That had me scratching my head. I bet he was thinking of Crescent Dunes. Should this be noted in the Explanation?[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

I understand the explanation, but what's the joke? {{unsigned ip|198.41.230.124}}

The title text says "The Hertzsprung-Russell diagram is located in its own lower right corner, unless you're viewing it on an unusually big screen." But it's clearly on the top left corner... Am I missing something? [[Special:Contributions/108.162.219.106|108.162.219.106]] 18:47, 20 June 2018 (UTC)

:Why would it be at the top left...? The diagram itself is not particularly luminous, so would not be at the top, and its apparent temperature is quite low, so it would not be on the left. {{unsigned ip|108.162.212.89}}

::The joke is that while these type of graphs are typically used for illustrating the output of stars in relation to their age; Randall has extended its range to apply it to planets, boats, whales, & astronomers. Most items in the lower right are neither very luminous (compared to the total luminosity of a star) nor very hot (as compared to a star) & certainly their output on either scale does not bear a reliable correlation to their age. Randall is once again weighing things with the wrong measuring stick, so to speak.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

:::Adding to this, the title text is joking that if you were to measure the diagram's luminosity and effective temperature, then place a point representing that on a copy of the diagram, the resulting point would be in the copy's lower right corner. This type of joke is similar to the one in 688: Self-Description. [[Special:Contributions/172.68.34.28|172.68.34.28]] 05:07, 23 June 2018 (UTC)

Why is a blue whale considered more luminous than a campfire? Blue whales don't generate any light. {{unsigned ip|108.162.212.89}}
:It would if your took it out of the water (to reduce convective losses), but it would emit in the infrared. The 78 kW cited here would equate to 588 million kcal of krill per year. That's in the ballpark of other estimates I found (e.g. 490 million[https://www.washingtoncitypaper.com/columns/straight-dope/article/13041278/straight-dope-does-the-average-american-use-more-energy-than]). I agree that this is one of the more surprising facts to find on this chart. --[[User:Quantum7|Quantum7]] ([[User talk:Quantum7|talk]]) 08:10, 21 June 2018 (UTC)
:: Size counts for a lot of that. By ounce, a campfire would be hotter, but these graphs go by total, not per-ton of mass.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

In one of the interesting parts of this diagram not that many mundane objects (or at least smaller than earth objects) are much hotter than most stars (surface temperature)... Not mentioned now.--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:33, 20 June 2018 (UTC)
:I'm beginning to think the Explanation should highlight the fact that these graphs go by total output, not output per kilogram or anything relative like that. Body temperature of a blue-whale is almost certainly higher than the average temperature of a cruise ship, but a cruise ship is *much* bigger, thereby almost certainly outputting more heat. That said, I'm pretty sure these charts are only supposed to go by ''surface'' thermal output, which could throw a lot of these listings way off. Anyone know what the ''surface'' temperature of a blue-whale is? I've never seen one shown in infrared.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

I think the current explanation is still taking some of the graph too literally, thereby missing some of the jokes. After all, Randall creates comics, sometimes using innuendo or subtlety to make a point. I still think some of the items on the graph are plotted using luminosity as a measure of "brightness" in the sense of smartness. No offense intended, but he must have had a reason for including France below the planets and the blue whale above the astronomer. Furthermore, the title text is likely talking about the actual HR diagram not being very "bright" in the same way the astronomer is in the lower-right corner of the graph, except when it is displayed on a jumbotron. If you're an astronomer, you might not like hearing this, but the meaning of the HR diagram is difficult to grasp correctly. To leave out any mention of smartness is likely missing the most significant jokes in the comic. Please feel free to disagree, but remember it's still just a comic! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 00:37, 21 June 2018 (UTC)

: More specifically to my point, this part of the explanation
:: "the title text notes that the screen displaying the diagram would probably be plotted..."
: is not correct. The title text states the diagram itself would probably be plotted in the lower-right corner, not the screen displaying it - the screen was only related to the second part of the title text! This IS the primary joke in the comic and likely why Randall is making fun of it in the first place. This is also likely the reason for the astronomer to ALSO be plotted in this corner - I doubt that is just a coincidence. Maybe Randall was too subtle for his point to get through to readers! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:37, 21 June 2018 (UTC)

:: I noticed that too. I've added it to the explanation. The diagram itself doesn't have either of the properties measured in the diagram, though a screen displaying the diagram would. As that is an easy misreading to make, and the literal reading makes no sense, one can assume that technical misreading is what was meant.[[User:WingedCat|WingedCat]] ([[User talk:WingedCat|talk]]) 21:12, 27 June 2018 (UTC)

: Just in case I'm also being too subtle, I think Randall is saying that the HR diagram is neat to look at (as in really cool) but also stupid (as in not very bright), putting it in the lower-right corner of itself (cool and dim)! There, I said it! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:45, 21 June 2018 (UTC)

::I believe it is definitely about total luminosity & thermal output, ''not'' "brightness" as a measure of intelligence. France is below the planets because it has much less total surface area & thereby less luminosity than the planet itself. If the graph listed by average luminosity per square inch, France would be higher than Earth. There is no joke about intelligence here, only that total luminosity & total heat output are not reliably linked to the age of non-stellar scale objects.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

:::I will concede on the question of intelligence related to objects on the diagram, as various comments have clarified each such object. Note that the detail on Venus needs to be fixed per another comment here suggesting it's not an error, and I'm pretty sure Randall meant Europa rather than mistyping Europe, so that should be removed from the explanation too. However, the title text explanation is still wrong - it is not about the display of the diagram but the diagram itself. This needs to be addressed! [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 01:44, 22 June 2018 (UTC)

:::: I'd favor removing any speculation that Randall could have meant Europe, rather than Europa, from the explanation. Though maybe include a note clarifying that he did NOT mean Europe? I understand people might have confused the two upon a first reading, but surely the sub-100K temperature leaves no doubt here? [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:42, 16 July 2018 (UTC)

How come this diagram says an LED bulb is hotter than a lightbulb, and both are hotter than a campfire? That doesn't seem right. [[User:YM Industries|YM Industries]] ([[User talk:YM Industries|talk]]) 01:49, 21 June 2018 (UTC)
:The confusion is coming from the fact that the arrow at the top is pointing toward lower temperatures. I'm not sure if this is intentional, or if it is a mistake, but seems to be confusing a lot of people (including myself until I read the actual numbers)[[User:Probably not Douglas Hofstadter|Probably not Douglas Hofstadter]] ([[User talk:Probably not Douglas Hofstadter|talk]]) 03:09, 21 June 2018 (UTC)
:: I noticed that the arrow was pointing in a confusing direction, but LED bulb is to the left of the campfire. The diagram clearly says it's hotter. I'm very confused by this comic. [[User:YM Industries|YM Industries]] ([[User talk:YM Industries|talk]]) 05:22, 21 June 2018 (UTC)

: The location of the LED and Lightbulb temperatures may be related to the actual light source points of these objects (diode junction and wire filament) rather than the outer shells that we can touch. I don't know enough about their internal temperatures to say for sure, but that might explain their positions. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 05:05, 21 June 2018 (UTC)

:Worked it out, it's referring to the colour temperature. [[User:YM Industries|YM Industries]] ([[User talk:YM Industries|talk]]) 05:24, 21 June 2018 (UTC)
::Right. The color temperature of an LED bulb can be much higher than a blackbody of the same power and area because it emits in only a small spectral region.[[Special:Contributions/108.162.238.47|108.162.238.47]] 05:32, 21 June 2018 (UTC)
:::'''''A pun! That's another joke; Should definitely be noted in the transcript.''''' Also, if he ''were'' referring to internal temperatures, not surface temperatures, it would be the only place in this chart he seems to have done so. The other listings are consistent with surface temperatures, not average internal temps.[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 14:25, 21 June 2018 (UTC)

I'm pretty sure there shouldn't be a table in the transcript? I've moved it, but now the table needs to be filled and the transcript needs some work. [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 03:10, 21 June 2018 (UTC)

Venus' temperature is correct. Randall is using planetary equilibrium temperature https://en.wikipedia.org/wiki/Planetary_equilibrium_temperature [[User:Astronorn|Astronorn]] ([[User talk:Astronorn|talk]]) 04:56, 21 June 2018 (UTC)

Seriously, can we get a mention that this graph relates to ''total'' output by surface area, not relative output by mass or anything like that? Obviously per square inch, a campfire is much more luminous than a whale, but the whale gives off more radiation in total due to its greater surface area. The distinction seems to be a source of confusion to a lot of people. {{unsigned|ProphetZarquon}}

The France entry might relate to the fact that our commune here in France (Pessac, 33) now turns off its streetlights between 0100-0500; and there are many communes that do the same or use more sophisticated schemes, like motion sensors or partial extinction, and turning off lighted signage for shops, etc.. [[User:BeeVee|BeeVee]] ([[User talk:BeeVee|talk]]) 14:48, 21 June 2018 (UTC)
:If so, '''that might be another joke''': If the graph went by lumens per area of surface, ''any'' marginally developed country would be shown ''higher'' (with more light output per area) than the Earth as a whole (yes, even countries turning off most of their lights at night), ''because'' '''''oceans'''''. On the other hand, with the graph the way it ''is'' shown, even comparing France to another region of roughly equal area & average reported surface temperature it would be difficult to discern whether its placement on this graph is any higher or lower due to switching the streetlights off at night; Most populous regions of comparable area are probably well within one order of magnitude in terms of light output (citation needed?), so any two comparable regions would be within about one pixel of each other. Listing France next to a comparable region doesn't help, but ''not listing anywhere else'' actually hints at the issue in question (turning off lights)! {{unsigned|ProphetZarquon}}

;Missing Next and Last buttons?
As I type this, an entry for comic 2010 exists, but the Next and Last buttons on 2009 don't exist. I've refreshed a bunch and also confirmed in Incognito and a different browser. So not a cache issue on my end. [[User:Davidgro|davidgro]] ([[User talk:Davidgro|talk]]) 23:07, 22 June 2018 (UTC)
:Must be a cache issue; maybe on the server. I can't reproduce this. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 10:51, 23 June 2018 (UTC)

;It's possible that the title text refers to the overall temperature of the chart, in which case if you had a big enough screen, the chart would show temperatures lower than the chart itself is at.[[Special:Contributions/173.245.52.133|173.245.52.133]] 19:00, 26 June 2018 (UTC)

I added some info on the four stars to the table. When I have time I'll try adding something on the main sequence and other star designations, but can't promise when I'll get to it. -- [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 00:44, 21 July 2018 (UTC)
:1. FYI, the star descriptions I added earlier are primarily comparisons to our sun.
:2. Added description of HD 189733 b, primarily a comparison to Jupiter.
:3. Added entries for the different star classifications (plus brown dwarfs) that appear in the chart. I put these descriptions AFTER the named stars -- not sure if that's the best place for them though.
:[[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 21:41, 21 July 2018 (UTC)
Among other edits, I added a description for the nuclear fireball: "The glowing, rising mass of air that appears just after a nuclear bomb is detonated." Not sure how strictly accurate that is, so feel free to edit. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 23:02, 27 July 2018 (UTC)

2009: Hertzsprung-Russell Diagram

2018-07-27T22:58:16Z

Redbelly98: /* Table */ Rearranged order in table so star classifications now at top. Minor tweaks to descriptions for stars, lightbulb, and LED descriptions. Added descriptions for nuclear fireball and arc lamp. Corrected arc lamp temperature (6500,not 65,000, K)

{{comic
| number = 2009
| date = June 20, 2018
| title = Hertzsprung-Russell Diagram
| image = hertzsprung_russell_diagram.png
| titletext = The Hertzsprung-Russell diagram is located in its own lower right corner, unless you're viewing it on an unusually big screen.
}}

==Explanation==
{{incomplete|Fill out the table. Do NOT delete this tag too soon.}}

The {{w|Hertzsprung–Russell diagram}} is a scatterplot showing absolute luminosities of stars against its effective temperature or color. It's generally used to understand a star's age.

The axes are labeled in {{w|Kelvin}} (degrees {{w|Celsius}} above {{w|absolute zero}}) for {{w|effective temperature}} and, unlike many Hertzsprung–Russell diagrams, {{w|Watts}} for {{w|luminosity}}. While most Hertzsprung–Russell diagrams are labelled in units of {{w|solar luminosity}} or {{w|absolute magnitude}}, all three are perfectly valid measures of {{w|luminosity}}, which refers to the total power emitted by the star (or other body). {{w|Effective temperature}} refers to temperature of a blackbody with the same surface area and luminosity. This is meant to provide an estimate of the surface temperature of the object.

Roughly speaking, the luminosity (i.e. total power radiated) by an object is proportional to (1) the total surface area of the object, multiplied by (2) the (absolute) temperature raised to the fourth power. So a high luminosity generally results from either a very hot or a very large object, or a combination of the two. The surface-area dependence explains why the whale and the cruise ship are more luminous than the hotter campfire.

Regular Hertzsprung–Russell diagrams cover ranges of about 1,000K to 30,000K, and what is labeled on this diagram as 1021 to 1033 watts—i.e. the upper-left corner. Extended diagrams increase the luminosity range only to include the "Brown Dwarfs". This diagram has been extended to much lower magnitudes on both axes. The joke comes from the absurdity of a diagram meant for stars including much smaller objects, such as planets ... and astronomers.

Though not included in the diagram, the title text notes that the diagram itself would probably be plotted somewhere in the lower right corner due to its (relatively) low power output and temperature. On its face this is nonsensical - the diagram itself, being mere information, possesses neither power output nor temperature - but one can read this as the power output and temperature of a typical screen displaying the diagram. Bigger screens have a higher total output (in terms of luminosity) and are thus positioned further towards the diagram's top. An "unusually big screen" would have to be something like a JumboTron or a projector for its luminosity or temperature to put it outside of the lower right corner.

==Table==

{| class="wikitable"
!style="width:10%"|Item
!style="width:10%"|Effective Temperature
!style="width:10%"|Luminosity
!style="width:70%"|Explanation
|-
|{{w|Main sequence}}
|
|
|Most stars lie along the main sequence, one of several labelled regions in a typical {{w|Hertzsprung–Russell diagram|Hertzsprung-Russell (HR) diagram}}, and are thus classified as main sequence stars. Progressing from the lower-right toward the upper-left end of the main sequence, stars become more massive, hotter, and more luminous. The HR diagram in this comic includes three main sequence stars.
|-
|{{w|Giant star|Giants}}
|
|
|A giant star is larger and more luminous than a main sequence star of the same temperature. The HR diagram in this comic does not specifically include any giant stars.
|-
|{{w|Supergiant star|Supergiants}}
|
|
|Supergiant stars are among the largest and most luminous stars that exist. The HR diagram in this comic includes the supergiant star Betelgeuse.
|-
|{{w|White dwarf|White dwarfs}}
|
|
|In a white dwarf star, nuclear fusion has ceased. A white dwarf still radiates energy due to stored heat that was generated from fusion earlier in the star's life, but white dwarfs are much less luminous than stars that are still undergoing fusion. The HR diagram in this comic does not specifically include any white dwarf stars.
|-
|{{w|Brown dwarf|Brown dwarfs}}
|
|
|Brown dwarfs are too small to be classified as stars, but are larger than planets. The HR diagram in this comic does not specifically include any brown dwarfs.
|-
|{{w|Betelgeuse}}
|3200 K
|1.6 * 1031 W
|Betelgeuse is a red supergiant star. At 3200 K, it is cooler than the sun but has a higher luminosity owing to its larger size.
|-
|{{w|Vega}}
|10,000 K
|1.8 * 1028 W
|Vega is a main sequence star that is both hotter and more luminous than the sun.
|-
|{{w|Sun}}
|5800 K
|3.6 * 1026 W
|The sun is a main sequence star. On a typical {{w|Hertzsprung–Russell diagram|HR diagram}}, the luminosity of the sun is usually the basis of the luminosity scale, i.e. the sun is at "1" or 100 on the diagram's vertical scale.
|-
|{{w|Proxima Centauri}}
|2700 K
|2.0 * 1023 W
|Proxima Centauri, the closest star to the sun, is a main sequence star that is both cooler and less luminous than the sun.
|-
|{{w|HD 189733 b}}
|2100 K
|4.8 * 1021 W
|This is an exoplanet discovered in 2005. It is comparable in size to Jupiter, but hotter and more luminous owing to its close proximity to its own sun.
|-
|Interior of a {{w|Thermonuclear weapon|hydrogen bomb}} during detonation
|~108 K
|~1020 W
|
|-
|{{w|Jupiter}}
|285 K
|1.2 * 1018 W
|
|-
|{{w|Venus}}
|330 K
|5.0 * 1017 W
|
|-
|{{w|Earth}}
|300 K
|3.0 * 1017 W
|Non-luminous objects on Earth are typically the same temperature as Earth, around 300 K. As shown in the diagram, Earth-based objects like France, the cruise ship, the blue whale, and the astronomer all have temperatures in the vicinity of 300 K.
|-
|{{w|Mars}}
|255 K
|2.0 * 1016 W
|
|-
|{{w|Moon}}
|300 K
|1.2 * 1016 W
|
|-
|Nuclear Fireball
|8000 K
|2.0 * 1014 W
|The glowing, rising mass of air that appears just after a nuclear bomb is detonated.
|-
|{{w|France}}
|300 K
|2.0 * 1014 W
|This is part of Earth (and more precisely a part of Europe), the same temperature as Earth, but less luminous in proportion to its surface area. Including this may be a joke referencing the two possible meanings of ‘Europa’ (see the next entry). [https://goo.gl/images/H8Dmu3 France emits less light at night than neighbouring countries], perhaps due to lower population density.
|-
|{{w|Europa (moon)|Europa}}
|90 K
|3.5 * 1014 W
|While this term could refer to Europe (a part of Earth, of which France (the previous entry) is a further part), the temperature and luminosity are both too small for that, so it must refer to the moon of Jupiter instead.
|-
|Lightning Bolt
|30,000 K
|30 GW
|
|-
|{{w|Ivanpah Solar Power Facility|Ivanpah Solar Plant}} Salt Tank
|1200 K
|1.2 GW
|The [[wikipedia:Ivanpah_Solar_Power_Facility|Ivanpah Solar Power Facility]] is a large solar power generator in the Californian Mojave desert. It concentrates sunlight from 173,500 reflectors onto three water-boiler towers. Randall appears to have mistakenly confused this power plant with the nearby Crescent Dunes, which uses tanks of molten salt to store energy. https://insideclimatenews.org/news/16012018/csp-concentrated-solar-molten-salt-storage-24-hour-renewable-energy-crescent-dunes-nevada
|-
|Medium-sized Lava Lake
|800 K
|32 MW
|
|-
|Cruise Ship
|325 K
|30 MW
|
|-
|Campfire
|870 K
|7.0 kW
|
|-
|{{w|Blue whale}}
|280 K
|78 kW
|Must be average surface temperature as whales are warm-blooded @ ~100F/37C internally, interestingly this and the cruise ship may be the only entries where a significant amount of power produced is conducted away rather than radiated. Also the power seems high compared to what I can find. [https://www.researchgate.net/publication/321972840/figure/fig1/AS:574004013604864@1513864629274/Visible-and-infrared-spectrum-images-of-various-humpback-whale-surfacing-features.png These images] suggest a surface temperature around 295K - 300K for a Humpback whale when surfacing
|-
|{{w|Arc lamp}}
|6500 K
|150 W
|A light source that passes an electrical current through a gas (as in a mercury or sodium vapor lamp) rather than a solid filament (as in a standard incandescent lightbulb) or a semiconductor (as in an LED).
|-
|Lightbulb
|4800 K
|75 W
|The temperature value here refers to colour temperature, which for an incandescent bulb is the same as the filament temperature. However tungsten filament lights, commonly referred to as "bulbs", have a colour temperature of between 2400 and 3600 K, and tungsten melts at 3695 K.
|-
|LED Bulb
|5800 K
|8 W
|The temperature value here refers to colour temperature, not physical temperature. Color temperature is a better match to effective temperature than physical temperature. As typical semiconductors might be rated for a maximum of 150 C or about 420 K, the physical temperature of an LED Bulb is considerably lower than its colour temperature.
|-
|Astronomer
|310 K
|100 W
| The body temperature of a human (astronomer or otherwise) is about 310K (37°C). Skin Surface Temperature (which would fit the meaning of effective temperature better) is typically 31°C - 35°C. An astronomer standing outside in a thick coat on a cold night would have a much lower surface temperature.

A human being generating 100W for 24 hours needs 2065 kcal or 8,64 MJ. According to the UN FAO this is e.g. the typical daily energy output of women with weight 55kg between 18 and 59 years having a light activity lifestyle of 1.55xBMR (basic metabolic rate).

|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:Expanded Hertzsprung-Russell Diagram
:[A scatter plot is shown, with the x-axis labeled Effective Temperature (in kelvins), and the y-axis Luminosity (watts).]
:

{{comic discussion}}

[[Category:Scatter plots]]
[[Category:Astronomy]]

User:Redbelly98

2018-07-22T16:36:06Z

Redbelly98: Added pages I'm watching

Happy to help out with the physics comics, but can't help much with the programming ones.

----

Pages I'm watching, and perhaps contribute to as time permits:

[[2009:_Hertzsprung-Russell_Diagram]]
[[1047:_Approximations]] Check if ''g'' approximation is "within actual variation"
[[453:_Upcoming_Hurricanes]] "cos vs. sin", see also 184 & 1047

User talk:Redbelly98

2018-07-22T14:36:28Z

Redbelly98: Created blank page

Talk:2009: Hertzsprung-Russell Diagram

2018-07-21T21:41:16Z

Redbelly98:

2009: Hertzsprung-Russell Diagram

2018-07-21T21:23:21Z

Redbelly98: /* Table */ Added entries for the different star classifications that appear in the chart. Added description of HD 189733 b. Minor edits to star descriptions.

{{comic
| number = 2009
| date = June 20, 2018
| title = Hertzsprung-Russell Diagram
| image = hertzsprung_russell_diagram.png
| titletext = The Hertzsprung-Russell diagram is located in its own lower right corner, unless you're viewing it on an unusually big screen.
}}

==Explanation==
{{incomplete|Fill out the table. Do NOT delete this tag too soon.}}

The {{w|Hertzsprung–Russell diagram}} is a scatterplot showing absolute luminosities of stars against its effective temperature or color. It's generally used to understand a star's age.

The axes are labeled in {{w|Kelvin}} (degrees {{w|Celsius}} above {{w|absolute zero}}) for {{w|effective temperature}} and, unlike many Hertzsprung–Russell diagrams, {{w|Watts}} for {{w|luminosity}}. While most Hertzsprung–Russell diagrams are labelled in units of {{w|solar luminosity}} or {{w|absolute magnitude}}, all three are perfectly valid measures of {{w|luminosity}}, which refers to the total power emitted by the star (or other body). {{w|Effective temperature}} refers to temperature of a blackbody with the same surface area and luminosity. This is meant to provide an estimate of the surface temperature of the object.

Roughly speaking, the luminosity (i.e. total power radiated) by an object is proportional to (1) the total surface area of the object, multiplied by (2) the (absolute) temperature raised to the fourth power. So a high luminosity generally results from either a very hot or a very large object, or a combination of the two. The surface-area dependence explains why the whale and the cruise ship are more luminous than the hotter campfire.

Regular Hertzsprung–Russell diagrams cover ranges of about 1,000K to 30,000K, and what is labeled on this diagram as 1021 to 1033 watts—i.e. the upper-left corner. Extended diagrams increase the luminosity range only to include the "Brown Dwarfs". This diagram has been extended to much lower magnitudes on both axes. The joke comes from the absurdity of a diagram meant for stars including much smaller objects, such as planets ... and astronomers.

Though not included in the diagram, the title text notes that the diagram itself would probably be plotted somewhere in the lower right corner due to its (relatively) low power output and temperature. On its face this is nonsensical - the diagram itself, being mere information, possesses neither power output nor temperature - but one can read this as the power output and temperature of a typical screen displaying the diagram. Bigger screens have a higher total output (in terms of luminosity) and are thus positioned further towards the diagram's top. An "unusually big screen" would have to be something like a JumboTron or a projector for its luminosity or temperature to put it outside of the lower right corner.

==Table==

{| class="wikitable"
!style="width:10%"|Item
!style="width:10%"|Effective Temperature
!style="width:10%"|Luminosity
!style="width:70%"|Explanation
|-
|{{w|Betelgeuse}}
|3200 K
|1.6 * 1031 W
|Betelgeuse is a red supergiant star in the constellation Orion. At 3200 K, it is cooler than the sun but has a higher luminosity owing to its larger size.
|-
|{{w|Vega}}
|10,000 K
|1.8 * 1028 W
|Vega is a main sequence star in the constellation Lyra. It is both hotter and more luminous than the sun.
|-
|{{w|Sun}}
|5800 K
|3.6 * 1026 W
|The sun is a main sequence star. On a typical {{w|Hertzsprung–Russell diagram}}, the luminosity of the sun is usually the basis of the luminosity scale. So the vertical scale would have the "1" or 100 located at the sun.
|-
|{{w|Proxima Centauri}}
|2700 K
|2.0 * 1023 W
|Proxima Centauri, the closest star to the sun, is a main sequence star in the constellation Centaurus. It is both cooler and less luminous than the sun.
|-
|{{w|Main sequence}}
|
|
|Most stars are main sequence stars. Progressing from the lower-right toward the upper-left end of the main sequence, stars become more massive, hotter, and more luminous.
|-
|{{w|Giant star|Giants}}
|
|
|A giant star is larger and more luminous than a main sequence star of the same temperature.
|-
|{{w|Supergiant star|Supergiants}}
|
|
|Supergiant stars are among the largest and most luminous stars that exist.
|-
|{{w|White dwarf|White dwarfs}}
|
|
|In a white dwarf star, nuclear fusion has ceased. It still radiates energy due to its stored heat, but is much less luminous than stars that are still undergoing fusion.
|-
|{{w|Brown dwarf|Brown dwarfs}}
|
|
|Brown dwarfs are too small to be classified as a star, but are larger than planets.
|-
|{{w|HD 189733 b}}
|2100 K
|4.8 * 1021 W
|This is an exoplanet discovered in 2005. It is comparable in size to Jupiter, but hotter and more luminous owing to its close proximity to its own sun.
|-
|Interior of a {{w|Thermonuclear weapon|hydrogen bomb}} during detonation
|~108 K
|~1020 W
|
|-
|{{w|Jupiter}}
|285 K
|1.2 * 1018 W
|
|-
|{{w|Venus}}
|330 K
|5.0 * 1017 W
|
|-
|{{w|Earth}}
|300 K
|3.0 * 1017 W
|Non-luminous objects on Earth are typically the same temperature as Earth, around 300 K. As shown in the diagram, Earth-based objects like France, the cruise ship, the blue whale, and the astronomer all have temperatures in the vicinity of 300 K.
|-
|{{w|Mars}}
|255 K
|2.0 * 1016 W
|
|-
|{{w|Moon}}
|300 K
|1.2 * 1016 W
|
|-
|Nuclear Fireball
|8000 K
|2.0 * 1014 W
|
|-
|{{w|France}}
|300 K
|2.0 * 1014 W
|This is part of Earth (and more precisely a part of Europe), the same temperature as Earth, but less luminous in proportion to its surface area. Including this may be a joke referencing the two possible meanings of ‘Europa’ (see the next entry). [https://goo.gl/images/H8Dmu3 France emits less light at night than neighbouring countries], perhaps due to lower population density.
|-
|{{w|Europa (moon)|Europa}}
|90 K
|3.5 * 1014 W
|While this term could refer to Europe (a part of Earth, of which France (the previous entry) is a further part), the temperature and luminosity are both too small for that, so it must refer to the moon of Jupiter instead.
|-
|Lightning Bolt
|30,000 K
|30 GW
|
|-
|{{w|Ivanpah Solar Power Facility|Ivanpah Solar Plant}} Salt Tank
|1200 K
|1.2 GW
|The [[wikipedia:Ivanpah_Solar_Power_Facility|Ivanpah Solar Power Facility]] is a large solar power generator in the Californian Mojave desert. It concentrates sunlight from 173,500 reflectors onto three water-boiler towers. Randall appears to have mistakenly confused this power plant with the nearby Crescent Dunes, which uses tanks of molten salt to store energy. https://insideclimatenews.org/news/16012018/csp-concentrated-solar-molten-salt-storage-24-hour-renewable-energy-crescent-dunes-nevada
|-
|Medium-sized Lava Lake
|800 K
|32 MW
|
|-
|Cruise Ship
|325 K
|30 MW
|
|-
|Campfire
|870 K
|7.0 kW
|
|-
|{{w|Blue whale}}
|280 K
|78 kW
|Must be average surface temperature as whales are warm-blooded @ ~100F/37C internally, interestingly this and the cruise ship may be the only entries where a significant amount of power produced is conducted away rather than radiated. Also the power seems high compared to what I can find. [https://www.researchgate.net/publication/321972840/figure/fig1/AS:574004013604864@1513864629274/Visible-and-infrared-spectrum-images-of-various-humpback-whale-surfacing-features.png These images] suggest a surface temperature around 295K - 300K for a Humpback whale when surfacing
|-
|{{w|Arc lamp}}
|65,000 K
|150 W
|
|-
|Lightbulb
|4800 K
|75 W
|The temperature value here refers to colour temperature, which for an incandescent bulb is the same as the filament temperature. However tungsten filament lights, commonly referred to as "bulbs", have a colour temperature of between 2400 and 3600 K.
|-
|LED Bulb
|5800 K
|8 W
|The temperature value here refers to colour temperature, not physical temperature. Color temperature is a better match to effective temperature than physical temperature.
|-
|Astronomer
|310 K
|100 W
| The body temperature of a human (astronomer or otherwise) is about 310K (37°C). Skin Surface Temperature (which would fit the meaning of effective temperature better) is typically 31°C - 35°C. An astronomer standing outside in a thick coat on a cold night would have a much lower surface temperature.

A human being generating 100W for 24 hours needs 2065 kcal or 8,64 MJ. According to the UN FAO this is e.g. the typical daily energy output of women with weight 55kg between 18 and 59 years having a light activity lifestyle of 1.55xBMR (basic metabolic rate).

|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:Expanded Hertzsprung-Russell Diagram
:[A scatter plot is shown, with the x-axis labeled Effective Temperature (in kelvins), and the y-axis Luminosity (watts).]
:

{{comic discussion}}

[[Category:Scatter plots]]
[[Category:Astronomy]]

Talk:482: Height

2018-07-21T20:21:40Z

Redbelly98:

Are you sure it reads "missing winds"? It looks like "missing WMDs" to me, which would suggest a political reference to the US engagement of 2003 in Iraq.
[[Special:Contributions/109.40.138.109|109.40.138.109]] 02:48, 22 May 2013 (UTC)
:Yeah. Agreed. Changed. [[User:PinkAmpersand|PinkAmpersand]] ([[User talk:PinkAmpersand|talk]]) 11:23, 23 May 2013 (UTC)

"The comic starts with Black Hat throwing a cat off the edge of the universe, probably a reference to Schrodinger's cat"
::Has the editor here never heard of the "cats always land on their feet" myth? Black Hat would appear to be testing this from the extreme. Anonymous 01:43, 4 December 2013 (UTC) (and yes, that would be WMDs)
:::If I am not mistaken, this is a wiki; there is no set editor. If you have a suggestion for how to improve a page, it would be apt to edit it yourself. The discussion tends to be a forum for matters that may be tangentially related to the comic, or uncertain suggestions for improving the article. '''[[User:Davidy22|{{Color|#707|David}}y²²]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 03:18, 4 December 2013 (UTC)
::Sorry, I wasn't aware of the proper terminology. I'll add my line shortly. Anonymous 05:13, 13 December 2013 (UTC)

Why is there a "(?)" in "Oort Cloud"? [[Special:Contributions/108.162.212.196|108.162.212.196]] 02:10, 15 December 2013 (UTC)
:Because it's not known if this cloud really does exist. Many objects are assumed to be there at that vast distance to the sun, but that distance is also the reason they could not be detected from earth. {{w|Voyager 1}}, the farthest humanmade object from Earth, will reach that region in many thousand years. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:37, 15 December 2013 (UTC)
: I think this is a very important point, and have added this to the Objects table entry for Oort cloud. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 20:21, 21 July 2018 (UTC)

Why is Snoop Dogg in space? {{unsigned ip|108.162.219.223}}
:Because he's high as shit, man--he's so high, he's the second-furthest any person's ever been from the earth. [[Special:Contributions/108.162.216.76|108.162.216.76]] 10:12, 6 February 2014 (UTC)

Diameter of milky way: 100 - 120 kly (Lets call it 110 kly)
Suns distance to galactic centre: 27.2 kly
Distance to edge of galaxy: (0.5*110)-27.2 = 27.8 kly = 263E18

Is my understanding and maths right? --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 08:08, 11 September 2014 (UTC)

;Conversion of pixels to height
Because it is a log graph for the y axis
heightfinal = heightinitial * factor
pixels = Logbase(height)

Using identities to show that a vertical distance on this graph represents a multiplicative change in true distance from the starting point of measure, and that a vertical change (delta) in the same number of pixels represents a corresponding multiplicative factor on total height.
pixelsfinal = Logbase(heightinitial * factor) = Logbase(initial) + Logbase(factor)
pixelsfinal - pixelsinitial = Logbase(factor) = pixelsdelta

Solving for the factor and the base of the log function
factor = basepixelsdelta
base = factor1/pixelsdelta

From the diagram it appears that a change (delta) of 550 pixels represents a change of x*1000000 therefore we can determine the base and determine the multiplicative factor for any change in pixels in the original drawing.
base = 10000001/550
factor = (10000001/550)pixelsdelta = 1000000pixelsdelta/550

Therefore:
heightfinal = heightinitial * 1000000pixelsdelta/550
The above can be used as an equation to estimate and validate the heights on the diagram, where heightinitial is the height of the reference point in meters, pixelsdelta is the vertical change in pixels on the diagram, and is positive if height increases and negative if height decreases.

[[Special:Contributions/108.162.216.149|108.162.216.149]] 12:40, 30 September 2014 (UTC)

:We just need to be careful that the existing heights (which in ''most'' cases have been fairly thoroughly researched) are not replaced by heights determined by their 'pixel position'. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 11:16, 1 October 2014 (UTC)
::Wrong, the explanation is intended to explain the comic not the real world. Before you get excited though let me explain, we may be on the same page.
Many height values can be determined from external research, and can be shown to be consistent with the graph (e.g. center of the galaxy). In these cases the researched number should be used in the height column, as clearly these numbers represent the authors intent.
There or other cases where the height is labeled. These should always be used as height, as these numbers represent the authors intent. If they are inconsistent with the scale of the graph this should be noted in the description.
There are other cases, such as where the space shuttle disintegrated, where we can research the numbers, but they are inconstant with the graph by more than an order of magnitude. Any large inconsistencies should be noted in the description, but in these cases the graph position, not the actual position should be in the height column, because this is the closest representation we can have to authors intent.
[[Special:Contributions/108.162.216.106|108.162.216.106]] 11:50, 1 October 2014 (UTC)

:Completely agree with the basis that authors intent is priority, and with pretty much everything written above. What I was concerned about was the possibility of someone indiscriminately changing existing height values based solely on its pixel position, with no cross-checking against the real world height. I would venture that the heights of the real items on the graph are intended by Randall to be at their correct positions, but there may be exceptions. I have a personal bias here, in that I spent quite considerable time doing research on many of the heights. That said, I don't in any way expect the height entries I worked on to be taken as correct, simply that there is some degree of reasoning behind the existing heights, and to change them without checking any discrepancies would be reckless. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 12:48, 1 October 2014 (UTC)

::The Bodes Law ratio of one planet to the next but one is:
:::Pi^(9/4Pi): 20Pi^(3/2Pi)
::thus rendering:

*Mercury : Mars
*Venus: Jupiter
*Earth : Saturn
*Mars : Uranus
*Asteroids : Neptune

Not that the inner asteroids appear between Mars and Jupiter on the right hand column.

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 01:09, 31 January 2015 (UTC)

I think the "pulsar" at the top right might actually be a quasar (an active galaxy). They certainly are distant objects, so someone more versed with the wiki may want to have a look. [[Special:Contributions/141.101.99.123|141.101.99.123]] 20:10, 14 April 2015 (UTC)

[[Special:Contributions/108.162.229.129|108.162.229.129]] 15:00, 18 August 2015 (UTC)
Randall is stating that this is the longest distance that a ray of light has ever traveled to reach Earth, which implies that the universe is about 46 billion years old
Never hear of the expanding space?
[[Special:Contributions/108.162.229.129|108.162.229.129]] 15:00, 18 August 2015 (UTC)

482: Height

2018-07-21T20:17:37Z

Redbelly98: /* Objects */ Added note that existence of Oort cloud is questionable.

{{comic
| number = 482
| date = September 29, 2008
| title = Height
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = height.png
| titletext = Interestingly, on a true vertical log plot, I think the Eiffel Tower's sides would really be straight lines.
}}
{{TOC}}

==Explanation==
''Height'' uses a {{w|logarithmic scale}} to depict the contents of the {{w|universe}} at progressively smaller distances from Earth (less high above the Earth), starting at the highest possible "point", the edge of the {{w|observable universe}}, going all the way down to the grass beneath our feet. The comic is a direct companion piece to [[485: Depth]], also released on a Monday the week after this one. ''Depth'' similarly uses the logarithmic scale to depict the Earth at progressively greater magnification (going "deeper" down), from Earth's surface (the grass) to the interior of a single proton.

At the very top the top (edge) of the observable universe is described as being 46 billion {{w|light years}} above the Earth. The universe is "only" about {{w|Age of the universe|13.8 billion years old}}, so the {{w|cosmic background radiation}} that reaches the Earth today, has also only traveled 13.8 billion light years. However, during that time {{w|Metric expansion of space|the universe has expanded}}, so the galaxies that formed from that spot where this background radiation was emitted 13.8 billion years ago, would now be 46 billion light years away. This has lead to many {{w|Observable_universe#Misconceptions_on_its_size|misconceptions regarding the size}} the most typical being that the radius of the observable universe is "only" 13.8 billion light years. See this video, ''[https://www.youtube.com/watch?v=QXfhGxZFcVE How Do You Measure the Size of the Universe?]'' for a great explanation of the 46 billion light years.

To the right of the text, [[Black Hat]] stands atop the comic, having just dropped a cat off the edge head first; he is clearly going to test if the cat will land on its feet, being a jerk per his usual character. It will take some time though, before the cat reaches Earth...

As one scrolls down, the depicted distances become less compressed, until arriving at the surface of Earth, all the while approaching a 1:1 scale with real-life distances. As shown in [[1162: Log Scale]], if [[Randall]] didn't do this, the comic would be much, MUCH longer.

In this comic, most objects that are grounded on Earth are scaled logarithmically on the vertical axes and linearly on the horizontal axes (some are scaled linearly on both axes). Displaying objects in this manner noticeably distorts their shape; the Great Pyramid, for instance, looks not like a pyramid but like a bullet.

Outside of the Earth's atmosphere, the objects are placed at their actual distances from Earth on the log scale, but their shapes are not subjected to the logarithmic scaling of Earth objects, instead appearing as they would be seen (otherwise, round objects like the sun would appear more egg shaped, with the flatter side facing upward). However, objects are still much larger or much smaller than they would be in real life, in order to allow them to be properly seen.

In the title text, Randall muses on how the inwardly-curved sides of the {{w|Eiffel Tower}} might actually become perfectly straightened when subjected to this logarithmic distortion, although it is shown to bulge in the comic proper, meaning Randall probably doesn't fully believe his own musings. The actual shape of the Tower approximates an {{w|Exponential function|exponential curve}}, which would indeed give a straight line on a log scale, although it was actually designed by {{w|Gustave Eiffel}} to minimize wind resistance rather than to be mathematically exact (the design is so perfect that the amount the Tower sways in the wind is less than the amount it is distorted due to thermal expansion of the sunlit side).

===Objects===
All objects are sorted from bottom to top by their maximum distance from earth for objects in a solar orbit, and their current distance for others.

{| class="wikitable"
|-
! Distance
! Object
! Description
|-
| 435 ×1024m
| Black Hat and cat
| Black Hat kicking a cat off the top of the comic, presumably to determine whether it will land on its feet.
|-
| 435 ×1024m
| colspan="2" align="center" style="background: #ffdead;" | Top of {{w|observable universe}}
|-
| 11.3 ×1024m
| {{w|Hubble Deep Field}} objects
| Objects of extremely distant galaxies found in a long-exposure photograph by of the Hubble telescope, 12 billion light-years away. The right most object is probably intended to be a pulsar, schematically shown from the side.
|-
| 9.46 ×1024m
| colspan="2" align="center" style="background: #ffdead;" | One billion light years
|-
| 3.1 ×1024m
| {{w|Quasar}}
| A supermassive black hole at the center of some young, distant galaxies, the energy released by stuff as it falls into them makes them the brightest known objects, the black hole eventually gets too big so the huge amounts of energy can't escape, but while they're active, they outshine entire clusters of galaxies.
|-
| 2.36 ×1024m
| {{w|Great Attractor}}
| An unusual concentration of intergalactic mass. (It could also just be [[502: Dark Flow|Your Mom]]).
|-
| 425 ×1021m
| {{w|Antennae Galaxies}} (colliding)
| A pair of colliding galaxies.
|-
| 23.6 ×1021m
| {{w|Andromeda Galaxy}}
| A sibling to our Milky Way. It is the nearest spiral galaxy to ours.
|-
| 23.6 ×1021m
| Holy crap lots of space
| There is a lot of {{w|Void (astronomy)|nearly empty space between galaxies}}.
|-
| 9.46 ×1021m
| colspan="2" align="center" style="background: #ffdead;" | One million light years
|-
| 2.38 ×1021m
| [http://knowyourmeme.com/memes/cat-on-a-keyboard-in-space Cat on a keyboard in space]
| An internet meme featuring a picture of a cat sitting on a musical keyboard, superimposed on an image of space.
|-
| 1.56 ×1021m
| {{w|Magellanic Clouds}}
| These clouds are a pair of nearby dwarf galaxies.
|-
| 263 ×1018m
| Edge of Galaxy
| The edge of the {{w|Milky Way}} galaxy, the galaxy in which we reside.
|-
| 245 ×1018m
| {{w|Galactic Center}}
| The center of the Milky Way galaxy.
|-
| 61.5 ×1018m
| {{w|Crab Nebula}}
| Nebula are supernova remnants.
|-
| 14.2 ×1018m
| {{w|Horsehead Nebula}}
| A dark nebula that is part of the Orion Constellation.
|-
| 12.7 ×1018m
| {{w|Orion Nebula}}
| A nebula that is part of the Orion Constellation, just south of Orion's Belt.
|-
| 8.14 ×1018m
| {{w|Rigel}}
| The brightest star in the Orion Constellation it is actually a triple star system known alternatively as Beta Orionis.
|-
| 6.08 ×1018m
| {{w|Betelgeuse}}
| The star Betelgeuse is displayed along with the location of {{w|Ford_Prefect (character)|Ford Prefect}} on his home planet which orbits Betelgeuse. Ford Prefect is a fictional character from the science fiction parody {{w|The Hitchhiker's Guide to the Galaxy}}.
|-
| 4.20 ×1018m
| {{w|Pleiades}}
| The Pleiades also have a derogatory remark (for those who do not know how to recognize them), as per [[66: Abusive Astronomy]]. This is probably because they are Randall's favorite astronomical entity as is stated at the very bottom of the [http://www.xkcd.com/about/ about] page on xkcd.
|-
| 2.90 ×1018m
| The [http://en.memory-alpha.org/wiki/Romulan_Neutral_Zone Romulan Neutral Zone]
| This marks the edge of the {{w|Star Trek}} Federation.
|-
| 931 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | The first radio broadcast was in January 1910. Since radio waves travel at the speed of light, and this was published in September 2008 this the radio waves traveled about 98.5 light years. See {{w|Contact (1997 film)}} for a depiction of this. This is also referenced in [[1212: Interstellar Memes]].
|-
| 350 ×1015m
| {{w|Arcturus}}
| An orange giant star that is part of the Boötes constellation.
|-
| 320 ×1015m
| {{w|Pollux}}
| One of the most distinct stars in the Gemini Constellation it is large Orange Giant with an apparent visual magnitude of 1.1
|-
| 242 ×1015m
| The edge of {{w|Federation Sector 0-0-1}}
| The sector of space assigned to Earth in {{w|Star Trek}}.
|-
| 224 ×1015m
| {{w|Iraq and weapons of mass destruction|"missing WMDs"}}
| A reference to the alleged weapons of mass destruction that were used as a pretense to mobilize the world population against Iraq, and start the Iraq war.
|-
| 81.3 ×1015m
| {{w|Sirius}}
|Also known as Alpha Canis Majoris or the Dog Star, it is actually a binary system of Stars consisting of a main sequence white star and a small white dwarf.
|-
| 56.6 ×1015m
| {{w|Barnard's Star}}
| Barnard's star is a very small red dwarf that is of great interest to astronomers as an achievement in the SIM ({{w|Space Interferometry Mission}}) to find a celestial object out of solar system that is as small as 3 earth masses
|-
| 41.3 ×1015m
| {{w|Alpha Centauri}}
| Alpha Centauri is the closest star system to our planet.
|-
| 30.9 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | One {{w|parsec}} (= 3.26 light-years).
|-
| 9.46 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | One {{w|light-year}}.
|-
| 15.0 ×1015m
| {{w|Oort cloud}}
| A halo of ice balls surrounding our solar system, but missing the {{w|Kuiper belt}} between Neptune and the Oort cloud. The Oort cloud is only theorized to exist, with no confirmed direct observations, so Randall has written a question mark (?) next to this region of the graph.
|-
| 350 ×1012m
| {{w|Bupkis}}
| Yiddish for "nothing". Only a handful of objects are known to orbit between the Kuiper Belt and the Oort Cloud.
|-
| 55.0 ×1012m
| A comet which will destroy earth in late 2063
| To coincide with the latest biblically based prophesy for the [http://www.askelm.com/prophecy/p971105.htm end of the world].
|-
| 19.5 ×1012m
| {{w|Voyager 1}}
| An early space probe. Distance correct as of 20th Nov 2014, click [http://voyager.jpl.nasa.gov/where/ here] to see NASA's live distance counter.
|-
| 16.7 ×1012m
| {{w|Pioneer 10}}
| Listed distance is an estimate based on {{w|Pioneer_10#Current_status|this information}}.
|-
| 17.7 ×1012m
| {{w|Pioneer 11}}
| By the similarity in appearance to Pioneer 10 this unlabeled probe must be Pioneer 11. Listed distance is an estimate based on {{w|Pioneer_11#Current_status|this information}}.
|-
| 14.5 ×1012m
| {{w|Eris (dwarf planet)|Eris}}
| One of a pair of {{w|Trans-Neptunian object}}s now classified as {{w|dwarf planet}}s. The "All hail Discordia!" after Eris is a reference to {{w|Discordianism}}, a somewhat tongue-in-cheek religion based around the goddess Eris. The distance is the maximum distance from earth.
|-
| 7.50 ×1012m
| {{w|Pluto}}
| One of a pair of {{w|Trans-Neptunian object}}s now classified as {{w|dwarf planet}}s. Pluto was originally classified as the 9th planet of the Solar system. Many people were appalled when it was suddenly degraded to dwarf planet. Obviously Randall does not think much of these people thus the comment: ''Not a planet. Neener neener''. The distance is the maximum distance of Pluto from Earth.
|-
| 4.70 ×1012m
| {{w|Neptune}}
| Neptune is displayed here with its moons. Neptune is the eighth and final planet in our solar system.
|-
| 3.20 ×1012m
| {{w|Uranus}}
| Uranus is dispayed here with its moons. Uranus is the seventh planet in our solar system.
|-
| 1.67 ×1012m
| {{w|Saturn}}
| Saturn is displayed along with its moons. One of Saturn's moons, most likely {{w|Enceladus}}, is labeled as a potential location to find life. Enceladus was known in 2008 to have a possible subsurface ocean and active geysers, and a paper co-authored by well-known planetary scientist Caroline Porco in Astrobiology during that year (when the comic was published) spelt out the case for searching for life there (McKay et al. 2008 "The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume", Astrobiology 8(5):909-919). In 2015, the {{w|Cassini probe}} sampled material thought to be from Enceladus' geysers, and scientists have found evidence that it's subsurface ocean closely resembles a particular kind of deep sea hydrothermal environment on Earth known to harbor life.

A more distant possibility is that Randall is referencing Saturn's largest (and much more well known moons) {{w|Titan (moon)|Titan}}, the only known moon to have an atmosphere and lakes. It was long predicted that there may be bodies of liquid on the surface filled with liquid methane and ethane (Titan is too cold for liquid water and life as we know it, but ethane and methane remain a liquid at those temperatures). There is some speculation that exotic forms of life based on extremely cold exotic chemistries may form in such conditions, with liquid hydrocarbons playing the role of the solvent (the role water plays in terrestrial life).
|-
| 928 ×109m
| {{w|Jupiter}}
| Jupiter is displayed along with its moons. One of Jupiter's moons, {{w|Europa (moon)|Europa}}, is labeled as a potential location to find life. Europa may be covered by a deep ocean of water found under a layer of ice many kilometers thick. Some hypothesize that life could have formed in such oceans.
|-
| 222 ×109m
| Asteroids
| The {{w|Asteroid|Asteroid belt}} contains a spaceship from {{w|Asteroids (video game)}}
|-
| 133 ×109m
| {{w|Mars}}
| Note the path, reflecting the fact that their distances from Earth vary as the planets move in their orbits with a maximum distance of 401 million km and a minimum of 54.6 million km.
|-
| 114 ×109m
| {{w|Venus}}
| Note the path, reflecting the fact that their distances from Earth vary as the planets move in their orbits with a maximum distance of 261 million km and a minimum of 37.7 million km.
|-
| 138 ×109m
| {{w|Mercury}}
| Mercury is the innermost planet in our solar system. The distance shown is the maximum distance from Earth.
|-
| 149 ×109m
| {{w|Sun}}
| The Sun is the star at the center of our solar system, around which the Earth and the other planets orbits.
|-
| 16.3 ×109m
| {{w|Discovery One}}
| The Discovery One from {{w|2001: A Space Odyssey}}, referring to the quote "open the pod bay door, HAL." Also may be a reference to [[375: Pod Bay Doors]].
|-
| 9.43 ×109m
| Planet Express
| The spaceplane is most likely the Planet Express from {{w|Futurama}}, where Fry once discussed "a big heaping bowl of salt."
|-
| 400 ×106m
| Human Altitude Record
| Achieved by the team of {{w|Apollo 13}} approximately 100 km higher than the remaining Apollo missions.
|-
| 384 ×106m
| {{w|Moon}}
| The Moon is the Earth's only natural satellite.
|-
| 90.4 ×106m
| {{w|Snoop Dogg}}
| A tongue-in-cheek reference to a rapper notorious for smoking marijuana, shown as having the second-highest altitude record. Someone who is taking drugs is said to be getting high.
|-
| 60.5 ×106m
| {{w|Space elevator}}
| A proposed method of transporting cargo or people into orbit, consisting of a large mass beyond geosynchronous orbit, a station at the geosynchronous point, a cable connecting it to the Earth, and a climber that can scale the cable. Space elevators are also seen in [[697: Tensile vs. Shear Strength]] and [[536: Space Elevators]].
|-
| 42.1 ×106m
| colspan="2" align="center" style="background: #ffdead;" | {{w|Geosynchronous orbit|Geosynchronous Orbit}}
|-
| 20.2 ×106m
| {{w|GPS (satellite)|GPS Satellites}}
| GPS satellites are used for global positioning.
|-
| 3.94 ×106m
| {{w|Lunar Lander}}
| The quote is a reference to {{w|Contact (1997 film)}} where the main character Ellie Arroway after witnessing a celestial light show up close says "Poetry! They should've sent a poet.".
|-
| 800 ×103m
| {{w|Space debris|Space Junk}}
| There is a large quantity of defunct objects in orbit around the earth. Amongst other things, this includes old satellites, rocket stages and fragments from collisions or disintegration. Space junk is also referenced in [[1242: Scary Names]] under the title {{w|Kessler syndrome}}
|-
| 422.5 ×103m
| {{w|International Space Station}}
| The ISS (International Space Station) is a multinational effort to put a research vessel in space. It is currently the largest artificial object in Earth's orbit, as well as the location of the longest continuous human presence in space.
|-
| 100 ×103m
| colspan="2" align="center" style="background: #ffdead;" | The {{w|Edge of space|official edge of space}} as defined by the {{w|Kármán line}}
|-
| 76.0 ×103m
| {{w|Meteors}}
| Meteors are chunks of rock (usually asteroids) that burn up in the atmosphere, producing the bright light associated with them. If they are large enough to hit the ground, they become meteorites, which is why Munroe labeled them only in the upper atmosphere.
|-
| 25.0 ×103m
| {{w|High-altitude balloon|High-altitude balloons}}
| Unmanned balloons, typically filled with helium or hydrogen. The current altitude record was set in 2002 by a balloon named BU60-1 which reached 53,000m.
|-
| 16.1 ×103m
| colspan="2" align="center" style="background: #ffdead;" | 1/10 ATM = 0.1 {{w|Atmospheric pressure|atmosphere of pressure}}
|-
| 12.0 ×103m
| {{w|Airliner|Airliners}}
| This is a typical cruising altitude of jet aircraft, equating to roughly 40,000 feet. (Aircraft altitude tends to be specified in feet rather than metres (yay!?))
|-
| 8.84 ×103m
| {{w|Mount Everest}}
| The Earths highest mountain, located in the {{w|Himalayas|Himalayan mountain range}} in South Asia.
|-
| 8.00 ×103m
| {{w|Cory Doctorow}}
| Cory Doctorow is a [[:Category:Comics featuring Cory Doctorow|recurring theme]] in xkcd. He was first seen in a balloon in [[239: Blagofaire]].
|-
| 6.34 ×103m
| {{w|Space Shuttle Columbia disaster}}
| The {{w|Space Shuttle Columbia}} and its seven crew were lost when it disintegrated at [http://books.google.co.uk/books?id=6v16AgAAQBAJ&lpg=PA7&ots=LDKQ3nsNHs&dq=shuttle%20columbia%20altitude&pg=PA7#v=onepage&q=shuttle%20columbia%20altitude&f=false approximately 63,400m] in 2003. This number is inconsistent with the height of the graph by a factor of 10 probably a mistype by Randall.
|-
| 6.00 ×103m
| {{w|Helicopter}}
| Though the record for helicopter altitude (without payload) is 12,442m, normal flying is usually performed much lower. In the US, 6000m is into {{w|Class A airspace}}, which is restricted and requires flight under {{w|Instrument Flight Rules}}.
|-
| 6.00 ×103m
| {{w|Cloud}}
| Though not actually labeled there are a couple of clouds shown. While different cloud types vary in height, 6000m is roughly in the middle of the height range for [http://weatherfaqs.org.uk/node/21 clouds in temperate regions].
|-
| 5.49 ×103m
| colspan="2" align="center" style="background: #ffdead;" | 1/2 ATM = 0.5 {{w|Atmospheric pressure|atmosphere of pressure}}
|-
| 1.78 ×103m
| [[Cueball]]
| Apparently still using Python as shown in comic [[353: Python]].
|-
| 800 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 800 meters
|-
| 800 ×100m
| {{w|Burj Khalifa|Burj Dubai}}
| Now known as the Burj Khalifa, is the tallest building in the world. This was also a main feature in [[1110: Click and Drag]].
|-
| 500 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 500 meters
|-
| 400 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 400 meters
|-
| 325 ×100m
| {{w|Eiffel Tower}}
| A famous landmark in Paris, France.
|-
| 300 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 300 meters
|-
| 200 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 200 meters
|-
| 150 ×100m
| Kite
| Kite string is commonly sold in large spools; a nice thick spool will probably hold 150 meters. Kites are a [[:Category:Kites|recurring theme]] in xkcd, see for instance [[235: Kite]].
|-
| 140 ×100m
| {{w|Great Pyramid of Giza}}
| One of the Seven Wonders of the Ancient World. It is located in Egypt.
|-
| 120 ×100m
| {{w|Pop fly}}
| In {{w|Baseball}} a 'Pop Fly' is when the batter mis-hits the baseball, which then follows a tall arc deep into the infield where it's easy picking for the other team to catch on its way down. The highest recorded pop fly, not including those that landed in foul territory, was 172 meters.
|-
| 115 ×100m
| {{w|Redwood Tree|Redwood trees}}
| The tallest trees in the world. At 115.61 m (379.3 ft) {{w|Hyperion (tree)|Hyperion}}, a Coast Redwood, holds the record for the tallest tree in the world.
|-
| 100 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 100 meters
|-
| 20.0 ×100m
| {{w|Oak}}
| While oaks may grow to be in excess of 40m in height, heights of around 20m are more typical. The person in the tree saying, "Hey, squirrels!" is a reference to [[167: Nihilism]].
|-
| 16.4 ×100m
| Tallest stilts
| The tallest {{w|stilts}} recorded by the Guinness Book of World Records (as of November 2006) were 16.4 meters, or nearly 54 feet. See also [http://www.explainxkcd.com/wiki/images/8/89/1608_1038x1095y_Hamsterball_and_stilts_room.png these tall stilts] from [[1608: Hoverboard]].
|-
| 13.0 ×100m
| {{w|Brachiosaurus|Brachiosaur}}
| A large genus of dinosaur.
|-
| 8.00 ×100m
| {{w|Giraffe}}
| The tallest living terrestrial animal, with fully grown adults reaching in excess of 5 m. While labeled 8m in the comic, the [http://www.big-animals.com/the-giraffe-the-worlds-tallest-animal/ record] for height is reported at 5.8m. Has been used by Randall for measuring heights, most prominently in the [[what if?]] ''{{what if|44|High Throw}}''.
|-
| 1.70 ×100m
| {{w|Human height|Folks}}
| Determining an average height of the world population is fraught with complications, but as a ballpark figure 1.7m is fairly accurate.
|}

==Transcript==
:'''Top of observable universe'''
:[Black Hat is standing on top, throwing a black kitty down.]
:Black Cat: Mrowl!
:[Map of the universe from observable universe to Earth. Each area of item is labeled. Labels left to right, up to down:]
:(46 billion light years up)
::Hubble Deep Field Objects
:-One billion light years-
::Great Attractor
::Antennae Galaxies (colliding)
::Andromeda
::Holy crap lots of space
:-One million light years-
::Magellanic Clouds
::Edge of galaxy
::Galactic center
::Crab Nebula
::Orion Nebula
::Horsehead Nebula
::Romulan neutral zone
::The Pleiades, duh!
::Rigel
::Betelgeuse
::Ford Prefect
:[Three arrows are pointing up above three lines with the following label:]
:-Expanding shell of radio transmissions-
::[Above a dotted line:]
::Edge of federation sector 0-0-1
::Pollux
::Arcturus
::Missing WMDs
::Sirius
::Barnard's Star
::Alpha Centauri
:-One parsec-
:-One light year-
::Oort Cloud (?)
::Bupkis
::Comet which will destroy Earth in late 2063
::Pioneer 10
::Voyager I
::Eris (All hail Discordia!)
::Pluto (Not a planet. Neener neener.)
::Neptune
::Uranus
::Saturn
::[Two arrows point to two moons, one next to each of the planets aboe and below.]
::<-- Life -->
::Jupiter
::Asteroids
::Mars
::Venus
::Sun
::Mercury
::Spaceship Planet Express: Hey, a heaping bowl of salt!
::Spaceship Discovery One: Open the fridge door, Hal.
::Moon
::Human altitude record (Apollo 13)
::2nd place: Snoop Dogg
::Space elevator - One of these days, promise!
::Geosynchronous Orbit
::GPS satellites
::Lunar lander: In retrospect, they shouldn't have sent a poet. I have no idea how to land.
::International Space Station
::Space junk
:-Official edge of space (100 km)-
::Meteors
:-1/10 ATM-
::High altitude balloons
::Airliners
::Shuttle Columbia lost
:-1/2 ATM-
::Cory Doctrow
::Everest
::Helicopters (6000 m)
::Cueball: Woo Python!
::[A vertical scale is drawn along the right side of the picture, starting at 1 km and getting progressivly smaller and smaller.]
:1 km
:-800 m-
::Burj Dubai (~800 m)
:500
:400
::Eiffel Tower (325 m)
:200
::Kites
::Great Pyramid (140 m)
::Pop fly
::Redwood (115 m)
:100m
::Oak (20 m)
::A person in the oak: Hey squirrels!
::Tallest stilts
::Brachiosaur (13 m)
::Giraffe (8 m)
::[Megan and Cueball holding the kite are labeled:]
::Folks
:'''The observable universe, from top to bottom'''
::~On a log scale~
::Sizes are not to scale, but heights above the Earth's surface are accurate on a log scale. (That is, each step up is double the height.)

{{comic discussion}}

[[Category:Charts]]
[[Category:Large drawings]]
[[Category:Comics with inverted brightness]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Cory Doctorow]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Space probes]]
[[Category:Astronomy]]
[[Category:Space]]
[[Category:Elevators]] 
[[Category:Baseball]]
[[Category:Animals]]
[[Category:Dinosaurs]]
[[Category:Giraffes]]
[[Category:Squirrels]] 
[[Category:Programming]] 
[[Category:Kites]]
[[Category:Star Trek]]

Talk:930: Days of the Week

2018-07-21T19:39:01Z

Redbelly98:

I *might* buy the print of this, but it looks like the kind of thing that varies quickly, and I want a poster that I can refer to easily and won't become outdated after a year. '''[[User:Davidy22|{{Color|purple|David}}y²²]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 09:17, 9 March 2013 (UTC)

Just think, If I hadn't got this far in my pilgrimage, I would never have heard of Rebecca Black. So duhh! how did a computer hack?

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 16:43, 23 January 2015 (UTC)

Randall missed a real opportunity to go full meta and put a ring that said "Gotta go read the new xkcd" ''{{Color|#555555|-Yh}}'' 1:09, 24 January 2016 (US Central) {{unsigned|Yhsanave}}

Anyone notice the Transcript misses Wednesday? --[[Special:Contributions/141.101.98.229|141.101.98.229]] 03:57, 4 December 2016 (UTC)
:No it doesn't (at least not by July 2017): the "source" list is defined for Wednesday.[[Special:Contributions/172.68.47.126|172.68.47.126]] 01:46, 28 July 2017 (UTC)

"So drunk" has a mid-week peak on Wednesday. This could be a consequence of Ladies Night. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 19:39, 21 July 2018 (UTC)

Talk:1442: Chemistry

2018-07-21T13:05:27Z

Redbelly98:

:"I" would have two in Randall's system as a sans-serif element, and four as a serif element. [[Special:Contributions/108.162.249.202|108.162.249.202]] 00:51, 4 November 2014 (UTC)

::The crossbar on "I" is actually not a serif, it's a part of the letter. Some popular sans-serif fonts that have a crossbar on "I" include Tahoma and Verdana. --[[User:Zagorath|Zagorath]] ([[User talk:Zagorath|talk]]) 13:24, 6 November 2014 (UTC)

What is the force that holds the two or three glyphs of an atom together called? How many bonds does the i's dot in Ti have? Ann how dangerous is comic sans cheMStry? [[Special:Contributions/141.101.104.39|141.101.104.39]] 06:52, 3 November 2014 (UTC)
:The letter i can only form one bond, as the other side is bonded with its dot. This is pretty basic chemestry![[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 08:20, 3 November 2014 (UTC)

::Ok. Let's look at something advanced. Fe. Os. {{w|Ununtrium|Uut}}. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 12:20, 3 November 2014 (UTC)
:::Sorry, but you mean {{w|Nh|Nh}}.
:::Ah, binary atoms. Probably too advanced for this discussion. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 13:03, 21 July 2018 (UTC)

Presumably hydrocarbon chains are still supported, albeit with hydrogens forming the backbone in a zip-like arrangement. You'd need phosphorous on the end, with a sans serif valence of 1. [[User:SleekWeasel|SleekWeasel]] ([[User talk:SleekWeasel|talk]]) 08:09, 3 November 2014 (UTC)

I believe he is making fun of incompetent chemistry students. I've seen some draw CH4 as C-H-H-H-H, i.e. according to some random and weird rules that have nothing to do with chemistry. - This comic proposes an equally nonsensical new paradigm. - Aeneas, 3rd November 2014, 10:01 CET

The crystalline structure is not like real-life crystalline carbon (neither diamond nor graphite). I removed that but someone should add a bit about it.[[Special:Contributions/141.101.99.39|141.101.99.39]] 11:48, 3 November 2014 (UTC)

Old English Krypton is particularly hazardous and may explode on contact. Dark matter is composed entirely of cursive script elements. [[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 12:01, 3 November 2014 (UTC)

"Mydrane" is a trade mark for a company that markets miscellaneous medical supplies. "Hydrane" is a process for coal gasification by hydrogenation, producing ideally mostly light hydrocarbon gases (mostly methane) and a minimum of liquid products. Not clear whether either is relevant here.[[User:Taibhse|Taibhse]] ([[User talk:Taibhse|talk]]) 12:29, 3 November 2014 (UTC)
::Hydrane is probally relevant. The real Mydrane almost certainly isn't. However, two other words come to mind; Mydriasis (the dialation of the pupil) and Myopia (near-sightedness), which could be what was happening to us Chemistry geeks when we first saw that. Also, the "compound" he claims to be Mydrane does somewhat resemble a pair of eyes or a pair of glasses. -[[Special:Contributions/173.245.48.137|173.245.48.137]] 17:42, 3 November 2014 (UTC)

Amount vs. number.
In the explanation: "the formation of bonds between elements often relies on the amount of valence electrons an element has." Should read, "the formation of bonds between elements often relies on the NUMBER of valence electrons an element has…"

-Avenue

It would be a very interesting exercise to invent a new set of symbols that WERE accurate using this system.[[User:Seebert|Seebert]] ([[User talk:Seebert|talk]]) 12:47, 3 November 2014 (UTC)

I don't know how relevant this is, but Hydrogen does exist in a metallic phase unde rhigh pressure and temperatures. It's liquid, though, and not crystalline. Also, C2H does also exist, but as a very unstable radical (basically an Acetylene Radical) which seems to be found in space. I have NO idea where Mydrane comes from. There are a lot of Hydrogencompounds ending with -ane (Borane, Silane, Methane), but no idea how this applies here. --[[Special:Contributions/108.162.231.188|108.162.231.188]] 14:21, 3 November 2014 (UTC)

Question: does N(itrogen) only have two bonds, or are those angles a different kind of bond (perhaps ionic vs covalent)? If so, tungsten (W) would be interesting, for a start... (In fact, going though the elements in my head, from the monoglyph elements it would be the most complex under this system. The diglyphs might give Meitnerium (Mt... but was that previously Une as a systematic triglyph?) or Thulium (Tm) some interesting qualities, depending on how the system actually works. Triglyphs are always intended to be replaced, so I think those are moot.
:Wow, is this a serious question or are you just trolling for conspiracy nuts? Of course the conspiracy theorists will tell you that before the invention of printing all the angles were curves, and they were compressed to tight angles to make blocks of movable type smaller and cheaper. Reputable experimental chemists, however, have reported that the bonds between two tungstens is stronger than between two uraniums and we can attribute the difference to the angles. It is fairly evident that right angles (e.g. at the upper left corners of "F" and "P") are essentially inert, and it appears that bond strength increases as the angle becomes more acute. Opposing angles (e.g. "K") seem to Kancel each other out. This is still a very contentious topic![[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 05:09, 4 November 2014 (UTC)

As for symbols that ''are'' accurate, there are a number of systems. Hydrogen is represented on the "gold discs" on the Voyager spacecraft (as a starting key to easily decode other information on there) but without a complete overhaul of a system, I'd imagine ''no'' advanced civilisation will have started out with "let's show it how it actually works" (accurately, and without elements such as phlogiston creeping in!) before giving arbitrary names. Electron-orbital diagrams probably work well, though, for some things. And something that reveals the (for example) pi-bonds works better in combinatory diagrams. I think. It's been a while since I did any serious chemistry.[[Special:Contributions/141.101.99.112|141.101.99.112]] 14:41, 3 November 2014 (UTC)

Oxygen has 6 valence electrons, not two. It forms two bonds because it's got room for two more. [[Special:Contributions/108.162.216.105|108.162.216.105]] 16:49, 3 November 2014 (UTC)

Could Mydrane be My Dr -ane where -ane is the common ending for an alkane. My Dr = CCH...which could be Cape Code Healthcare? ~~rbnm

I wonder how many bonds the capital letter "I" would have-- two or four? Seeing as how Randall writes it in this comic, I'm guessing two. Also, would it be possible for carbon to bond with itself ad infinitum in a chain which looks like the teeth on a zipper ("C", upside-down "C", and so on)? [[Special:Contributions/108.162.238.177|108.162.238.177]] 00:29, 4 November 2014 (UTC)
::Yes, Carbon can form very long chains, and also carbon rings (but only with an even number of carbon atoms).[[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 04:23, 4 November 2014 (UTC)
:::Assuming that you're talking Comic Universe, I don't see why it ''can't'' be an odd number of carbons in a ring. Even if we're forced to bend round a ...∩U∩U... sort of thing (only end-connected, between characters, not end-snuggled, IYSWIM) you can have one that bends round outside of the plane of the page similar to a mobius strip and could still 'zipper' in a closed circuit with an odd number.
:::IRL, of course, there's {{w|Cyclopentane}} and {{w|Cyclopropane}} (3- and 5-carbon rings), among others, and {{w|Cycloundecane}} (11-carbon saturated ring, with an irregular and aperiodic "wiggle" around the circuit) shows one way that the Fictional Cyclocarbon could (just with a greater angle of bond between successive carbons, and no hydrogens involved) work with odd numbers. [[Special:Contributions/141.101.99.112|141.101.99.112]] 07:56, 5 November 2014 (UTC)
::::My bad - I thought the comic universe was only two dimensional and it would have to be an even number. I need to upgrade my screen! [[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 02:51, 6 November 2014 (UTC)

Me is not the designation of two carbon chains. Methane is CH4. [[Special:Contributions/108.162.221.147|108.162.221.147]]rbnm

Any idea why the title text says "usually" more reactive? Do we have examples of where serifs could be less reactive than their sans serif counterparts?[[Special:Contributions/108.162.229.90|108.162.229.90]] 11:51, 9 November 2014 (UTC)
:Usually: For example, serif oxygen and sans-serif oxygen are both inert.[[Special:Contributions/199.27.133.126|199.27.133.126]] 23:45, 9 November 2014 (UTC)

Now if someone comes up with a species with the formula C2H, we know what to call it. Maybe the ion C-≡CH? [[User:Promethean|Promethean]] ([[User talk:Promethean|talk]])

Talk:1442: Chemistry

2018-07-21T13:03:56Z

Redbelly98:

:"I" would have two in Randall's system as a sans-serif element, and four as a serif element. [[Special:Contributions/108.162.249.202|108.162.249.202]] 00:51, 4 November 2014 (UTC)

::The crossbar on "I" is actually not a serif, it's a part of the letter. Some popular sans-serif fonts that have a crossbar on "I" include Tahoma and Verdana. --[[User:Zagorath|Zagorath]] ([[User talk:Zagorath|talk]]) 13:24, 6 November 2014 (UTC)

What is the force that holds the two or three glyphs of an atom together called? How many bonds does the i's dot in Ti have? Ann how dangerous is comic sans cheMStry? [[Special:Contributions/141.101.104.39|141.101.104.39]] 06:52, 3 November 2014 (UTC)
:The letter i can only form one bond, as the other side is bonded with its dot. This is pretty basic chemestry![[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 08:20, 3 November 2014 (UTC)

::Ok. Let's look at something advanced. Fe. Os. {{w|Ununtrium|Uut}}. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 12:20, 3 November 2014 (UTC)
:::Sorry, but you mean {{w|Nh|Nh}}.
:::Ah, binary atoms. Now we're getting into some advanced stuff. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 13:03, 21 July 2018 (UTC)

Presumably hydrocarbon chains are still supported, albeit with hydrogens forming the backbone in a zip-like arrangement. You'd need phosphorous on the end, with a sans serif valence of 1. [[User:SleekWeasel|SleekWeasel]] ([[User talk:SleekWeasel|talk]]) 08:09, 3 November 2014 (UTC)

I believe he is making fun of incompetent chemistry students. I've seen some draw CH4 as C-H-H-H-H, i.e. according to some random and weird rules that have nothing to do with chemistry. - This comic proposes an equally nonsensical new paradigm. - Aeneas, 3rd November 2014, 10:01 CET

The crystalline structure is not like real-life crystalline carbon (neither diamond nor graphite). I removed that but someone should add a bit about it.[[Special:Contributions/141.101.99.39|141.101.99.39]] 11:48, 3 November 2014 (UTC)

Old English Krypton is particularly hazardous and may explode on contact. Dark matter is composed entirely of cursive script elements. [[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 12:01, 3 November 2014 (UTC)

"Mydrane" is a trade mark for a company that markets miscellaneous medical supplies. "Hydrane" is a process for coal gasification by hydrogenation, producing ideally mostly light hydrocarbon gases (mostly methane) and a minimum of liquid products. Not clear whether either is relevant here.[[User:Taibhse|Taibhse]] ([[User talk:Taibhse|talk]]) 12:29, 3 November 2014 (UTC)
::Hydrane is probally relevant. The real Mydrane almost certainly isn't. However, two other words come to mind; Mydriasis (the dialation of the pupil) and Myopia (near-sightedness), which could be what was happening to us Chemistry geeks when we first saw that. Also, the "compound" he claims to be Mydrane does somewhat resemble a pair of eyes or a pair of glasses. -[[Special:Contributions/173.245.48.137|173.245.48.137]] 17:42, 3 November 2014 (UTC)

Amount vs. number.
In the explanation: "the formation of bonds between elements often relies on the amount of valence electrons an element has." Should read, "the formation of bonds between elements often relies on the NUMBER of valence electrons an element has…"

-Avenue

It would be a very interesting exercise to invent a new set of symbols that WERE accurate using this system.[[User:Seebert|Seebert]] ([[User talk:Seebert|talk]]) 12:47, 3 November 2014 (UTC)

I don't know how relevant this is, but Hydrogen does exist in a metallic phase unde rhigh pressure and temperatures. It's liquid, though, and not crystalline. Also, C2H does also exist, but as a very unstable radical (basically an Acetylene Radical) which seems to be found in space. I have NO idea where Mydrane comes from. There are a lot of Hydrogencompounds ending with -ane (Borane, Silane, Methane), but no idea how this applies here. --[[Special:Contributions/108.162.231.188|108.162.231.188]] 14:21, 3 November 2014 (UTC)

Question: does N(itrogen) only have two bonds, or are those angles a different kind of bond (perhaps ionic vs covalent)? If so, tungsten (W) would be interesting, for a start... (In fact, going though the elements in my head, from the monoglyph elements it would be the most complex under this system. The diglyphs might give Meitnerium (Mt... but was that previously Une as a systematic triglyph?) or Thulium (Tm) some interesting qualities, depending on how the system actually works. Triglyphs are always intended to be replaced, so I think those are moot.
:Wow, is this a serious question or are you just trolling for conspiracy nuts? Of course the conspiracy theorists will tell you that before the invention of printing all the angles were curves, and they were compressed to tight angles to make blocks of movable type smaller and cheaper. Reputable experimental chemists, however, have reported that the bonds between two tungstens is stronger than between two uraniums and we can attribute the difference to the angles. It is fairly evident that right angles (e.g. at the upper left corners of "F" and "P") are essentially inert, and it appears that bond strength increases as the angle becomes more acute. Opposing angles (e.g. "K") seem to Kancel each other out. This is still a very contentious topic![[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 05:09, 4 November 2014 (UTC)

As for symbols that ''are'' accurate, there are a number of systems. Hydrogen is represented on the "gold discs" on the Voyager spacecraft (as a starting key to easily decode other information on there) but without a complete overhaul of a system, I'd imagine ''no'' advanced civilisation will have started out with "let's show it how it actually works" (accurately, and without elements such as phlogiston creeping in!) before giving arbitrary names. Electron-orbital diagrams probably work well, though, for some things. And something that reveals the (for example) pi-bonds works better in combinatory diagrams. I think. It's been a while since I did any serious chemistry.[[Special:Contributions/141.101.99.112|141.101.99.112]] 14:41, 3 November 2014 (UTC)

Oxygen has 6 valence electrons, not two. It forms two bonds because it's got room for two more. [[Special:Contributions/108.162.216.105|108.162.216.105]] 16:49, 3 November 2014 (UTC)

Could Mydrane be My Dr -ane where -ane is the common ending for an alkane. My Dr = CCH...which could be Cape Code Healthcare? ~~rbnm

I wonder how many bonds the capital letter "I" would have-- two or four? Seeing as how Randall writes it in this comic, I'm guessing two. Also, would it be possible for carbon to bond with itself ad infinitum in a chain which looks like the teeth on a zipper ("C", upside-down "C", and so on)? [[Special:Contributions/108.162.238.177|108.162.238.177]] 00:29, 4 November 2014 (UTC)
::Yes, Carbon can form very long chains, and also carbon rings (but only with an even number of carbon atoms).[[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 04:23, 4 November 2014 (UTC)
:::Assuming that you're talking Comic Universe, I don't see why it ''can't'' be an odd number of carbons in a ring. Even if we're forced to bend round a ...∩U∩U... sort of thing (only end-connected, between characters, not end-snuggled, IYSWIM) you can have one that bends round outside of the plane of the page similar to a mobius strip and could still 'zipper' in a closed circuit with an odd number.
:::IRL, of course, there's {{w|Cyclopentane}} and {{w|Cyclopropane}} (3- and 5-carbon rings), among others, and {{w|Cycloundecane}} (11-carbon saturated ring, with an irregular and aperiodic "wiggle" around the circuit) shows one way that the Fictional Cyclocarbon could (just with a greater angle of bond between successive carbons, and no hydrogens involved) work with odd numbers. [[Special:Contributions/141.101.99.112|141.101.99.112]] 07:56, 5 November 2014 (UTC)
::::My bad - I thought the comic universe was only two dimensional and it would have to be an even number. I need to upgrade my screen! [[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 02:51, 6 November 2014 (UTC)

Me is not the designation of two carbon chains. Methane is CH4. [[Special:Contributions/108.162.221.147|108.162.221.147]]rbnm

Any idea why the title text says "usually" more reactive? Do we have examples of where serifs could be less reactive than their sans serif counterparts?[[Special:Contributions/108.162.229.90|108.162.229.90]] 11:51, 9 November 2014 (UTC)
:Usually: For example, serif oxygen and sans-serif oxygen are both inert.[[Special:Contributions/199.27.133.126|199.27.133.126]] 23:45, 9 November 2014 (UTC)

Now if someone comes up with a species with the formula C2H, we know what to call it. Maybe the ion C-≡CH? [[User:Promethean|Promethean]] ([[User talk:Promethean|talk]])

User:Redbelly98

2018-07-21T02:08:14Z

Redbelly98: Created page with "Happy to help out with the physics comics, but can't help much with the programming ones."

Happy to help out with the physics comics, but can't help much with the programming ones.

Talk:2007: Brookhaven RHIC

2018-07-21T02:05:24Z

Redbelly98:

I think the correct explanation has to do with relativistic mass. Accelerated gold ions will have an increased (relativistic) mass. Therefore, the gold coming out of the accelerator will have a higher value than the input. You just have to sell by mass. --[[Special:Contributions/172.68.78.22|172.68.78.22]] 16:14, 15 June 2018 (UTC)
:The relativistic mass angle and calculation is interesting and amusing, but my impression of the intention is simply that--from a certain point of view--the entire accelerator is nothing but an extremely expensive and convoluted way to transport gold from Point A to Point B. An extremely small quantity of gold, yes--but that is part of the point.

:By adding the gold shop into the loop, he is simply pointing up the "gold delivery" aspect of the accelerator. Again, this isn't a really efficient gold delivery scheme but the very ridiculousness of it is the point. [[Special:Contributions/172.68.150.52|172.68.150.52]] 01:37, 24 June 2018 (UTC)

:Yeah, we need to calculate the increase of mass at 99.99, 99,999, 99,9999 percent of the speed of light. I didn't check but I'm curious how many 9s we need to reach the mass of the Earth for a single gold nuclei. Nevertheless the speed is zero again when you collect them, or you have to move at the same speed, but than you can't measure that increase because you're in the same reference -- and back on Earth your own mass would have grown out far beyond the mass of our Milky Way. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 18:11, 15 June 2018 (UTC)
::Mass is an invariant quantity. What is increased is the total energy, E=sqrt(p^2+m^2). As previously mentioned, when they are delivered they would have to be measured in a comoving frame in which case no increase in "mass" would be noticed.-- [[Special:Contributions/162.158.146.70|162.158.146.70]] 20:46, 15 June 2018 (UTC)
:::Sorry, you know what ''invariant'' means in physics? And you can't sum p and m (simply squared both) by using the Einstein conventions c=1, it's in fact E2=m4+p2 -- I fear most people still don't understand. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 22:02, 15 June 2018 (UTC)
::::Comes across a bit condescending considering m^2c^4=(mc^2)^2, not (mc)^4. The mass is the rest mass, which is always the same, considering it is measured at rest. It is a misnomer to call the total energy the mass. The physics you're describing is correct, I just take issue with the wording. I'm sorry if I didn't make myself clear enough. --[[Special:Contributions/162.158.146.70|162.158.146.70]] 22:29, 15 June 2018 (UTC)

: I don't think the relativistic mass is at all relevant. Presumably the gold would have to be brought to rest to be sold anyway, and I see nothing in the comic indicating that the gold would be sold based on this higher mass value. Also, these days physicists typically use "mass" to refer to what has historically been referred to as "rest mass", and have largely abandoned the idea that the mass of a particle increases with speed. [[User:Redbelly98|Redbelly98]] ([[User talk:Redbelly98|talk]]) 02:02, 21 July 2018 (UTC)

Isn't a typical cash-for-gold store where you would take your gold and walk out with cash for your gold? It sounds like Randall's proposal is gold-for-cash stores instead. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 19:03, 15 June 2018 (UTC)
: It makes sense if his proposal is to sell the gold to the stores, where he would just need the stores to agree to buy the high speed particles. I thought he was suggesting consumers would buy the excess gold particles in the stores, but that's probably not what he meant. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 19:14, 15 June 2018 (UTC)

My first thought here was that he was proposing a gold-ion particle beam weapon. [[Special:Contributions/162.158.106.240|162.158.106.240]] 20:10, 15 June 2018 (UTC)

The destination in the middle appears to be the actual location of a cash for gold shop [https://www.google.com/maps/place/Cash+for+Gold/@40.8009993,-72.8694024,13z/data=!4m8!1m2!2m1!1scash+for+gold!3m4!1s0x0:0xd50dc29c3fa0b22f!8m2!3d40.8023428!4d-72.8620523?hl=en according to google maps]. The other ones don't seem to exist though.
[[Special:Contributions/162.158.88.176|162.158.88.176]] 01:43, 16 June 2018 (UTC)
: Actually all three locations exists in real life. From left to right (north to south): New York Gold Center, Cash for Gold, and Gold Traders Inc. --[[Special:Contributions/162.158.134.142|162.158.134.142]] 07:03, 16 June 2018 (UTC)

If anyone wants to calculate the revenue of the project: particles move at 0.99995c and according to one source they use less than 1/1000000 Gramm of gold in 20years(idk they could probably use more if they wanted). Current gold price is about 1280€ per kg
19:22, 16 June 2018 (UTC)some dude that forgot highschool physics19:22, 16 June 2018 (UTC)~21.10:16 June 2018 (UTC) {{unsigned ip|172.68.51.202}}

I suppose that RHIC will generate gold nuclei only, not providing electrons to build-up complete atoms. Thus the objection is "I won't buy gold without electrons, because I will find highly positive electric charges from protons-only projectiles". {{unsigned ip|172.68.10.184}}

My thought was, that Randall proposes to use existing gold particles in shops for the collision, instead of using gold provided by the research program. Thus potentially saving miniscule amounts of gold. - MN (anonymous) {{unsigned ip|141.101.76.82}}
:When I read this, it felt possible to me, but then I realized: calling that spot "Diverter" indicates the flow is the other way. Then I noticed the grey arrows ALSO indicating the flow is the other way. [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:16, 19 June 2018 (UTC)

The comic proper was pushing the envelope of weirdness, but the pun in the title text is golden. [[Special:Contributions/172.68.246.158|172.68.246.158]] 12:29, 18 June 2018 (UTC)

Ok im gonna atempt to calculate the revenue. At the start of the RHIC is EBIS Electron Beem Ion Scource. Acourding to to (https://de.wikipedia.org/wiki/Electron_Beam_Ion_Trap) it can contain anything from a few thousands to many millions of Particles. Im goingt to assume 1 Million particles at the time for gold. The paricles in Ebis are charged for 30 milliseconds (https://www.bnl.gov/rhic/video.php?v=156).Im therefore going to assume a possible firerate of 50 milliseconds = 0,05s. This amounts to 630720000 poosible fireings per year. and therfore roughtly 630720000*10^6=63072*10^10 paricles per year. This is around 1.05*10^(-9)Mol. Sice one Mol of gold is 197 gramm this is about 2*10^(-7)gramm= 20 mikrogramms. The paricles travel at 0.99995c. I'm affaid of the last step of the calc so im gonna let someone else do it. The Current gold price is at 36493€ per Kg (Source Google).13:24, 18 June 2018 (UTC)me mathstudent13:24, 18 June 2018 (UTC) {{unsigned ip|172.68.51.166}}
:Ok I overcame my fear asked Wolfram alpha and it said that at 0.99995c 20 mikorgramm equal around 600kg,ok 600*36493=21835800€13:50, 18 June 2018 (UTC)~me a mathsstudent13:50, 18 June 2018 (UTC)~ {{unsigned ip|172.68.51.64}}

All of this is just fine - so long as the gold stores don't stop the gold moving in order to weigh it. Honestly, I think he'd be better off using Heisenburg's uncertainty principle - if they try to weigh the gold very accurately, then because they won't be able to determine its precise position, he can sell it to all three stores at once. {{unsigned ip|172.69.69.34}}

Somehow, coming here and finding out this is a real map, and those are real stores, makes this like 1,000 times funnier to me, LOL! Maybe Randall noticed the alignment, how these three stores are roughly in a line, and he got inspired. [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:16, 19 June 2018 (UTC)