explain xkcd - User contributions [en]

1249: Meteor Showers

2018-07-10T03:31:21Z

141.101.88.184: removed a far-fetched and completely baseless theory

{{comic
| number = 1249
| date = August 9, 2013
| title = Meteor Showers
| image = meteor showers.png
| titletext = Remember, meteors always hit the tallest object around.
}}

==Explanation==
This comic spoofs the way that astronomical events are often reported in the mass media — events are often tagged with undeserved superlatives or described as being more dramatic than they actually are. In some cases, outright misinformation is spread. This phenomenon occurs in part by the result of over-eager scientists, but mostly because of journalists with no deeper knowledge on the subject they write about.

Meteor showers typically occur regularly each year. It always happens at the same days because the Earth is crossing the dust path of a particular {{w|comet}}. Sometimes meteor showers are in fact likely to be relatively spectacular when the peak of the shower occurs while your part of the world is in darkness and there is little moonlight. However, even in these cases it must be understood that there is nothing unusual about the meteor shower itself. The shower just consist of small particles at a size about roughly one millimeter, only the high speed is the reason that is can be seen from Earth's surface. The names of the showers refer to the star {{w|constellation}} where they visually belong to.

Most of the meteor showers listed in the comic are real, but some are made up (and indicated as such below).

*''{{w|Quadrantids}} - January 4th - Bring pets inside during peak activity''
:While keeping pets inside may be reasonable on days when fireworks are let off in the beginning of a new year, no regular meteor shower poses much danger to pets.
*(made-up) ''Tricuspids - January 21st - Not viewable in region 2 countries''
:Apparently a play on the {{w|tricuspid valve}} in mammalian hearts, or possibly on bicuspid teeth. The mention of "Region 2" is a reference to {{w|region locking}}, a digital rights management (DRM) scheme intended to restrict media to certain areas. DRM of course does not apply to natural events. However, meteor showers are also geographically restricted, and the visible area might roughly coincide with a DRM region (Though Region 2 covers a large and scattered area, not being strictly geographical).
*({{w|Alpha Centaurids|Alpha}} / {{w|Theta Centaurids|Theta}}) ''Centaurids - February 6th - Too faint to see without going outside''
:Since indoor lights and window glass make them harder to see, it would take a ''very'' bright meteor (like the Chelyabids two entries below) to be visible without going outside.
*(made-up) ''Beta Aquariids - February 10th - Inverted shower converges toward Aquarius instead of radiating away''
:This fictional shower would collect shooting stars into the origin to prepare for the real {{w|Eta Aquariids}} meteor shower associated with Halley's comet and ''diverging'' from {{w|Eta Aquarii}} in Aquarius; the real shower peaks around May 6th.
:Due to perspective, meteor showers appear to radiate outwards from a certain point in the sky. Meteor showers may be seen to converge on a point on the opposite side of the sky, but with the earth in the way there would only be a few visible going past the edge, seen as nearly parallel streaks overhead, so the convergence point would hardly be notable.
*(made-up) ''Chelyabids - February 15th - Only one meteor per shower, but it's big.''
:A reference to the February 15, 2013, {{w|Chelyabinsk meteor}} whose explosion shattered windows within a large radius.
*''{{w|Lyrids}} - April 22nd - Meteors sometimes scream''
:A meteor large enough to reach the lower atmosphere could produce sound audible to observers on the ground, but this is very unusual.
*''Daytime {{w|Zeta Perseids}} - June 9th - Likely a NASA hoax''
:This shower is mostly observed via its effects on radio and TV signals, and therefore a good target for conspiracy theorists responding to [http://science1.nasa.gov/science-news/science-at-nasa/2000/ast06jun_1m/ June's Invisible Meteors - NASA Science].
*''{{w|June Bootids|June Boötids}} - June 27th - 50/50 mix of meteors and shooting stars''
:The "50/50 mix of meteors and shooting stars" is a joke, as "meteor" and "shooting star" are synonymous.
*''{{w|Southern Delta Aquariids}} - July 19th - Meteors very bright, but stationary''
:This is saying that they are indistinguishable from stars, or that the stars themselves are actually meteors.
*(made-up) ''Dromaeosaurids - July 22nd - Fast, highly intelligent, can open doors''
:{{w|Dromaeosauridae|Dromaeosaurids}} are a family of dinosaurs containing the genus ''Velociraptor'', well-known from the movie Jurassic Park in which they are presented as a deadly menace, fast and especially intelligent to the point of understanding how to open a door; this representation of Velociraptors is a [[:Category:Velociraptors|recurrent topic in xkcd]].
*''{{w|Perseids}} - August 12th - Instead of falling from sky, meteors erupt from ground''
:Erupting from the ground is the funny inverse of falling from the sky, what meteors always do.
*(made-up) ''Tau Pyramids - August 15th - Visible even when eyes are closed''
:Probably a reference to {{w|Pyramidal cells}}, a type of neuron. The "tau" reference has two possibilities. The "visible even when eyes are closed" could refer to the Tau particle, a heavy sibling of the electron. When they traveled outside of Earth's magnetosphere on their way to the Moon, Apollo astronauts saw flashes of light about every three minutes even with their eyes closed; these were caused by high energy particles (cosmic rays) penetrating their eyes and brain. The other possibility is that it refers to {{w|Tau protein}}, a normal structural protein within brain neurons. In Alzheimer's Disease, abnormal Tau proteins can aggregate within pyramidal cells to form insoluble skeins. The number of these "{{w|Neurofibrillary tangle|neurofibrillary tangles}}" roughly correlate with the severity of cognitive impairment.
*''{{w|Draconids}} - October 8th - Very slow, but follow you if you run''
:This may have something to do with the fact that "draconids" etymologically means "of the dragon", which could make for a fearsome meteor shower. And if you run it will track you down, albeit slowly. This may also be a reference to {{w|Boo (character)|Boo}}, a character in the Mario series of video games that is slow but follows you if you turn your back on them.
*''{{w|Orionids}} - October 21st - Entire shower happens at once''
:As noted in [[1020|comic 1020]], the Orion constellation (in which the Orionids are located) has a 'dong'. Possibly a joke about a {{w|Golden shower|"golden" shower}}. Maybe.
*''{{w|Leonids}} - November 17th - In 1966, unusually active Leonid shower killed God''
:There ''was'' a very active Leonid shower (a "meteor storm") in 1966, and a precursor to it in 1965. The article ''{{w|Is God Dead?}}'' was published in ''Time Magazine'' on April 8 of 1966. Perhaps this suggests that the meteors killed God earlier in the year when they and He were further out in the solar system?
*''{{w|Geminids}} - December 13th - Can be deflected with tennis rackets''

The title text refers to the folk wisdom that ''lightning'' strikes the tallest thing around, but this has never been applied to meteors, where it is basically the size (area) that determines the likelihood of an impact with a given object. [[Randall]] expressed frustration over how "maddeningly inexact" the lightning statement is, and elaborated on the problem mathematically, in the [[what if?]] ''{{what if|16|Today's topic: Lightning}}''.

==Transcript==
:[A list of 16 meteor showers, with a caption above, labels on the three columns and then every other row in gray, beginning with a gray row beneath the line below the column labels.]
:{| border="1" cellpadding="1" cellspacing="1" class="wikitable" style="width: 60%; text-align: left;"
!colspan="3"|The <big><big>xkcd guide</big></big> to <big><big>meteor showers</big></big>
|-
|'''Name'''
|'''Peak'''
|'''Notes'''
|-
|Quadrantids
|January 4th
|Bring pets inside during peak activity
|-
|Tricuspids
|January 21st
|Not viewable in region 2 countries
|-
|Centaurids
|February 6th
|Too faint to see without going outside
|-
|Beta Aquariids
|February 10th
|Inverted shower converges toward Aquarius instead of radiating away
|-
|Chelyabids
|February 15th
|Only one meteor per shower, but it's big.
|-
|Lyrids
|April 22nd
|Meteors sometimes scream
|-
|Daytime Zeta Perseids
|June 9th
|Likely a NASA hoax
|-
|June Boötids
|June 27th
|50/50 mix of meteors and shooting stars
|-
|Southern Delta Aquariids
|July 19th
|Meteors very bright, but stationary
|-
|Dromaeosaurids
|July 22th
|Fast, highly intelligent, can open doors
|-
|Perseids
|August 12th
|Instead of falling from sky, meteors erupt from ground
|-
|Tau Pyramids
|August 15th
|Visible even when eyes are closed
|-
|Draconids
|October 8th
|Very slow, but follow you if you run
|-
|Orionids
|October 21st
|Entire shower happens at once
|-
|Leonids
|November 17th
|In 1966, unusually active Leonid shower killed God
|-
|Geminids
|December 13th
|Can be deflected with tennis rackets
|}

==Trivia==
*In the [http://www.explainxkcd.com/wiki/images/archive/8/8a/20130809215612!meteor_showers.png original] version of this comic the date beneath the Dromaeosaurids shower was June 12th, the date of the velociraptor attacks in the Jurassic Park movie. To get the order of the dates correct it was probably easier to change just the date rather than move the Dromaeosaurids to the entry below June 9th.

{{comic discussion}}

[[Category:Charts]]
[[Category:Astronomy]]
[[Category:Velociraptors]]
[[Category:Jurassic Park]]
[[Category:Animals]] 
[[Category:Sport]] 
[[Category:Religion]]

696: Strip Games

2017-07-18T13:59:47Z

141.101.88.184: /* Explanation */ explained reference to Terry Pratchett books

{{comic
| number = 696
| date = February 1, 2010
| title = Strip Games
| image = strip_games.png
| titletext = HOW ABOUT A NICE GAME OF STRIP GLOBAL THERMONUCLEAR WAR?
}}
==Explanation==
The frequency of strip versions of various games is measured by means of Google search results. Strip versions of popular games are a common activity at parties, especially when alcohol is involved. The obligation to remove pieces of clothing is supposed to add an extra zest to the game. A very widespread variant is {{w|Strip Poker}}, followed by strip versions of regular party games like {{w|Truth or Dare}} or {{w|Spin the Bottle}}.

However, the comic also suggests playing other games in a way that involves stripping. In reality, playing such games as "Strip {{w|Tennis}}" or "Strip {{w|Agricola (board game)|Agricola}}" is rather unusual. ''{{w|Jumanji}}'' is a Robin Williams movie about a magical board game that manifests dangerous creatures and traps from the jungle and lost civilization therein; a theoretical Strip Jumanji would probably not remain very titillating during the chaos.

The last column features games of which strip versions are (according to Google) nonexistent. While the other columns named sports or board games where a strip variant would be at least conceivable, the last one includes the {{w|zero-player game|zero-player}} {{w|Conway's Game of Life|Game of Life}} and the {{w|Prisoner's Dilemma|Iterated Prisoner's Dilemma}}, which is a theoretical example in {{w|game theory}}. It is therefore left to the reader to imagine how a strip version of these pseudo-games would appear.

{{w|Poohsticks}} is a children's sport mentioned in the {{w|Winnie-the-Pooh|Winnie-the-Pooh books}} played by dropping sticks into a river and watching them reappear on the other side of a bridge. Despite the kid-friendly origins, and unlike the other games below it, a "strip" version of Poohsticks is actually viable.

[http://starwars.wikia.com/wiki/Podracing Podracing] appears in the {{w|Star Wars}} films as a racing competition held with hovering vehicles. How a "strip" version would work between two racers is unclear, but a determined set of spectators "wagering" their clothes on the races could probably hammer out a system.

{{w|Chess by mail}} could conceivably work if the players include increasingly-nude photographs of themselves in their correspondences. The problem is, a game by e-mail can take days to finish, and a game by snail-mail can take upwards of ''several months''. The titillation factor is far too spread out to satisfy the desires of anyone who would elect to play a game of strip chess in the first place.

"Global Thermonuclear War" in the title text is a reference to the film "{{w|WarGames}}", where a young hacker accesses a US military supercomputer and starts a nuclear war simulation, believing it to be only a computer game. The film ends with showing the computer that nuclear war is "a strange game" in which "the only winning move is not to play", and proposes "a nice game of chess".

Strip global thermonuclear war is a patently absurd idea; while it is a common trope for people to engage in one last moment of intimate pleasure before certain doom, foreplay (including strip games of any type) is a time-consuming practice, and time is something you don't have much of considering that the bomb could drop on your place of residence at any moment. Besides all that, the act of betting on which city is going to go up next in a nuclear inferno tends not to be an effective aphrodisiac for most people.{{Citation needed}}

The all-capital letters title text is probably a reference to the Death character in Terry Pratchett books.

==Transcript==
:Frequency of Strip Versions of Various Games

:n = google hits for "strip <game name>" / google hits for "<game name>"
:(at the time of this writing)

:Frequent
:(n > 1%)
:-Poker
:-Spin the Bottle
:-Beer Pong
:-Never Have I Ever
:-Truth or Dare

:Rare
:(1% >= n > 0.01%)
:-Chess
:-Blackjack
:-Tennis
:-Settlers of Catan
:-Pictionary

:Extremely Rare
:(0.01% >= n > 0)
:-Cricket
:-Magic: the Gathering
:-Stickball
:-Agricola
:-Jumanji

:Nonexistent
:(n = 0)
:-Poohsticks
:-Podracing
:-Iterated Prisoner's Dilemma
:-Chess by Mail
:-Conway's Game of Life

{{comic discussion}}
[[Category:Charts]]
[[Category:Sport]]
[[Category:Chess]]

1826: Birdwatching

2017-04-19T16:42:25Z

141.101.88.184: /* Trivia */

{{comic
| number = 1826
| date = April 19, 2017
| title = Birdwatching
| image = birdwatching_small.png
| titletext = No, tell the park rangers to calm down, it's fine--I put a screen on the front. I just want to get the birds a little closer.
}}

==Explanation==
{{incomplete|Needs more information on birdwatching.}}

{{w|Birdwatching}} is an activity to observe birds. Usually this is done at a distance, as birds are flying in the air, and are far away. Cueball notes that even with {{w|binoculars}} (or a camera?), the birds are different to see because of their distance.

Cueball's solution is to use a {{w|vacuum cleaner}}, specifically a {{w|shop vac}}, to pull in the birds. This is physically impossible with such a small device. Even if the shop vac created a perfect vacuum, it can only pull out air at the speed of sound, which amounts to approximately 1 cubic meter per second considering the apparent size of the hose. This is not enough to create a significant amount of wind or affect the atmosphere.

The title text refers to {{w|park ranger}}s, who would naturally be distressed by birds being forced to coalesce via an extremely powerful vacuum. If such a vacuum were created and used for this purpose, it probably would pose a threat to said birds. Cueball says he has solved this problem by placing a perforated screen in front. In doing so, he can safely attract the birds without trapping them inside the vacuum. He implies that this should remove the danger to the birds, which is not the case. While the birds can no longer enter the vacuum itself, having a large number of birds pulled into a (presumably small) screen would probably fare poorly for the birds, so Cueball's solution is rather poor.

==Trivia==
This comic was originally published with a very large picture, much larger than the standard screen. The original image was named [https://imgs.xkcd.com/comics/birdwatching_huge.png birdwatching_huge.png] (the image at that location has also been downsized to normal dimensions). It was later updated to use an image without the _huge in its name, at the usual size. While this unexpected size may have been interpreted as being part of the joke (the reader was only seeing an inconvenient subset of the magnyfied image through a screen, while Cueball was experiencing an inconvenient subset of the magnyfied sky through his binoculars), it seems it wasn't the case, as both the size and name of the image were later corrected.

==Transcript==
:[Cueball and Beanie Man are standing with camera and binoculars.]
:Cueball: Birdwatching is hard. They're all too small and far away.

:[Both raise tool eyepiece.]
:Cueball: That Hawk is over a mile up! How did you even spot it?

:[Both, lower eyepiece. Cueball looks down, fuming.]

:[Cueball now has a SHOP VAC and has it pointed to the sky.]
:Shop Vac: WHRRRRRR
:[Beanie Guy looks at Cueball, confused.]

{{comic discussion}}

1826: Birdwatching

2017-04-19T16:40:55Z

141.101.88.184: /* Trivia */

{{comic
| number = 1826
| date = April 19, 2017
| title = Birdwatching
| image = birdwatching_small.png
| titletext = No, tell the park rangers to calm down, it's fine--I put a screen on the front. I just want to get the birds a little closer.
}}

==Explanation==
{{incomplete|Needs more information on birdwatching.}}

{{w|Birdwatching}} is an activity to observe birds. Usually this is done at a distance, as birds are flying in the air, and are far away. Cueball notes that even with {{w|binoculars}} (or a camera?), the birds are different to see because of their distance.

Cueball's solution is to use a {{w|vacuum cleaner}}, specifically a {{w|shop vac}}, to pull in the birds. This is physically impossible with such a small device. Even if the shop vac created a perfect vacuum, it can only pull out air at the speed of sound, which amounts to approximately 1 cubic meter per second considering the apparent size of the hose. This is not enough to create a significant amount of wind or affect the atmosphere.

The title text refers to {{w|park ranger}}s, who would naturally be distressed by birds being forced to coalesce via an extremely powerful vacuum. If such a vacuum were created and used for this purpose, it probably would pose a threat to said birds. Cueball says he has solved this problem by placing a perforated screen in front. In doing so, he can safely attract the birds without trapping them inside the vacuum. He implies that this should remove the danger to the birds, which is not the case. While the birds can no longer enter the vacuum itself, having a large number of birds pulled into a (presumably small) screen would probably fare poorly for the birds, so Cueball's solution is rather poor.

==Trivia==
This comic was originally published with a very large picture, much larger than the standard screen. The original image was named [https://imgs.xkcd.com/comics/birdwatching_huge.png birdwatching_huge.png] (the image at that location has also been downsized to normal dimensions). It was later updated to use an image without the _huge in its name, at the usual size. While this unexpected size may have been interpreted as being part of the joke (the reader was only seeing an inconvenient subset of the big image through a screen, while Cueball was experiencing an inconvenient subset of the sky through his binoculars), it seems it wasn't the case, as both the size and name of the image were later corrected.

==Transcript==
:[Cueball and Beanie Man are standing with camera and binoculars.]
:Cueball: Birdwatching is hard. They're all too small and far away.

:[Both raise tool eyepiece.]
:Cueball: That Hawk is over a mile up! How did you even spot it?

:[Both, lower eyepiece. Cueball looks down, fuming.]

:[Cueball now has a SHOP VAC and has it pointed to the sky.]
:Shop Vac: WHRRRRRR
:[Beanie Guy looks at Cueball, confused.]

{{comic discussion}}

Talk:1514: PermaCal

2017-04-18T11:58:31Z

141.101.88.184: Special capital letter case

In Megan's response, the "h" in "19th" is backwards.
[[Special:Contributions/108.162.214.239|108.162.214.239]] 05:47, 20 April 2015 (UTC)
:I believe the fully formed uppercase 'h' to be the mistake. What you describe was common in 1190. I think the section should be removed, then readded to the comic that first made use of it (which could be before 1190).[[User:Azule|Azule]] ([[User talk:Azule|talk]]) 18:13, 21 April 2015 (UTC)
:I'm pretty sure that's a mistake since lowercase letters normally aren't used. [[User:Mikemk|Mikemk]] ([[User talk:Mikemk|talk]]) 05:49, 20 April 2015 (UTC)
:Looks like he forgot the line on the upper left. He used the capital 19TH for Cueball. [[Special:Contributions/173.245.48.60|173.245.48.60]] 07:24, 20 April 2015 (UTC)
:I think it's intentional. All the H's after a T have shortened upperleft lines. Probably for nice http://www.explainxkcd.com/wiki/index.php/kerning [[User:ToaVin|ToaVin]] ([[User talk:ToaVin|talk]]) 10:12, 20 April 2015 (UTC)
::I recall other examples where Randall's lettering style includes 'stroke obscurations' (preferable to merging of letters, probably).[[Special:Contributions/141.101.98.160|141.101.98.160]] 16:10, 20 April 2015 (UTC)

Leap seconds have nothing to do with the length of the year: corrected. [[Special:Contributions/108.162.249.162|108.162.249.162]] 07:49, 20 April 2015 (UTC)

"Leap seconds normally account for the differences in the length of our 24 hour day and the time taken for the world to rotate 360 degrees on its axis" - this sentence mixes two unrelated concepts. First, a day is not a rotation of 360 degrees. Because the Earth also orbit the sun, the rotation from noon one day to noon the following day is a bit more than 360 degrees (360.9856 or so) (rotation measured relative to the stars) - this is why constellations appear to move throughout the year. Second, leap seconds are required because the leap day corrections of the Gregorian calendar are good, but not perfect, at matching the difference between Earth orbits (years) and Earth rotations (days). Every so often, a small correction is required. The corrections are not regular because the causes of the drift are numerous: tidal effects, orbital eccentricity, the underlying (small) flaws in the calendar, etc. I have not made any changes in the explanation. --[[Special:Contributions/141.101.104.66|141.101.104.66]] 08:41, 20 April 2015 (UTC)

Not unrelated concept. Just not fully understood. Rotate 360 degrees is a simple way of putting things that ignores the diffrence between solar days and sidereal days. Incorrect not because someone doesn't understand the topic being discussed but because someone hasn't studied astronomy or seriously thought about how the movement of the Earth effects the length of the day--[[Special:Contributions/108.162.237.183|108.162.237.183]] 13:00, 20 April 2015 (UTC).
:Guilty. No excuse either, because I actually knew (but just forgot) about the difference between sidereal and solar days. [[Special:Contributions/108.162.249.162|108.162.249.162]] 01:14, 21 April 2015 (UTC)

While you are true on one part, that Earth doesn't take 24 hours to rotate 360 degrees (it takes around 23 hours and 56 minutes if I recall correctly), leap seconds are used to account for differences between 24 hours and a solar day. If it was used to adjust the length of the year the time of day would drift, it would also be fairly pointless as the leap days take us out by 1/4 of a day.[[Special:Contributions/108.162.250.175|108.162.250.175]] 10:41, 20 April 2015 (UTC)

Do we know for sure that this comic was released on a Sunday - the 19th instead of the 20th? The first entry in this page is from the 20th. Of course there are some references to the 19th, but then again it is obvious that it is on the 20th that Megan asks. Anyone who can find out if this is the correct date, or just a mistake by someone who misunderstood something based on the dates in the comic? --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 11:19, 20 April 2015 (UTC)
:Yes, it was released on the 19th, at about 10 PM CST. All of the recent comics have been released a few hours early though, so if you want the date set at 20, fine. [[User:Mikemk|Mikemk]] ([[User talk:Mikemk|talk]]) 15:05, 20 April 2015 (UTC)
:The archive claims that it was released on the 20th.--[[User:17jiangz1|17jiangz1]] ([[User talk:17jiangz1|talk]]) 15:08, 20 April 2015 (UTC)
Apropos a "permanent calendar", Isaac Asimov proposed just such a calendar. http://calendars.wikia.com/wiki/World_Season_Calendar This web page unfortunately doesn't go into details, but there were several advantages. The same calendar is used for all years, your birthday is always on the same day of the week, no need to remember "30 days hath Sept. ...", and several other advantages I can't remember right now. --[[User:RenniePet|RenniePet]] ([[User talk:RenniePet|talk]]) 12:45, 20 April 2015 (UTC)

There is some confusion between the different types of astronomical time: a day in mean solar time is 24 hours, with a difference of + or - up to 1 second (compared to time on an atomic clock), in apparent solar time is 24 hours + or - up to 30 seconds, and in mean sidereal time is 23 hours, 56 minutes, 4.0916 seconds (according to Wikipedia), and there is one extra sidereal day (about 366.25) in a sidereal year. [[User:The Dining Logician|The Dining Logician]] ([[User talk:The Dining Logician|talk]]) 13:55, 20 April 2015 (UTC)

It seems like our collective favorite word just might be "portmanteau" [[User:YourLifeisaLie|The Goyim speaks]] ([[User talk:YourLifeisaLie|talk]]) 13:42, 20 April 2015 (UTC)

The explanation seems unclear where it addresses the title text. I'm not sure what is meant by "maybe 100ms every few months," but it seems to miss the point of the comic. If a leap day is added each time the previous day ends, then at millisecond resolution, a new leap-millisecond would be added every millisecond! Hence the resulting DDOS when pushing so many NTP notifications... [[Special:Contributions/199.27.133.104|199.27.133.104]] 16:05, 20 April 2015 (UTC)
:I think that's wrong, too. Just my vote towards encouraging someone who wants to consider rewording it.[[Special:Contributions/141.101.98.160|141.101.98.160]] 16:10, 20 April 2015 (UTC)

I want to clarify a bit here. Leap days account for the fact that the rotation period of the Earth does not evenly divide into the revolution period. As such we can predict when each leap day will happen in the future. Leap seconds on the other hand are due to variance in the Earths rotation caused by various factors. Leap seconds cannot be predicted and must be observed by measurement and corrected for after the fact. It is based on the fact that the Earth's rotation varies.

I am so happy Randall decided to mock leap seconds. The human race just needs to accept that the rotation of the Earth is not a constant and stop pretending that it is. If we ingored leap seconds it would only add up to a few hours a lifetime. So what if 12pm is a different time as the years pass? It may be annoying but that is the world we live one. We can still have noon be the height of the sun if we want, it will just be a different time. [[Special:Contributions/199.27.133.73|199.27.133.73]] 17:25, 20 April 2015 (UTC)
:Does that last paragraph add anything to the article? The title text is mocking leap seconds about as much as the main comic is mocking leap days (ie- not really), and the odds that a server is able to handle NTP corrections due to regular clock drift, but unable to handle a 1 second jump in a single NTP correction seems like very poor mojo. I have no idea why the linux hrtimer subsystem cared about the wall-clock time, since it's a well known fact that the wall-clock time can change for a large number of reasons, and so you can't have your system go haywire every time it does. Google hasn't actually fixed anything, they are simply offering an NTP service that provides leap second corrections over a long smear - at the cost of being out of sync with UTC for up to a second at a time.
::If anything, that link to livescience needs to be removed as the worst kind of fear-mongering and click-bait. GPS doesn't care about leap seconds, and GPS time is well-known to drift from UTC; if your GPS receiver is making adjustments for leap seconds, then it's going to be inaccurate in every other way, as well.
::Also, given enough time, the day will be 25 hours long, for a few hours a week drift if you want to stick to UT as your arbitrary timekeeping system! [[Special:Contributions/108.162.249.162|108.162.249.162]] 01:32, 21 April 2015 (UTC)
::: I concur, the last sentence adds nothing to the explanation and should probably be removed. [[User:Spongebog|Spongebog]] ([[User talk:Spongebog|talk]]) 03:53, 21 April 2015 (UTC)

[[Special:Contributions/108.162.250.169|108.162.250.169]] 12:49, 21 April 2015 (UTC) An illustrative quote comes to mind: "By an equally suspicious freak of temporal relastatics, it is nearly always Saturday afternoon just before the bars close." Description of Ursa Minor Beta, The Restaurant At The End of The Universe, chapter 4.

[[Special:Contributions/108.162.238.156|108.162.238.156]] 20:27, 21 April 2015 (UTC)
For a really good explanation of how incredibly complex the seemingly trivial act of keeping track of time is, see this [https://www.youtube.com/watch?v=blSzwPcL5Dw video by ComputerPhile]

<blockquote>Also only '''capital letters''' are used in the comics (except in special '''cases''').</blockquote>
Pun intended? [[Special:Contributions/141.101.88.184|141.101.88.184]] 11:58, 18 April 2017 (UTC)

Talk:1815: Flag

2017-03-24T16:08:44Z

141.101.88.184: I don't think the bar was a mistake on Randall's side

A vote for me is a vote for bread on every table and a [https://smile.amazon.com/Off-Be-Wizard-Magic-2-0/dp/1612184715/ 73% battery level] until the end of time! [[User:Jameslucas|jameslucas]] ([[User talk:Jameslucas|" "]] / [[Special:Contributions/Jameslucas|+]]) 14:02, 24 March 2017 (UTC)

Given that the design is a screenshot, the flag could be part of an existing logo, e.g. of a U.S. sport association.--[[Special:Contributions/162.158.150.82|162.158.150.82]] 14:15, 24 March 2017 (UTC)

The comic states "our NEW country" so I removed the theory it could be a new US flag.
The most recent sovereign state, according to Wikipedia, is South Sudan created in 2011 so we could assume Randall never intended to talk about a real-life country [[Special:Contributions/162.158.234.28|162.158.234.28]] 14:25, 24 March 2017 (UTC)

:It could be referring to new country proposals by techno-libertarians and the like? [https://en.wikipedia.org/wiki/Seasteading] -[[User:Jules.LT|Jules.LT]] ([[User talk:Jules.LT|talk]]) 14:32, 24 March 2017 (UTC)
:: for instance https://www.cnet.com/news/asgardia-will-be-a-new-nation-in-space-and-you-can-be-a-citizen/ [[User:WhiteDragon|WhiteDragon]] ([[User talk:WhiteDragon|talk]]) 14:44, 24 March 2017 (UTC)

Note that official flags have an aspect ratio of 3:2 (with a few exceptions, like Switzerland and Nepal). The proposed flag including the notification bar measures 474 x 316 pixels (3*158 x 2*158 pixels), following the standard. If one removes the notification bar the resulting flag is somewhat wider than the standard. [[Special:Contributions/188.114.110.250|188.114.110.250]] 15:06, 24 March 2017 (UTC)
:Those "few" exceptions include 106 of the 189 or so sovereign states. Even that overstates the popularity of 3:2 since some nations have multiple different official flag specifications for different uses or users. --[[Special:Contributions/162.158.62.21|162.158.62.21]] 15:29, 24 March 2017 (UTC)

According to [https://developer.apple.com/ios/human-interface-guidelines/ui-bars/status-bars/ Apple's own documentation], this kind of bar is referred to as a "status bar", and not a "notification bar". --[[User:Jonhaugen|Jonhaugen]] ([[User talk:Jonhaugen|talk]]) 15:28, 24 March 2017 (UTC)

Since the screenshot is part of the editing process, I don't think this can be interpreted as a mistake. It probably is entirely deliberate. The joke relies on the fact that most of the times when this bar appears, it is a side effect of the way the relevant data (the rest of the image) has been obtained, rather than part of the information itself. Actually, not only can the bar be ignored most of the time, but this is so often true that some people may not pay any attention to it at all. The committee's mistake might not have been that they failed to understand that Randall actually meant for the bar to be there, they might have not noticed it at all (even more likely if they looked at the image in full screen on a similar device). [[Special:Contributions/141.101.88.184|141.101.88.184]] 16:08, 24 March 2017 (UTC)

Talk:1796: Focus Knob

2017-02-08T13:19:11Z

141.101.88.184:

Maybe Randall is implying that he has issues with keeping the big picture in mind while doing detail work and gets lost in the details of implementation and vice versa.
This means that for him the knob is more of an on/off or selection switch. Pulse Width Modulation would then allow him to use this on/off switch more like the knob in the picture shown. (... or whoevers voice Randall is speaking in as many people probably have issues with this, myself included.)
I wonder if he obsessed over how to implement this comic:
1. As an on/off switch?
2. As a knob with limited none-usefull settings with "ideal" labeled between the actual settings available?
3. Like this, for simplicity, keeping the big picture in mind and not obsessing over the details of how it may under some circumstances be viewed?
--[[Special:Contributions/162.158.91.95|162.158.91.95]] 10:19, 8 February 2017 (UTC)cdm

If the knob only has discrete positions, none of which lies within the balanced region, he could use PWM to simulate that position.
Let's say the focus variable goes from 0 to 10, the knob can only stay on integer values and the "sweet spot" is around 7,38.
He can make a cycle that rests on 7 62% of the time and at 8 38% of the time, and repeat this cycle with a high enough frequency so that his mind wouldn't know the difference from actually being at 7.38 focus level.

[[Special:Contributions/108.162.241.82|108.162.241.82]] 12:55, 8 February 2017 (UTC)the knob's focused on the approximate mirror location of the "healthy balance" section.
I don't really have anything to suggest based on that though :/
[[Special:Contributions/108.162.241.82|108.162.241.82]] 12:55, 8 February 2017 (UTC)
:IMHO it's just a visual thing to balance the whole image. If you search for watch ads on google images, you'll see that the analogical ones pretty much always show an hour close to 10:10. Beside being balanced, I think those positions are chosen to look "random" (which is paradoxical), or "without a specific meaning", when a 0°, 45° or 90° would seem to have been chosen on purpose. [[Special:Contributions/141.101.88.184|141.101.88.184]] 13:19, 8 February 2017 (UTC)

1796: Focus Knob

2017-02-08T12:17:59Z

141.101.88.184: More information on the PWM and its implication

{{comic
| number = 1796
| date = February 8, 2017
| title = Focus Knob
| image = focus_knob.png
| titletext = Maybe if I spin it back and forth really fast I can do some kind of pulse-width modulation.
}}

==Explanation==
{{incomplete|Created by a BOT then edited by a human, I think.}}
The image is of a rotary {{w|control knob}} used for adjusting parameters in instruments. Apparently this one is for adjusting [[Randall]]'s personal focus level, with the extremes of focus being towards small details and big picture respectively.

While performing any task, it is easy to get so lost in the details that you forget the big picture. It is also equally easy to think much about the big picture and make vague plans while missing out on the details.

One can get lost doing small tasks that might increase efficiency for long projects (e.g. fiddling with email settings), but these might make one lose track of the big picture.

The healthy balance, Randall suggests, is focusing mostly towards the big picture, while keeping an eye on the details. Focusing too much on the big picture can ensure nothing gets done, leading to panic and existential crises.

In the title text, Randall imagines spinning the dial to and fro, causing {{w|Pulse-width modulation}} (a technique often used to encode data in waves). This techniques consists of shifting between a set of fixed values (often 2) so that the average is the expected output. For exemple switching back and forth between 0 and 1, spending half the time in each position will lead to a mean value of 0.5. To code 0.7, you have to spend more time in the 1 position (70% of the time). One feature of this modulation is that the expected value is not actually reached by the signal before applying the low-pass filter (averaging), so using a PWM-like method would mean alternating between being too much and too little attention to detail to have an average on the healthy balance, but never actually reach it. As cool as the idea may sound, it is probably not very healthy.

Many people having a project to complete will usually cycle through the various available settings, often going directly from fiddling the email to panic and existential crisis in a matter of minutes. Maintaining a healthy balance throughout the project is difficult, because it occupies such a small place on the knob.

Of course, not everyone is knob-headed, so some people can panic and have an existential crisis while simultaneously fiddling with email settings.

==Transcript==
:Personal Focus

:[A rotary control knob divided into 36 steps. The counterclockwise order of the labeled settings are:]
:[Left extreme:]
:Detail-Oriented
:[First 23 steps:]
:Fiddling with email settings
:[One narrow step:]
:Healthy balance
:[Last 12 steps:]
:Panic and existential crisis
:[Right extreme:]
:Big Picture

{{comic discussion}}

1017: Backward in Time

2017-01-27T17:13:25Z

141.101.88.184: /* Explanation */ Added explanation on the punchline: the end of downloads now seem to pass in "such a rush" for Cueball.

{{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.
}}

==Explanation==
[https://docs.google.com/spreadsheet/pub?key=0Ak43bGxHGI1adDMtOHVWVXZrYzhKd2VtbFJJMmJPTEE&single=true&gid=1&output=html Here's the 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.

[[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.

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{{Citation needed}} and progress would instead seem to get slower and slower.

[[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]]