explain xkcd - User contributions [en]

3044: Humidifier Review

2025-01-30T21:54:38Z

172.71.154.140: /* Explanation */

{{comic
| number = 3044
| date = January 29, 2025
| title = Humidifier Review
| image = humidifier_review_2x.png
| imagesize = 285x287px
| noexpand = true
| titletext = They should add a little sticker that certifies that the humidifier supports water conservation, but in the sense of energy conservation or momentum conservation.
}}

==Explanation==
{{incomplete|Created by a 101% EFFICIENT TOASTER. This page was clearly autogenerated by an AI that does not understand the comic nor humidity engineering. I tried to improve the first paragraph. Do NOT delete this tag too soon.}}

This comic shows a review of a {{w|humidifier}}, which complains that it uses too much water to increase the humidity of the room to 45%. On the face of it, someone buying a humidifier for the first time might not have an understanding of how much water the device needs, and could be taken by surprise (possibly when their water bill arrives). The review in the comic has taken it a step further, voicing their complaint as a flaw in this specific humidifier and wishing another model could somehow achieve the same results with less water.

A humidifier works by evaporating water from a tank, causing the air around it to become more humid. The law of {{w|conservation of mass}} states that the amount of matter in the universe must stay constant. Therefore, the amount of water used by the humidifier must be at least the amount gained by the air. Aside from small efficiency improvements (and [[2710: Hydropower Breakthrough|machinery made by Beret Guy]]), it is very hard to reduce the amount of water used to humidify a room without sealing the room better to prevent humid air from leaving it, which has nothing to do with the humidifier. The humour is thus at the expense of people who don't understand the requirements of their appliances (or other hypothetical services) and complain in ignorance about the impossible not being made possible for their conveniences.

Strictly speaking there are other ways to increase the humidity of a room, though all of them are still constrained by the laws of conservation. In theory a humidifier could start a chemical reaction to create water from some other chemicals - which would still need to be supplied. A humidifier could also increase relative humidity by cooling the air, even using no water at all, since humidity (when given as a percentage measure such as the stated 45%) is relative to the water capacity of the air at its current temperature — this is not always viable, and depending on the climate could require more energy than evaporating the water.

Other examples of commonly-used, commonly-reviewed household devices whose operational efficiency is limited by the laws of physics themselves include {{w|space heater|space heaters}}, {{w|electric water boiler|electric kettles}}, {{w|air conditioning|air conditioners}}, and {{w|refrigerator|refrigerators}}. For instance, a space heater {{what if|35|cannot produce more heat than the electrical energy it consumes}}, as dictated by the laws of thermodynamics. Similarly, an electric kettle cannot heat water with less energy than the amount required to raise its temperature, due to the specific heat capacity of water. Air conditioners and refrigerators operate by transferring heat rather than creating "cold," and their efficiency is constrained by the {{w|Carnot cycle}}, which defines the maximum possible efficiency of a heat engine.

Reviews which indicate the ignorance or [[937:_TornadoGuard|gullibility]] of the reviewer, or which indicate the [[325:_A-Minus-Minus|vindictive nature]] of the vendor, are a common theme in XKCD.

The joke in the title text is based on different senses of the word "conservation". To most people this refers to reducing wasted use of some material, e.g. "water conservation" means avoiding waste of water. But to physicists, it means that some quantity in a system stays the same; for instance, conservation of energy means that energy can neither be created nor destroyed. For many years, most appliances have had {{w|Energy Star}} stickers that indicate their impact on the environment; by adopting the physicists' sense, they can trivially say they support water conservation.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[A product review appears within a panel. At the top left is a small drawing of a humidifier within a rectangle. To the right of that rectangle, the following text appears:]
:HydroPro Humidifier
:[A line of illegible text appears below the product name, followed by a shorter line of illegible text within a rectangle.]
:Reviews
:[A horizontal line separates the above from a small close-up drawing of Hairy in a circle, with two lines of illegible text to his right.]
:[(3/5 stars)] '''Good but inefficient'''
:It keeps the humidity at 45% pretty well. I'd give it 5 stars if it didn't use so much water.

:[Caption below the panel:]
:My favorite reviews are the ones that penalize products for not violating the laws of physics.

{{comic discussion}}
[[Category:Physics]]
[[Category:Online reviews]]
[[Category:Comics featuring Hairy]]

Talk:3033: Origami Black Hole

2025-01-04T01:22:50Z

172.71.154.140: Emo Philips

First post! [[User:RadiantRainwing|RadiantRainwing]] ([[User talk:RadiantRainwing|talk]]) 19:08, 3 January 2025 (UTC)

All six gross attempts to follow these instructions have ended with the attemptor vanishing into themselves before reaching step 175.[[Special:Contributions/172.70.47.105|172.70.47.105]] 19:17, 3 January 2025 (UTC)

e[[Special:Contributions/162.158.10.131|162.158.10.131]] 20:14, 3 January 2025 (UTC)

Should we also add a mention of the /Mythbusters/ doing this? I don't remember the details or I would put it in. [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 21:48, 3 January 2025 (UTC)

I started convincing chatgpt to tell me how to fold this origami at https://chatgpt.com/share/67785de4-9a4c-800e-80f5-31d12d999999 before running out of free credits. [[Special:Contributions/172.68.54.157|172.68.54.157]] 22:00, 3 January 2025 (UTC)

Using rice paper you could easily reach 9 steps by pure hand pressure, although reaching fusion point -at or around 80 steps- would definitely require strong fingers indeed. Black holes clearly cannot exist, because they would require folding Chinese paper more than a red-blooded American can do, and this is not an option.{{unsigned ip|141.101.68.192|22:13, 3 January 2025}}

The current explanation that it's impossible to create a black hole by folding paper is only right in practical terms. If you manage to keep folding while keeping the same thickness the density of the paper will be far beyond that of a neutron star.--[[User:Pere prlpz|Pere prlpz]] ([[User talk:Pere prlpz|talk]]) 22:42, 3 January 2025 (UTC)

I would be impressed if you did manage to keep folding, since the goal size can be measured in Planck lengths with only six digits. Would you define it as a 'fold' after the entire thing fits inside an electron? (Tangentially, I'm not sure what theory suggests here - can a black hole exist at a scale which makes quantum tunnelling trivial?) {{unsigned ip|172.68.210.114|23:09, 3 January 2025}}
:I don't think we'll be able to answer that until we unify QM and GR. I don't think we currently have a theory that addresses quantum-sized black holes. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 23:23, 3 January 2025 (UTC)

This strip loosely follows a routine by Emo Philips in the 1980's where he describes tearing a piece of paper in half repeatedly until it explodes. He didn't give a count though. [[Special:Contributions/172.71.154.140|172.71.154.140]] 01:22, 4 January 2025 (UTC)

3026: Linear Sort

2024-12-20T23:59:34Z

172.71.154.140: relatively small lists could be better than the 'previous' big o. the order makes sense at larger list values

{{comic
| number = 3026
| date = December 18, 2024
| title = Linear Sort
| image = linear_sort_2x.png
| imagesize = 385x181px
| noexpand = true
| titletext = The best case is O(n), and the worst case is that someone checks why.
}}

==Explanation==
{{incomplete|Created in Θ(N) TIME by an iterative Insertion Sorter working on a multidimensional array - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

A common task to have computers do is to sort a list, such as from A to Z or from the smallest to the largest number. There are dozens of algorithms created to accomplish this task through the years, from simple to complex, each with its own merits with regard to how easiness of implementation, memory usage, and efficiency; in order to understand the last one, computer scientists created {{w|Big O Notation}}. There are two aspects of Big O notation to know:

1. It is ''asymptotic''; meaning that it simply expresses the base relation between the size of the list and the time needed to sort. O(2''n'') is written simply as O(''n''), because Big O is more concerned about indicating the sort time scaling linearly rather than accurately giving you a formula to calculate how long it'll take. Likewise, O(2''n'' + ''n''2) might be written as O(2''n'') because the value of ''n''2 would eventually become small enough (relative to 2''n'') to be rounded off.

2.Big O notation is only an average estimation. The actual figure depends on the hardware, software, and the initial state of the list - consider if you needed to sort a pile of books by title you might luck to find most books are already in the correct position and only need to move one or two, or they might be hopelessly jumbled up and necessitate moving most, even all of them. Big O notation is mainly used to examine various methods to accomplish the same task, running on the same hardware, rather than being real-world benchmarks.

A few common Big O notations are listed below, from smallest to largest:
<ul><li>O(1) - Constant time, which means the sorting will always take X seconds no matter how big the data is</li>
<li>O(''n'') - Linear time, which means the execution time grows in direct proportion to the size of the data</li>
<li>O(''n'' log(''n'')) - The execution time grows proportionally to ''n'' * the {{w|logarithm}} of ''n''. For small lists, this value would be smaller than O(n) (meaning it'll take less time), but as the lists grow it will generally take more time (again, on average).</li>
<li>O(''n''2) - Quadratic time, meaning the execution time grows proportionally to the ''square'' of the size of the data.</li></ul>

As one can image in most contexts one would wish for sorting to be done as fast as possible, so O(1) is better than O(n), which is in turn better than O(n*log(n)) etc (at least assuming your lists are relatively large). The code in the comic describes a 'linear' sort that first sorts the list using {{w|merge sort}}, which is known to take time O(''n'' log(''n'')), and then `sleep()`s (pauses with no activity) for an amount of time equal to subtracting the time taken for the sort from the number of elements multiplied by 1 million (1e6) seconds. Here the joke is that, rather than creating an algorithm that actually takes O(n) time it simply disguises an algorithm that takes O(n*log(n)) and makes it appear to be O(n). The runtime is much longer than the mergesort, but it increases linear with the length of the list. So it appears to be O(n). This is obviously unideal as waiting around doing nothing is the opposite of optimization.

This joke is carried on by the title text, which refers to the {{w|Best, worst and average case|best and worst case}} of a sort, which are additional measures of its runtime to describe the shortest and longest potential times. A more optimal sort may decide how much of a list needs to be passed over again after its first pass of shuffling elements around; scanning a pre-sorted list (and deducing that it has no more checking to do) could mean that no more effort is needed, resulting in a best case of O(''n''). Depending upon the algorithm, presenting a list that is in an ordering that happens to challenge it the most (such as exactly reversed) may mean even an 'average O(''n'' log ''n'')' process would have to exceed this, resulting in a worst-case number of operations that may be O(''n2''). It can be very useful to know that a given sorting method ''may'' take the average order of time, but have the possibility of a much shorter ''or'' longer runtime... especially when the method is expected to be [[1185: Ineffective Sorts|far, far worse than others]], where only particular and more idealistic input lets it approach the more satisfyingly fast average/best responses.

By forcing all practical searches to take O(''n'') time, regardless of how otherwise identical data is presorted, the best case (and worst case, for that matter) will also be O(''n''). The last part of the text then plays on another meaning of best case and worst case, as best- and {{w|worst-case scenario}}s for a situation, by saying that the worst outcome for the code's author is when someone decides to investigate the code (perhaps owing to its absurd runtime, or else just justifiably skeptical of the declared optimality), whereupon that investigator will discover the deception and ruin the author's reputation.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The panel shows five lines of code:]
:function LinearSort(list):
::StartTime=Time()
::MergeSort(list)
::Sleep(1e6*length(list)-(Time()-StartTime))
::return

:[Caption below the panel:]
:How to sort a list in linear time

{{comic discussion}}

[[Category:Programming]]

Talk:3015: D&D Combinatorics

2024-11-24T03:17:26Z

172.71.154.140: /* The physical difficulties of an M-of-N locking system */

The bot originally created this page as “D Combinatorics”. I renamed it to the correct title and tried to get as many of the references as possible (including a few redirects). [[User:JBYoshi|JBYoshi]] ([[User talk:JBYoshi|talk]]) 00:54, 23 November 2024 (UTC)

:The title in the Atom feed (which I'm assuming the bot consumes) is "D Combinatorics". I'm guessing something in Randall's pipeline didn't like the ampersand. --[[Special:Contributions/162.158.154.160|162.158.154.160]] 01:41, 23 November 2024 (UTC)

::Yup, if you look at [https://xkcd.com/3015/info.0.json 3015's JSON] you see that <code>title</code> and <code>safe_title</code> differ, and if you look at the HTML page source you'll see '''3''' different things: <code><title>xkcd: D Combinatorics</title></code>, <code><meta property="og:title" content="D&amp;D Combinatorics"></code>, and <code><div id="ctitle">D&D Combinatorics</div></code>! So probably what happened is Randall entered D&D but was supposed to enter D&amp;D, and the openGraph tags adder code, having to be HTML-aware, decoded & normalized D&D as HTML would, but the other parts of the pipeline just ate it for some reason.

:By raw combinatorics: 71 + 52 + 34 + 20 + 10 + 4 + 1 ways to get each of 16 - 22 respectively, for a total of 192, out of 4(6^3) = 864 total. 192/864 simplifies to exactly 2/9. I have no idea how Randall found this; if anyone has an idea, please let me know. [[User:Kaisheng21|Kaisheng21]] ([[User talk:Kaisheng21|talk]]) 01:33, 23 November 2024 (UTC)
::I used some simple python code to loop over every dice and confirm and it's 2/9 [[Special:Contributions/162.158.158.111|162.158.158.111]] 12:11, 23 November 2024 (UTC)

It seems like we edited the transcript at the same time. The odds of rolling 16 or higher in this situation seem to be 2/9? [[User:Darkmatterisntsquirrels|Darkmatterisntsquirrels]] ([[User talk:Darkmatterisntsquirrels|talk]]) 01:29, 23 November 2024 (UTC)

: There are 864 possible rolls (6 * 6 * 6 * 4). If you enumerate all of the rolls you will find that 192 are 16 or higher. 192/864 = 2/9, the value from the explanation. [[Special:Contributions/172.68.54.139|172.68.54.139]] 01:41, 23 November 2024 (UTC)

I added a table of outcomes to clarify how it works out to 2/9, anyone know how to make it pretty? -- Laurence Cheers

A much simpler approach: Roll two six sided dice and sum the result. You are successful if the result is 5 or 9. That happens 8 times out of 36. 8/36 = 2/9. (Or successful if the sum is 4 or 6, or 2 or 7, or 2,3,4 or 11, or several other combinations.) [[Special:Contributions/172.68.54.139|172.68.54.139]] 01:41, 23 November 2024 (UTC)
:Clever, but dice rolls in D&D involving summing all the dice, applying modifiers, if any, and then comparing to one or more threshold values. Your method makes it very difficult to apply modifiers. [[Special:Contributions/162.158.41.8|162.158.41.8]] 02:49, 23 November 2024 (UTC)
::I think you misunderstand the problem here. This is not skill, no modifiers apply, it's purely probability [[Special:Contributions/162.158.158.111|162.158.158.111]] 12:11, 23 November 2024 (UTC)

Minor quibble, arrows aren't fired (unless they're flaming or self-propelled, perhaps), they are shot. (Shotguns are fired of course.) [[Special:Contributions/162.158.41.73|162.158.41.73]] 02:52, 23 November 2024 (UTC)
:Arrows are "loosed", even more accurately. At least to avoid the confusion from how so many things may be shot, or ''a'' shot. (Many different nouns, from a physical measure of liquer/coffee/vaccine to a projectile, or an even abstract fundemental of chance; and, as verb, projectiles perhps may be shot, then so may their targets.) [[Special:Contributions/172.68.205.178|172.68.205.178]] 14:32, 23 November 2024 (UTC)

Rolling 22 or lower on percentile dice (or, equivalently, 79 or higher) is close enough, and easier to come up with. (Give or take whether 00 is treated as 100 or zero.) Or directly represent the action: roll a d10. If it's 1-5, you lose. If it's 6-10, roll again; if it's 1-5 you lose, 6-9 you win, 10 roll again. (Modify slightly if you want to distinguish the case of grabbing *two* cursed arrows.) [[User:Jordan Brown|Jordan Brown]] ([[User talk:Jordan Brown|talk]]) 03:26, 23 November 2024 (UTC)

== Alternative exact solution for getting this probability using dice ==

Roll: 1d8, 2d6, 1d4 succeed on 19 or higher.

== Alternative way to calculate the probability of drawing two non-cursed arrows ==

I couldn’t remember the formula for binomial coefficients (“n choose k”), but there’s an easy way to calculate that the probability of drawing no cursed arrows is 2/9 without that formula. You just need to multiply the probabilities that each of the arrows drawn is not cursed. Since only two arrows are drawn, you only have to multiply two numbers.

The probability that the first arrow is not cursed is 5/10 – there are 5 non-cursed arrows and 5 cursed arrows out of 10 total. After taking out one non-cursed arrow, there are 4 non-cursed arrows and 5 cursed arrows out of 9 total, so the probability that the second arrow is not cursed is 4/9. Multiplying the two probabilities, the probability of drawing two non-cursed arrows is (4*5)/(10*9) = 20/90 = 2/9.

I was considering writing this observation in the Explanation section of the page, but I’m not if it belongs there. This solution avoids using formulas from combinatorics, so it might not be connected enough to the comic.—[[User:Roryokane|Roryokane]] ([[User talk:Roryokane|talk]]) 06:02, 23 November 2024 (UTC)

== My simple-minded approach ==

• Roll d10 once for your first arrow: if 1 to 5, the arrow is cursed, otherwise not;

• Roll d10 again for your second arrow: same rules, but repeat until you have a different number from the first one (so d10 is in fact only a d9 this time)

• I won't calculate probabilities – these are your arrows, live with it ;-)
[[Special:Contributions/172.69.109.51|172.69.109.51]] 07:33, 23 November 2024 (UTC)
:That has the benefit (over 3d6+1d4) of telling you which arrow(s) (if either) was cursed. [[User:RegularSizedGuy|RegularSizedGuy]] ([[User talk:RegularSizedGuy|talk]]) 07:52, 23 November 2024 (UTC)

== The physical difficulties of an M-of-N locking system ==
There seems to be doubt that a "N locks and M keys to unlock them" system could be easily accomplished. I think it could be trivial, with strategically interlocking locked-restraints. A chain formed of bike-locks can give a larger locked loop that can be unlocked by just unlocking any ''single'' one of the constituent locks, leaving the other locked loops to not matter (or you could also try the {{w|Borromean rings}} system, whereby it is again secure against itself, until just one ring is opened up to reveal that the rest now ''aren't even locked at all''...). With almost arbitrary ability to cross-link (or, if you will, repeated/alternating-reflected Borromean triplet connections), you can extend the requirements to more than one unlocking being required (by looping chain elements to mre than just the 'adjacent' loops, sideways onto a parallel meta-loop or up/down the chain, all you might do is allow some slack (could be sufficient to get a thing held directly closed by the taut loop-of-loops, but not enough if the passage of the loop through a hasp/sneck actually prevents the otherwise free movement of the final slide-to-unlock action to occur), but a second (or third, or fourth) unlocking can be required to open-end the whole metaloop of locks. At the top end, M=N solutions are also trivial (e.g. two keys, two locks popularly of safety deposit boxes or [[2677: Two Key System|other things]]). Which is not to say that a specific M-of-N puzzle (where 1<M<N) might not need a ''little'' bit of thought to actually design and implement, but there's no obvious reason why all such combinations shouldn't be nicely doable. [[Special:Contributions/172.69.79.165|172.69.79.165]] 14:56, 23 November 2024 (UTC)
:Can we first confirm that the M-of-N Encryption was what Randall was referencing in the first place? [[Special:Contributions/172.71.154.140|172.71.154.140]] 03:17, 24 November 2024 (UTC)

==Polyhedral Dice==
"other polyhedral dice, with the number of faces denoted by dX (e.g., d10 is a 10-sided die, with numbers from 1 to 10 on it)." - the d10 may be a poor choice as exemplar here; Back in the last century, when I was playing D&D, d10 were typically (and uniquely) numbered 0-9, not 1-10. This may no longer be the case, and I may be showing my age, but if it is still the norm, the d8 or d20 might be a better choice of example. [[Special:Contributions/172.68.210.6|172.68.210.6]] 02:40, 24 November 2024 (UTC)

3008: Proterozoic Rocks

2024-11-07T18:46:45Z

172.71.154.140:

{{comic
| number = 3008
| date = November 6, 2024
| title = Proterozoic Rocks
| image = proterozoic_rocks_2x.png
| imagesize = 740x272px
| noexpand = true
| titletext = These rocks are from a time before eyes, brains, and bones, pieces of a land warmed by an unseen sun.
}}

==Explanation==
{{incomplete|Created by a BLIND PROTEROZOIC BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

{{w|Proterozoic}} rocks such as the 1.1 billion-year-old rocks in the comic were formed 2500 to 538.8 million years ago, and some of them survived the tectonic movements until today. Proterozoic rocks which were formed from sediment at the bottom of an inland sea such as the former {{w|Western Interior Seaway}} would be placed in North America today.

Animal life and the first animal [https://www.pnas.org/doi/10.1073/pnas.1716824114 eyes developed on trilobites] half a billion years ago, around the transition between the proterozoic and the phanerozoic {{w|Cambrian}} period, which saw a great proliferation of biological diversity, also known as the Cambrian Explosion.

In the last two panels Cueball talks about feeling a connection to the rock, which spans "a vast abyss of time that stretches back as far as the eye can see. And then 500 million years farther." This could be interpreted as expressing the need to connect to something that exists vastly beyond the current turbulent era, to put it into perspective and to find strength in knowing that nature transcends human troubles. The distant past without complex eye-bearing life is illustrated by the ultimate panel in black (because there were no eyes). An alternative viewpoint might be to use the dark far past as an analogy for the darkened far future, beyond the immediate cares of the current world, which would also apply perspective upon any and all present worldviews.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Cueball is seen at a distance, walking amid a rocky landscape.]
:I love being near Proterozoic rocks.
:These ones are 1.1 billion years old.
:That's so, '''''so''''' old.

:[Cueball standing next to a rock.]
:Eyes evolved half a billion years ago. The first time a rock was ever looked at, these rocks were already 500 million years old.

:[Cueball sitting atop a large rock.]
:People say geologic time makes them feel small. But when I touch this rock, it's like I'm a part of it, spanning a vast abyss of time that stretches back as far as the eye can see.

:[A completely black panel except for text in white lettering.]
:And then 500 million years farther.

== Trivia ==

This comic was published on the day when {{w|Donald Trump}}'s re-election as president of the USA was announced. Randall was vocal in his support for oppositional candidate {{w|Kamala Harris}}; the xkcd homepage featured [https://web.archive.org/web/20241106175959im_/https://imgs.xkcd.com/news/harris_news@2x.png a drawing with a "Vote for Harris" sign] [https://web.archive.org/web/20241106215812/https://xkcd.com/ during the run-up to the election].

{{comic discussion}}

[[Category:All Comics]]
[[Category:Comics featuring Cueball]]
[[Category:Geology]]
[[Category:Biology]]
[[Category:Comics with inverted brightness]]

2993: Ingredients

2024-10-04T04:09:09Z

172.71.154.140: Reverted vandalism

{{comic
| number = 2993
| date = October 2, 2024
| title = Ingredients
| image = ingredients_2x.png
| imagesize = 417x473px
| noexpand = true
| titletext = Add main-belt asteroids to taste.
}}

==Explanation==
{{incomplete|Created by a THE FIVE BEST EXPLAINXKCD USERS COMBINED INTO ONE - Table of each moons with its special ingredients as well as the volume and surface area, and compare the combined volume and combined surface area to that of Mars (also check both the actual surface area of the five as well as the surface area of a sphere with the total moons volume, which would be a much smaller surface area than of the five moons sum of surface area... Do NOT delete this tag too soon.}}

This comic jokes that it is possible (and perhaps intended) to use the five largest moons in the outer solar system (the {{w|Galilean moons}} and {{w|Titan (moon)|Titan}}) as ingredients to create a “better” planet that has the “coolest features”. Apparently, though, Randall couldn't actually think of anything cool that {{w|Ganymede (moon)|Ganymede}} and {{w|Callisto (moon)|Callisto}} could contribute, so these have just been used as 'filler'. (Though Ganymede has a magnetic field, which is kind of cool...)

Note that {{w|Moon|Earth's moon}} is the fifth-largest moon of the solar system overall ({{w|Europa (moon)|Europa}} is the sixth), so it would have been included had "outer solar system" not been specified.

{| class=wikitable
! scope="col" | Name of Moon
! Scope=“col” | Ingredient
! scope="col" | Volume (km3)
! Scope=“col” | Surface Area (km2)
! scope="col" | Mass (kg)
|-
| Io || Sulfur || 2.53×1010 || 4.17×107 || 0.894×1023
|-
| Europa || Oceans || 1.59×1010 || 3.09×107 || 0.480×1023
|-
| Titan || Hydrocarbons || 7.16×1010 || 8.33×107 || 1.345×1023
|-
| Ganymede || Filler || 7.66×1010 || 8.72×107 || 1.482×1023
|-
| Callisto || Filler || 5.87×1010 || 7.30×107 || 1.076×1023
|-
|}

If all of these moons were lumped together, the total volume of “Randall's planet” would be 2.48×1011 km3, assuming no further material compaction, with a surface area of 1.91×108 km2. This is about 1½ times the volume of Mars, or roughly a 15% larger diameter. The combined mass, however, is smaller than that of Mars.

The title text takes it further, treating asteroids as a “to-taste” ingredient in this “recipe”, treating it more like preparing a food dish rather than making a new {{w|Mars}}-sized planet.

There are a number of science fiction works that posit that advanced alien civilizations left puzzles in the solar system for future humans to solve. Examples for this trope would be {{w|Pushing Ice}} by Alastair Reynolds or {{w|Rogue Moon}} by Algis Budrys. The Arthur C. Clarke stories {{w|The Sentinel (short story)|The Sentinel}}, {{w|Encounter in the Dawn}} (and the more well-known {{w|2001: A Space Odyssey (novel)|book}} and {{w|2001: A Space Odyssey|film}} treatments that together they later helped inspire) each feature various different partial treatments of this concept.

==Transcript==
:[A planet is shown with several different features like oceans and large lakes as well as and craters. It seems like the continent is fused together from five different segments, with cracks between where there is either ocean or rivers. There are four labels above the planet with lines going down to different areas of the planet, but not necessarily pointing to any particular part on the surface, but rather to the entire planet:]
:Sulfur chemistry from Io
:Cool oceans from Europa
:Hydrocarbons from Titan
:Ganymede and Callisto (filler)

:[Caption beneath the panel:]
:Scientists now think the five biggest outer solar system moons are actually just ingredients; we're supposed to combine them to create a single Mars-sized planet that's cooler than any of them.

{{comic discussion}}

[[Category:Space]]
[[Category:Food]]

2986: Every Scientific Field

2024-09-17T08:31:45Z

172.71.154.140: /* Explanation */

{{comic
| number = 2986
| date = September 17, 2024
| title = Every Scientific Field
| image = every scientific field.png
| imagesize =
| noexpand = true
| titletext = Conveniently for everyone, it turns out that dark energy is produced by subterranean parasitoid wasps.
}}

==Explanation==
{{incomplete|Created by a DARK MATTER PARASITOID MICROBE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Randall is making the case that most scientific fields — such as cosmology, microbiology, or entomology as mentioned in the pie chart — spends a disproportionately huge amount of study on only a small number of subjects, which the common layperson might not have even heard of.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

{{comic discussion}}

[[Category:Science]]
[[Category:Charts]]

2966: Exam Numbers

2024-07-31T19:43:48Z

172.71.154.140: /* Explanation */ TITLE TEXT CALLIGRAPHY

{{comic
| number = 2966
| date = July 31, 2024
| title = Exam Numbers
| image = exam_numbers_2x.png
| imagesize = 553x400px
| noexpand = true
| titletext = Calligraphy exam: Write down the number 37, spelled out, nicely.
}}

==Explanation==
{{incomplete|Created by a MATH TEACHER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

The comic depicts various similarly formatted examination questions that might appear on test papers at various points in a student's potential academic careeer. While they all share a similar feel, they are asking for different things, some of which might be considered more serious and examinable proofs of study than others.
{| class="wikitable"
|+ Exam numbers
! Exam level !! Question !! Answer
|-
| Kindergarten math || Write down the biggest number you can think of || At a kindergarden-level education, it is assumed that an individual might write down a relatively small number like 300, depending upon whether they have encountered the concept of hundreds. It might also be interpreted as "what's the highest number that you (think you) can count up to". Given the nature of a child's exuberant glee at learning about ''really'' big (but otherwise normal) numbers, they may even try an answer something like "a million billion squillion gazillion". It is not certain what criteria would be used to mark this question correct or orherwise, it may actually by a stealth question in child psychology or a question that everybody 'gets right' so long as they answer it.
|-
| Pre-algebra || Write down the value of x if x=3x-8 || 4
3x refers to the multiplication of 3 and x. 3x is a convenient shorthand.

By subtracting 3x from both sides, -2x = -8. Divide both sides by -2 to find x=4.

(Verify by plugging x=4 into the original equation. 4 = 3*4 - 8 -> 4 = 12 - 8 -> 4 = 4.)
|-
| Calculus || Write down the value of ∫_0^π x sin^2 x dx || The integral of the expression is (−2x sin(2x)+cos(2x)−2x)/28 + C. Plugging in values for x gives the result as π^2/4, or approximately 2.4674.
|-
| PhD Cosmology || Write down the Hubble constant to within 1% || The exact value of the Hubble constant is not known to this level of accuracy; it is about 2.3 * 10^-18 Hz.
|-
| Game Theory || Write down 10 more than the average of the class's answers || There appears at first glance to be no Nash equilibrium, since no matter what, there will be someone who is incentivised to change their answer to a higher number. However, since the box is of finite size, only finitely many numbers can be written - if everyone writes down a number ten less than a value that cannot be written, everyone scores nothing. There are some very large numbers that can be written succinctly, such as TREE(3), but there are only finitely many.
|-
| Postgraduate Math || Write down the biggest number you can think of || This question echoes the very first example, but would be expected to be answered very differently (unlike a revisiting of most of the others).
Postgraduate math students can probably think of ''very'' large numbers. The 'best' answer could be "infinity" since, depending on your definition of the word "number", infinity may be the largest possible number that you will have encountered. This might heavily depend upon the branch of mathematics you are studying, however, as named (finite) numbers or ones with specific and useful notations might satisfy some questioning contexts, whilst the existence of a whole further set of trans-finite numbers (i.e. increasingly large types of "infinity") would be important considerations in others.

As with the kindergarten question, they may be no previously anticipated 'correct' answer. It could be another "correct nust so long as you answer it" (or perhaps 'sensibly' so) or the mark goes only to those giving the greatest number across all submissions.
|-
| Calligraphy (title text) || Write down the number 37, spelled out (as "thirty-seven" or "thirty seven"), nicely || Calligraphy, in a nutshell, is the art of fancy writing. The title text expands the joke outside the realm of math and points out that since calligraphy does not require any math skills, the only way a calligraphy exam would even mention numbers is if one had to write them out in such a way as to showcase their calligraphic skill.
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[6 different math test questions.]

:[The first panel:]
:Kindergarten math final exam
:Q. Write down the biggest number you can think of
:A. [empty box]

:[The second panel:]
:Pre-algebra final exam
:Q. Write down the value of x if x=3x-8
:A. [empty box]

:[The third panel:]
:Calculus final exam
:Q. Write down the value of [integral sign, from 0 to pi] x sin^2 x dx
:A. [empty box]

:[The fourth panel:]
:PhD cosmology final exam
:Q. Write down the Hubble constant to within 1%
:A. [empty box]

:[The fifth panel:]
:Game theory final exam
:Q. Write down 10 more than the average of the class's answers
:A. [empty box]

:[The sixth panel:]
:Postgraduate math final exam
:Q. Write down the biggest number you can think of
:A. [empty box]

{{comic discussion}}

[[Category:Math]]
[[Category:Cosmology]]

==References==
<references />

2929: Good and Bad Ideas

2024-05-07T23:27:39Z

172.71.154.140: /* Table of the entries */

{{comic
| number = 2929
| date = May 6, 2024
| title = Good and Bad Ideas
| image = good_and_bad_ideas_2x.png
| imagesize = 595x522px
| noexpand = true
| titletext = While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.
}}

==Explanation==
{{incomplete|Created by a BLOOD FOR THE BLOOD GOD- Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This is a scatter plot comparing how good an idea sounds to how good the idea is. For example, leaded gasoline sounded like a good idea due to its anti-knocking effects, but is a bad idea due to lead toxicity. Fake prank fire extinguishers both sound bad and ''are'' bad, as they can make a dangerous situation worse. Putting mold on infections sounds like a bad idea, but some molds, like ones containing penicillin, have helpful antibiotic effects.

The title text combines leaded gasoline and a fake prank fire extinguisher into something worse than either. The fire extinguisher is fake and releases flammable material onto the fire, and there is additional lead toxicity.

===Table of the entries===
{| class="wikitable"
|-
! Idea !! What it means !! How good it sounds !! How good it actually is !! Explanation
|-
|Leaded gasoline||Adding {{w|Tetraethyllead|tetraethyl lead}} as an antiknocking agent to allow for increased performance||++||---||Leaded gasoline was introduced in the early 1920s to allow higher pressures and temperatures in an engine without causing {{w|Engine_knocking|detonation (knocking)}}, allowing for increased fuel efficiency and engine performance; it also works to prevent engine valve wear. In essence, it artificially raises the {{w|octane rating}} of the fuel, reducing the need for fuel refinement, thus reducing waste and/or expense. Lead, however, is both toxic and bioaccumulative, meaning that lead released into the air over decades built up to harmful levels in people (as well as other animals) and almost certainly contributed to a host of health issues. Some scientists even suppose that {{w|Lead–crime hypothesis|crime level depends on lead exposure}}. (It should be noted that this only "[sounded] like a good idea" due to deliberate campaigns to obscure the known dangers).
|-
|Bloodletting||Releasing "bad blood" from the veins||---||---||You need (most of) your blood. Losing [https://www.ncbi.nlm.nih.gov/books/NBK542273/#:~:text=In%20a%20healthy%20adult%2C%20there,deviations%20in%20their%20vital%20signs. more than 15%] of a person's total blood volume results in adverse effects. Bloodletting has been performed as a medical procedure for at least 2000 years until the 19th century. The idea was to withdraw blood to balance the body's "humors". Despite this long history, the notion that bleeding someone is bad seems like basic common sense, and it's now well-understood that blood-letting (outside of [https://what-if.xkcd.com/98/#:~:text=if%20you%20drink%20blood%20regularly%2C%20over%20a%20long%20period%20of%20time%20the%20buildup%20of%20iron%20in%20your%20system%20can%20cause%20iron%20overload.%20this%20syndrome%2C%20which%20sometimes%20affects%20people%20who%20have%20repeated%20blood%20transfusions%2C%20is%20one%20of%20the%20few%20conditions%20for%20which%20the%20correct%20treatment%20is%20bloodletting.%5B6%5D certain rare and specific cases]) does no good, causes significant harm and quite certainly causes many deaths when it is used.
|-
|{{w|Asbestos}}||Mineral which does not burn, tolerates extremely high temperatures and forms small fibers. These qualities make it excellent for insulation and fire protection||+++||---||Asbestos was used extensively in ships and buildings throughout most of the 20th century. Unfortunately, the microscopic fibers that make up asbestos greatly increase the risk of cancer when inhaled, causing its use to be banned in most countries.
|-
|Extension cords with prongs on both ends||allows easy connection between 2 female connectors||0 (neutral)||---||Prongs on both ends would make it easier to plug the extension cord in on either side. But once plugged into an outlet, the other end becomes a serious shock hazard, as seen in [https://www.youtube.com/watch?v=L08LjkN1k70 this Backyard Scientist video].
|-
|Stair kayaking||Riding down a flight of stairs in a {{w|kayak}}||--||---|| Stair kayaking is a stunt where a person positions a kayak at the top of a flight of stairs and then, using their paddle to push off, rides the kayak down the stairs (Example video showing kayaking down an escalator shown [https://youtu.be/46BjHAxgddU?t=154 here]). This poses significant easily foreseeable risks of injury or death, as well as being very bad for the kayak, which is designed to ride on {{w|Kayak|water}}, not stairs.{{Citation needed}}
|-
|Fake prank fire extinguishers||||---||---|| The idea of placing fake fire extinguishers as a prank, presumably so that a person who thinks they are grabbing a real fire extinguisher will instead find a decoy, sounds very dangerous and potentially life-threatening for many people, and it would be highly dangerous. In the United States, (and presumably most countries), this would also be a felony in most, if not all, jurisdictions. An example of a similar situation, although not intended as a prank, can be found [https://twitter.com/ThatSamWinkler/status/1657154071051239424 here].
The title text expands this idea by having the prank fire extinguishers filled with (leaded) gasoline. This is literally adding fuel to the fire.
|-
|Always saying what you think||...regardless of the feelings of others or other considerations||++||--||Openness and honesty are seen as positive character traits in people. However, taking it to the extreme of ''always'' telling people what you think about them, can lead to awkward or unpleasant situations. It may harm your relationship with the other person if they don't like what you think, or they may reply without concern for ''your'' feelings or other considerations. Keeping negative thoughts to yourself or telling "white lies" can be considered a better alternative in some situations.
|-
|Replying to spammers||Clicking on the "Reply" button from spam mails and writing (and sending) a reply (or worse, clicking on the links in these emails)||--||--||At best, you confirm your email address and identify yourself as someone likely to respond to such unsolicited messages and so encourage the spammers to deluge you with even more messages. At worst, the spammer may use your correspondence to extract sensitive information about you or make you a victim of a scam.
|-
|Solar cars||Having {{w|Solar panel|solar panels}} on the car's surface (mostly hood and roof) for power generation||+++||-||Powering electric vehicles with solar panels seems like an excellent idea: it would provide free power with no increased land use, and theoretically could allow a vehicle to operate indefinitely without being fueled or charged. However, such vehicles couldn't operate without batteries (due to power requirements, weather conditions, shade from roadside features and nighttime driving), so they'd have increased complexity compared to plug-in or hybrid cars. Adding solar panels would add cost, weight, manufacturing complexity and maintenance requirements. Solar panels on moving cars are less efficient than in stationary installations and subject to damage from both collisions and road debris. Solar cars do exist (the {{w|World Solar Challenge}} is a competition for such cars), but as a practical form of transportation, the negatives likely outweigh the positives.
|-
|Heelies||{{w|Heelys}} are shoes with an inline skate wheel embedded in the sole, at the heel. ||+||-||Heelys allow the wearer (usually children) to shift between normal walking and rolling like being on skates. This sounds like fun but led to numerous injuries. See: Childs, Dan (2009-02-10) [2007-06-04]. [https://web.archive.org/web/20221001021115/https://abcnews.go.com/Health/Exercise/story?id=3242181&page=1 "Heelys Hazardous for Kids, Study Finds"]. ''ABC News Medical Unit''. Archived from [https://abcnews.go.com/Health/Exercise/story?id=3242181&page=1 the original] on 2022-10-01. Retrieved 2024-05-07.
|-
|Prequels||A work of fiction (mostly movie) telling the "story before the story" of another work of fiction.||+++||-||More of a good story sounds great on the surface, and audiences who are invested in a set of characters and/or a setting often love the idea of finding out what led up to certain events. But there are several pitfalls. Any spin-off of a popular property risks becoming a low-quality cash grab. Prequels, specifically, are constrained by the fact that they have to lead to the story that's already been released, which can lead to contrived storytelling. There's less room for suspense since the future of the storyline has already been established. There's a tendency to invent or fill in detailed backstories, which can undermine character arcs, and/or destroy the mystery and nuance of certain characters. Prequels can be good, of course, but there are a lot of ways they can go wrong.
|-
|Transitions® lenses||A brand name for {{w|Photochromic_lens|photochromic lenses}} in glasses, which get darker (like sunglasses) in bright light.||+||-||Photochromic lenses are clear lenses that darken when exposed to UV light, then turn clear again when the exposure is removed. The advantage is that wearers of glasses don't need to buy separate (prescription) sunglasses. However, the process is relatively slow (about a minute) so not so useful when there is a quick succession of shade and bright light, perhaps in a forest or when driving. Also, the car windscreen filters out UV light to some degree, which prevents the glasses from darkening as required. Finally, the process is temperature dependent, so in hot weather, the glasses don't become as dark, and in cold weather they might stay dark for too long.
|-
|Cutting pizza in squares||Cutting (a presumably round) pizza in squares||-||-||Most people cut pizza into wedges and hold it by the crust. Cutting it into squares allows for more pieces to be shared, but pieces near the center will have no crust to hold it by, getting cheese and sauce all over your fingers. There will also be lots of leftover tiny pieces. While hardly a disaster like the other items in its quadrant, square pizza pieces are just not very useful and rather inefficient. Cutting a rectangular pizza into squares might not suffer from the problems above, but, unless the pizza itself is square and cut only into four squares, some people will end up with a higher crust-to-topping ratio than others. Cutting a round pizza into squares is popular in Chicago and is sometimes called tavern-style or party-cut and some<nowiki>[</nowiki>''{{w|Wikipedia:Manual_of_Style/Words_to_watch#Unsupported_attributions|who?}}''<nowiki>]</nowiki> consider it the real Chicago style pizza rather than deep dish pizza<nowiki>[</nowiki>''{{w|Wikipedia:Accuracy_dispute#Disputed_statement|dubious}}''<nowiki>]</nowiki>.
|-
|{{w|Project Orion (nuclear propulsion)|Project Orion}}||Study by the U.S. government looking into nuclear pulse propulsion for spacecraft.||---||-||Using repeated nuclear explosions to generate motion sounds bad for both the spacecraft and everything else, especially with a ground launch, but there are ways to address a lot of the concerns, so it isn't as bad as it sounds. Project Orion's theorized specific impulse and thrust would also be far higher than anything chemical rockets can accomplish. The efficiency of Project Orion is extremely low, however, and the {{w|ablation}} issues are extremely difficult to overcome.

See also [[2423:_Project_Orion | comic 2423: Project Orion]].
|-
|Soup||{{w|Soup}}||0 (neutral)||0 (neutral)||Soup is probably one of the oldest foods created by prehistoric cooks. Many people enjoy it, though some consider many soups somewhat lacking as a meal on their own, or boring.
|-
|Combo washer dryers||A device that combines washing machine and laundry dryer into one device||+++||+||Better at space efficiency, but worse at each task than separate devices.
|-
|Cutting sandwiches diagonally||Cutting sandwiches diagonally||+||+||[https://www.popularmechanics.com/science/math/a32690399/triangles-rectangles-best-way-cut-sandwich-math/ Generally] [https://www.npr.org/2009/11/28/120914097/rectangles-vs-triangles-the-great-sandwich-debate regarded] as the superior way to slice a sandwich, providing more aesthetically pleasing display of the contents, better support in the hand and fewer all-crust bites. Required in the assembly of a club sandwich,{{actual citation needed}} where the diagonal components are stacked again.
|-
|{{w|Diverging diamond interchange}}s||Road junction where the two (sets of) lanes cross over to switch sides (so if you normally drive on the right, now you drive on the left), then switch back to normal after the junction||-||+||Highway engineers believe the shape improves safety and traffic flow through the interchange because switching to the other side facilitates merging to and from the other road in the junction. However, the shape appears to be insanity to an unfamiliar driver.
|-
|Toasting sandwiches||Making a sandwich first and then cooking it, as in a dedicated {{w|Pie_iron|sandwich toaster}}, a {{w|toaster oven|toaster oven}}, frying pan or under a grill.||++||++||The grilled cheese sandwich is a familiar form to most people, and many other sandwiches are improved by toasting as a final step. Others, such as the {{w|western sandwich|Western}} or {{w|club sandwich|club}} are prepared using toast. The {{w|peanut butter, banana and bacon sandwich|Elvis}} is a specific case of a sandwich that normally wouldn't be toasted, but is improved by it - peanut butter, bacon, banana, and jelly, with the assembly lightly fried.
|-
|Crumple zones||Designated areas of a car that crumple in case of a crash. ||--||++||Most peoples' intuition would be that stronger cars are safer, and intending parts of a vehicle to collapse ''by design'' might seem crazy. But engineered crumple zones are designed to absorb the kinetic energy in a vehicle collision, and do so in such a way as to protect the passenger cabin. This significantly reduces the danger of injury or death from crashes.
|-
|Sliced bread||Bread, sliced by the baker before packaging for sale||+++||++||It's far more convenient for making sandwiches or toast, but unfortunately pre-sliced bread will go stale faster and some applications may be better off thicker or thinner than the slices provided. Sliced bread is often used as a comparator for how good something is in the phrase 'the best thing since sliced bread'.
|-
|Pizza||{{w|Pizza}}||++||++||Pizza is a widely popular dish throughout much of the world, uncontroversial {{w|Anchovies_as_food|except}} {{w|Pineapple|certain}} [https://www.taste.com.au/recipes/nutty-choc-pizza-fresh-berries/2c0220a4-8463-45ff-b2ba-ac7e5012a006 toppings].
|-
|Eating citrus fruit while at sea||Having a supply of {{w|citrus fruit}} on long sea journeys, especially during the {{w|Age of Sail}} ||0 (neutral)||+++||For a long time, {{w|Scurvy|scurvy}} was a danger to sailors, who generally subsisted on a monotonous diet with low vitamin content while on ships. Most citrus fruits are rich in vitamin C, which prevents scurvy. Eating orange or lemons doesn't seem like a significant activity one way or the other, but it's an easy way to prevent a disease that causes serious ill-health and possibly a painful death.
|-
|Putting mold on infections||Seemingly a reference to the ancient practice of pressing moldy bread against infected wounds||---||++||While this sounds like a good way to get a fungal infection, with the correct mold this is a primitive antibiotic, and led to the discovery of {{w|penicillin}}.
|-
|Wheels on luggage||Some luggage bags have small wheels inset on their frame and a carrying handle.||+++||+++||A relatively simple fitting for rigid or semi-rigid luggage that substantially eases its transport over long distances on flat surfaces such as travel terminals.
|-
|{{w|Heat pump}}s||Refrigeration (or air conditioning) technology operated in reverse to heat an area instead.||++||+++||Heat pumps use refrigeration cycles to warm a space or mass, but aren't designed to generate heat. Instead, they extract thermal energy from the surrounding environment. This allows a space to be heated with significantly less energy use than a furnace or resistance heater. Because these units are operated by electricity, they can provide heating with renewable energy (potentially using {{w|thermal energy storage}} for load-shifting), reduce or eliminate the need for natural gas connections, and prevent several risks that come with traditional furnaces (such a carbon monoxide leaks and fires). In addition, heat pumps use the same refrigeration cycles as air conditioners, so a single unit can be designed to both heat and cool a building. It sounds like a good idea and works out pretty well in real life.
|-
|Laser eye surgery||Surgical techniques using lasers for precision cutting in the eyeball.||-||+++||In the popular imagination, lasers are often thought of as something used for destroying their target. Firing them into people's eyes, then, does not sound like a great idea. However. this technology has substantially improved the eyesight of millions of people worldwide by allowing the treatment of eye problems otherwise only corrected by lenses or entirely untreatable. Randall has previously commented on laser eye surgery, amongst other ideas both good and bad, in [[1681: Laser Products]].
|-
|Fecal transplants||Transfer of the gut microbiome of a healthy person to the sterilized gut of an ill person.||---||+++||The gut microbiome is a collection of bacteria that lives in our guts. It can influence our health. It is responsible for the last stages of digesting our food. It can also produce neurotransmitters that are carried by blood to our brain influencing our behavior. A healthy microbiome can be destroyed by bad eating habits, unhealthy lifestyles, acquired infections or the use of antibiotics. The important part is the composition of different species of bacteria that compromise the biome. Sometimes it may be necessary to completely sterilize the gut and then take a sample of a healthy biome from another person. A sample is enough as the bacteria will multiply. As long as the patient eats correctly, the microbiome after transplant should develop correctly.

It sounds bad because we tend to think of our feces as something gross, to be discarded. It is called fecal transplant as our feces contain about 50% of gut bacteria, but nowadays the sample usually takes the form of a coated pill that is applied rectally.
|-
|}

==Transcript==
:[Two axes with double arrows cross each other in the middle. At the end of each arrow, there are labels. Scattered over the chart are 28 entries. Below these entries are given for each of the four quadrants, plus three that are on the Y-axis. For each quadrant the entries are listed in reading order, top to bottom left to right.]

:[X axis from left to right:]
:Sounds like a good idea
:Sounds like a bad idea

:[Y axis from top to bottom:]
:Actually a bad idea
:Actually a good idea

:[Top left quadrant (sounds like a good idea, actually a bad idea):]
:Leaded gasoline
:Asbestos
:Always saying what you think
:Solar cars
:Heelies
:Prequels
:Transitions® lenses

:[Top middle (actually a bad idea):]
:Extension cords with prongs on both ends

:[Top right quadrant (sounds like a bad idea, actually a bad idea):]
:Bloodletting
:Fake prank fire extinguishers
:Stair kayaking
:Replying to spammers
:Cutting pizza in squares
:Project Orion

:[Center (neutral):]
:Soup

:[Bottom left quadrant (sounds like a good idea, actually a good idea):]
:Combo washer dryers
:Cutting sandwiches diagonally
:Toasting sandwiches
:Sliced bread
:Pizza
:Wheels on luggage
:Heat pumps

:[Bottom middle (actually a good idea):]
:Eating citrus fruit while at sea

:[Bottom right quadrant (sounds like a bad idea, actually a good idea):]
:Diverging diamond interchanges
:Crumple zones
:Putting mold on infections
:Laser eye surgery
:Fecal transplants

==Trivia==
*A much leaner version of this comic appeared in the first [[What If? (book) | "What If?" book]], chapter "Weird (and Worrying) Questions from the What If? Inbox, #9".

{{comic discussion}}

[[Category:Charts]]
[[Category:Scatter plots]]
[[Category:Rankings]]
[[Category:Food]]

2929: Good and Bad Ideas

2024-05-07T23:26:49Z

172.71.154.140: /* Explanation */

{{comic
| number = 2929
| date = May 6, 2024
| title = Good and Bad Ideas
| image = good_and_bad_ideas_2x.png
| imagesize = 595x522px
| noexpand = true
| titletext = While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.
}}

==Explanation==
{{incomplete|Created by a BLOOD FOR THE BLOOD GOD- Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This is a scatter plot comparing how good an idea sounds to how good the idea is. For example, leaded gasoline sounded like a good idea due to its anti-knocking effects, but is a bad idea due to lead toxicity. Fake prank fire extinguishers both sound bad and ''are'' bad, as they can make a dangerous situation worse. Putting mold on infections sounds like a bad idea, but some molds, like ones containing penicillin, have helpful antibiotic effects.

The title text combines leaded gasoline and a fake prank fire extinguisher into something worse than either. The fire extinguisher is fake and releases flammable material onto the fire, and there is additional lead toxicity.

===Table of the entries===
{| class="wikitable"
|-
! Idea !! What it means !! How good it sounds !! How good it actually is !! Explanation
|-
|Leaded gasoline||Adding {{w|Tetraethyllead|tetraethyl lead}} as an antiknocking agent to allow for increased performance||++||---||Leaded gasoline was introduced in the early 1920s to allow higher pressures and temperatures in an engine without causing {{w|Engine_knocking|detonation (knocking)}}, allowing for increased fuel efficiency and engine performance; it also works to prevent engine valve wear. In essence, it artificially raises the {{w|octane rating}} of the fuel, reducing the need for fuel refinement, thus reducing waste and/or expense. Lead, however, is both toxic and bioaccumulative, meaning that lead released into the air over decades built up to harmful levels in people (as well as other animals) and almost certainly contributed to a host of health issues. Some scientists even suppose that {{w|Lead–crime hypothesis|crime level depends on lead exposure}}. (It should be noted that this only "[sounded] like a good idea" due to deliberate campaigns to obscure the known dangers).
|-
|Bloodletting||Releasing "bad blood" from the veins||---||---||You need (most of) your blood. Losing [https://www.ncbi.nlm.nih.gov/books/NBK542273/#:~:text=In%20a%20healthy%20adult%2C%20there,deviations%20in%20their%20vital%20signs. more than 15%] of a person's total blood volume results in adverse effects. Bloodletting has been performed as a medical procedure for at least 2000 years until the 19th century. The idea was to withdraw blood to balance the body's "humors". Despite this long history, the notion that bleeding someone is bad seems like basic common sense, and it's now well-understood that blood-letting (outside of {{https://what-if.xkcd.com/98/#:~:text=if%20you%20drink%20blood%20regularly%2C%20over%20a%20long%20period%20of%20time%20the%20buildup%20of%20iron%20in%20your%20system%20can%20cause%20iron%20overload.%20this%20syndrome%2C%20which%20sometimes%20affects%20people%20who%20have%20repeated%20blood%20transfusions%2C%20is%20one%20of%20the%20few%20conditions%20for%20which%20the%20correct%20treatment%20is%20bloodletting.%5B6%5D|certain rare and specific cases}}) does no good, causes significant harm and quite certainly causes many deaths when it is used.
|-
|{{w|Asbestos}}||Mineral which does not burn, tolerates extremely high temperatures and forms small fibers. These qualities make it excellent for insulation and fire protection||+++||---||Asbestos was used extensively in ships and buildings throughout most of the 20th century. Unfortunately, the microscopic fibers that make up asbestos greatly increase the risk of cancer when inhaled, causing its use to be banned in most countries.
|-
|Extension cords with prongs on both ends||allows easy connection between 2 female connectors||0 (neutral)||---||Prongs on both ends would make it easier to plug the extension cord in on either side. But once plugged into an outlet, the other end becomes a serious shock hazard, as seen in [https://www.youtube.com/watch?v=L08LjkN1k70 this Backyard Scientist video].
|-
|Stair kayaking||Riding down a flight of stairs in a {{w|kayak}}||--||---|| Stair kayaking is a stunt where a person positions a kayak at the top of a flight of stairs and then, using their paddle to push off, rides the kayak down the stairs (Example video showing kayaking down an escalator shown [https://youtu.be/46BjHAxgddU?t=154 here]). This poses significant easily foreseeable risks of injury or death, as well as being very bad for the kayak, which is designed to ride on {{w|Kayak|water}}, not stairs.{{Citation needed}}
|-
|Fake prank fire extinguishers||||---||---|| The idea of placing fake fire extinguishers as a prank, presumably so that a person who thinks they are grabbing a real fire extinguisher will instead find a decoy, sounds very dangerous and potentially life-threatening for many people, and it would be highly dangerous. In the United States, (and presumably most countries), this would also be a felony in most, if not all, jurisdictions. An example of a similar situation, although not intended as a prank, can be found [https://twitter.com/ThatSamWinkler/status/1657154071051239424 here].
The title text expands this idea by having the prank fire extinguishers filled with (leaded) gasoline. This is literally adding fuel to the fire.
|-
|Always saying what you think||...regardless of the feelings of others or other considerations||++||--||Openness and honesty are seen as positive character traits in people. However, taking it to the extreme of ''always'' telling people what you think about them, can lead to awkward or unpleasant situations. It may harm your relationship with the other person if they don't like what you think, or they may reply without concern for ''your'' feelings or other considerations. Keeping negative thoughts to yourself or telling "white lies" can be considered a better alternative in some situations.
|-
|Replying to spammers||Clicking on the "Reply" button from spam mails and writing (and sending) a reply (or worse, clicking on the links in these emails)||--||--||At best, you confirm your email address and identify yourself as someone likely to respond to such unsolicited messages and so encourage the spammers to deluge you with even more messages. At worst, the spammer may use your correspondence to extract sensitive information about you or make you a victim of a scam.
|-
|Solar cars||Having {{w|Solar panel|solar panels}} on the car's surface (mostly hood and roof) for power generation||+++||-||Powering electric vehicles with solar panels seems like an excellent idea: it would provide free power with no increased land use, and theoretically could allow a vehicle to operate indefinitely without being fueled or charged. However, such vehicles couldn't operate without batteries (due to power requirements, weather conditions, shade from roadside features and nighttime driving), so they'd have increased complexity compared to plug-in or hybrid cars. Adding solar panels would add cost, weight, manufacturing complexity and maintenance requirements. Solar panels on moving cars are less efficient than in stationary installations and subject to damage from both collisions and road debris. Solar cars do exist (the {{w|World Solar Challenge}} is a competition for such cars), but as a practical form of transportation, the negatives likely outweigh the positives.
|-
|Heelies||{{w|Heelys}} are shoes with an inline skate wheel embedded in the sole, at the heel. ||+||-||Heelys allow the wearer (usually children) to shift between normal walking and rolling like being on skates. This sounds like fun but led to numerous injuries. See: Childs, Dan (2009-02-10) [2007-06-04]. [https://web.archive.org/web/20221001021115/https://abcnews.go.com/Health/Exercise/story?id=3242181&page=1 "Heelys Hazardous for Kids, Study Finds"]. ''ABC News Medical Unit''. Archived from [https://abcnews.go.com/Health/Exercise/story?id=3242181&page=1 the original] on 2022-10-01. Retrieved 2024-05-07.
|-
|Prequels||A work of fiction (mostly movie) telling the "story before the story" of another work of fiction.||+++||-||More of a good story sounds great on the surface, and audiences who are invested in a set of characters and/or a setting often love the idea of finding out what led up to certain events. But there are several pitfalls. Any spin-off of a popular property risks becoming a low-quality cash grab. Prequels, specifically, are constrained by the fact that they have to lead to the story that's already been released, which can lead to contrived storytelling. There's less room for suspense since the future of the storyline has already been established. There's a tendency to invent or fill in detailed backstories, which can undermine character arcs, and/or destroy the mystery and nuance of certain characters. Prequels can be good, of course, but there are a lot of ways they can go wrong.
|-
|Transitions® lenses||A brand name for {{w|Photochromic_lens|photochromic lenses}} in glasses, which get darker (like sunglasses) in bright light.||+||-||Photochromic lenses are clear lenses that darken when exposed to UV light, then turn clear again when the exposure is removed. The advantage is that wearers of glasses don't need to buy separate (prescription) sunglasses. However, the process is relatively slow (about a minute) so not so useful when there is a quick succession of shade and bright light, perhaps in a forest or when driving. Also, the car windscreen filters out UV light to some degree, which prevents the glasses from darkening as required. Finally, the process is temperature dependent, so in hot weather, the glasses don't become as dark, and in cold weather they might stay dark for too long.
|-
|Cutting pizza in squares||Cutting (a presumably round) pizza in squares||-||-||Most people cut pizza into wedges and hold it by the crust. Cutting it into squares allows for more pieces to be shared, but pieces near the center will have no crust to hold it by, getting cheese and sauce all over your fingers. There will also be lots of leftover tiny pieces. While hardly a disaster like the other items in its quadrant, square pizza pieces are just not very useful and rather inefficient. Cutting a rectangular pizza into squares might not suffer from the problems above, but, unless the pizza itself is square and cut only into four squares, some people will end up with a higher crust-to-topping ratio than others. Cutting a round pizza into squares is popular in Chicago and is sometimes called tavern-style or party-cut and some<nowiki>[</nowiki>''{{w|Wikipedia:Manual_of_Style/Words_to_watch#Unsupported_attributions|who?}}''<nowiki>]</nowiki> consider it the real Chicago style pizza rather than deep dish pizza<nowiki>[</nowiki>''{{w|Wikipedia:Accuracy_dispute#Disputed_statement|dubious}}''<nowiki>]</nowiki>.
|-
|{{w|Project Orion (nuclear propulsion)|Project Orion}}||Study by the U.S. government looking into nuclear pulse propulsion for spacecraft.||---||-||Using repeated nuclear explosions to generate motion sounds bad for both the spacecraft and everything else, especially with a ground launch, but there are ways to address a lot of the concerns, so it isn't as bad as it sounds. Project Orion's theorized specific impulse and thrust would also be far higher than anything chemical rockets can accomplish. The efficiency of Project Orion is extremely low, however, and the {{w|ablation}} issues are extremely difficult to overcome.

See also [[2423:_Project_Orion | comic 2423: Project Orion]].
|-
|Soup||{{w|Soup}}||0 (neutral)||0 (neutral)||Soup is probably one of the oldest foods created by prehistoric cooks. Many people enjoy it, though some consider many soups somewhat lacking as a meal on their own, or boring.
|-
|Combo washer dryers||A device that combines washing machine and laundry dryer into one device||+++||+||Better at space efficiency, but worse at each task than separate devices.
|-
|Cutting sandwiches diagonally||Cutting sandwiches diagonally||+||+||[https://www.popularmechanics.com/science/math/a32690399/triangles-rectangles-best-way-cut-sandwich-math/ Generally] [https://www.npr.org/2009/11/28/120914097/rectangles-vs-triangles-the-great-sandwich-debate regarded] as the superior way to slice a sandwich, providing more aesthetically pleasing display of the contents, better support in the hand and fewer all-crust bites. Required in the assembly of a club sandwich,{{actual citation needed}} where the diagonal components are stacked again.
|-
|{{w|Diverging diamond interchange}}s||Road junction where the two (sets of) lanes cross over to switch sides (so if you normally drive on the right, now you drive on the left), then switch back to normal after the junction||-||+||Highway engineers believe the shape improves safety and traffic flow through the interchange because switching to the other side facilitates merging to and from the other road in the junction. However, the shape appears to be insanity to an unfamiliar driver.
|-
|Toasting sandwiches||Making a sandwich first and then cooking it, as in a dedicated {{w|Pie_iron|sandwich toaster}}, a {{w|toaster oven|toaster oven}}, frying pan or under a grill.||++||++||The grilled cheese sandwich is a familiar form to most people, and many other sandwiches are improved by toasting as a final step. Others, such as the {{w|western sandwich|Western}} or {{w|club sandwich|club}} are prepared using toast. The {{w|peanut butter, banana and bacon sandwich|Elvis}} is a specific case of a sandwich that normally wouldn't be toasted, but is improved by it - peanut butter, bacon, banana, and jelly, with the assembly lightly fried.
|-
|Crumple zones||Designated areas of a car that crumple in case of a crash. ||--||++||Most peoples' intuition would be that stronger cars are safer, and intending parts of a vehicle to collapse ''by design'' might seem crazy. But engineered crumple zones are designed to absorb the kinetic energy in a vehicle collision, and do so in such a way as to protect the passenger cabin. This significantly reduces the danger of injury or death from crashes.
|-
|Sliced bread||Bread, sliced by the baker before packaging for sale||+++||++||It's far more convenient for making sandwiches or toast, but unfortunately pre-sliced bread will go stale faster and some applications may be better off thicker or thinner than the slices provided. Sliced bread is often used as a comparator for how good something is in the phrase 'the best thing since sliced bread'.
|-
|Pizza||{{w|Pizza}}||++||++||Pizza is a widely popular dish throughout much of the world, uncontroversial {{w|Anchovies_as_food|except}} {{w|Pineapple|certain}} [https://www.taste.com.au/recipes/nutty-choc-pizza-fresh-berries/2c0220a4-8463-45ff-b2ba-ac7e5012a006 toppings].
|-
|Eating citrus fruit while at sea||Having a supply of {{w|citrus fruit}} on long sea journeys, especially during the {{w|Age of Sail}} ||0 (neutral)||+++||For a long time, {{w|Scurvy|scurvy}} was a danger to sailors, who generally subsisted on a monotonous diet with low vitamin content while on ships. Most citrus fruits are rich in vitamin C, which prevents scurvy. Eating orange or lemons doesn't seem like a significant activity one way or the other, but it's an easy way to prevent a disease that causes serious ill-health and possibly a painful death.
|-
|Putting mold on infections||Seemingly a reference to the ancient practice of pressing moldy bread against infected wounds||---||++||While this sounds like a good way to get a fungal infection, with the correct mold this is a primitive antibiotic, and led to the discovery of {{w|penicillin}}.
|-
|Wheels on luggage||Some luggage bags have small wheels inset on their frame and a carrying handle.||+++||+++||A relatively simple fitting for rigid or semi-rigid luggage that substantially eases its transport over long distances on flat surfaces such as travel terminals.
|-
|{{w|Heat pump}}s||Refrigeration (or air conditioning) technology operated in reverse to heat an area instead.||++||+++||Heat pumps use refrigeration cycles to warm a space or mass, but aren't designed to generate heat. Instead, they extract thermal energy from the surrounding environment. This allows a space to be heated with significantly less energy use than a furnace or resistance heater. Because these units are operated by electricity, they can provide heating with renewable energy (potentially using {{w|thermal energy storage}} for load-shifting), reduce or eliminate the need for natural gas connections, and prevent several risks that come with traditional furnaces (such a carbon monoxide leaks and fires). In addition, heat pumps use the same refrigeration cycles as air conditioners, so a single unit can be designed to both heat and cool a building. It sounds like a good idea and works out pretty well in real life.
|-
|Laser eye surgery||Surgical techniques using lasers for precision cutting in the eyeball.||-||+++||In the popular imagination, lasers are often thought of as something used for destroying their target. Firing them into people's eyes, then, does not sound like a great idea. However. this technology has substantially improved the eyesight of millions of people worldwide by allowing the treatment of eye problems otherwise only corrected by lenses or entirely untreatable. Randall has previously commented on laser eye surgery, amongst other ideas both good and bad, in [[1681: Laser Products]].
|-
|Fecal transplants||Transfer of the gut microbiome of a healthy person to the sterilized gut of an ill person.||---||+++||The gut microbiome is a collection of bacteria that lives in our guts. It can influence our health. It is responsible for the last stages of digesting our food. It can also produce neurotransmitters that are carried by blood to our brain influencing our behavior. A healthy microbiome can be destroyed by bad eating habits, unhealthy lifestyles, acquired infections or the use of antibiotics. The important part is the composition of different species of bacteria that compromise the biome. Sometimes it may be necessary to completely sterilize the gut and then take a sample of a healthy biome from another person. A sample is enough as the bacteria will multiply. As long as the patient eats correctly, the microbiome after transplant should develop correctly.

It sounds bad because we tend to think of our feces as something gross, to be discarded. It is called fecal transplant as our feces contain about 50% of gut bacteria, but nowadays the sample usually takes the form of a coated pill that is applied rectally.
|-
|}

==Transcript==
:[Two axes with double arrows cross each other in the middle. At the end of each arrow, there are labels. Scattered over the chart are 28 entries. Below these entries are given for each of the four quadrants, plus three that are on the Y-axis. For each quadrant the entries are listed in reading order, top to bottom left to right.]

:[X axis from left to right:]
:Sounds like a good idea
:Sounds like a bad idea

:[Y axis from top to bottom:]
:Actually a bad idea
:Actually a good idea

:[Top left quadrant (sounds like a good idea, actually a bad idea):]
:Leaded gasoline
:Asbestos
:Always saying what you think
:Solar cars
:Heelies
:Prequels
:Transitions® lenses

:[Top middle (actually a bad idea):]
:Extension cords with prongs on both ends

:[Top right quadrant (sounds like a bad idea, actually a bad idea):]
:Bloodletting
:Fake prank fire extinguishers
:Stair kayaking
:Replying to spammers
:Cutting pizza in squares
:Project Orion

:[Center (neutral):]
:Soup

:[Bottom left quadrant (sounds like a good idea, actually a good idea):]
:Combo washer dryers
:Cutting sandwiches diagonally
:Toasting sandwiches
:Sliced bread
:Pizza
:Wheels on luggage
:Heat pumps

:[Bottom middle (actually a good idea):]
:Eating citrus fruit while at sea

:[Bottom right quadrant (sounds like a bad idea, actually a good idea):]
:Diverging diamond interchanges
:Crumple zones
:Putting mold on infections
:Laser eye surgery
:Fecal transplants

==Trivia==
*A much leaner version of this comic appeared in the first [[What If? (book) | "What If?" book]], chapter "Weird (and Worrying) Questions from the What If? Inbox, #9".

{{comic discussion}}

[[Category:Charts]]
[[Category:Scatter plots]]
[[Category:Rankings]]
[[Category:Food]]

1017: Backward in Time

2024-04-30T21:55:16Z

172.71.154.140:

{{comic
| number = 1017
| date = February 15, 2012
| title = Backward in Time
| image = backward_in_time.png
| titletext = People tell me I have too much time on my hands, but really the problem is that there's too much time, PERIOD.
}}

Clicking the image at xkcd.com links to [https://docs.google.com/spreadsheet/pub?key=0Ak43bGxHGI1adDMtOHVWVXZrYzhKd2VtbFJJMmJPTEE&single=true&gid=1&output=html this spreadsheet], which [[Randall]] used to calculate the times and dates for the comic. It also has a lot of other percentages and dates, so take a look if you are interested.

==Explanation==

[[Cueball]]/[[Randall]] creates this formula which helps him wait for long stretches of time which goes increasingly faster into the past as more time goes by, which gives him the effect of looking like the time goes by quickly. Which assists in the waiting process.

As far as the actual math is concerned, the formula is an {{w|exponential function}} (i.e. the variable appears in the exponent). The effect that the function grows faster and faster as p grows, is due to T(p) being exponential. More precisely, when you repeatedly add some constant to the exponent, you will repeatedly multiply some (other) constant with the value of the function. Compare how "slow" a value grows by adding even high values (1, 1001, 2001, 3001, 4001, 5001…) and how fast it grows by multiplying even low values (1, 10, 100, 1000, 10000, 100000…)

Now, the function has to be adjusted so that, as Randall put it, "the time spent in each part of the past is loosely proportional to how well I know it." The most important adjustment is putting p to the power of three. That lowers the amount added to the exponent for low values (0.1³=0.001, 0.2³=0.008, i.e. only 7/1000 have been added for 10% workflow) and increases the amount for high values (0.8³=0.512, 0.9³=0.729, i.e. more than 1/5 has been added for 10% workflow). That means the recent past will pass even slower and the historic past even faster than it already does by choosing an exponential function.
The remaining adjustments are technical. The coefficient in front of p³ adjusts the constant by which the result will be multiplied while adding some constant to p, while it also roughly ensures that p=1 yields the lifetime of the universe. The 3 added to the product in the exponent further adjusts the actual values of the power without touching the slope (the multiplicative constant). In the parentheses, e³ is subtracted to put the time to 0 when p=0. Otherwise the function would start approx. 20 yrs and 1 month ago. For bigger p, this offset does not matter much. Imagine subtracting 20 yrs from the lifetime of the universe!

Finally, the result is subtracted from the current date for aesthetical reasons. The formula could tell you "20 yrs ago", or it could read "February 1992". Randall decided the latter would be better.

There is actually a mathematical error in this comic; the inverse function in grey writing off at the bottom right of the main formula involves a square root, when the actual inverse of Randall's main function would involve a cube root. In addition, this function does not contain the current date, meaning that T, in the inverse, refers to how long ago a point in time was, rather than the point in time itself. When the T in the inverse is 20, it means that the date referenced by T is 20 years ago.

The punchline "Swoosh!" is about how fast the last few percents of Cueball's download happen in "such a rush". For most humans waiting for a download to complete tends to become really boring and progress would instead seem to get slower and slower.

{| class="wikitable"
|-
! Percent || Amount of Time Ago || Around This Time: || Explanation of Time Period
|-
| 0% || Now (As of the comics writing this would have been Feburary 15 2012) || N/A || It is {{w|Singles Awareness Day}}.
|-
| 7.308% || December 18 2011 || Kim Jong-il Dies, US Leaves Iraq|| ...
|-
| 10% || Sep. 2011 || N/A || This would be around the date of the tenth aniversary of the {{w|9/11 Attacks}}. Randall also got married around this time.
|-
| 20% || 2008 || N/A || ...
|-
| 30% || 1997 || N/A || {{w|O.J. Simpson|OJ Simpson}} was found liable for the deaths of {{W|Nicole Brown}} and {{w|Ronald Goldman}}. OJ owed the two families $35.5 million. Princess Diana died.
|-
| 31.12% || February 1995 || Windows 95 Debuts, OJ Found Not Guilty|| The {{w|Murder trial of O. J. Simpson|OJ Simson trial}} was a famous trial where OJ was tried for the murders of his ex-wife Nicole Brown Simpson and her friend Ronald Goldman. DNA evidence almost proved his guilt, however the defense pointed out the evidence wasn't collected correctly and could have been cross contaminated. Because of this, the jury found OJ not guilty of the double murder.
|-
| 40% || 1958 || N/A || ...
|-
| 47.91% || 1844 || Rubber Vulcanized, Bicycle Invented, Wrench Patented || ...
|-
| 50% || 1776 || N/A || On July 4th, the American colonies {{w|Lee Resolution|declared independence}} from Great Britain. This event started a {{w|American Revolutionary War|7 year war}}, in which, the colonies won their indepence.
|-
| 60% || 405 AD || N/A || The {{w|War of Radagaisus}} started. Radagaisus lead a group of about 100,000 men across the Alps into Rome. Six of the nine {{w|Sibylline Books}} were burned.
|-
| 70% || 22,000 Years Ago || N/A || ...
|-
| 70.33 || 24,Years Ago || Caves Painted, Ceramic Art Made. Neanderthals Extict || ...
|-
| 80% || 671,000 Years Ago || N/A || ...
|-
| 90% || 55 Million Years Ago || N/A || ...
|-
| 90.42% || 68 Million Years Ago || First flowering plants. Chicxulub impact kills off most dinosaurs. || ...
|-
| 100% || 13.76 billion years ago || Universe begins. First stars ignite. || ...
|}
[[940|(Also, the workout website, Fitocracy has been mentioned previously in xkcd.)]]

Note that as of the time that this page was last cached, the comic was uploaded at {{#expr:100*(((ln(({{#time:U}}-1329195600)/31536000+e^3)-3)/20.3444)^.5)}}% progress.

==Transcript==
:When I have a boring task to get through — a three-hour lecture, a giant file download, or a long term point goal in fitocracy — I use this formula to convert the percentage completed (p) into a date:

:T=(Current Date) - (e^(20.3444*p^3+3) - e^3) years

:When the task is 0% done, it gives today's date, and as I make progress, I move further and further back in time

:(inverse given in lighter colors)
:Inverse: p = sqrt((ln(T+e^3)-3)/20.3444)

:[Line Graph explaining the correlation between completion percentages and temporal deltas.]
:0% = now (Date of comic is 2012-02-14T00:00-0500, approx. 1329195600 UNIX)
:10% = September 2011
:20% = 2008
:30% = 1997
:40% = 1958
:50% = 1776
:60% = 405 AD
:70% = 22,000 years ago
:80% = 671,000 years ago
:90% = 55 million years ago
:100% = 13.8 billion years ago

:It moves slowly through the first few years, then steadily accelerates. I tuned the formula so the time spent in each part of the past is loosely proportional to how well I know it. This means I hit familiar landmarks with each bit of progress, giving me a satisfying sense of movement.

:[The following are panels detailing completion percentages, correlated time periods, and notable events from this time period.]

:7.308% December 18, 2011
:Around this time:
:Kim Jong-Il dies. US leaves Iraq.

:31.12% February 1995
:Around this time:
:Windows 95 debuts. OJ found not guilty.

:47.91% 1844
:Around this time:
:Rubber vulcanized, bicycle invented, wrench patented.

:70.33% 24,000 years ago
:Around this time:
:Caves painted, ceramic art made. Neanderthals extinct.

:90.42% 68 million years ago
:Around this time:
:First flowering plants. Chicxulub impact kills off most dinosaurs.

:100% 13.76 billion years ago
:Around this time:
:Universe begins. First stars ignite.

:Download complete.

:[Cueball watches a download progress on a laptop in amazement and happiness. Megan stands nearby and looks at Cueball with a bemused posture.]
:Cueball: Swoosh! Watching all that time blur past is such a rush!
:Megan: So...you've tried to make an extreme sport out of...''waiting''.
:Cueball: ''Swoosh!''

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Charts]]
[[Category:Timelines]]
[[Category:Math]]

2916: Machine

2024-04-07T18:36:05Z

172.71.154.140: consistency with table

{{comic
| number = 2916
| date = April 5, 2024
| title = Machine
| image = machine_2x.png
| imagesize = 740x740px
| noexpand = true
| titletext = The Credible Machine
}}* To experience the interactivity, visit the [https://xkcd.com/2916/ original comic].

==Explanation==
{{incomplete|Created by a WELL OILED ROBOT. Do NOT delete this tag too soon.}}
This is the 14th [[:Category:April fools' comics|April fools' comic]] released by [[Randall]]. The previous April fools' comic was [[2765: Escape Speed]] from 2023, which was released on Wednesday, April 19, 2023.

Once again an April Fool's Day Comic came out late, as Randall did not release this on April 1st, even though April 1st did fall on a Monday, a normal release day. It first came four days later with the Friday release on April 5th. That this is to be considered an April fools' comic, in spite of the later release, was confirmed on the xkcd Facebook page, see the [[#Trivia|trivia section]] below.

This is a spin on the game {{w|The Incredible Machine}}.

Upon loading the page, you are presented with marbles being added to a box by geared wheels, with a button to open a “tool panel”. You are encouraged by Cueball to direct the marbles into a little “output” gear, and that marbles have a lifespan of 30 seconds to reduce clutter. There are large and small boards available for use, as well as some gimmicky stuff like prisms (which deflect marbles) and fans (that blow marbles around).

The comic starts in a main screen where the user can create a {{w|Rube Goldberg machine}} in a "Cell" where the goal is to route a constant stream of colored balls from an input on the ceiling or a wall to outputs of a matching color on the walls or floor. After the comic is first opened a window pops up over the machine where Cueball in a lab coat tells you to route the balls from the inputs to the outputs. If any balls are left in your cell for more than 30 seconds, they fade away. The first time a ball fades away another popup informs you that the balls are removed for security reasons. When you have built a machine which succeeds in routing enough balls to the output, a popup will prompt you to submit your cell to be added to the public machine.

<gallery heights="200" widths="150">
File:2916_popup_intro.png|Introduction popup
File:2916_popup_time.png|Time limit popup
File:2916_popup_submit.png|Submission popup
</gallery>

The button in the bottom right corner brings you to a page where you can drag around to view all of the machines that have been submitted, with a title for each in the upper left corner. In this view you can see that all of the outputs are also inputs for another cell, except for the top row where the inputs come from off screen and the lowest row which output through a launcher of some kind to a set of four colored-coded containers far below. Any empty cells are marked off by yellow tape with the words "UNDER CONSTRUCTION" as well as "DJIA ↑ 31415" once in each cell. "DJIA" stands for the Dow Jones Industrial Average, with "DJIA ↑ 31415" indicating that it rose to 31415 points, 31415 being the first five digits of pi, without the period.

When you press submit, you will see your creation placed on the grid. However if you refresh that cell will likely be under construction or replaced with someone else's machine. However, other people's machines are consistently placed, so it appears that there is some moderation process selecting a machine for each cell out of the machines submitted by users.

The grid is 12 cells wide, and grows in height. The largest size observed so far is 12x44, for a total of 528 cells. The machine's height is determined by the lowest cell; This can be either your submitted cell, or a cell created by another user.

Whenever balls reach the bottom of the grid, they are directed towards 4 containers, one of each color. Below the containers is a pit. If no balls are entering the containers or pit, it will be empty. If one or two streams of balls are making it, Cueball and Megan sit in a small boat named the USS Buoyancy. More streams of balls are likely to add more changes.

===Toolbox items===
{| class="wikitable" style="margin:auto"
|+ List of objects
|-
! Description !! Effect !! Image
|-
| Plank || Static || [[File:2916_plank.png|frameless|upright=0.25]]
|-
| Hammer || Static || [[File:2916_hammer.png|frameless|upright=0.25]]
|-
| Sword || Static || [[File:2916_sword.png|frameless|upright=0.25]]
|-
| Hinged scoop || Rotates around its hinge, tries to stay upright with a springy effect || [[File:2916_scoop.png|frameless|upright=0.25]]
|-
| Anvil || Static || [[File:2916_anvil.png|frameless|upright=0.125]]
|-
| Brick || Static || [[File:2916_brick.png|frameless|upright=0.125]]
|-
| Fan || Blows away balls in front of it. Different colors are affected by differing amounts (yellow balls are lightest, and can be levitated above an upward-facing fan).|| [[File:2916_fan.png|frameless|upright=0.125]]
|-
| Pillow || Balls will not bounce if they hit it || [[File:2916_pillow.png|frameless|upright=0.125]]
|-
| Round bumper || Bounces balls away at significantly higher speed || [[File:2916_round_bumper.png|frameless|upright=0.125]]
|-
| Triangle bumper left || Bounces balls away at significantly higher speed || [[File:2916_bumper_left.png|frameless|upright=0.125]]
|-
| Triangle bumper right || Bounces balls away at significantly higher speed || [[File:2916_bumper_right.png|frameless|upright=0.125]]
|-
| Attractor/Black Hole || Pulls balls toward center, can be resized || [[File:2916_attractor.png|frameless|upright=0.125]]
|-
| Repulsor/White hole || Repels balls away from center, can be resized || [[File:2916_repulsor.png|frameless|upright=0.125]]
|-
| Prism || "Refracts" balls as they enter and exit || [[File:2916_prism.png|frameless|upright=0.125]]
|-
| Wheel || Spins normally (anticlockwise), deflects balls, can jam with enough resistance (e.g. glut of balls or against other elements). || [[File:2916_wheel.png|frameless|upright=0.125]]
|-
| "Good job" trophy || Static || [[File:2916_trophy.png|frameless|upright=0.125]]
|-
| Glass cup || Static || [[File:2916_cup.png|frameless|upright=0.125]]
|}

{| class="wikitable" style="margin:auto"
|+ Characters
|-
! Description !! Image
|-
| Ponytail with raised arms || [[File:2916_ponytail_arms.png|frameless|upright=0.125]]
|-
| Ponytail standing || [[File:2916_ponytail.png|frameless|upright=0.125]]
|-
| Cueball with raised arms || [[File:2916_cueball_arms.png|frameless|upright=0.125]]
|-
| White Hat || [[File:2916_whitehat.png|frameless|upright=0.125]]
|-
| Knit Cap sliding or resting? || [[File:2916_knitcap_resting.png|frameless|upright=0.25]]
|-
| Knit Cap || [[File:2916_knitcap.png|frameless|upright=0.125]]
|-
| Helmet? || [[File:2916_helmet.png|frameless|upright=0.125]]
|-
| Probably Deterministic sign || [[File:2916_deterministic.png|frameless|upright=0.25]]
|-
| Squirrel || [[File:2916_squirrel.png|frameless|upright=0.125]]
|-
| Rabbit || [[File:2916_rabbit.png|frameless|upright=0.125]]
|-
| Cat || [[File:2916_cat.png|frameless|upright=0.125]]
|}

=== Color routing ===
The different ball colors have different physical properties. Red balls are more bouncy than other balls, green balls are heavier, and yellow balls are lighter and slightly bouncy. The following values were extracted from the code:
{| class="wikitable sortable"
! Color
! Mass
! Density
! Restitution (bounciness)
! Linear damping (drag)
|-
! data-sort-key="00F" | Blue
| 0.08
| 1
| 0
| 0
|-
! data-sort-key="F00" | Red
| 0.08
| 1
| 0.8
| 0
|-
! data-sort-key="0F0" | Green
| 0.75
| 9.325
| 0
| 0
|-
! data-sort-key="FF0" | Yellow
| 0.024
| 0.3
| 0.6
| 2
|}

For certain combinations of inlet and outlet 'gates', it is necessary to 'cross the streams'. e.g. to direct righthand-entry balls to a lefthand-exit and vice-versa. It is possible to just construct the field to send two (or more!) sets of balls to fly across a common gap, to land on an appropriate reception area that leads to the chosen exit. But, though this is not {{w|Proton pack#Crossing the streams|completely inadvised}}, the timing of the balls cannot be guaranteed to be in sync (or, rather, anti-sync) with each other and collisions ''will'' occur, especially under the variations of delivery that might significantly alter the ballistic path across the gap. Even if the trial machine works, in isolation with a steady stream of all balls entering the field of play, once submitted it will inevitably be fed by a more chaotically-routed preceeding construction.

In order to maintain sufficient correct arrivals at exits, it may be necessary to add a method of filtering the hues.

This could just mean introducing a 'wrong hue trap' beyond any crossing point(s) that send the occasionally wrong ball back to the cross point (or let them time-out in a dead-end, relying upon few enough failures from the rest of the balls, along with all colliding balls that subsequently missed ''any'' chance of reaching an exit). Alternatively, two (or more) feeds of marbles could be fed through a deliberate 'sorter' that does a sufficiently reasonable job of separating the combined sets out towards their intended target-exits.

The various physical qualities of the balls suggest a number of methods for redirecting separate hues to separate onward journeys. This can be done by isolating a hue from every other hue, then passing on (if necessary) to a setup extracting a different one from the remainder, and perhaps also a third time. It may also be possible to merge 'arrangements' of sorting mechanics to efficiently distribute straight into three ''or even four'' onward tracks towards the desired outputs, but that is left as an exercise to the reader.


{| class="wikitable"
! style="background-color:black; color:white" | To separate !! style="background-color:lightblue" | Blue !! style="background-color:lightgreen" | Green !! style="background-color:yellow" | Yellow !! style="background-color:red" | Red
|-
! style="background-color:red" | Red
| *R/B* | '''Use 'bounce''''
The sole difference is how much balls will rebound from objects. Well managed and constrained ricochets should allow a sorting action.
| *R/G* | '''Use mass or 'bounce''''
Green balls cannot be levitated by a vertical fan. An incline across any such fan(s) will levitate only non-Greens. Green, like Blue, rebounds differently to Red. Green balls are also effected by black holes much less than all other balls.
| *R/Y* | ''See Y/B''
| *R/R* style="text-align: center; background-color:black; color:white" | n/a
|-
! style="background-color:yellow" | Yellow
| *Y/B* | '''All methods'''
Yellow, alone, exhibits high drag against any unforced motion. It is also unique in all other ways; e.g. can be levitated highest, against all other hues (though most profoundly against Green).
| *Y/G* | ''See Y/B''
| *Y/Y* style="text-align: center; background-color:black; color:white" | n/a
| *Y/R* style="text-align: center; background-color:gray" | ''See Y/B'' 
|-
! style="background-color:lightgreen" | Green
| *G/B* | '''Use mass'''
Green balls cannot be levitated by a vertical fan. There is also a not so marginal difference in density that might be exploited, such as by using black holes, which only minimally effects green.
| *G/G* style="text-align: center; background-color:black; color:white" | n/a
| *G/Y* style="text-align: center; background-color:gray" | ''See Y/B'' 
| *G/R* style="text-align: center; background-color:gray" | See R/G
|-
! style="background-color:lightblue" | Blue
| *B/B* style="text-align: center; background-color:black; color:white" | n/a
| *B/G* style="text-align: center; background-color:gray" | See G/B
| *B/Y* style="text-align: center; background-color:gray" | See Y/B
| *B/R* style="text-align: center; background-color:gray" | See R/B
|}

Even when not strictly necessary for one's own submission, once submitted into the full playing grid the player's own contribution may find itself working with less 'pure' delivered ball-streams (from an imperfectly separating feed-in contribution). It is possible that this more interactive disruption can make the new setup behave erratically or even entirely incorrectly.

It might be thought good practice (but not ''necessary'') to deliberately combine any or all inputs and do a full job of splitting them again, just in anticipation of possibly having to deal with such cross-contamination and being able to 'clean up' the onward stream(s) for the benefit of others. This would of course be particularly difficult if the isolated building-phase does not provide all four hues to 'test' against, so any speculatively added filtering would have to be added 'blind' (and only on the offchance that any anticipated incorrect balls will actually enter the arena) and without any legitimate exits to which such rejects could be shunted (therefore could accumulate, up until any 'time out' that might apply to any ball once operational as part of the combined grid).

Single-input/single-output designs might not particularly require ''any'' sorting mechanism, in theory, though the unexpected 'contamination' of the system with balls of different masses/etc could perhaps introduce malfunctioning passage from the added chaos it might succumb to.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[The placeholder image shows four balls, colored red, green, yellow and blue, bouncing on top of three white blocks. Text in the center: "[visit xkcd.com to view]"]

:[Cueball with lab coat, intro popup]
:Cueball: Balls falling into your cell should be routed to the outputs at a steady rate.

:[Cueball with lab coat, warning popup]
:Cueball: For security reasons, balls that remain in your device for more than 30 seconds will be removed and destroyed.

:[Cueball with lab coat, submit popup]
:Cueball: Congratulations! Your contraption has passed all tests. Press [submit button] to submit it to be added to the machine!

==Trivia==
*Randall acknowledges the people who helped him create this comic in a [[Header_text#Machine|comic-specific header text]].
**With 11 different involved apart from Randall this is by far the comic with most people involved.
*When Randall posted a [https://www.facebook.com/TheXKCD/posts/pfbid0Cs97awQZi1ZiaEXouAex9tXrwAS3qJV3RmAiuCq5uvZQwqZVMgDmcqJ7JU9LYodYl link to this comic] on his [https://www.facebook.com/TheXKCD Facebook feed], he directly wrote that it was a late April Fools' Day!
**MACHINE
**Happy Belated April Fool's Day!
*This thus ends any discussion of whether this should be seen as an April Fool's comic or not.
**It just came out 4 days late. This has also happened several times since [[Garden]].
[[File:2916 Machine Facebook April fools' confirmation.png]]

{{comic discussion}}

[[Category:April fools' comics]]
[[Category:Comics with color]]
[[Category:Dynamic comics]]
[[Category:Comics with animation]]
[[Category:Interactive comics]]

2524: Comet Visitor

2024-02-29T00:54:29Z

172.71.154.140: /* Explanation */

{{comic
| number = 2524
| date = October 4, 2021
| title = Comet Visitor
| image = comet_visitor.png
| titletext = It's a myth that the Great Wall of China is the only human-made structure visible from space--there are LOTS of structures for us to feel self-conscious about!
}}

==Explanation==
{{w|C/2014 UN271 (Bernardinelli-Bernstein)|Comet C/2014 UN271}} is a large comet that was discovered in 2014 almost as far from the Sun as the orbit of Neptune, and it will reach its closest approach in 2031, near Saturn's orbit. It's an {{w|Oort Cloud}} comet, with a {{w|Orbital period|period}} of more than 4 million years. Since modern humans ({{w|homo sapiens}}) evolved about 300,000 years ago (although tool-making ancestors were around about 2.5 million years ago), the last time it was among the planets was indeed long before humans evolved.

When a long-period comet comes into the inner Solar System, it's often figuratively called a "visit". But Megan and Cueball treat this more literally (or perhaps more sarcastically). Just as one usually neatens up their home when they're expecting guests, to make a good impression, they realize they need to clean up the Earth and its vicinity in preparation for this "visitor". Cueball starts handing out assignments -- he'll clean up the {{w|Pacific Garbage Patch}}, and suggests that Megan take care of all the {{w|Space debris|debris in orbit}}.

Cueball and Megan also make notes to sweep up the lunar footprints that NASA astronauts left on the Moon during the Apollo missions and put away the [[:Category:Mars rovers|Mars rovers]]. It's also common for people expecting visitors to put various objects out of view with the intention of returning them to their normal place after the visit, usually because the objects are considered unsightly that under normal circumstances is outweighed by the convenience of being out in the open.

However, since the comet will not come anywhere close to Earth and Mars, all this hardly seems necessary; it would be like cleaning up your home because the President or some other dignitary will be visiting your town. In addition, while a dignitary would theoretically be able to see one's house, although comets have {{w|comet tails|tails}}, they do not have eyes,{{Citation needed}} so they would not be able to perceive any difference between Earth before and after tidying up (even if the {{w|comet nucleus|nucleus}} had an eye, it would not be able to see because it is in a {{w|Coma (cometary)|coma}}, [[No Pun Intended|no pun intended]]). Furthermore, sweeping footprints in the Moon, that Cueball sees as a way of tidying up, would be seen as [https://www.smithsonianmag.com/science-nature/nasa-looks-to-protect-historic-sites-on-the-moon-47186092/ destroying an invaluable archaeological sites by NASA and other people].

Alternatively, Megan and Cueball aren't "cleaning up" for a visitor as one might do if the visitor was a friend of theirs. They're [[1377|hiding themselves and contraband]] as one might do if they were worried the police were visiting. Or more likely in this context that it could be an alien visit, and they would like to make it difficult to spot the human civilization from space. In that case they might need to shut down all light in every big city on Earth as well.

The title text debunks the claim that the {{w|Great Wall of China}} is the only {{w|Artificial_structures_visible_from_space|human-made structure visible from outer space}}; in fact the Great Wall cannot easily be distinguished from space (as it is very long but not wide), but some other human constructions such as the Pyramids can (and cities are easily visible at night because they emit light).

==Transcript==

:[Megan sits at a desk in front of a computer, looking to the left off-panel and pointing at the screen]
:Megan: Have you seen this big comet, C/2014 UN271?
:Megan: It'll pass near Saturn's orbit in 10 years.

:[In a frameless panel, Cueball stands behind Megan, who is now looking at the computer and typing]
:Cueball: Wow, look at the orbital period.
:Megan: Yeah, it hasn't been to this part of the solar system since humans evolved.
:Megan: At '''''least.'''''

:[Cueball starts running off-panel, holding his finger in the air. Megan looks towards him with both arms resting on the back of her chair]
:Cueball: Well, we definitely need to tidy up. I'll start on the Pacific Garbage Patch, you tackle orbital debris.
:Megan: What about the moon footprints?
:Cueball: Sweep them up. Collect the Mars rovers, too!
:Cueball: We can put them back once it's gone.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Astronomy]]
[[Category:Mars rovers]]

2784: Drainage Basins

2023-06-03T19:14:27Z

172.71.154.140: /* Explanation */ by

{{comic
| number = 2784
| date = June 2, 2023
| title = Drainage Basins
| image = drainage_basins_2x.png
| imagesize = 659x500px
| noexpand = true
| titletext = After a pail of water was thrown on the Wicked Witch of the West outside Salt Lake City, Utah's Great Salt Lake was measured to be 7 parts per trillion witch by volume.
}}

==Explanation==
{{incomplete|Created by a LIQUID 90s KID. Do NOT delete this tag too soon.}}
Alex Mack, the main character in the Nickelodeon show ''{{w|The Secret World of Alex Mack}}'' [https://web.archive.org/web/20120516025126/http://articles.latimes.com/1994-10-02/news/tv-45351_1_alex-mack], developed superpowers after being drenched by an experimental substance. One of these is the ability to turn into a puddle of liquid.

A {{w|drainage basin}} is an area of land where all flowing water converges by one or more outlets to the same body of water. The comic shows a {{w|Drainage divide|watershed map}} for the United States, by depicting the drainage basins.

When Randall sees a map of the US's major drainage basins, he thinks of Alex turning into liquid and flowing as part of the basin she happens to be in at the time.

The title text refers to the {{w|Wicked Witch of the West}}, a character from ''{{w|The Wonderful Wizard of Oz}}''. When a bucket of water is thrown on her, causing her to dissolve into a puddle. If this happens near {{w|Salt Lake City}} she'll flow into Utah's {{w|Great Salt Lake}}. If its dissolved particles are measured, a tiny fraction will be witch. Seven trillionths of its 18.93 cubic km volume is about 130 liters, which is approximately twice the volume of a typical human being — Randall may be including the Witch's sister, the Wicked Witch of the East as well. The {{w|Land of Oz}} is descibed to be somewhere else entirely, surrounded by desert and thus perhaps has its own salt-lake basin(s); but famously it is not in Kansas, from which any witch-water would have ultimately flowed down to the Gulf of Mexico via the Mississippi.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Title, scribbled out in red:] <s>US Drainage Basins</s>
:[New title, in red, added below:] Where Alex Mack Will End Up

:[Map of the United States, the state borders in light pen; the national borders, seaboards and major lakes in black pen, plus additional boundaries as appropriate between the following labeled drainage basins:]
:[Much or all of Washington, Idaho, Oregon, California, Arizona and about half of Utah:] Pacific Ocean
:[Hawaiian islands, in typical US map repositioning:] Pacific Ocean
:[Alaska, in typical map repositioning, below a line approximately the three quarters up from the south:] Pacific Ocean
:[Remainder of Alaska:] Arctic Ocean
:[Most of Nevada, the western half of Utah (including the Great Salt Lake, outlined) and about a third of California (with the Salton Sea outlined):] Great Basin
:[A small patch of Wyoming, a triangle of New Mexico lying on the Mexican border and a separate thin swathe through parts of New Mexico and Texas:] Various Basins
:[About half of North Dakota and a small section of northern Minnesota:] Hudson Bay
:[From northeast Minnesota across two thirds of Wisconsin, Michigan, a bit of northern Indiana, northern half of Ohio, and most of the eastern seaboard states of Maine, Vermont, New Hampshire, Massachusetts, New York, Long Island, New Jersey, Maryland, Virginia (not West Virginia), North and South Carolinas, half of Georgia and half of Florida (Lake Okeechobee visible):] Atlantic Ocean
:[All remaining states or parts of states:] Gulf of Mexico

:[Caption below the panel:]
:How I still think of these maps, deep down

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Comics with red corrections]]
[[Category:Geography]]
[[Category:US maps]]
[[Category:Fiction]]

2783: Ruling Out

2023-06-02T20:46:05Z

172.71.154.140: /* Explanation */ typo in prior edit

{{comic
| number = 2783
| date = May 31, 2023
| title = Ruling Out
| image = ruling_out_2x.png
| imagesize = 295x396px
| noexpand = true
| titletext = We were able to replicate and confirm prior authors' detection of a moon orbiting the Earth with high confidence.
}}

==Explanation==
{{incomplete|Created by a TECTONICALLY-ACTIVE BOT WITH SUBSURFACE OCEANS. Do NOT rule out this tag too soon.}}

Most science studies are intended to discover new knowledge. In astronomy, the goal is often to find different types of objects in space, or learn how astronomical objects are formed and behave. But often from studying things that exist, we also learn about limits of the kinds of things that ''can'' exist; when this happens, we say that we've "ruled out" the excluded phenomena.

[[Cueball]] lists five obviously impossible objects.

* "Earthlike stars": A play on "Earth-like planets" which scientists are very interested in finding. The Earth is not a star, hence stars cannot be Earthlike.
: Searches for both {{w|List of potentially habitable exoplanets|Earth-like planets}} and {{w|Solar analog|Sun-like stars}} go unabated, with various near matches found.

* "Exoplanets in our solar system": {{w|Exoplanet}}s are by definition not in our solar system.
: Planets in our solar system (even {{w|Planets beyond Neptune|undiscovered ones}}) are unaffected, as is the {{w|List of exoplanet search projects|search for exoplanets}} around other stars, with conclusive evidence of both.

* "Habitable-zone quasars": {{w|Quasar}}s in the {{w|habitable zone}}s of stars are only theoretically feasible for small {{w|black hole}}s with active {{w|accretion disk}}s inside our habitable zone with Earth and brighter than the Sun, because of the technical criteria for classifying them in terms of their {{w|apparent magnitude}} relative to that of their galaxy.[https://iopscience.iop.org/article/10.1088/0004-637X/728/1/26] None such have ever been observed.{{fact}} While typical galaxies usually have only one quasar in their center, merging galaxies often have two far apart.
:While not certain, habitable zones around some quasars have not been ruled out.[https://iopscience.iop.org/article/10.3847/1538-4357/ab1b2f/meta][https://iopscience.iop.org/article/10.1088/1742-6596/2364/1/012057/meta]

* "Stars with subsurface oceans": Because the temperatures inside stars are higher than that which can support the existence of liquids as we understand them, stars cannot have subsurface oceans. After many billions of years, a {{w|white dwarf}} will cool to the point where it no longer emits significant heat or light, becoming a {{w|black dwarf}}, eventually cooling to the point where it might develop subsurface liquids.{{acn}} However, the universe is not old enough for any black dwarfs to exist yet,[https://iopscience.iop.org/article/10.1086/375341/pdf] and sufficiently cool black dwarfs might not even be considered stars, but rather {{w|rogue planet}}s.
: The possibility of subsurface oceans within various planets and moons is an {{w|Extraterrestrial liquid water|active subject of study}}. and was previously mentioned 10 comics ago in [[2773: Planetary Scientist]].

* "Tectonically active black holes": Black holes do not have {{w|tectonic plate}}s, so they cannot be tectonically active.
: There are theories that neutron stars can exhibit {{w|Quake (natural phenomenon)#Starquake|tectonic-like movements}} (as some of the more typical rocky bodies certainly do), but the physics of the 'inside' of a black hole are thought to involve {{w|Black hole#Singularity|strange physics}} incompatible with any form of geology, and cannot be observed anyway – it is believed that the only externally-observable properties of black holes are mass, electric charge, and angular momentum, poetically called the '{{w|no-hair theorem}}'.

The joke is that you don't actually have to study anything to come to these almost patently obvious conclusions. The counter-proposals would need far more effort to even justify them as valid theories, by common understanding, and greater still to try to observe any supporting proof.

Some studies are also done to confirm the results of previous studies, to ensure that the conclusions were not mistaken or a fluke. The title text describes a study that was done to confirm the existence of a moon orbiting Earth, even though the existence of the Moon has been known for at least as long as humanity has existed, and the fact that it orbits the Earth has been assumed or known for upwards of 3000 years. The ancient Greeks and Babylonians, for example, thought that the Moon orbited the Earth, though they lacked a detailed physical understanding of the system (they also believed, erroneously,{{Citation needed}} that {{w|Geocentric model|everything else in the universe orbited the Earth too}}). {{w|Anaxagoras}} (c. 500–428 BC) is credited with the correct explanation of lunar eclipses, and reportedly was the first to explain that the Moon shines due to reflected light from the Sun. However, it was not until the work of {{w|Nicolaus Copernicus}} in the 16th century that a detailed and accurate model of the Moon's orbit around the Earth was developed. Regardless, at this stage, a study to confirm the validity of Copernican orbits would contribute nothing to the scientific process, much less a study confirming the mere existence of the Moon.

==Transcript==

:[Cueball is talking to Megan.]
:Cueball: So far our astronomy group has published studies ruling out the existence of Earthlike stars, exoplanets in our solar system, habitable-zone quasars, stars with subsurface oceans, and tectonically active black holes.

:[Caption below the panel:]
:Science got way easier when we realized you were allowed to do studies just to rule stuff out.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Astronomy]]
[[Category:Science]]