explain xkcd - User contributions [en]

1935: 2018

2017-12-31T08:40:43Z

PeR: /* Trivia */ only the last two digits of a number are needed...

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==

In this [[:Category:New Year|New Year comic]], [[Megan]] wonders if 2018 will be a {{w|Leap year|leap year}}. [[Cueball]] thinks 2018 will not be a leap year, and Megan responds that she "doubts anyone knows at this point." This appears to be a jab at the complexity of the leap year system. As Cueball says, leap years occur every four years (though there are a few exceptions), adding an extra day to account for the fact that Earth takes a bit longer than 365 days to orbit the Sun. Therefore, most years that are a multiple of four are leap years. As Megan says, this is easy for odd-numbered years, since no odd numbers are divisible by four. However, for even-numbered years, it isn't always obvious.

The last panel expresses a misunderstanding of modern {{w|Cryptography|cryptography}}, which relies on the fact that it is difficult to factorize large numbers. Megan is applying this concept to the year, claiming that it is hard to determine whether or not 2018 is a multiple of four and hence is a leap year. In reality, factorization is not needed here, since we already know the factor, which is four. Megan states that if it were possible to factor large numbers with a calculator, modern cryptography would collapse. While true, it is only true for truly large numbers (hundreds of digits), and no factorization is needed in this case.

At the end of the strip, Megan hopes the answer can be {{w|Brute-force attack|brute-forced}} by February. Brute force is a method of breaking cryptography by trying every possible option until one works. This is a misdirection upon misdirection, in that even if we needed to factorize 2018 (which we don't), the simplest brute forcing algorithm would only need to try 43 numbers - from 2 to square root of 2018 (44). In cryptography, the algorithms use numbers much, much bigger than 2018 -- on the order of hundreds (or even thousands) of digits.

The title text refers to calculating which day of the week {{w|Christmas}} (in western countries) will fall on. Given that any calendar will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 were not leap years, but the years 1600 and 2000 were.

*Since 100 is divisible by 4, only the last two digits of a number are needed to determine if that number is divisible by 4. So to determine if 2018 is divisible by 4, we only need to check whether 18 is divisible by 4, which is easy.

*2018 is not divisible by 4, so the year is not a leap year. 2016 and 2020 are leap years. Assuming your calendar is Gregorian! A year is roughly 365.2422 days long. (Actually, also the case if it is 2018 on the old Julian calendar. The century year rules for leap years are different on the Gregorian calendar from the Julian, but the non-century year rules are the same).

*{{w|Eastern Christian Churches}} celebrate Christmas also on December 25 but of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar.

*This is the third year in a row with New Year's comics with only the year used as the title, before that there were two more comics with such titles, but those two (and thus the first three) were only released in the even years: [[998: 2012]] in 2012, [[1311: 2014]] in 2014, [[1624: 2016]] in 2016 and [[1779: 2017]] in 2017.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]

1162: Log Scale

2017-09-26T14:11:47Z

PeR: /* Explanation */

{{comic
| number = 1162
| date = January 18, 2013
| title = Log Scale
| image = log scale.png
| titletext = Knuth Paper-Stack Notation: Write down the number on pages. Stack them. If the stack is too tall to fit in the room, write down the number of pages it would take to write down the number. THAT number won't fit in the room? Repeat. When a stack fits, write the number of iterations on a card. Pin it to the stack.
}}

==Explanation==
Uranium is stated to have 76 million MJ/kg, while the next highest material shown on the graph (gasoline) has 46 MJ/kg. Thus the uranium graph should be taller by a factor of 76,000,000/46 = 1.652 million. So, if the gasoline graph were 9mm in height, the uranium graph should be a bit more than 14.868 million mm tall, or nearly 15 km (9.2 miles) tall. Thus the need to fold the paper.

It should be noted that the method of extracting energy from the first 4 materials ({{w|combustion}}) is completely different from the method used with uranium ({{w|nuclear fission}}). If the technology existed to use {{w|nuclear fusion}}, then the first 4 materials would yield a higher energy density than uranium.

A {{w|Logarithmic scale|log scale}} is a way of showing largely unequal data sizes in a comprehensible way, using an exponential function between each notch on the y axis of a graph. So for example the first on a Y axis of a graph using a log-10-scale would be 1, then 10, then 100 and 1000 for the fourth. A {{w|logarithm|log/logarithmic function}} is the {{w|inverse function|inverse}} of a corresponding {{w|Exponential growth|exponential function}}. A log-scale version of the chart in the comic would look like this:

[[File:Log_Chart_1162.png]]

The log scale can also be abused to make data look more uniform than it really is. On a log scale the energy density of uranium looks larger than that of the other materials, but not dramatically so. The joke is that if one wanted to make their point "properly," they would go ahead and use ridiculous amounts of paper to show the difference between bars using a linear scale; this method would focus more on the shock factor of the differences in question, and less on actual communication/representation of data. Cueball seems to be passionate about the MJ/kg of uranium, so he would rather demonstrate the grandeur of the data than use a more efficient scale.

See {{w|Logarithmic scale#Common usages|these examples}} for well known day-to-day measurements which are measured on a log-scale.

The Science tip is quite possibly related to the protip comics.

The title text mentions computer scientist {{w|Donald Knuth}}; the fictional notation is a parody of {{w|Knuth's up-arrow notation}}. Using paper thickness as the basis for a log scale would probably give the exponential function a very large base. However, it can be noted that Knuth's up-arrow notation can handle numbers far, far larger than this paper stack notation; for example the number 3↑↑↑3, very compact in up-arrow notation, would require a number of iterations pinned to the stack on the order of several trillion. 3↑↑↑↑3 would require a number of iterations that is not only too large to write down, but attempting to write that number using the same paper stack notation would require printing off a ''second'' stack of several trillion iterations just to hold the ''number'' pinned to the first stack.

It should be noted that Randall has used log scales in past comics.

==Transcript==
:[A bar chart showing fuel energy density of different materials in megajoules/kg.]
:Sugar: 19, Coal: 24, Fat: 39, Gasoline: 46, Uranium 76,000,000
:[The uranium bar on the chart goes off the page onto a huge strip of paper folded up into a stack slightly taller than Cueball.]
:Science Tip: Log scales are for quitters who can't find enough paper to make their point ''properly''.

==Trivia==
This comic was seen in the [[What If?]] book.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Bar chart]]
[[Category:Physics]]
[[Category:Math]]

1764: XKCDE

2016-11-25T13:58:57Z

PeR: /* Explanation */ CDE = Collaborative development environment

{{comic
| number = 1764
| date = November 25, 2016
| title = XKCDE
| image = xkcde.png
| titletext = 4. They unplug the root machine but the thousands of leaf VMs scatter in the wind and start spinning up new instances wherever they land
}}

==Explanation==
{{incomplete|Barebones and possibly inaccurate.}}

Randall has created a theoretical software environment named XKCDE (a pun on XKCD + CDE = Collaborative Development Environment), which relies on the user creating a series of nested virtual machines inside each other, which would likely cause extreme strain on the resources of the machine running it.

He suggests continuing that process until the user gets fired, which will very likely lead to the environment not having many active users, a very counter-productive approach to software development.

A software environment which disables both the machine it runs on and the user that runs it could be thought of as a useless machine.

==Transcript==
:[Some text is displayed above a box, listing some steps.]
:Installing the xkcd development environment

:1. Spin up a VM
:2. Spin up a VM inside that VM
:3. Continue spinning up nested VMs and containers until you get fired

{{comic discussion}}

See also https://www.pcsteps.com/508-nested-virtualization/ where someone actually tried this and got four layers deep.

1754: Tornado Safety Tips

2016-11-02T15:07:05Z

PeR: /* Explanation */ The joke is that...

{{comic
| number = 1754
| date = November 2, 2016
| title = Tornado Safety Tips
| image = tornado_safety_tips.png
| titletext = It's a myth that you can never cross mountains safely, but be sure you understand how the climatic situation there will affect your parent thunderstorm.
}}
==Explanation==
There is a Public Safety Advisory (PSA) poster with safety tips with regards to {{w|tornadoes}}. At first glance, you would think it contains information about how to stay safe in tornadoes, but since [[Black Hat]] has made the poster you should take a better look.

It turns out that is is actually written for tornadoes themselves on how to stay safe, i.e. continue to exist.
The joke is that just as, for example, a "climber safety" poster is directed at climbers, the "tornado safety" poster is directed at tornadoes.

It is thus in no way helpful for people who actually live in an area that experience tornadoes. It is not possible to follow most of the guidelines, as they are intended for tornadoes. But the advice a human could follow would only take you towards places which can sustain tornadoes.

The title text simply adds more tornado advice.

===Table of tips===
{{incomplete|Fill out explanations}}
{|class="wikitable"
! Tornado Safety Tips
! Explanation
|-
|Avoid low-lying cool air ||
|-
|Keep your downdrafts and updrafts from mixing ||
|-
|Seek out warm and humid surface air layers ||
|-
|Don't let rain-cooled air choke off your circulation ||
|-
|Avoid letting your supercell merge with a squall line ||
|-
|'''Title text''': It's a myth that you can never cross mountains safely, but be sure you understand how the climatic situation there will affect your parent thunderstorm. || Tornadoes have difficulty crossing mountains, but the title text assures this is a problem to the storm, not the tornado.
|}

==Transcript==
:[Beneath a large caption there are two pictures above each other to the left and a bullet list with five points to the right of the pictures. The top picture shows a black tornado beneath a white cloud. It is wreaking something on the ground. To the right of the debris is a house and to the left some trees. The picture below shows Black Hat from the waist and up.]
:<big>'''Tornado Safety Tips'''</big>
:* Avoid low-lying cool air
:* Keep your downdrafts and updrafts from mixing
:* Seek out warm and humid surface air layers
:* Don't let rain-cooled air choke off your circulation
:* Avoid letting your supercell merge with a squall line

{{comic discussion}}

[[Category:Comics featuring Black Hat]]
[[Category:Tornadoes]]

1132: Frequentists vs. Bayesians

2016-03-16T14:41:47Z

PeR: /* Trivia */ The Sun will never explode as a supernova, because it does not have enough mass.

{{comic
| number = 1132
| date = November 9, 2012
| title = Frequentists vs. Bayesians
| image = frequentists_vs_bayesians.png
| titletext = 'Detector! What would the Bayesian statistician say if I asked him whether the--' [roll] 'I AM A NEUTRINO DETECTOR, NOT A LABYRINTH GUARD. SERIOUSLY, DID YOUR BRAIN FALL OUT?' [roll] '... yes.'}}

==Explanation==
This comic is a joke about jumping to conclusions based on a simplistic understanding of probability. The "{{w|base rate fallacy}}" is a mistake where an unlikely explanation is dismissed, even though the alternative is even less likely. In the comic, a device tests for the (highly unlikely) event that the sun has exploded. A degree of random error is introduced, by rolling two {{w|dice}} and lying if the result is double sixes. Double sixes are unlikely (1 in 36, or about 3% likely), so the statistician on the left dismisses it. The statistician on the right has (we assume) correctly reasoned that the sun exploding is ''far more'' unlikely, and so is willing to stake money on his interpretation.

The labels given to the two statisticians, in their panels and in the comic's title, are not particularly fair or accurate, a fact which [[Randall]] has acknowledged:<ref name="munroe-on-gelman">[http://web.archive.org/web/20130117080920/http://andrewgelman.com/2012/11/16808/#comment-109366 Comment by Randall Munroe] to "I don’t like this cartoon", blog post by Andrew Gelman in ''Statistical Modeling, Causal Inference, and Social Science''. Archived Jan 17 2013 by the Wayback Machine.</ref>
<blockquote>I seem to have stepped on a hornet’s nest, though, by adding “Frequentist” and “Bayesian” titles to the panels. This came as a surprise to me, in part because I actually added them as an afterthought, along with the final punchline. … The truth is, I genuinely didn’t realize Frequentists and Bayesians were actual camps of people—all of whom are now emailing me. I thought they were loosely-applied labels—perhaps just labels appropriated by the books I had happened to read recently—for the standard textbook approach we learned in science class versus an approach which more carefully incorporates the ideas of prior probabilities.</blockquote>

The "frequentist" statistician is (mis)applying the common standard of "{{w|P-value|p}}<0.05". In a scientific study, a result is presumed to provide strong evidence if there is less than a 5% chance that the result was merely random. (More formally, this probability is defined in terms of the {{w|null hypothesis}}, or a default position that the observations are unrelated. The null hypothesis was also referenced in [[892: Null Hypothesis]].)

Since the likelihood of rolling double sixes is below this 5% threshold, the "frequentist" decides (by this rule of thumb) to accept the detector's output as correct. The "Bayesian" statistician has, instead, applied at least a small measure of probabilistic reasoning ({{w|Bayesian inference}}) to determine that the unlikeliness of the detector lying is greatly outweighed by the unlikeliness of the sun exploding. Therefore, he concludes that the sun has ''not'' exploded and the detector is lying.

The line, "Bet you $50 it hasn't", is a reference to the approach of a leading bayesian scholar, {{w|Bruno de Finetti}}, who made extensive use of bets in his examples and thought experiments. See {{w|Coherence (philosophical gambling strategy)}} for more information on his work. In this case, however, the bet is also a joke because we would all be dead if the sun exploded, therefore money would be worthless. This is a tongue-in-cheek reference to the absurdity of the premise, and a reference to the need to consider things in context.

The title text refers to a classic series of logic puzzles known as {{w|Knights and Knaves#Fork in the road|Knights and Knaves}}, where there are two guards in front of two exit doors, one of which is real and the other leads to death. One guard is a liar and the other tells the truth. The visitor doesn't know which is which, and is allowed to ask one question to one guard. The solution is to ask either guard what the other one would say is the real exit, then choose the opposite. Two such guards were featured in the 1986 Jim Henson movie ''[[246|Labyrinth]]'', hence the mention of "A LABYRINTH GUARD" here.

===Mathematical and scientific details===
As mentioned, this is an instance of the {{w|base rate fallacy}}. If we treat the "truth or lie" setup as simply modelling an inaccurate test, then it is also specifically an illustration of the {{w|false positive paradox}}: A test that is rarely wrong, but which tests for an event that is even rarer, will be more often wrong than right when it says that the event has occurred.

The test in this case is a neutrino detector. It relies on the fact that neutrinos can pass through the earth, so a neutrino detector would detect neutrinos from the sun at all times, day and night. The detector is stated to give false results ("lie") 1/36th of the time.

There is no record of any star ever spontaneously exploding—they always show signs of deterioration long before their explosion—so the probability is near zero. For the sake of a number, though, consider that the sun's estimated lifespan is 10 billion years. Let's say the test is run every hour, twelve hours a day (at night time). This gives us a probability of the Sun exploding at one in 4.38×1013. Assuming this detector is otherwise reliable, when the detector reports a solar explosion, there are two possibilities:
# The sun '''has''' exploded (one in 4.38×1013) and the detector '''is''' telling the truth (35 in 36). This event has a total probability of about 1/(4.38×1013) × 35/36 or about one in 4.50×1013.
# The sun '''hasn't''' exploded (4.38×1013 − 1 in 4.38×1013) and the detector '''is not''' telling the truth (1 in 36). This event has a total probability of about (4.38×1013 − 1) / 4.38×1013 × 1/36 or about one in 36.

Clearly the sun exploding is not the most likely option.

===Presidential election predictions===
[[File:Nate Silver Tweet.png|.@JoeNBC: If you think it's a toss-up, let's bet. If Obama wins, you donate $1,000 to the American Red Cross. If Romney wins, I do. Deal?|right]]

This comic may be about the accuracy of presidential election predictions that used statistical models, such as Nate Silver's ''538'' and Professor Sam Wang's ''PEC''. The bet may refer to a well-publicized bet that Nate Silver tried to make with Joe Scarborough regarding the outcome of the election (see tweet on the right).

==Trivia==
* The Sun will never explode as a supernova, because it does not have enough mass.
*In the same blog comment as cited above<ref name="munroe-on-gelman"/>, Randall explains that he chose the "sun exploding" scenario as a more clearly absurd example than those usually used:
<blockquote>…I realized that in the common examples used to illustrate this sort of error, like the cancer screening/drug test false positive ones, the correct result is surprising or unintuitive. So I came up with the sun-explosion example, to illustrate a case where naïve application of that significance test can give a result that’s obviously nonsense.</blockquote>
*"Bayesian" statistics is named for Thomas Bayes, who studied conditional probability — the likelihood that one event is true when given information about some other related event. From {{w|Bayes Theorem|Wikipedia}}: "Bayesian interpretation expresses how a subjective degree of belief should rationally change to account for evidence".
* The "frequentist" says that 1/36 = 0.027. It's actually 0.02777…, which should round to 0.028.
* Using neutrino detectors to get an advance warning of a supernova is possible, and the {{w|Supernova Early Warning System}} does just this. The neutrinos arrive ahead of the photons, because they can escape from the core of the star before the supernova explosion reaches the mantle.

==Transcript==
:Did the sun just explode? (It's night, so we're not sure)

:[Two statisticians stand alongside an adorable little computer that is suspiciously similar to K-9 that speaks in Westminster typeface.]
:Frequentist Statistician: This neutrino detector measures whether the sun has gone nova.
:Bayesian Statistician: Then, it rolls two dice. If they both come up as six, it lies to us. Otherwise, it tells the truth.
:Frequentist Statistician: Let's try. [to the detector] Detector! Has the sun gone nova?
:Detector: ''roll'' YES.

:Frequentist Statistician:
:Frequentist Statistician: The probability of this result happening by chance is 1/36=0.027. Since p<0.05, I conclude that the sun has exploded.

:Bayesian Statistician:
:Bayesian Statistician: Bet you $50 it hasn't.

==References==
<references/>

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Math]]
[[Category:Statistics]]
[[Category:Physics]]

1132: Frequentists vs. Bayesians

2016-03-16T14:41:13Z

PeR: /* Trivia */

{{comic
| number = 1132
| date = November 9, 2012
| title = Frequentists vs. Bayesians
| image = frequentists_vs_bayesians.png
| titletext = 'Detector! What would the Bayesian statistician say if I asked him whether the--' [roll] 'I AM A NEUTRINO DETECTOR, NOT A LABYRINTH GUARD. SERIOUSLY, DID YOUR BRAIN FALL OUT?' [roll] '... yes.'}}

==Explanation==
This comic is a joke about jumping to conclusions based on a simplistic understanding of probability. The "{{w|base rate fallacy}}" is a mistake where an unlikely explanation is dismissed, even though the alternative is even less likely. In the comic, a device tests for the (highly unlikely) event that the sun has exploded. A degree of random error is introduced, by rolling two {{w|dice}} and lying if the result is double sixes. Double sixes are unlikely (1 in 36, or about 3% likely), so the statistician on the left dismisses it. The statistician on the right has (we assume) correctly reasoned that the sun exploding is ''far more'' unlikely, and so is willing to stake money on his interpretation.

The labels given to the two statisticians, in their panels and in the comic's title, are not particularly fair or accurate, a fact which [[Randall]] has acknowledged:<ref name="munroe-on-gelman">[http://web.archive.org/web/20130117080920/http://andrewgelman.com/2012/11/16808/#comment-109366 Comment by Randall Munroe] to "I don’t like this cartoon", blog post by Andrew Gelman in ''Statistical Modeling, Causal Inference, and Social Science''. Archived Jan 17 2013 by the Wayback Machine.</ref>
<blockquote>I seem to have stepped on a hornet’s nest, though, by adding “Frequentist” and “Bayesian” titles to the panels. This came as a surprise to me, in part because I actually added them as an afterthought, along with the final punchline. … The truth is, I genuinely didn’t realize Frequentists and Bayesians were actual camps of people—all of whom are now emailing me. I thought they were loosely-applied labels—perhaps just labels appropriated by the books I had happened to read recently—for the standard textbook approach we learned in science class versus an approach which more carefully incorporates the ideas of prior probabilities.</blockquote>

The "frequentist" statistician is (mis)applying the common standard of "{{w|P-value|p}}<0.05". In a scientific study, a result is presumed to provide strong evidence if there is less than a 5% chance that the result was merely random. (More formally, this probability is defined in terms of the {{w|null hypothesis}}, or a default position that the observations are unrelated. The null hypothesis was also referenced in [[892: Null Hypothesis]].)

Since the likelihood of rolling double sixes is below this 5% threshold, the "frequentist" decides (by this rule of thumb) to accept the detector's output as correct. The "Bayesian" statistician has, instead, applied at least a small measure of probabilistic reasoning ({{w|Bayesian inference}}) to determine that the unlikeliness of the detector lying is greatly outweighed by the unlikeliness of the sun exploding. Therefore, he concludes that the sun has ''not'' exploded and the detector is lying.

The line, "Bet you $50 it hasn't", is a reference to the approach of a leading bayesian scholar, {{w|Bruno de Finetti}}, who made extensive use of bets in his examples and thought experiments. See {{w|Coherence (philosophical gambling strategy)}} for more information on his work. In this case, however, the bet is also a joke because we would all be dead if the sun exploded, therefore money would be worthless. This is a tongue-in-cheek reference to the absurdity of the premise, and a reference to the need to consider things in context.

The title text refers to a classic series of logic puzzles known as {{w|Knights and Knaves#Fork in the road|Knights and Knaves}}, where there are two guards in front of two exit doors, one of which is real and the other leads to death. One guard is a liar and the other tells the truth. The visitor doesn't know which is which, and is allowed to ask one question to one guard. The solution is to ask either guard what the other one would say is the real exit, then choose the opposite. Two such guards were featured in the 1986 Jim Henson movie ''[[246|Labyrinth]]'', hence the mention of "A LABYRINTH GUARD" here.

===Mathematical and scientific details===
As mentioned, this is an instance of the {{w|base rate fallacy}}. If we treat the "truth or lie" setup as simply modelling an inaccurate test, then it is also specifically an illustration of the {{w|false positive paradox}}: A test that is rarely wrong, but which tests for an event that is even rarer, will be more often wrong than right when it says that the event has occurred.

The test in this case is a neutrino detector. It relies on the fact that neutrinos can pass through the earth, so a neutrino detector would detect neutrinos from the sun at all times, day and night. The detector is stated to give false results ("lie") 1/36th of the time.

There is no record of any star ever spontaneously exploding—they always show signs of deterioration long before their explosion—so the probability is near zero. For the sake of a number, though, consider that the sun's estimated lifespan is 10 billion years. Let's say the test is run every hour, twelve hours a day (at night time). This gives us a probability of the Sun exploding at one in 4.38×1013. Assuming this detector is otherwise reliable, when the detector reports a solar explosion, there are two possibilities:
# The sun '''has''' exploded (one in 4.38×1013) and the detector '''is''' telling the truth (35 in 36). This event has a total probability of about 1/(4.38×1013) × 35/36 or about one in 4.50×1013.
# The sun '''hasn't''' exploded (4.38×1013 − 1 in 4.38×1013) and the detector '''is not''' telling the truth (1 in 36). This event has a total probability of about (4.38×1013 − 1) / 4.38×1013 × 1/36 or about one in 36.

Clearly the sun exploding is not the most likely option.

===Presidential election predictions===
[[File:Nate Silver Tweet.png|.@JoeNBC: If you think it's a toss-up, let's bet. If Obama wins, you donate $1,000 to the American Red Cross. If Romney wins, I do. Deal?|right]]

This comic may be about the accuracy of presidential election predictions that used statistical models, such as Nate Silver's ''538'' and Professor Sam Wang's ''PEC''. The bet may refer to a well-publicized bet that Nate Silver tried to make with Joe Scarborough regarding the outcome of the election (see tweet on the right).

==Trivia==
*In the same blog comment as cited above<ref name="munroe-on-gelman"/>, Randall explains that he chose the "sun exploding" scenario as a more clearly absurd example than those usually used:
<blockquote>…I realized that in the common examples used to illustrate this sort of error, like the cancer screening/drug test false positive ones, the correct result is surprising or unintuitive. So I came up with the sun-explosion example, to illustrate a case where naïve application of that significance test can give a result that’s obviously nonsense.</blockquote>
*"Bayesian" statistics is named for Thomas Bayes, who studied conditional probability — the likelihood that one event is true when given information about some other related event. From {{w|Bayes Theorem|Wikipedia}}: "Bayesian interpretation expresses how a subjective degree of belief should rationally change to account for evidence".
* The "frequentist" says that 1/36 = 0.027. It's actually 0.02777…, which should round to 0.028.
* Using neutrino detectors to get an advance warning of a supernova is possible, and the {{w|Supernova Early Warning System}} does just this. The neutrinos arrive ahead of the photons, because they can escape from the core of the star before the supernova explosion reaches the mantle.

==Transcript==
:Did the sun just explode? (It's night, so we're not sure)

:[Two statisticians stand alongside an adorable little computer that is suspiciously similar to K-9 that speaks in Westminster typeface.]
:Frequentist Statistician: This neutrino detector measures whether the sun has gone nova.
:Bayesian Statistician: Then, it rolls two dice. If they both come up as six, it lies to us. Otherwise, it tells the truth.
:Frequentist Statistician: Let's try. [to the detector] Detector! Has the sun gone nova?
:Detector: ''roll'' YES.

:Frequentist Statistician:
:Frequentist Statistician: The probability of this result happening by chance is 1/36=0.027. Since p<0.05, I conclude that the sun has exploded.

:Bayesian Statistician:
:Bayesian Statistician: Bet you $50 it hasn't.

==References==
<references/>

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Math]]
[[Category:Statistics]]
[[Category:Physics]]

1132: Frequentists vs. Bayesians

2016-03-16T14:40:31Z

PeR: /* Trivia */ Neutrino supernova detectors.

{{comic
| number = 1132
| date = November 9, 2012
| title = Frequentists vs. Bayesians
| image = frequentists_vs_bayesians.png
| titletext = 'Detector! What would the Bayesian statistician say if I asked him whether the--' [roll] 'I AM A NEUTRINO DETECTOR, NOT A LABYRINTH GUARD. SERIOUSLY, DID YOUR BRAIN FALL OUT?' [roll] '... yes.'}}

==Explanation==
This comic is a joke about jumping to conclusions based on a simplistic understanding of probability. The "{{w|base rate fallacy}}" is a mistake where an unlikely explanation is dismissed, even though the alternative is even less likely. In the comic, a device tests for the (highly unlikely) event that the sun has exploded. A degree of random error is introduced, by rolling two {{w|dice}} and lying if the result is double sixes. Double sixes are unlikely (1 in 36, or about 3% likely), so the statistician on the left dismisses it. The statistician on the right has (we assume) correctly reasoned that the sun exploding is ''far more'' unlikely, and so is willing to stake money on his interpretation.

The labels given to the two statisticians, in their panels and in the comic's title, are not particularly fair or accurate, a fact which [[Randall]] has acknowledged:<ref name="munroe-on-gelman">[http://web.archive.org/web/20130117080920/http://andrewgelman.com/2012/11/16808/#comment-109366 Comment by Randall Munroe] to "I don’t like this cartoon", blog post by Andrew Gelman in ''Statistical Modeling, Causal Inference, and Social Science''. Archived Jan 17 2013 by the Wayback Machine.</ref>
<blockquote>I seem to have stepped on a hornet’s nest, though, by adding “Frequentist” and “Bayesian” titles to the panels. This came as a surprise to me, in part because I actually added them as an afterthought, along with the final punchline. … The truth is, I genuinely didn’t realize Frequentists and Bayesians were actual camps of people—all of whom are now emailing me. I thought they were loosely-applied labels—perhaps just labels appropriated by the books I had happened to read recently—for the standard textbook approach we learned in science class versus an approach which more carefully incorporates the ideas of prior probabilities.</blockquote>

The "frequentist" statistician is (mis)applying the common standard of "{{w|P-value|p}}<0.05". In a scientific study, a result is presumed to provide strong evidence if there is less than a 5% chance that the result was merely random. (More formally, this probability is defined in terms of the {{w|null hypothesis}}, or a default position that the observations are unrelated. The null hypothesis was also referenced in [[892: Null Hypothesis]].)

Since the likelihood of rolling double sixes is below this 5% threshold, the "frequentist" decides (by this rule of thumb) to accept the detector's output as correct. The "Bayesian" statistician has, instead, applied at least a small measure of probabilistic reasoning ({{w|Bayesian inference}}) to determine that the unlikeliness of the detector lying is greatly outweighed by the unlikeliness of the sun exploding. Therefore, he concludes that the sun has ''not'' exploded and the detector is lying.

The line, "Bet you $50 it hasn't", is a reference to the approach of a leading bayesian scholar, {{w|Bruno de Finetti}}, who made extensive use of bets in his examples and thought experiments. See {{w|Coherence (philosophical gambling strategy)}} for more information on his work. In this case, however, the bet is also a joke because we would all be dead if the sun exploded, therefore money would be worthless. This is a tongue-in-cheek reference to the absurdity of the premise, and a reference to the need to consider things in context.

The title text refers to a classic series of logic puzzles known as {{w|Knights and Knaves#Fork in the road|Knights and Knaves}}, where there are two guards in front of two exit doors, one of which is real and the other leads to death. One guard is a liar and the other tells the truth. The visitor doesn't know which is which, and is allowed to ask one question to one guard. The solution is to ask either guard what the other one would say is the real exit, then choose the opposite. Two such guards were featured in the 1986 Jim Henson movie ''[[246|Labyrinth]]'', hence the mention of "A LABYRINTH GUARD" here.

===Mathematical and scientific details===
As mentioned, this is an instance of the {{w|base rate fallacy}}. If we treat the "truth or lie" setup as simply modelling an inaccurate test, then it is also specifically an illustration of the {{w|false positive paradox}}: A test that is rarely wrong, but which tests for an event that is even rarer, will be more often wrong than right when it says that the event has occurred.

The test in this case is a neutrino detector. It relies on the fact that neutrinos can pass through the earth, so a neutrino detector would detect neutrinos from the sun at all times, day and night. The detector is stated to give false results ("lie") 1/36th of the time.

There is no record of any star ever spontaneously exploding—they always show signs of deterioration long before their explosion—so the probability is near zero. For the sake of a number, though, consider that the sun's estimated lifespan is 10 billion years. Let's say the test is run every hour, twelve hours a day (at night time). This gives us a probability of the Sun exploding at one in 4.38×1013. Assuming this detector is otherwise reliable, when the detector reports a solar explosion, there are two possibilities:
# The sun '''has''' exploded (one in 4.38×1013) and the detector '''is''' telling the truth (35 in 36). This event has a total probability of about 1/(4.38×1013) × 35/36 or about one in 4.50×1013.
# The sun '''hasn't''' exploded (4.38×1013 − 1 in 4.38×1013) and the detector '''is not''' telling the truth (1 in 36). This event has a total probability of about (4.38×1013 − 1) / 4.38×1013 × 1/36 or about one in 36.

Clearly the sun exploding is not the most likely option.

===Presidential election predictions===
[[File:Nate Silver Tweet.png|.@JoeNBC: If you think it's a toss-up, let's bet. If Obama wins, you donate $1,000 to the American Red Cross. If Romney wins, I do. Deal?|right]]

This comic may be about the accuracy of presidential election predictions that used statistical models, such as Nate Silver's ''538'' and Professor Sam Wang's ''PEC''. The bet may refer to a well-publicized bet that Nate Silver tried to make with Joe Scarborough regarding the outcome of the election (see tweet on the right).

==Trivia==
*In the same blog comment as cited above<ref name="munroe-on-gelman"/>, Randall explains that he chose the "sun exploding" scenario as a more clearly absurd example than those usually used:
<blockquote>…I realized that in the common examples used to illustrate this sort of error, like the cancer screening/drug test false positive ones, the correct result is surprising or unintuitive. So I came up with the sun-explosion example, to illustrate a case where naïve application of that significance test can give a result that’s obviously nonsense.</blockquote>
*"Bayesian" statistics is named for Thomas Bayes, who studied conditional probability — the likelihood that one event is true when given information about some other related event. From {{w|Bayes Theorem|Wikipedia}}: "Bayesian interpretation expresses how a subjective degree of belief should rationally change to account for evidence".
* The "frequentist" says that 1/36 = 0.027. It's actually 0.02777…, which should round to 0.028.
* Using neutrino detectors as an advance warning of a supernova is possible, and the {{w|Supernova Early Warning System}} does just this. The neutrinos arrive ahead of the photons, because they can escape from the core of the star before the supernova explosion reaches the mantle.

==Transcript==
:Did the sun just explode? (It's night, so we're not sure)

:[Two statisticians stand alongside an adorable little computer that is suspiciously similar to K-9 that speaks in Westminster typeface.]
:Frequentist Statistician: This neutrino detector measures whether the sun has gone nova.
:Bayesian Statistician: Then, it rolls two dice. If they both come up as six, it lies to us. Otherwise, it tells the truth.
:Frequentist Statistician: Let's try. [to the detector] Detector! Has the sun gone nova?
:Detector: ''roll'' YES.

:Frequentist Statistician:
:Frequentist Statistician: The probability of this result happening by chance is 1/36=0.027. Since p<0.05, I conclude that the sun has exploded.

:Bayesian Statistician:
:Bayesian Statistician: Bet you $50 it hasn't.

==References==
<references/>

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Math]]
[[Category:Statistics]]
[[Category:Physics]]

395: Morning

2016-02-23T11:03:15Z

PeR: /* Explanation */ No reason to assume that dead pixels are there "just to annoy the reader". They are explicitly referenced in the text.

{{comic
| number = 395
| date = March 12, 2008
| title = Morning
| image = morning.png
| titletext = I'd press on them to try to unstick them, but I can't reach. Can we try cycling day and night really fast?
}}

==Explanation==
This comic makes reference to the idea, as presented in the movie {{w|The Matrix}}, that reality is a computer simulation. In {{w|Liquid-crystal display|LCD screens}}, especially {{w|TFT LCD}}, a {{w|Defective pixel|dead pixel}} is a pixel that does not work properly, usually set as black or as some other color. Megan realizes that the reality is a computer simulation when she sees dead pixels in the sky, indicating that what she sees is an LCD screen.

In last panel of the comic, there are two red and one green pixel that look exactly like actual dead pixels.

The title text refers to usual techniques for fixing a dead pixel are applying pressure and releasing it, which isn't possible for Megan due to the distance of the sky, and making that area of the screen change colors really quickly, which could happen if the day-and-night cycle was fast enough.

==Transcript==
:[Megan is standing to one side.]
:We've all seen The Matrix
:We've all joked about "What resolution is life"
:But it doesn't blunt the shock
:Of waking up one morning
:[Megan looks up from field and sees several colored pixels in the sky.]
:And seeing dead pixels in the sky.

{{comic discussion}}
[[Category:Comics featuring Megan]]

273: Electromagnetic Spectrum

2015-12-01T09:32:19Z

PeR: /* The comic in detail */

{{comic
| number = 273
| date = June 6, 2007
| title = Electromagnetic Spectrum
| image = electromagnetic spectrum.png
| titletext = Sometimes I try to picture what everything would look like if the whole spectrum were compressed into the visible spectrum. Also sometimes I try to picture your sister naked.
}}

==Explanation==
This panel is a play on the {{w|Electromagnetic spectrum}}, showing a large piece of the spectrum and examples of phenomena that absorb or emit light along the spectra. Such spectra are commonly used in physics or astronomy education contexts when discussing the nature of light. This comic extends it to absurd lengths by including examples that may be variously hyper-specific, humorous, or non-EM phenomena.

The first two scales at the bottom show the wavelength λ (in meters) and the frequency f (in Hertz) of the wave. The values are related as λ=c/f, where c is the speed of light. The last line showing Q(Gal²/Coloumb) is nonsense; Gal ({{w|Gallon}}) is a unit of liquid volume measurement, and Coloumb is a likely typo for {{w|Coulomb}}, the SI unit of electric charge. Photons do not have volume in the traditional sense of the word, and are electrically neutral (thus carrying no charge).

In 1887 the {{w|Michelson–Morley experiment}} proved for the first time that the {{w|aether theory}} was wrong. The year (1897) cited underneath the comic title may be an incorrectly-dated reference to this experiment. Nevertheless, after that time many physicists like {{w|Hendrik Lorentz}} or {{w|Joseph Larmor}} were still working on some aether theories. {{w|Albert Einstein}}s theory of {{w|Special Relativity}} in 1905 helped explain the theoretical basis for lack of aether and was a definitive step in discarding previous work.

===The comic in detail===
The wavelength starts at high values on the left and decreases in a {{w|logarithmic scale}} to the right. As a result of the inverse relationship between frequency and wavelength, the frequency scale starts at low values and increases logarithmically. The nonsense ''Q'' parameter does not change monotonically with either frequency or wavelength.

Both scales are labeled with powers of ten and with {{w|metric prefix}}es. For frequencies above 100 {{w|tera-}}Hertz, it just says "other entertaining Greek prefixes like {{w|peta-}} and {{w|exa-}} and zappa-". The last prefix should be {{w|zetta-}} (denoting a factor of 1021), but is intentionally mislabeled, referencing musician {{w|Frank Zappa}}.

'''Other waves'''

Three drawings of other types of waves than the electromagnetic type:
*Slinky waves by a coil. These can be either longitudinal or transverse waves, depending on the manner in which the Slinky is driven. Notably Randall has drawn the Slinky as tangled up; if you've ever played with a Slinky you know how frustrating it is to untangle it.
*The human audio spectrum (from 20 Hz to 20 kHz). The "high-pitched noise in empty rooms" refers to {{w|tinnitus}}.
*"{{w|Wave (audience)|The Wave}}" in a stadium, a transverse wave phenomenon that travels through people.

'''Power and Telephone'''
*"{{w|CIA}} (Secret)" is a joke about all the wiretapping on phones and such.

'''Radio and TV'''
*"Shouting car dealership commercials" is a reference to the massive and often extreme advertising for car retailers.
*{{w|Ham radio}} is a private amateur radio used for communication.
*"Kosher radio" is playing with ambiguousness of the word HAM. {{w|Kosher}} is a Jewish law for food and it states, amongst other, that Jews are never allowed to eat meat from the unclean pigs - so no ham!
*Some frequencies of famous FM broadcast stations. "99.3 The Fox" is a modern rock station in {{w|Vancouver, British Columbia}}. "101.5 The Badger" is a classic rock station in {{w|Madison, Wisconsin}} (home of the University of Wisconsin, whose mascot is a badger). "106.3 The Frightened Squirrel" is not a real station, but makes a play off the animal names commonly used as nicknames for either radio stations, programs, or hosts.
*The rays controlling {{w|Steve Ballmer}} are nonsense, but may reference real {{w|Balmer series}}, a set of transitions in the hydrogen atom that produce photons in the optical and ultraviolet light range.
*AM {{w|Amplitude modulation}}, VHF {{w|Very high frequency}}, and UHF {{w|Ultra high frequency}} are frequency ranges approved for commercial broadcasting companies.
*Cell phone cancer rays is playing with the belief of many people that cell phones may cause cancer (see also [[925: Cell Phones]]).
*Aliens belong to a range slightly higher than the frequencies used by human communications. So they can't hear us.

'''Microwaves'''
*{{w|SETI}} is the "Search for ExtraTerrestrial Intelligence" project trying to find messages from aliens. Most genuine astronomical research in this area concentrates in the microwave and radio regimes. Since aliens work at different frequencies on this diagram, that might explain why there has of yet been no positive results from SETI.
*{{w|WIFI}} is the standard for wireless computer communications.
*FHF is probably "Fucking high frequency"; it is not an abbreviation for any broadcasting frequency ranges and lies above the (real) V(ery)HF and U(ltra)HF.
*{{w|Gravity wave}}s are a phenomenon in fluid dynamics, and distinct from {{w|Gravitational wave}}s. Neither is related to electromagnetic emission.
*Brain waves could be a reference to {{w|Neural oscillation}}.
*{{w|Sulawesi}} is an island in the Indian Ocean that belongs to Indonesia.

'''Toasters'''
*This is a pun on the microwave oven, which emits light at its namesake frequencies to cook food. It also takes a stab at people who claim that microwaved food is dangerous, by pointing out that toasters also heat food using electromagnetic radiation, of frequencies just higher than microwaves. (The actual spectrum of a toaster goes all the way into visible frequencies.)

'''IR (infrared)'''
*{{w|Infrared}} belongs to heat. The reference to {{w|Superman}} covers his heat vision power, which has been used many times within the canon. American comedian {{w|Jack Black}} starred in a proposed scifi/comedy television show in 1999 titled "{{w|Heat Vision and Jack}}", which covered the adventures of an astronaut and his talking motorcycle.

'''Visible light'''
*At the bottom it is split into "visible light" and "visible dark". While dark is the opposite of light in many grammatical context, in the physical sense it only reflects the absence of visible photons.
*The human visible spectrum is shown by all colors, including {{w|octarine}}, the colour of magic on the fictional {{w|Discworld}} (in the books by {{w|Terry Pratchett}}).
*On top there are two {{w|absorption spectrum|absorption spectra}}, hydrogen and helium. These are the two most common elements in the Sun, and their presence in the Sun's outer envelope and Earth's atmosphere does block some small frequencies from the Sun. Next come two cases of {{w|Absorption (chemistry)|absorption}} in the chemical/technical meaning:
**{{w|Depends}} is a brand of underwear for adults experiencing urinary or fecal incontinence. The color is consequently yellow.
**{{w|Tampax}} is a brand of tampon. The color is red.

'''UV (ultraviolet)'''
*{{w|Ultraviolet}} light can not be seen by humans. No entries here.

'''Miller Light'''
*{{w|Miller Lite}} is a lager beer. "Light beer" typically has a lower alcohol content and calorie count, although it is also usually a light color for beer.

'''Empty section'''
*"Main Death Star Laser" is a reference to {{w|Star Wars}}.

'''Censored under {{w|Patriot Act}}'''
*No entry because it's censored; this is a humorous exaggeration of how much authority the government can supposedly exercise under said bill.

'''X-rays'''
*Potatoes absorb and reflect radiation waves the same way humans do, because their chemistry and water content is very similar to the human body. Look here: [http://www.usatoday.com/story/todayinthesky/2012/12/24/boeing-wifi-potatoes/1789109/ Boeing uses potatoes to improve Wi-Fi signals].
*Mail-order x-ray glasses refers to {{w|X-Ray Specs (novelty)|a novelty item}} based on an optical effect, not actual x-rays. {{w|Google Glass}} did not exist at the time when this comic was created.

'''Gamma/Cosmic rays'''
*Blogorays are emitted by the {{w|Blogosphere}}; apparently only [[Randall]] can detect them.
*Sinister Google Projects: The first result at a search on {{w|Google}} is this: [http://ca.askmen.com/top_10/entertainment/top-10-sinister-google-activities.html Top 10: Sinister Google Activities].

And finally the '''Title Text''': Randall likes to speculate what the world would look like if humans could see radio waves, gamma waves, etc. Such a thought experiment would be pretty abstract due to the total lack of a frame of reference (since everything outside the visible light spectrum is by definition invisible and thus beyond human comprehension) but for many people that's also what makes it enticing. Randall immediately turns this profound train of thought around with a crude joke that he wants to know what the viewer's sister would look like in the nude.

==Transcript==
:[Everything is one big panel.]

:The Electromagnetic Spectrum

:These waves travel through the electromagnetic field. They were formerly carried by the aether, which was decommissioned in 1897 due to budget cuts.

:Other waves:
:*Slinky waves [Cueball and Megan hold the ends of a tangled slinky.]
:*Sound waves [There is a snippet of a frequency band. Between 20 Hz and 20 KHz is labeled "Audible Sound." Towards the top is a line labeled "That high-pitched noise in empty rooms."]
:*The wave [A row of people does a wave.]

:[Three parallel scales are across the bottom. The first is lambda (m), ranging from 100Mm to 100fm; second is f (Hz), which starts at 1 Hz and reaches 100 THz about 2/3 of the way along, after which the labels read "other entertaining greek prefixes like peta- exa- and zappa-"; last is Q (Gal^2/Coloumb), whose labels are 17, 117, pi, 17, 42, theta, e^pi-pi, -2, 540^50, and 11^2. Above the scales and lined up accurately with the first two are the following:]

:*Power & Telephone (100Mm to 1km)
:*Radio & TV (1km to somewhere between 1m and 10cm); above that are many boxes showing subranges (AM, VHF, UHF, 14/7 NPR pledge drives, a very thin band for the space rays controlling Steve Ballmer, 99.3 "The Fox," 101.5 "The Badger," 106.3 "The Frightened Squirrel," cell phone cancer rays, CIA, ham radio, kosher radio, shouting car dealership commercials.)
:*Microwaves (a bit more than 10cm to a bit more than 1mm); it also has subranges (aliens, just below SETI, wifi, FHF, brain waves, sulawesi, gravity)
:*Toasters (about 1mm to about 100 micrometers)
:*IR (about 100 micrometers to somewhere between 1 micrometer and 1 nm); above that is a bell graph labeled "Superman"s heat vision," with a motorcycle driving up the left side labeled "Jack Black's Heat Vision."
:*Visible light (and, under it, visible dark); above that is a bell graph labeled "sunlight." There's a breakout chart above it showing the visible spectrum from 700nm (red) to 450nm (violet). There's an arrow pointing to where octarine would be, somewhere off to the side. Above that are bars showing the absorption spectra for hydrogen, helium, Depends(R) (yellow only) and Tampax(R) (red only).
:*UV (about 100nm to about 10nm)
:*Miller Light (a thin bar around 10nm)
:*An unlabeled section with a thin line above it showing the frequency of the main death star laser
:*A blocked-off portion labeled "Censored Under Patriot Act."
:*X-rays (from about 1nm to about 10pm); a line above shows the frequency of mail-order x-ray glasses. Somewhere vaguely above the 10pm mark is a potato.
:*Gamma/cosmic rays (10pm and smaller); above that is a bar marked Sinister Google Projects which also trails off into higher frequencies, and blogorays, which are slightly lower.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Science]]
[[Category:Comics with color]]
[[Category:Charts]]

586: Mission to Culture

2015-11-02T10:20:42Z

PeR: /* Explanation */ Link to 339: Classic)

{{comic
| number = 586
| date = May 20, 2009
| title = Mission to Culture
| image = mission to culture.png
| titletext = It can't be very MUCH money... they apparently can't even afford a sampler. I mean, with a little remixing, some of this could be kinda good!
}}

==Explanation==
[[Cueball]] wants to take [[Megan]] out for his idea of a cultural experience. The inference is that Megan's culturally impoverished because 'all she ever listens to is techno'. After much griping on various levels, for instance complaining that all the other attending is above 60 years old, she starts to get into the experience — sort of. The big 'cultural lesson' she [mis-]gleans from the experience is similar to what a sporting aficionado would gain from watching a sports event.

Her observation regards the seating configuration of a typical modern orchestra, in which the violinists all sit audience-left, while the violists, cellists and bassists are on the right.

The title text basically just ices the cake. A {{w|sampler (musical instrument)|sampler}} is an instrument frequently used in techno music that samples other sounds and plays them back, usually electronically altered. {{w|Remix|Remixing}} is a process, also often used in techno, of editing recorded music to get a different sound. Many classical pieces have had success as techno remixes. One example is Pachelbel's Canon in D major, referred to in the title text of [[339: Classic]].

Three of the old people in the line looks very similar to the old people in [[572: Together]]. In he very next comic [[587: Crime Scene]] a man is again shown with hair only around his neck.

==Transcript==
:[Cueball is pulling Megan by her feet. She is holding onto the carpet, which visibly folds under her tug.]
:Cueball: We're getting some culture in you if it ''kills'' you.
:Megan: Don't wanna.

:[Cueball is pushing Megan at the front door, with steps leading down outside. Megan is curled up with both her feet and her hands up on the middle of the door, her back arching out towards Cueball.]
:Cueball: All you listen to is techno.
:Megan: But... the ''symphony?''

:[Cueball and Megan stand in line between two other couples; A guy, who only has hair around his neck and a cane, and Hair Bun Girl stands behind them. A guy with a sailor cap and a woman with a big hair stands before them.]
:Megan: I think we're the only people here under 60.
:Cueball: Shhh.

:[The couple sit in the audience just before the concert.]
:Megan: The right side is definitely better.
:Cueball: Better?
:Megan: They've all got bigger instruments. I bet they make more money.
:Cueball: *Sigh*

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hair Bun Girl]]
[[Category:Music]]

1561: Water Phase Diagram

2015-08-08T16:32:55Z

PeR: /* Original version */

{{comic
| number = 1561
| date = August 7, 2015
| title = Water Phase Diagram
| image = water_phase_diagram.png
| titletext = Vanilla Ice was produced in small quantities for years, but it wasn't until the 90s that experimenters collaborated to produce a sample that could survive at room temperature for several months.
}}

==Explanation==
This is a modified version of the {{w|phase diagram}} for water. A "phase diagram" is a chart that shows the states, or "phases", that a substance will be in under various temperatures and pressures. Water's phases are particularly well-studied; on a [http://ergodic.ugr.es/termo/lecciones/water1.html real phase diagram for water], there are a great many phases listed.

Most people are familiar with three phases of water—solid, liquid, and gas—and with the fact that an increase in temperature will cause water to change from one state to another. The gas and liquid phases ("water vapor" and "liquid water") are quite straightforward; however, there is in fact not one single solid phase of water ("ice"), but a variety of numbered phases ("ice I" through "ice XV" are currently recognized), several of which are divided into sub-categories. Ordinary, everyday ice is known as "{{w|Ice Ih|ice Ih}}" ("ice one-h"). Most of the more unusual forms of ice only form under very high pressures.

Randall's phase diagram starts out realistically, though slightly simplified in several ways. For one, it simply uses the name "ice" for the usual form(s). It is focused in on a narrower area than the more complete diagram linked earlier; on that version, the "ice V" region is quite small, and "ice III" is barely visible, whereas both are quite plain to see on Randall's diagram. Lastly, Randall has the pressure scale increase downwards (which facilitates the David Bowie/Queen entry being "under" pressure), where most phase diagrams have pressure increase upwards.

As the diagram continues downwards and the pressure increases, the jokes begin. Beyond the moderately high-pressure forms of ice (ice II, III and V), a real phase diagram has ice VI; Randall has "Vanilla Ice (ice VI)". {{w|Vanilla Ice}} is the stage name of a white rap/hip-hop artist from the 1990s; the initials of Vanilla Ice, and the Roman numeral six, are both VI.

Vanilla Ice's biggest hit, "{{w|Ice Ice Baby}}", used samples from the earlier song "{{w|Under Pressure}}", by {{w|David Bowie}} and {{w|Queen (band)|Queen}}; accordingly, on Randall's diagram, the "Vanilla Ice" region transitions to "David Bowie & Queen" when it is under (even higher) pressure.

Further references to "Ice Ice Baby" are found in the title text. Near the beginning of the song, Vanilla Ice raps the line, "All right stop, collaborate and listen". The unusual choice of "collaborate" in this line has made it memorable, and the word is used in the title text (in a more typical context). The phrase "survive at room temperature for several months" is likely a reference to "Ice Ice Baby" being Vanilla Ice's only major hit, humorously suggesting he faded out of the public view after a few months of fame. Finally, even the word "sample" may be deliberately chosen as a reference to the sampling of "Under Pressure".

===Original version===
[[File:WaterPhaseEdit.png|frame| The original comic, with a lower contrast, showing [https://commons.wikimedia.org/wiki/File:Phase_diagram_of_water.svg the real phase diagram for water] from Wikipedia]]
When originally published, another image was faintly visible just below and to the right of the "Water vapor" label. It appeared to be a copy of [http://commons.wikimedia.org/wiki/File:Phase_diagram_of_water.svg an actual phase diagram for water from Wikipedia]. The image has since been removed, lending support to speculation that it was an error (perhaps an image Randall referred to in drawing the comic, but accidentally left in the final result). Alternatively, it may have been deliberate—suggestions include its presence being a ''water''mark, or a reference to the "Full text of the Wikipedia article on pareidolia" joke in the [[1551: Pluto]] comic.

===Related comics===
Randall has referenced "Ice Ice Baby" and "Under Pressure", separately and together, on many previous occasions, notably in [[159: Boombox]]. The gag of having the performers of "Under Pressure" also being literally under pressure was also used in [[1040: Lakes and Oceans]].

The [[what if?]] that was current at the time of this comic's publication was [http://what-if.xkcd.com/138/ 138: Jupiter Submarine], which began with an even more fanciful phase diagram: that of a submarine. It also contains a reference to the songs "Under Pressure" and "Ice Ice Baby" in one figure.

The title text of [[1434: Where Do Birds Go]] whimsically suggests another possible phase of water/ice.

As mentioned above, the small image on the [[#Original version|original version]] could be a reference to the "Full text of the Wikipedia article on pareidolia" joke in the [[1551: Pluto]] comic.

==Transcript==
:[A phase diagram is shown with eight labeled regions]

:[The horizontal axis, increasing in value to the the right is labeled:]
:Temperature

:[The vertical axis, increasing in value downwards is labeled:]
:Pressure

:[Region alongside the "Pressure" axis covering about half of its length is labeled:]
:Ice

:[Region spanning top-right corner of graph, i.e. higher temperatures and lower pressures. Below and to the right of the label there seems to be an insert of a small picture of the real phase diagram. The region is labeled:]
:Water vapor

:[Region below "Water vapor" and to the right of "Ice" is labeled:]
:Liquid water

:[Three small regions below "Ice" are going from left to right on the same pressure region, the last ending just under "Liquid water". They are each labeled:]
:Ice II
:Ice III
:Ice V

:[Region below "Ice II", "Ice III", "Ice V" and "Liquid water" is labeled:]
:Vanilla Ice
:(Ice VI)

:[Below "Vanilla Ice" there is a dashed line with two arrows pointing downwards. The region below the dashed line is labeled:]
:David Bowie & Queen

{{comic discussion}}

[[Category: Charts]]

1561: Water Phase Diagram

2015-08-07T11:54:52Z

PeR: /* Explanation */ source of faint image

{{comic
| number = 1561
| date = August 7, 2015
| title = Water Phase Diagram
| image = water_phase_diagram.png
| titletext = Vanilla Ice was produced in small quantities for years, but it wasn't until the 90s that experimenters collaborated to produce a sample that could survive at room temperature for several months.
}}

==Explanation==
{{incomplete| Ethion of scientific detail required.}}

This is a modified version of the {{w|phase diagram}} for water. A "phase diagram" is a chart that shows the states, or "phases", that a substance will be in under various temperatures and pressures. Water's phases are particularly well-studied; on a [http://ergodic.ugr.es/termo/lecciones/water1.html real phase diagram for water], there are a great many phases listed.

Most people are familiar with three phases of water—solid, liquid, and gas—and with the fact that an increase in temperature will cause water to change from one state to another. The gas and liquid phases ("water vapor" and "liquid water") are quite straightforward; however, there is in fact not one single solid phase of water ("ice"), but a variety of numbered phases ("ice I" through "ice XV" are currently recognized), several of which are divided into sub-categories. Ordinary, everyday ice is known as "ice Ih" ("ice one-h"). Most of the more unusual forms of ice only form under very high pressures.

Randall's phase diagram starts out realistically, though slightly simplified in several ways. For one, it simply uses the name "ice" for the usual form(s). It is focused in on a narrower area than the more complete diagram linked earlier; on that version, the "ice V" region is quite small, and "ice III" is barely visible, whereas both are quite plain to see on Randall's diagram. Lastly, Randall has the pressure scale increase downwards (probably so that the jokes are at the bottom), where most phase diagrams have pressure increase upwards.

As the diagram continues downwards and the pressure increases, the jokes begin. Beyond the moderately high-pressure forms of ice (ice II, III and V), a real phase diagram has ice VI; Randall has "{{w|Vanilla Ice}}" (the name of a white rap/hip-hop artist from the 1990s). Vanilla Ice's biggest hit, "Ice Ice Baby", used samples from the earlier song "Under Pressure", by David Bowie and Queen; accordingly, on Randall's diagram, the "Vanilla Ice" region transitions to "David Bowie & Queen" when it is under (even higher) pressure.

Further references to "Ice Ice Baby" are found in the title text. Near the beginning of the song, Vanilla Ice raps the line, "All right stop, collaborate and listen". The unusual choice of "collaborate" in this line has made it memorable, and the word is used in the title text (in a more typical context). The phrase "survive at room temperature for several months" is likely a reference to "Ice Ice Baby" being Vanilla Ice's only major hit, humorously suggesting he faded out of the public view after a few months of fame. Finally, even the word "sample" may be deliberately chosen as a reference to the sampling of "Under Pressure".

Lastly, another image is faintly visible just below and to the right of the "Water Vapor" label. It appears to be a copy of an actual phase diagram for water [https://commons.wikimedia.org/wiki/File:Phase_diagram_of_water.svg from Wikipedia]. It is unclear why this image is present in the picture; it may be some sort of hidden message, or perhaps an error.

===Related comics===
Randall has referenced "Ice Ice Baby" and "Under Pressure", separately and together, on many previous occasions, notably in [[159: Boombox]].

The [[what if?]] that was current at the time of this comic's publication was [http://what-if.xkcd.com/138/ 138: Jupiter Submarine], which began with an even more fanciful phase diagram: that of a submarine.
It also contains a reference to the songs "Under Pressure" and "Ice Ice Baby" in one figure.

==Transcript==
;Temperature
:[horizontal axis, increasing in value to the the right]
;Pressure
:[vertical axis, increasing in value downwards]
[From top to bottom and from left to right...]
:;Ice
::[region alongside to "Pressure" axis covering about half of its length]
:;Water vapor
::[region spanning top-right corner of graph, i.e. higher temperatures and lower pressures]
:;Liquid water
::[region below "Water vapor" and to the right of "Ice"]
:;Ice II
:;Ice III
:;Ice V
::[small regions below "Ice"]
:;Vanilla Ice (ice VI)
::[region below "Ice II", "Ice III", "Ice V" and "Liquid water"]
:[dashed line with arrows pointing downwards]
:;David Bowie & Queen
::[region below dashed line]

{{comic discussion}}

Talk:1534: Beer

2015-06-05T09:33:29Z

PeR:

I hate the taste and smell and associations (such as urine and vomit where they shouldn't be). A friend used to freely admit he didn't like the taste and only drank to get drunk. [[Special:Contributions/108.162.249.161|108.162.249.161]] 06:24, 5 June 2015 (UTC)

This is why there are so many different styles of beers, or wines, or other alcoholic beverages. I personally don't care for IPAs, but will rarely pass up a good Pilsner.[[Special:Contributions/108.162.238.189|108.162.238.189]] 07:37, 5 June 2015 (UTC)

Is it possible that the characters, being American, have only ever tasted American beer? So when Cueball says that "all beer tastes kind of bad" hat he really means is "all American beer tastes kind of bad"? That would make a lot more sense (especially if you assume that they only buy from the major brands, and haven't yet tried beer from microbreweries.) --[[User:PeR|PeR]] ([[User talk:PeR|talk]]) 09:30, 5 June 2015 (UTC)

Talk:1534: Beer

2015-06-05T09:30:47Z

PeR: American beer?

I hate the taste and smell and associations (such as urine and vomit where they shouldn't be). A friend used to freely admit he didn't like the taste and only drank to get drunk. [[Special:Contributions/108.162.249.161|108.162.249.161]] 06:24, 5 June 2015 (UTC)

This is why there are so many different styles of beers, or wines, or other alcoholic beverages. I personally don't care for IPAs, but will rarely pass up a good Pilsner.[[Special:Contributions/108.162.238.189|108.162.238.189]] 07:37, 5 June 2015 (UTC)

Is it possible that the characters, being American, have only ever tasted American beer? So when Cueball says that "all beer tastes kind of bad" hat he really means is "all American beer tastes kind of bad"? That would make a lot more sense. --[[User:PeR|PeR]] ([[User talk:PeR|talk]]) 09:30, 5 June 2015 (UTC)