explain xkcd - User contributions [en]

3061: Water Balloons

2025-03-11T23:28:34Z

172.70.110.214:

{{comic
| number = 3061
| date = March 10, 2025
| title = Water Balloons
| image = water_balloons_2x.png
| imagesize = 578x713px
| noexpand = true
| titletext = Update: The physics department has recruited an astronomer who studies meteor fireballs.
}}

==Explanation==
{{incomplete|Created by a BOT SHORT CIRCUITING DUE TO A WATER BALLOON - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
The comic graphs the mass vs the lifetime of three objects: {{w|meson}}s, {{w|water balloon}}s and {{w|planet}}s. Mesons, which are subatomic particles, have a very low mass and a very short lifetime, as they naturally decay into other fundamental particles.{{Actual citation needed}} "Flying water balloons" are depicted as having a mass centered around 1 kilogram, but the area outlined covers a very broad range of mass (from rontograms—a millionth of a billionth of a picogram—to an octillian metric tons), and a lifetime centered around 1 second (but the area outlined covers from a hundred-millionth of a nanosecond to ~3.2 trillion years), indicating the approximate amount of time that a water balloon survives after being thrown through the air. (Not all water balloons break on impact, and some are thrown directly into someone's face, thus flight time would be very short.) Finally, planets have a very large mass and a very long lifetime, as they tend to exist for billions of years.

This comparison is somewhat absurd because the objects being compared - mesons, water balloons, and planets - do not have much in common. The joke is revealed in the image caption: an "annual interdepartmental water balloon fight" where multiple departments of a facility/company are pit against each other.

Allegedly, because water balloons are so different from both mesons and planets in terms of size and lifetime (roughly the same number of orders of magnitude), meson particle physicists and planetary scientists are usually evenly matched in water balloon fights. This suggests that deep specialization in a field of study deprives a normal person of their basic aptitude to perform in more 'everyday' activities, but at least it equally disadvantages each of the two teams of researchers and makes for a more satisfyingly [[1819: Sweet 16|competitive match-up]] than with one team clearly far more proficient than the other. By the same logic, one might assume that more generalized physicists might study similar objects with the mass and lifetime of water balloons (if not water balloons themselves!), and other topics of education might also confer an 'advantage' (for example, biologists may study similarly-sized bodies of creatures, whilst chemists may monitor chemical reactions that could take an equivalent time to complete).

In real life, water balloon fights are completely unrelated to particle physics or planetary science, and there's nothing stopping a particle physicist or planetary scientist from ''also'' having experience with water balloons.

The title text continues the joke by stating that "The physics department has recruited an astronomer who studies meteor fireballs". This is likely referring to the fact that [[3049: Incoming Asteroid|meteors are closer in size and lifetime to water balloons]] than either mesons or planets, so having an astronomer with this area of expertise would be advantageous in a water balloon fight against scientists who study either of the latter. While "space rocks" that become meteors may have been around for approximately the age of the solar system (and longer than at least some planets), and may then sit on/beneath the ground for anything up to geologically significant lengths of time, being an actual meteor (and a flaming one, at that) implies we're only considering the period of time the space-rock is traveling through the Earth's atmosphere, specifically ending before it becomes a meteorite. This is a period of time that may be anything from a few seconds (the normal upper limit to the visible 'fireball' stage) to ''possibly'' a minute or two (starting from its first shallow-angle grazing of the atmosphere until it finally lands/burns up/passes back out of the atmosphere). Thus, by one team bringing in a more capable player (especially one arguably more closely aligned to their opponents), they apparently now have an {{wiktionary|ringer#Noun 4|unfair advantage}}.

Extrapolation and interpolation, often absurd, are [[:Category:Extrapolation|recurrent topics]] on xkcd.

==Transcript==
:[Graph with Y axis labeled "Mass" running from 10-30 kg to 1030 kg on a logarithmic scale and X axis labeled "Lifetime", also on a logarithmic scale, running from 10-20 to 1020 seconds.]

:[There are three elliptical blobs on the graph: one on the lower left corner labeled "Mesons", another on the upper right corner labeled "Planets", and another in the middle (1kg mass, 1s lifespan) labeled "Flying water balloons". There are two bidirectional arrows pointing from the center blob to the two other blobs.]

:[To the left of the chart are Cueball and Ponytail. Ponytail is throwing a water balloon, and Cueball is dodging from one. To the right are Megan and Hairy. Megan is preparing to throw a water balloon, and Hairy is slipping in a puddle of water, with a water balloon having landed near his foot with a "Sploosh!".]

:[Caption below the panel:]
:In the annual interdepartmental water balloon fight, meson particle physicists and planetary scientists are usually evenly matched, since they're both equally far outside their areas of expertise.

{{comic discussion}}

[[Category:Line graphs]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Extrapolation]]
[[Category:Astronomy]]
[[Category:Physics]]
[[Category:Games]]

3043: Muons

2025-01-28T04:32:01Z

172.70.110.214: /* Explanation */

{{comic
| number = 3043
| date = January 27, 2025
| title = Muons
| image = muons_2x.png
| imagesize = 284x388px
| noexpand = true
| titletext = Update: I've been banned from the physics department for the way I pronounce "Doppler effect."
}}

==Explanation==
{{incomplete|Created by a BOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOT moving at 99.97% of the speed of light resulting in 45x battery life. Do NOT delete this tag too soon.}}

{{w|Muon|Muons}} are particles released in {{w|air shower (physics)|air showers}} from high-energy {{w|cosmic ray}} protons causing nuclear decay in our upper atmosphere. These protons come from all over the universe from various interstellar events and have energies in excess of anything our species has created. Some of the muons created in these collisions are deflected away from us and decay quickly in the upper atmosphere. Other muons retain the high energy of the colliding protons effectively and travel so fast that they emit {{w|Cherenkov radiation}} from outpacing photons in air, which is used to visualize air showers with telescopes. Muons usually decay very quickly, but in part because of time dilation these high-energy muons are able to penetrate deep into the earth densely and are also used as a natural radiation source more powerful than x-rays for internal imaging especially of large opaque structures.

{{w|Time dilation}} is the concept from {{w|special relativity}} where faster moving objects travel through time faster than proportional, resulting in an appearance of it slowing down for them to an observer, as well as an ability to cross greater distances. Because the ‘regular speed’ {{w|Muon|muons}} are moving at a relatively normal speed, Cueball pronounces it properly, but because time slows down for the faster moving muons, Cueball adjusts this, and pronounces it much slower, as if he is being slowed down from talking about them.

Cueball is implying that when he says "muons", he is speaking in the same reference frame as them, with time traveling at the same speed for the listener and for the muon. In the same reference frame, muons decay very quickly. He implies that when he says "muuuoooons" very slowly, that he is now speaking in a reference frame where the muons have time dilated relative to the observer and appear to be aging very very slowly. This is the kind of reference frame in which muons are detected at the surface.

On average, a stationary muon decays after a bit over two microseconds. While moving at 99.97% of the speed of light, their lifespan (from our perspective) stretches to nearly ninety microseconds. If Cueball speaks at four syllables per second (a typical {{w|Speech tempo|speech tempo}} for English), it will take him about half of a second to name the "muons" created in the upper atmosphere; it will take him more than twenty seconds to name the fast-moving "muuuuuoooons."

The title text references the {{w|Doppler effect}}, the change in frequency of a wave when the observer is moving relative to the source. One common example of this is how the sound of a fast car or airplane starts as a high pitched 'squeal' but then gradually drops to a low droning noise as it passes the observer. By analogy with the time dilation example, Cueball likely imitates this change in pitch whenever pronouncing the phrase "Doppler effect"; as he has been banned for this we must assume that the first syllable or two were pronounced at an obnoxiously high volume and pitch.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Cueball is standing in front of a whiteboard, which contains a diagram depicting a muon passing through the atmosphere, a distance labeled with a cursive letter, the equation for the Lorentz factor, and some illegible text. He's facing away from the whiteboard and holding a pointer that points towards the diagram.]
:Cueball: ''Muons'' created in the upper atmosphere decay immediately, but fast moving ''muuuuuoooons'' are able to reach the surface due to their longer half-lives.

:[Caption below the panel:]
:Physics tip: Remember to adjust your pronunciations to account for time dilation.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Physics]]
[[Category:Tips]]

Talk:2777: Noise Filter

2023-05-18T12:24:24Z

172.70.110.214:

Took me a moment. It is very on-point for me. Randal proposes a sound level meter in such as Google reviews. Showing the real-time racket in a restaurant or other venue. Just this week I walked out of a new TOO-LOUD restaurant. I wish this feature existed! It is not total fantasy. Any Android cellphone "could" report location and sound-level to its masters.

I'm autistic. I would have liked this feature since I was first going places on my own.
[[Special:Contributions/162.158.2.167|162.158.2.167]] 02:31, 18 May 2023 (UTC)

Hear hear! (Pun intended.) There are several restaurants my family won't go back to because they're too loud. One was PAINFULLY loud - well over 80 dBA. Hmm. Maybe I should take my sound level meter with me next time we eat out, and put the readings into a review. [[Special:Contributions/172.70.110.214|172.70.110.214]] 12:24, 18 May 2023 (UTC)

426: Geohashing

2023-05-17T17:07:54Z

172.70.110.214:

{{comic
| number = 426
| date = May 21, 2008
| title = Geohashing
| image = geohashing.png
| titletext = Saturday is game night
}}

== Explanation ==

{{w|Geocaching}} is a sport where you have to find things hidden by other people based on geographical coordinates. Randall has had a similar idea before in [[201: Christmas GPS]].

[https://geohashing.site/ Geohashing] is a sport created by Randall based on reaching a random location determined by an [https://geohashing.site/geohashing/The_Algorithm algorithm] that uses a {{w|hash function}} that involves the current date, location, and the {{w|Dow Jones Industrial Average|Dow}} opening price. The Dow Jones Industrial Average is a {{w|stock market index}} dealt in New York City.

The algorithm is built in a way that:
* Makes it impossible to plan a meeting in advance of more than a few days and usually not more than a day.
** This is due to incorporation of the Dow opening as seed - there isn't a new value of the seed every day since the Dow doesn't open on weekends or holidays, but there is for most days. The reason Saturday is mentioned in the title-text is that the coordinates for that day are generated using Friday's open, giving a greater number of hours to plan the 4 PM local time meetup (how many depends on the time zone(s) of the graticule, hence the '30W' rule).
* Changes every day, due to the incorporation of the UTC date.
* Has only a vanishingly small chance of generating a point in the same exact location twice via hash collision. Some of them have gotten closeish to each other, however.
* Gathers people who are nearby - everyone within the same 1°×1° grid square ('graticule') gets the same position, and one hash in the von Neumann 3*3 neighborhood of surrounding graticules is guaranteed to be the closest to a hasher in the central graticule (not necessarily the one for that graticule, however).

The algorithm works as follows:
# Take the current date in the format yyyy-mm-dd and append the most recent opening value for the Dow Jones Industrial Average.
# Pass this string through the MD5 algorithm.
# Divide the hash value into two 16 character halves, and convert each half to a decimal.
# Take the integer portions of your current coordinates and append the decimal hash values.

{{w|MD5}} is a cryptographic hashing algorithm, and converts plaintext data into a seemingly random 128-bit (32 character) string. A good hashing algorithm should have three main properties: it is non-reversible, you cannot generate any plaintext data back from the hash, and a given sample of data will always produce the same hash value, but even a tiny change to the original plaintext should produce an entirely different hash.

The example co-ordinates are for the Google headquarters in California, as you can see here: [https://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=37.421542+-122.085589&aq=&sll=37.0625,-95.677068&sspn=73.209607,135.263672&vpsrc=0&ie=UTF8&t=m&z=17&iwloc=A 37.421542 -122.085589]. The example date, May 26 2005, may reference the fact that the first edition of the Dow came out on May 26, 1896. (Why 2005? Unclear. Perhaps since 2005 is the year xkcd started?)

While geohashing was originally intended as a joke{{citation needed}}, there are people who geohash regularly. Please see the link to the Geohashing wiki above.

The title-text may imply that people should bring games to their geohashing location on the Saturday following the comic's release. If they do so and take photos, they may post them to [https://geohashing.site/geohashing/games_we_play the Games We Play page].

==Transcript==
:Date (example): 2005-05-26
:That date's (or most recent) DOW opening: 10458.68
:[Concatenate, with a hyphen: 2005-05-26-10458.68]
:md5: db9318c2259923d08b672cb305440f97
:[Split it up into two pieces:]
:0.db9318c2259923d0, 0.8b672cb305440f97
:To decimal: 0.857713..., 0.544544...
:Your location (example): 37.421542, -122.085589
:[Combine integer part of location with fractional part of hash:]
:Destination Coordinates: 37.857713, -122.544544
:Sample Implementation: <nowiki>http://xkcd.com/geohashing/</nowiki>

==Trivia==
* In response to comic [[353: Python]], the Python developers implemented the module <code>antigravity</code> in version 2.7+. This module contains a reference geohashing function.
* Due to the 2019 hacking of the XKCD forum server, which the Geohashing wiki was also hosted at, the wiki was unavailable until February 2020. It is since back online under the new domain of [http://geohashing.site geohashing.site].

{{comic discussion}}
[[Category:Comics with color]]
[[Category:Stock Market]]

2486: Board Game Party Schedule

2023-04-19T10:54:35Z

172.70.110.214: /* Explanation */

{{comic
| number = 2486
| date = July 7, 2021
| title = Board Game Party Schedule
| image = board_game_party_schedule.png
| titletext = Several of the guests are secretly playing Meta Board Game Party. Every minute of parallel debate in the breakaway faction earns double victory points!
}}

==Explanation==

This comic shows a timeline of a gathering to play some sort of fairly complex board game. These games often have many pages of rules, and a long setup time. Often the very complex rules must be explained in detail, which can be extremely dull in a group environment.

Conversely, just beginning like at the time entry point "it will make sense once you play" without explanation often leads to new player frustration that, had they had a complete understanding, they would have made different choices and had a more reasonable chance at victory, or even worse, avoided constantly being informed of "illegal moves".

In addition, since it's a party, there are other activities that take place in addition to playing the game, notably ordering and eating food.

By the time you eat, prepare the game, and teach the new players, little time is left to actually play the game. This comic exaggerates this dynamic, for in the timeline, no one gets to play the game at all. Often during these gatherings the frustration with the factors above cause people to suggest settling on a simpler or more well known game.

The title text observes some of the guests supposedly playing a fictional board game, Meta Board Game Party – a game about board game parties. Because the quoted rule states that arguing in the "breakaway faction" is worth more victory points, it would be optimal strategy for them to do just that, for as long as possible. This seems to be a sarcastic explanation as to why they tried to get the whole group to play some other game and turned the ensuing debate into 45 minutes of bickering.

==Transcript==
:[Caption above:]
:Board Game Party Schedule

:[A timeline is shown, from about 6PM at the top to about 11PM at the bottom. Events are displayed as white rectangles, labeled as follows:]

:before 6PM: people filter in
:6:00–6:25: small talk
:6:25–6:55: debate which game to play
:6:55: remember that you need to order food
:6:55–7:15: debate where to order from
:7:15: pick a place, order
:7:15–7:40: pick a game and start setting up
:7:40–8:20: explain rules to new people
:8:20: food arrives
:8:20–9:00: eat food
:9:00–9:27: resume setting up
:9:27–9:52: more explanation
:9:52–10:13: restless faction tries to start simpler game
:10:13–10:38: general debate
:10:38–10:57: “It will make sense once you play”
:10:57–11:10: finish setting up
:after 11:10 PM: people head home

{{comic discussion}}
[[Category:Charts]]
[[Category:Board games]]