explain xkcd - User contributions [en]

1249: Meteor Showers

2018-01-07T20:00:35Z

141.101.104.173: /* Explanation */ Citation is NOT needed for proving DRM is not required for natural events. Common snese statements like this do not need citations, otherwise you'd need a citation for a citation... Which idiot put that in?

{{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''
:May possibly be a reference to the video game {{w|Kingdom Hearts: Chain of Memories}}, wherein the main character Sora claims he will 'beat [meteors] back into space' with a wooden sword.

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]]

1775: Things You Learn

2016-12-21T16:33:18Z

141.101.104.173: Expanded on the title text explanation.

{{comic
| number = 1775
| date = December 21, 2016
| title = Things You Learn
| image = things_you_learn.png
| titletext = Guess who has two thumbs and spent the night in an ER after trying to rescue a kitten that ran under his car at a stoplight and climbed up into the engine compartment? And, thanks to antibiotics, will continue having two thumbs? THIS GUY. (P.S. kitten is safe!)
}}

==Explanation==
{{incomplete|Title text, fill table.}}
This graph shows various items of information plotted by two criteria: a horizontal "How Bad Is It If You Don't Know [THING]" axis and a vertical "How Easy It Is To Grow Up Without Learning [THING]" axis.

{| class="wikitable sortable"
! Ignorance is Bad !! Ignorance is Easy !! Information !! Comments
|-
| || || 100 digits of pi || Most people don't know more than a few digits of pi, and don't need to.
|-
| || || Lyrics to "We Didn't Start The Fire" || The average person is more likely to know the lyrics to a popular song than 100 digits of pi, but not knowing them doesn't really have any serious consequences.
|-
| || || That cat bites are really serious and if bitten you need to wash the bite and call a doctor immediately || Most people assume that a cat bite is just a minor injury. In fact, it carries a fairly high risk of infection, which can be dangerous if not treated (by cleaning the bite to reduce the risk, and having a doctor examine the bite victim and apply additional treatments such as antibiotics if needed).
|-
| || || The red flags for an abusive relationship || It is fairly easy for someone to fall into a pattern of accepting abuse (particularly if the abuser is skilled at emotional manipulation) without realizing it, and the consequences can be mentally and physically devastating.
|-
| || || The signs of a stroke || The symptoms of a stroke are somewhat variable, depending on what areas of the brain are affected, and can be mistaken for other conditions. Identifying a stroke quickly and seeking treatment can make the difference between life and death, or between full recovery and permanent impairment.
|-
| || || Cough into your elbow, not your hand || Covering a cough with the inside of your elbow helps prevent spreading airborne germs and is generally recommended by medical organizations. Coughing into your hand deposits them onto your hand, where they are much more likely to be spread to another person (via handshake, food preparation, shared objects, etc)
|-
| || || How to ride a bike || Most children, especially in the United States, learn to ride a bike at a fairly young age. While this is a useful skill to know for both entertainment and transportation, it would generally not be terrible to not learn this skill.
|-
| || || How to escape movie quicksand || Quicksand in movies is a common trope, and while its physics often differ from real quicksand, escaping from it is commonly done using similar methods. Knowing how to escape from quicksand is important if you sink into it, which is a situation most people are very unlikely to encounter.
|-
| || || Lyrics to "12 Days of Christmas" || Hearing the same Christmas songs over and over each year makes it hard not to learn the lyrics over time. However, the consequences of not doing so are minimal; at most, ignorance of popular culture may leave your friends [[1769|a bit surprised and dismayed]].
|-
| || || TV theme songs || Most children in developed countries grow up watching at least some television. Many of these television shows play the same theme song before the show starts, and many of these have catchy lyrics. Therefore, by repetition, most children will learn at least one of these growing up, and often many.
|-
| || || That you have to empty the dryer lint trap || Most clothes dryers collect lint in a mesh "trap". Failing to remove the lint can cause the dryer to stop working effectively, introduce lint back onto your clothes, or (in extreme cases) start a fire.
|-
| || || Stop, drop, and roll || This is a technique to extinguish a fire on one's own clothing, and is frequently taught to children for safety. Not knowing it (or forgetting it in a panic when the situation arises) can result in severe burns that could have been avoided by following the recommendation.
|-
| || || That you have to pay taxes || Most residents of most countries are legally obligated to pay, or at least file, their taxes annually. Penalties for not doing so often include large fines, and possibly prison sentences. Fortunately, it is something that children hear about quite a bit so it is very difficult to grow up without learning that it must be done.
|-
|}

The title text describes an encounter Randall had the night before writing this comic where a cat climbed into the engine compartment or his car. It probably serves as an explanation for the seemingly out of place point on the graph about how serious cat bites are. Also, the start of the title text "Guess who has two thumbs and..." is a reference to dr. Bob Kelso from Scrubs, which might refer to the other end of the spectrum from cat bites: TV theme songs.

==Transcript==
{{incomplete transcript}}

{{comic discussion}}

Talk:1773: Negativity

2016-12-19T07:44:23Z

141.101.104.173:

Any chance that 'the pain and negativity of the internet' is a reference to [http://www.smbc-comics.com/comic/the-talk-4 this recent SMBC comic] where SMBC's artist Zach challenges Randall to 'out-nerd him now' (seen when you click the red button just below the comic).
I've been wondering whether the first XKCD after that (that is: today's XKCD comic) would refer to it.
[[Special:Contributions/141.101.104.173|141.101.104.173]] 14:55, 16 December 2016 (UTC)
: I kinda doubt it. SMBC wasn't being "negative" or objectionable - if anything it was a challenge - and even a kind of complement. An adequate response to that kind of a challenge might take longer than a few days to prepare. If we're going to see anything in response, I suspect it'll be more obvious. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 14:02, 17 December 2016 (UTC)
:: We better be seeing a string theory joke sometime in the next week... [[Special:Contributions/108.162.216.226|108.162.216.226]] 02:38, 19 December 2016 (UTC)
:: @SteveBaker That was my doubt too. Looking forward to an adequate response from Randall though :) [[Special:Contributions/141.101.104.173|141.101.104.173]] 07:44, 19 December 2016 (UTC)

Talk:1773: Negativity

2016-12-19T07:44:00Z

141.101.104.173:

Talk:1773: Negativity

2016-12-16T14:55:55Z

141.101.104.173: Added a suggestion

1430: Proteins

2014-10-07T10:24:22Z

141.101.104.173: /* Explanation */ grammar

{{comic
| number = 1430
| date = October 6, 2014
| title = Proteins
| image = proteins.png
| titletext = Check it out--when I tug the C-terminal tail, the binding tunnel squeezes!
}}

==Explanation==
In this comic, [[Cueball]] is asking [[Megan]] what she does, to which she replies that she works on software to predict protein folding. There are many folding prediction software programs. Some of the most well known are {{w|Folding@Home}}, {{w|Rosetta@Home}} and {{w|FoldIt}}.

{{w|Protein folding}} is the process by which proteins, which are floppy, unstructured chains of amino acids when initially synthesized in a cell, assume a stable, functional shape. If the folding process does not complete, or completes incorrectly, the resulting protein can be inactive or even toxic to the body. Misfolded proteins are responsible for several {{w|neurodegenerative}} diseases, including Alzheimer's disease, amyotrophic lateral sclerosis (ALS), and Parkinson's disease, as well as some non-neurodegenerative diseases such as cardiac amyloidosis.

Cueball asks Megan why it is such a hard computational problem, and Megan replies that it is like folding a live {{w|Crane (bird)|crane}}, not just a paper crane. The analogy is that a protein cannot just fold to a figurative representation of a bio-molecule (analogous to how a paper crane abstractly resembles the live crane). It must assume an exact, perfect fold in order to be functional.

{{w|Levinthal's paradox}} is a thought experiment, also constituting a self-reference in the theory of protein folding. In 1969, Cyrus Levinthal noted that, because of the very large number of degrees of freedom in an unfolded polypeptide chain, the molecule has an astronomical number of possible conformations. For example, a polypeptide of 100 {{w|residue|Residue (chemistry)}}s will have 99 peptide bonds, and therefore 198 different {{w|Dihedral angle|phi and psi bond angles}}. If each of these bond angles can be in one of three stable conformations, the protein may misfold into a maximum of 3^198 different conformations (including any possible folding redundancy). Therefore if a protein were to attain its correctly folded configuration by sequentially sampling all the possible conformations, it would require a time longer than the age of the universe to arrive at its correct native conformation. This is true even if conformations are sampled at rapid (nanosecond or picosecond) rates. The "paradox" is that most small proteins fold spontaneously on a millisecond or even microsecond time scale. This paradox is central to computational approaches to protein structure prediction.

Cueball asks whether he can make cuts during the folding process, as if this would then make folding a living crane somehow possible. This is probably a reference to proteins which begin as a single polypeptide chain before being cut into two chains by proteases (which may then join together again, by disulfide rather than by peptide bonds). [https://en.wikipedia.org/wiki/Insulin Insulin] is one such protein. Megan replies "if you can fold a Protease enzyme", an analogy to saying "if you can fold yourself some scissors". Protease enzymes are proteins whose job it is to break down (i.e. cut) other proteins, often in very specific ways. They are thus analogous to extremely specialized scissors. The meaning of this is that if, when trying to predict the folding trajectory in nature of protein A, one allows to make cuts - one is making the assumption that the Protease that cut protein A is already folded and functional. In other words, making cuts while folding just changes the question to how the protease doing the cutting was folded.

In origami, purists [http://www.barf.cc/jeremy/origami/BOOK/essays/origami_purism/origami_purism.htm] considered it as cheating if you cut the paper or use more than one sheet of paper, which is why Cueball asks if cuts are allowed.

The title text refers to the result of folding a paper crane in origami. Pulling the tail, the head will move forward and down. However, since the joke is about folding proteins, this idea is extrapolated to include the folded proteins. The C-terminus (end of the protein chain), in this case analogous of the tail, if "pulled" would cause a created cavity or tunnel to squeeze, much like pulling a knot would do the same.

{{w|Folding@Home}} (F@H) is a distributed computing project which aims to simulate protein folding for research purposes. Rather than the traditional model of using a supercomputer for computation, the project uses idle processing power of a network of personal computers in order to achieve massive computing power. Individuals can join the project by installing the F@H software, and are then able to track their contribution to the project. Individual members may join together as a team, with leaderboards measuring team and individual contributions.

Note that most modern computers do not "waste" computing time as much as older ones. They dynamically reduce their clock speed and other power consumption at times of low usage. If you donate computer time, you are probably also donating a bit of money to the cause in the form of your electricity bill. Many people consider this to be more fun, convenient and efficient than donating via credit card.

==Transcript==
:[Cueball is talking with Megan]
:Cueball: What do you do?
:Megan: I make software that predicts how proteins will fold.
:Cueball: Is that a hard problem?
:Megan: Someone may someday find a harder one.
:Cueball: Why is it so hard?
:Megan: Have you ever made a folded paper crane?
:Cueball: Yeah.
:Megan: Imagine figuring out the folds to make an actual living crane.
:Cueball: ...just folds? Can I make cuts?
:Megan: If you can fold a protease enzyme.

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

Talk:1410: California

2014-08-20T08:08:40Z

141.101.104.173: Created page with "''and remark that "They've gone plaid!"'' I heard them say: "They've gone Plait!""

''and remark that "They've gone plaid!"''

I heard them say:

"They've gone Plait!"

74: Su Doku

2014-06-30T21:49:55Z

141.101.104.173: /* Explanation */ rubbish, a 6x6 puzzle with 2x3 regions is a valid sudoku, and the default 9x9 puzzle has 81 positions, not 27.

{{comic
| number = 74
| date = March 10, 2006
| title = Su Doku
| image = su doku.jpg
| titletext = This one is from the Red Belt collection, of 'medium' difficulty
}}

==Explanation==
{{w|Su Doku}} (Japanese for "single number", and now usually written as "sudoku") is a type of number puzzle, in which the player must place digits in a matrix field in the correct order. The most common arrangement is a 9×9 grid subdivided into nine 3×3 grids where no digit is allowed to appear twice in a horizontal or vertical row on that full 9×9 matrix. The number and combination of pre-filled squares determines the difficulty of the puzzle. When the puzzle is solved each row and column will contain the numbers 1 to 9 in a particular order.

[[Randall Munroe|Randall]] presents just a {{w|binary}} sudoku puzzle. A normal sudoku uses 9 digits, usually 1 to 9, and so fits conveniently into our normal "decimal" counting system (ten digits).

The joke is that the binary system has only two digits (0 and 1), and therefore binary sudoku puzzles would be trivially easy and thus pointless. The puzzle in the comic would be completed by filling 0 in the top-left and 1 in the bottom-left empty box. The only other possible grid would have the 0s and 1s swapped. This fulfills the criteria of having no repeated digits in any row or column.

The title text appears to reference a series of published sudoku puzzle books called the "Martial Arts Sudoku". The difficulty of each book is denoted by a martial arts belt color, with each color representing a certain skill level. Since a red belt is a rather high level (second only to a black belt), the fictional authors of this sudoku collection apparently consider this incredibly simple puzzle is rather difficult.

==Transcript==
:[A square divided into 2x2 squares, the top-right one has an 1 in it, the bottom-right one has a 0, the two left ones are empty.]
:Binary Su Doku

{{comic discussion}}