explain xkcd - User contributions [en]

Talk:2749: Lymphocytes

2023-03-14T10:42:41Z

172.69.70.209:

Battery cells have nothing to do with cell phones. The "cell" in cell phone is short for "cellular" and refers to the communication cells around each tower. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 03:09, 14 March 2023 (UTC)

: And that's short for "sell you our phone" where the contract lets you buy it over an extended time that ends about the same time the spiffier replacement model is available. [[Special:Contributions/172.69.70.209|172.69.70.209]] 10:42, 14 March 2023 (UTC)

I was originally thinking the CD4+ would be a reference to ''Call of Duty 4'' and onwards, in which players scream (insults?) at each other while playing. But the feeling has subsided, after considering it. Mentioning it here, though, in leiu of adding it as 'factual'. [[Special:Contributions/172.70.162.47|172.70.162.47]] 06:06, 14 March 2023 (UTC)

It should have bee Natural Born Killer Cells, but some opportunities were always going to be missed... --[[Special:Contributions/172.71.178.187|172.71.178.187]] 07:16, 14 March 2023 (UTC)

"Gamma-Delta T cells" being "unknown/unclassified" could be a reference to Star Trek, which has the galaxy divided into 4 quadrants: Alpha, Beta, Gamma and Delta. The Delta Quadrant (setting of Start Trek Voyager) and the Gamma Quadrant (seen in Start Trek Deep Space Nine) are unexplored and uncharted from the Federation's point of view. [[Special:Contributions/162.158.129.51|162.158.129.51]] 09:23, 14 March 2023 (UTC)

2748: Radians Are Cursed

2023-03-11T03:14:59Z

172.69.70.209: Undo revision 307798 by Troonjak (talk) nah

{{comic
| number = 2748
| date = March 10, 2023
| title = Radians Are Cursed
| image = radians_are_cursed_2x.png
| imagesize = 394x437px
| noexpand = true
| titletext = Phil Plait once pointed out that you can calculate the total angular area of the sky this way. If the sky is a sphere with radius 57.3 degrees, then its area is 4*pi*r^2=41,253 square degrees. This makes dimensional analysts SO mad, but you can't argue with results.
}}

==Explanation==
{{incomplete|Created by a DIAMETER OF 114.6 DEGREES - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic presents a series of Math Facts, appearing to be in a sequential order.

The first fact states that the {{w|unit circle}} has a radius of one, which is precisely its definition. Randall labels this fact as being "normal," complete with a large green checkmark to verify this.

The second fact states that one {{w|radian}} is equal to the length of a circle's radius, which isn't actually the way that the unit is defined. Instead, radians are usually defined as the angle encompassing the arc of a circle equal to its radius. This comic's logic is thus somewhat erroneous at best. Also, while Randall uses the unit circle in the fact's associated diagram, any circle could theoretically be used to show the conventional definition. However, this fact is still labeled as also being "normal."

A correct version of the second fact would be that, under the standard definition of an {{w|angle}} as the ratio of the length of a circular arc to its radius, the radian is a dimensionless unit equal to 1. Thus, by the first fact, a radian is equal to the radius of the unit circle.

The third fact states that one radian is equal to 57.3 degrees. The more usual conversion factor between the two units is that pi radians is equal to 180 degrees, though the conversion given by Randall is still indeed true (albeit rounded). This is again labeled "normal."

The fourth and final fact states that because it was determined in earlier facts that a radian is equal to the radius of the unit circle as well as 57.3 degrees, then the radius of the unit circle must be equal to 57.3 degrees. This is usually not how degrees are supposed to work, because they are a measure of angle, not length. Hence, this fact is labeled "cursed" by Randall, leading to the comic's title. (However, since the radian is also an angular measure, the second fact could be viewed as equally cursed.)

The title text is referring to {{w|Phil Plait}}'s claim about the size of the sky, which was published on his blog: http://www.badastronomy.com/bitesize/bigsky.html. Dimensional analysis utilizes the rationale that both sides of an equation need to have the same unit. Radius typically refers to a length, which has SI units of meters. The surface area has SI units of square meters. The units of Phil Plait's "angular area" is as the title text mentions, {{w|square degrees}}. Thus the comic's {{w|dimensional analysis|dimensional analysts}} (not a profession, but instead the adherents of the mathematical technique) are said to be angered by this argument.

Randall has alluded to Plait's angular area tip previously in his own blog What If?, in a post that examined the chances of hitting various celestial objects with a laser blast aimed at random from Earth's surface.

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

:[Title:]
:Math facts

:[A diagram of a circle is shown with radius labeled as “1”]
:The unit circle has a radius of one  ✓ Normal
:[The diagram now has another (unlabeled and lighter) radius at a 57.3 degree angle. The arc between the points where the radii touch the circle is labeled as “1”]
:One radian equals the length of a circle’s radius  ✓ Normal
:[The diagram now is completely unlabeled except for the arc, which is labeled as “57.3°”]
:One radian is 57.3 degrees  ✓ Normal
:[The first diagram is shown; however, the radius is labeled as “57.3°”]
:The unit circle has a radius of 57.3 degrees  X Cursed

{{comic discussion}}

[[Category:Math]]
[[Category:Geometry]]
[[Category:Facts]]
[[Category:Comics featuring real people]]

Talk:2295: Garbage Math

2020-04-17T21:24:40Z

172.69.70.209:

This is not a Covid19 comic. One could think that this is a comment on the difficulties of modeling the corona virus outbreak, but since discussions of exponential functions are only a small part in the comic I believe it is just a general comment on floating point arithmetic mixed in with statistical considerations. --[[Special:Contributions/108.162.229.242|108.162.229.242]] 17:28, 17 April 2020 (UTC)
:I disagree that this is not a COVID-19 comic. I also believe the one about visualizing large numbers was COVID-19 related. On the other hand, I like the idea that Randall might produce exactly 19 comics related to SARS CoViD 2019, so I'm prepared to concede the point for the sake of arbitrary numerological appeal.
:[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 18:42, 17 April 2020 (UTC)
::I think Exa-Exabyte was a real stretch (the virus doesn't even have DNA), but there is a tenuous link so whatever. The idea that ''this'' comic is related, on the other hand, stretches past the breaking point. There's hardly anything that can't be linked to global events if we try hard enough, but that doesn't mean there's an actual link. Sometimes a comic about garbage math is just a comic about garbage math.
:::I think this one's much more likely to be a coronavirus comic than Exa-Exabyte was. There's an awful lot of COVID data, much of it either very imprecise or outright garbage; and the comic directly before this one ([[2294]]) involved bad modeling of said COVID data, so clearly COVID data (and its limitations) is something Randall's currently thinking of and drawing comics about. [[User:Pelosujamo|Pelosujamo]] ([[User talk:Pelosujamo|talk]]) 20:25, 17 April 2020 (UTC)
::::Exa-Exabyte was centered around biology, which gives reason to believe it was covid19 related. This one seems much more uncertain. Any conclusion that it is related is based on garbage. Jokes aside, It seems like much more of a stretch to me. Randall thinking in those terms is a reasonable argument, but personally I am going to assume this is the chain breaker unless a direct reference is made in the next couple comics since ending at 19 is would be appropriate. [[Special:Contributions/172.69.70.209|172.69.70.209]]
Well this is surprising came here thinking I understood it just to see what the discussion looked like. Ended up learning something new. I was able to understand intuitively the comic. But this is my first exposure to actually doing math on the error bars. I think I was supposed to do that in college but I don't remember anyone ever explaining how it should work. --[[Special:Contributions/162.158.63.208|162.158.63.208]] 18:14, 17 April 2020 (UTC)

In recent days, there have been a number of math "quizzes" in this same type of format, albeit generally with only addition and maybe multiplication, appearing on Facebook. Should the explanation include a reference to this as a possible contributing reason for Randall's comic? One could also argue that those quizzes have been appearing on Facebook as a way to spend/waste time during the coronavirus pandemic lockdown, making he comic at least tangentially related to Covid19.

What's the difference between relative error and absolute error? I don't understand these terms. Maybe add?

Are all of these equations consistent with garbage = infinity?

2013: Rock

2018-07-02T01:53:52Z

172.69.70.209: If you know how to skip a stone and have a ok stone you will get at LEAST two skips

{{comic
| number = 2013
| date = June 29, 2018
| title = Rock
| image = rock.png
| titletext = It traveled so far to reach me. I owed it my best.
}}

==Explanation==
{{incomplete|Created by a VOLCANO AT THE SOUTH POLE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Megan either knows enough about geology to tell on sight how this particular rock formed, or has brought this rock from a collection. Alternatively she’s simply guessing. Despite admiring its formation, all she wants is to use it as a skipping stone to give it "a weird day in its life", and possibly confuse future geologists.

Megan provides three pieces of information about the rock: It formed at the south pole, during an ice age, just before multicellular life developed. Unfortunately, due to disagreements among geologists and palaeontologists about when exactly the first multicellular life emerged it is unclear which time Megan refers to - and consequently where she is and what kind of rock she is holding. There are two possibilities:

# The {{w|Francevillian biota}}, living about 2.1 billion years ago, has been proposed as the first multicellular life. If Megan subscribes to this theory, then the Ice age just before would be the {{w|Huronian glaciation}} which extended from 2.4 to 2.1 billion years ago. The land which was at the South pole at that time would eventually [http://www.youtube.com/watch?v=UwWWuttntio become part of Africa].
# However, not all scientists accept the Francevillian biota as the first multicellular life. If Megan shares this view the first fossils multicellular life would be only 600 million years old (e.g. in the {{w|Doushantuo Formation}}). In this case the ice age "just before" would be the {{w|Cryogenian}} lasting from 720 million to 635 million years ago. The land occupying the South Pole at the time became present-day Scandinavia and Baltic sea.

Thus - assuming that Megan has accurately identified the stone - the stone is either from Western Africa or Northern Europe and has 'travelled' from there to get to her.

{{w|Stone skipping}} is the art of throwing a flat stone across water in such a way that it bounces off the surface. Most throws rarely result in more than two or three "skips",{{Citation needed}} so Megan skipping the stone five times is certainly an above-average throw. (It is, however, far short of the world record of 88 skips set by Kurt Steiner in 2013).

This comic is one of many that look at everyday things from a new, philosophical perspective.

==Transcript==
:[Cueball and Megan are looking at a rock that Megan is holding up in one hand.]
:Megan: This rock erupted from a volcano near the South Pole when the world was frozen over, just before multicellular life arose.

:[Zoom out reveals that Cueball and Megan are standing on the beach of a bay with hills in the background. The water surface is quite flat without any waves. Megan throws the rock which skips 5 times across the water before it sinks.]
:Stone: Skip Skip Skip Skip Skip Plunk

:[Zoom back on Cueball and Megan who are still looking in the direction she threw the stone.]
:Megan: Now it'll be covered in sediment that becomes a new rock layer. It will likely stay buried until it melts down, erodes away, or the earth is consumed by the sun.

:[Cueball and Megan still looking the same way.]
:Cueball: Today was a weird day in its incredibly long life.
:Megan: Five brief skips, then eons of darkness.
:Cueball: Five is a lot, though!
:Megan: It '''''was''''' a good throw.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Geography]]

Talk:2002: LeBron James and Stephen Curry

2018-06-04T16:31:11Z

172.69.70.209: My own comment that SSNs are no longer strictly geographically.

I have no idea what this is about, but wondered if Stephen Curry was related to the Curry twins Tom and Ben, who are both over 6' - or to Tim, who isn't except in heels.
[[User:Arachrah|Arachrah]] ([[User talk:Arachrah|talk]]) 07:53, 4 June 2018 (UTC)
: Both LeBron James and Stephen Curry are famous NBA players. [[Special:Contributions/172.69.190.4|172.69.190.4]] 08:46, 4 June 2018 (UTC)
::How would you not know that? And even if you don't know who they are, you must have at least heard about them before, right? [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 09:21, 4 June 2018 (UTC)
::: Not everyone is from USA. [[Special:Contributions/172.69.190.4|172.69.190.4]] 09:41, 4 June 2018 (UTC)
:::: That excuse could work, except your IP address is based in the USA :) [[User:Zachweix|Zachweix]] ([[User talk:Zachweix|talk]]) 12:01, 4 June 2018 (UTC)
::::: So is mine right now, but that doesn't mean I'm '''from''' here, and they didn't make us memorise every NBA player on the plane. (Hey cool, this IP has edited here before too) -[[Special:Contributions/162.158.186.60|162.158.186.60]] 15:36, 4 June 2018 (UTC)

::: I like Curry. You know, the dish. And the actor. Tim, that is. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 11:58, 4 June 2018 (UTC)
Not everyone in the USA follows sports. I've heard of LeBron James, but only in passing. The only Curry I know of is a fictional one from some old movie.
;Nate Silver

Nate Silver is famous for his numerical approach and extensive use of statistics and simulations.
He foresaw a probability of 28.6% for Donald to win the electoral college just before the election. That is a greater chance than most political commentators would have granted Donald. Typical betting sites saw Hillary 5:1 ahead at the evening of the election.
So I would not at all say that he got everything wrong in 2016. He predicted that Hillary would be a formidable number of votes ahead as most probable outcome, but also that many states would be very tight.
[[https://projects.fivethirtyeight.com/2016-election-forecast/]]. Sebastian --[[Special:Contributions/172.68.110.106|172.68.110.106]] 09:21, 4 June 2018 (UTC)

;Definitions needed
Hi! Could definitions be added for some of the terms used, such as "bleachers"? Thanks! [[Special:Contributions/162.158.155.200|162.158.155.200]] 11:30, 4 June 2018 (UTC)

;Magnetic North
I would have liked the "magnetic north" thing to be due to the geographical orientation of the teams home courts (if the Cavaliers are the only team to have a court that happens to be roughly north-south oriented, it would explain the higher points value). Looking at the Stupid Name Arena, however, it appears that the court inside is probably about NW-SE. Too bad. [[User:Chrullrich|Chrullrich]] ([[User talk:Chrullrich|talk]]) 14:15, 4 June 2018 (UTC)

;SSN to Free Throw%
Would it be too much of a stretch to add in the fact that Stephen Curry's point is highlighted on the chart, as a nod to the fact that (the majority of) one's SSN can actually be determined if one knows details about personal information such as where one was born? [[Special:Contributions/108.162.219.130|108.162.219.130]] 16:08, 4 June 2018 (UTC)
:Not anymore. My three kids were all born in the same hospital -- same wing; rooms only meters apart -- but have TOTALLY different SSN's. (No, I'm not sharing them as proof!) We even asked the local SS office what happened and they said they're starting to reuse numbers at random. I think it's not "reuse" as much as "reallocate", but either way the strict geographical basis is no longer valid. --'''BigMal''' // [[Special:Contributions/172.69.70.209|172.69.70.209]] 16:31, 4 June 2018 (UTC)