explain xkcd - User contributions [en]

Talk:2991: Beamsplitters

2024-09-30T16:19:45Z

172.68.110.188:

Pictures taken by telescope are filtered one colour at the time. If the filtered out colours could be diverted, those photons could be harvested without interfering with the scientific studies. Of course, it would still not be economically efficient. [[Special:Contributions/162.158.127.100|162.158.127.100]] 00:33, 28 September 2024 (UTC)
:Yes, a classic beam-splitter was the first color TV cameras. Three camera tubes (probably vidicons?) on the three outputs of two filtering beamsplitters. Later they did it all in one bottle; still later three chips on two beamsplitters. Color TV can be whacky. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 01:35, 28 September 2024 (UTC)
The wavefunction explanation at the time the electron is generated is "wrong". The photovoltaic cell and the electron get entangled. See Wigner's Friend watching Schrödinger's Cat. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 16:19, 30 September 2024 (UTC)

Talk:2985: Craters

2024-09-19T20:23:58Z

172.68.110.188: Mentioning misuse of “meteor” as something hitting the earth

==Delaware/Pennsylvania Arc==
The Delaware/Pennsylvania arc is a circle, sure, but so is every other allegedly "straight" line on the map. The 49N parallel looks like a straight line on some projections, but a polar projection shows that it is clearly a circle around a point on the Earth's axis. The Delaware/Pennsylvania arc is only unique for NOT being aligned with the axis. [[Special:Contributions/172.71.102.20|172.71.102.20]] 19:07, 13 September 2024 (UTC)
:The "Delaware/Pennsylvania arc" has a long and juicy history. Not a circle. [https://en.wikipedia.org/wiki/Twelve-Mile_Circle Twelve-Mile Circle] Signed- --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 20:36, 13 September 2024 (UTC)
:True about map projections, but the Venn section title here does say *Weird*. The Delaware/Pennsylvania arc is indeed "weird"; few other such arcs are found in regular map content, and the original story for it is indeed uncommon. <s>Great Circle</s> Parallel latitude "arcs" aren't weird in either way. [[Special:Contributions/172.68.34.64|172.68.34.64]] 20:52, 13 September 2024 (UTC)
::North-South lines are great-circle arcs, but non-equatorial East-West lines - as well as many diagonal ones - are minor-circle arcs (is that the right term?), just link the 12-Mile Circle. (Let's see if this retains my IP address from my top post.) [[Special:Contributions/172.70.46.109|172.70.46.109]] 21:29, 13 September 2024 (UTC)
:::Right you are! [[Special:Contributions/172.68.34.64|172.68.34.64]] 23:00, 14 September 2024 (UTC)

==Great Blue Hole==
There are two Great Blue Holes, one in Belize, one in Dahab, Egypt (Red Sea). [[Special:Contributions/172.71.102.20|172.71.102.20]] 19:11, 13 September 2024 (UTC)
==Recent Google Maps discovery==
This may be inspired Joël Lapointe's very recently announced discovery of a 15km-diameter "pit" he found near Marsal Lake (Quebec) using Google Maps. [https://www.cbc.ca/news/canada/montreal/quebec-meteorite-impact-crater-1.7313418 "He saw a suspicious pit on Google Maps. Experts say it could be a crater from an ancient space rock"] [[Special:Contributions/172.69.64.185|172.69.64.185]] 20:10, 13 September 2024 (UTC)

----

man, why are so many of these in Quebec? does it have a natural meteor/circle magnet? [[Special:Contributions/172.68.174.232|172.68.174.232]] 01:11, 14 September 2024 (UTC)

: Parce qu'on y parle français. [[Special:Contributions/172.69.71.68|172.69.71.68]] 12:39, 14 September 2024 (UTC)

==New Column==
I'm thinking about a new column or two: GPS coordinates (with an Open Earth link?) and a satellite image, or something. [[Special:Contributions/172.71.102.76|172.71.102.76]] 03:27, 14 September 2024 (UTC)

: The table seems incomplete without something like that. [[Special:Contributions/172.69.34.172|172.69.34.172]] 22:50, 14 September 2024 (UTC)

==Meta Reference: Venn Diagram Double Crater==
No comment yet on the fact that the two circles in the Venn Diagram refer to craters and circles... [[Special:Contributions/172.71.102.53|172.71.102.53]] 01:32, 15 September 2024 (UTC)

==Geographic bias by meteorites or Randall?==
Boy am I happy that I don't live in North or Central America, where 11 out of 13 "craters" are located... [[User:Mumiemonstret|Mumiemonstret]] ([[User talk:Mumiemonstret|talk]]) 07:44, 15 September 2024 (UTC)
:Maybe over here (rightpondia, oceania, down-under and the cradle of humanity itself), we just cleaned them up easier (or messed them up badly) so they were less obvious. (c.f. Nördlingen.) Y'all over thataway, however, haven't had time to do anything too drastic to obscure them. ;) [[Special:Contributions/172.70.163.48|172.70.163.48]] 14:10, 15 September 2024 (UTC)
:Haha, yeah, that was also my first thought when I googled the places I didn't know: very America-centric by either Randall or meteorite or other circle-creating entities... And even the other 2 places are in English speaking places (yes, I know English isn't the official language of India, but still one of the most common)--[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 04:28, 16 September 2024 (UTC)

I am tickled pink that two significant items in my life appear adjacent in this diagram: Stonehenge, and Crater Lake. My company name is Stonehenge (and I've been to the real rock pile a few times), and I'm a native Oregonian, using Crater Lake as my video-call background. [[User:RandalSchwartz|RandalSchwartz]] ([[User talk:RandalSchwartz|talk]]) 22:02, 15 September 2024 (UTC)

==Crater Lake==
So we're not going to talk about Crater Lake not being an actual crater? {{unsigned ip|172.69.134.107|22:12, 16 September 2024}}
:"Crater Lake (Klamath: Giiwas)[2] is a volcanic crater lake..." [[Special:Contributions/172.70.91.2|172.70.91.2]] 23:48, 16 September 2024 (UTC)

== no monday comic ==

silly randall [[Special:Contributions/172.70.86.146|172.70.86.146]] 07:17, 17 September 2024 (UTC)
:nvm [[Special:Contributions/141.101.99.136|141.101.99.136]] 08:28, 17 September 2024 (UTC)

==What's with the excessive use of headers in this chat?==
==Sinkholes==
Kingsley Lake is located Southwest of Jacksonville, FL and directly East of Starke, FL, on the grounds of Camp Blanding. If you look at it on Google Maps, you will notice that it is pretty much perfectly round. You would think that this was a meteor impact, but in fact it is just a really large sinkhole. Camp Blanding dates back to World War II when it was being used as a training camp for the Army and also as a POW camp for captured German soldiers.
[[User:Foozini|Foozini]] ([[User talk:Foozini|talk]]) 04:37, 19 September 2024 (UTC)

==Meteor impact craters???==
Meteors don't leave craters. Meteorites do. [[1405|Just saying.]] --[[Special:Contributions/172.68.110.188|172.68.110.188]] 20:23, 19 September 2024 (UTC)

899: Number Line

2024-08-22T13:12:42Z

172.68.110.188: /* Explanation */

{{comic
| number = 899
| date = May 16, 2011
| title = Number Line
| image = number line.png
| titletext = The Wikipedia page List of Numbers opens with "This list is incomplete; you can help by expanding it."
}}

== Explanation ==

Once again, [[Randall]] seems to be just messing around, this time with a number line.

*'''Negative numbers''' have the same magnitude as positive numbers but can only be used to represent the removal of that same magnitude (hence the term "difference" being used for subtraction). Negative numbers may be called imitator numbers in the comic because of their similarities to positive numbers.

*'''0.<span style="text-decoration: overline;">99</span>'''.... is {{w|0.999...|equal to 1}} because if you subtract any number from one, however small, you will get a number that is less than 0.<span style="text-decoration: overline;">99</span>. 1 − '''0.0000000372''' is 1 bit less than the {{w|IEEE_floating_point|IEEE 754 32-bit floating-point representation}} of 1.

*The '''{{w|golden ratio}}''' or '''ϕ''' (phi) is the number <math>\tfrac{1+\sqrt{5}}{2}</math>, about 1.61803. It has many interesting mathematical properties, mostly relating to geometry, and has occasional appearances in nature, such as spirals formed by the seeds in sunflowers. It is also subject to many less credible claims, such as the belief that phi appears in {{w|Parthenon}} (a well-disputed claim) or that rectangles proportioned after phi are more aesthetically pleasing. The speaker seems to drive off his listeners as soon as he brings it up; the golden ratio is infamous for being brought up by know-it-alls, which Randall has mocked in other comics.

* The approximate range from 2.1 to 2.3 is marked as '''The Forbidden Region'''. Why Randall marked this range as forbidden is really anyone's guess; it seems to be an entirely arbitrary designation.

*'''{{w|e (mathematical constant)|e}}''' (Euler's number) is 2.71828... and '''π''' (pi) is 3.14159265...

*'''2.9299372''' is probably a {{w|President's Day}} reference. It is the average of e and π just as the American Presidents' Day is always observed on the 3rd Monday of February (between {{w|George Washington}} and {{w|Abraham Lincoln}}'s birthdays). Washington and Lincoln were the 1st and 16th Presidents of the USA, respectively. Each has a celebrated place in American history.

*'''Gird''', '''ᛟ''' is a purely fictional number. (The glyph that Randall uses seems to resemble an older shape of the digit 4, such as seen on [https://web.archive.org/web/20230908075930/http://www.bl.uk/learning/images/mappinghist/large2296.html archaic maps].). The glyph bears some resamblance to the {{w|odal rune}} but given its associations (especially in the version with {{w|serifs}}) this was probably unintentional. Canon and orthodox could mean "accepted as the offical story" and "most science-based followers", but they could also reference to organised religions. Gird could be a reference to any or all of:
**[http://strangehorizons.com/fiction/the-secret-number/ Bleem] - a fictional integer between 3 and 4
**iCarly's [http://icarly.wikia.com/wiki/Derf Derf] - a fictional integer between 5 and 6
**George Carlin's [http://www.urbandictionary.com/define.php?term=bleen Bleen] - a fictional integer between 6 and 7
**[https://scp-wiki.wikidot.com/scp-033 SCP-033] - a fictional "missed number" consisting of complex formulae that causes mathematical systems to break down when it is introduced to them (manifesting as the physical destruction of the objects the mathematical formulae are contained in, such as paper and computers)
**Saturday Morning Breakfast Cereal's [http://www.smbc-comics.com/index.php?id=3913 Sorf] - a fictional integer between 2 and 3 

*'''Site of Battle of 4.108''' is another map joke, implying that 4.108 is an actual location, where an eponymous battle was previously fought. 4.108 was also referenced in [[2861: X Value]], though with an added 3 in the ten-thousandths place.

*An '''Unexplored''' region obscures the line approximately ranging all values from 4.5 to 6.7. In the days when the Earth was still being mapped out, territories that had yet to be properly explored and charted were labelled in a similar manner. The placement of the '''Unexplored''' region on the number line indicates that all numbers in that range, including the integers 5 and 6, are completely unknown. This is, of course, patently ridiculous,{{cn}} and the humor seems to derive solely from how nonsensical and unbelievable it is. Correspondingly, the digits 5 and 6 cannot be found in the comic.

*It is often the case in the media that "It has been 7 years..." or "In the last 7 years..." etc. It is made to seem like a believable statistic but cannot always be true. Alternatively, it is intended as an absurd joke that the number 7 is just "not to be believed".

*'''8''' is not the largest even {{w|prime number}}, nor is it a prime at all. The largest (and only) even prime is 2 (which is a subprime number). A joke intended for those who clearly know that the claim is false.

*The last entry seems to be a reference to certain fields of {{w|pure mathematics}}, which focus less on performing calculations with numbers and more on understanding structures that may be described using logic. It finishes off the tone of the comic that seems to be shaping the number line terms of what is commonly useful to certain areas of applied mathematics, rather than a complete, accurate version of the number line.
**A possible alternate reason for suggesting that any digit beyond 8 (i.e. 9) would not be 'real' mathematics is {{w|Benford's law}}. Taken at the level of individual digits, true data tends to have far fewer 9s in it than (in decimal representation) any other non-zero digit. While it would not be true to say that the presence of a 9 itself indicates invalid values, concocted or stochastically randomised values may have far more 9s than would naturally emerge from true data. Any use of those numbers would then be based upon lies, and highly suspect. The two-digit 10, also illustrated, might be excluded from any analysis of digit-frequency, or (prominantly featuring a trailing zero) might further underline the point by being being more likely rounded to the nearest ten (or even a convenient [[2205: Types of Approximation|order of magnitude]]), where its [[2696: Precision vs Accuracy|accuracy and precision]] are both more open to doubt than in the case of either 9 or (also neighbouring it, though not shown here or necessarily subject to any comment) 11.

The title text is a literalism joke; at the time the comic was published, all Wikipedia articles with incomplete lists began with the message template "This list is incomplete; you can help by expanding it." In the case of the {{w|List of numbers}} page, one could infer the absurd notion that Wikipedia wanted to have the list include every number from negative infinity to infinity. But because all Wikipedia articles are necessarily finite, such a list would always be incomplete, no matter how much it was expanded. It may also be referencing his previous statements about Wikipedia being the home of compulsive list-makers, who make the most astonishingly complete lists imaginable.

As of 2022, Wikipedia's {{w|List of numbers}} page, as well as all pages including lists that cannot ever reach a state of completion, are headed by the message template "This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources."

[[2956: Number Line Branch]] also features a number line with additional (fictional) numbers.

== Transcript ==
:[Number line ranging from −1 to 10.]
:[Arrow pointing left, towards negative numbers] Negative "imitator" numbers (do not use)
:[Line right before the number one] 0.99... (actually 0.0000000372 less than 1)
:[Line at the golden ratio.] Φ Parthenon; sunflowers; golden ratio; wait, come back, I have facts!
:[Line at a region between two and 2.2] forbidden region
:[Line at Euler's number.] e
:[Line a bit before 3] 2.9299372 (e and pi, observed)
:[Line at π.] π
:[Line at 3.5 with ᛟ as the numeral] Gird – accepted as canon by orthodox mathematicians
:[Line a bit after 4.] site of battle of 4.108
:[Blob between 4.5 and 6.5 labeled unexplored.]
:[Line at seven.] Number indicating a factoid is made up ("every 7 years...", "science says there are 7...", etc)
:[Line at eight.] Largest even prime
:[Line at 8.75.] If you encounter a number higher than this, you're not doing real math

== Trivia ==

* As for the "Gird" between 3 and 4, one might argue that the arithmetic square root of 11 may have some "integer" properties, because there exists an integer-to-integer{{Citation needed}} function f(x) such that f(f(x))=11x. (details needed)
* The "unexplored" area is actually famous for some numbers, such as twice π (also known as tau (τ), approximately 6.283185).

{{comic discussion}}
[[Category:Math]]
[[Category:Wikipedia]]

809: Los Alamos

2024-08-18T19:12:39Z

172.68.110.188: /* Explanation */

{{comic
| number = 809
| date = October 22, 2010
| title = Los Alamos
| image = los_alamos.png
| titletext = The test didn't (spoiler alert) destroy the world, but the fact that they were even doing those calculations makes theirs the coolest jobs ever.
}}

==Explanation==
This comic refers to the {{w|Manhattan Project}} at {{w|Los Alamos, New Mexico}}, where in 1945 their development of the first nuclear weapon had progressed to the point that they were going to explode "The Gadget" at {{w|Trinity Site}}. There was genuine concern that some unexpected result was possible, including the scenario about the atmosphere igniting. The scientists were almost certain that it would either work as expected, or just be a dud, but were unable to rule out several other scenarios. The test proceeded, and it worked as expected. Note that the "ignition" feared wasn't a chemical reaction (Nitrogen and oxygen reacting chemically is {{w|endothermic}}) but instead a ''nuclear'' fusion reaction involving atmospheric nitrogen and oxygen — which is to the atmosphere "burning" in the chemical sense as all nuclear weapons ever built is to a candle.

The joke part at the end is a reference to a common {{w|mnemonic}} device for basic {{w|trigonometric}} functions, namely identifying the relationships of ''sine'', ''cosine'', and ''tangent'' with respect to the lengths of a right triangle's edges: '''s'''ine = '''o'''pposite over '''h'''ypotenuse, '''c'''osine = '''a'''djacent over '''h'''ypotenuse, and '''t'''angent = '''o'''pposite over '''a'''djacent (in other words, SOH CAH TOA.) "Steve" becomes concerned by the seriousness of the situation, and wants to make sure that he has not made a mistake on stuff that should be ''very'' elementary to a scientist in his position.

The title text mentions that there are very few jobs where one can say that with seriousness, as normal jobs do not involve technology capable of destroying worlds.{{Citation needed}}

A Steve is referred to in a similar situation in comic [[1532: New Horizons]], where his miscalculations screw up the trajectory of the {{w|New Horizons}} space probe, sending it to Earth instead of Pluto. He would be at least 90 years old if it was to be the same Steve, though. A person named Steve also comes up with an inappropriate suggestion in [[1672: Women on 20s]].

==Transcript==
:[Cueball raising a hand points to Steve (see later) drawn as another shorter Cueball-like guy, and behind Cueball stand Hairy also looking at Steve. Partly behind Steve's head is a piece of paper on the wall with a circle around a central dot and four arrows pointing in towards the circle from each corner of the paper. Behind Hairy's head is another paper with a graph that looks like a positive third degree polynomial with three non-zero solutions. Between Cueball and Hairy at the level of their hands is a small square with two small dots at the two top corners. Seems like a part of the wall rather than a paper. During the next images the two on either side of Cueball moves their head in front or away from these papers so at least once the hole drawing can be seen. Over the panels top frame there is a frame with a caption:]
:Los Alamos, 1945...
:Cueball: We have a decision. If we've done our math right, this test will unleash heaven's fire and make us as gods.

:[Cueball turns towards Hairy holding his arms out.]
:Cueball: But it's possible we made a mistake, and the heat will ignite the atmosphere, destroying the planet in a cleansing conflagration.

:[In a frame-less panel Steven takes a hand to his chin, while the other two turns towards him.]
:Steve: Wow. Um. Question: Just to double-check— although I'm 99% sure—

:[Cueball, still facing Steve, face-palms himself while Hairy turns away from Steve.]
:Steve: Is it "SOH CAH TOA" or "COH SAH TOA"?
:Cueball: ''Oh, for the love of...'' can someone redo Steve's work?
:Hairy: I don't want to do the test anymore.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]
[[Category:Multiple Cueballs]]
[[Category:Math]]
[[Category:Physics]]
[[Category:Nuclear weapons]]

Talk:2853: Redshift

2023-11-11T15:41:07Z

172.68.110.188:

Does it make any sense to try and relate the two Z values to a more "normal" time? [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 21:08, 10 November 2023 (UTC)

I have added exactly that, using `astropy.cosmology` for the calculations [[User:Juandesant|Juandesant]] ([[User talk:Juandesant|talk]]) 21:16, 10 November 2023 (UTC)

There is a big error in the current explanation, saying it means they were interested in this since the early universe, but that would only be true if the z value was much closer to 1. I'm not exactly sure as I haven't done the math, but with that many decimal places of zero's it is probably near enough history to be during their lifetime. So the joke isn't being interested in the early universe since the early universe, but rather so interested in it that they talk about other things with the same terminology.--[[Special:Contributions/172.70.126.142|172.70.126.142]] 21:18, 10 November 2023 (UTC)

Why aren't these values expressed in scientific notation? Separately, do they make sense logarithmically? [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 07:12, 11 November 2023 (UTC)
:Part of the joke is that the values are unwieldy to use compared to everyday language and units. The scientific notation would have lessened this. However they are given in a universal standard time instead of some solar system or human related units, so they generally should be clearly preferred. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 15:37, 11 November 2023 (UTC)

Talk:2853: Redshift

2023-11-11T15:37:44Z

172.68.110.188:

Does it make any sense to try and relate the two Z values to a more "normal" time? [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 21:08, 10 November 2023 (UTC)

I have added exactly that, using `astropy.cosmology` for the calculations [[User:Juandesant|Juandesant]] ([[User talk:Juandesant|talk]]) 21:16, 10 November 2023 (UTC)

There is a big error in the current explanation, saying it means they were interested in this since the early universe, but that would only be true if the z value was much closer to 1. I'm not exactly sure as I haven't done the math, but with that many decimal places of zero's it is probably near enough history to be during their lifetime. So the joke isn't being interested in the early universe since the early universe, but rather so interested in it that they talk about other things with the same terminology.--[[Special:Contributions/172.70.126.142|172.70.126.142]] 21:18, 10 November 2023 (UTC)

Why aren't these values expressed in scientific notation? Separately, do they make sense logarithmically? [[User:JohnHawkinson|JohnHawkinson]] ([[User talk:JohnHawkinson|talk]]) 07:12, 11 November 2023 (UTC)
:Part of the joke is that the values are unwieldy to use compared to everyday language and units. The scientific notation would have lessened this. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 15:37, 11 November 2023 (UTC)