explain xkcd - User contributions [en]

1606: Five-Day Forecast

2025-04-20T23:01:32Z

172.70.58.50: Undo revision 373906 by 162.158.193.130 (talk) Nope.

{{comic
| number = 1606
| date = November 20, 2015
| title = Five-Day Forecast
| image = five_day_forecast.png
| titletext = You know what they say--if you don't like the weather here in the Solar System, just wait five billion years.
}}

==Explanation==
{{w|Weather forecasting}} is an extremely difficult task, even if it is only for five days. In numerical models, extremely small errors in initial values double roughly every five days for variables such as temperature and wind velocity. So most {{w|Meteorology#Meteorologists|meteorologists}} provide us with only a five-day forecast.

In this comic [[Randall]] takes this to the extreme by first showing a '''Five-Day Forecast''' and then progressing to five-month, year, million, billion and finally trillion-year forecasts, leading to {{tvtropes|WeirdWeather|weather patterns that we don't regularly see.}}

Since the first weather symbol is the same in all six rows, we can assume it indicates the weather today and not tomorrow, in a trillion years, etc. It is only in the second panel of each row that time has passed per the row's label. Consequently, the last column gives the predictions for four days, four months, ..., four trillion years from today.

When moving past the five-day prediction, the forecast is just a qualified guess based on the time of year. In a month it is Christmas as shown in the second panel of the second row. Then it is January and February so snow is likely, but certainly not something that happens on all days of a winter month.

Looking at the five-year forecast, guesses are made as to what the weather will be like at the same time of year. For these first three predictions the weather symbols are all of the same three types: Sun, clouds and some kind of {{w|precipitation}}, rain or snow, with the temperature ranging from 21 to 44 °F (-6.1 to 6.6 °C) - late-{{w|Autumn#Date definitions|autumn/fall}} (perhaps early-{{w|Winter#Astronomical and other calendar-based reckoning|winter}}) temperatures.

Then we go into the far future, jumping a million years from panel to panel. But still the weather symbols stay the same. In 3 million years, however, aliens (or advanced humans) attack with energy beams from {{w|flying saucers}}. They are absent a million years later, or at least not actively attacking in any visible way during this later snapshot. The temperature range remains the same across the panels except that it rises to 52 °F (11 °C), a possible reference to global warming, in one panel, and while the attack is going on it rises to 275 °F (135 °C).

Once we get to the billion-year mark it actually becomes more meaningful to try to predict the "weather", because now we reach the times when the {{w|Sun}} begins to change. Although the Sun will continue to burn hydrogen for about 5 billion years yet (while in its {{w|Sun#Main sequence|main sequence|}}), it will grow in diameter as it begins to exhaust its supply of fuel. The core will contract to increase the temperature, and the outer layer will then compensate by expanding slightly. This is what is indicated in panels two and three, where the color of the Sun changes towards red as the surface becomes cooler as it expands away from the center of the Sun. The temperature will rise on Earth as indicated in the panels (105 °F = 40.5 °C and 371 °F = 188 °C). The temperature will get hot enough in about [http://phys.org/news/2015-02-sun-wont-die-billion-years.html a billion years] that the Earth's oceans will boil away.

Once it {{w|Sun#After core hydrogen exhaustion|no longer has enough hydrogen}}, the Sun will expand into a {{w|red giant}}. This should not happen until around {{w|Sun#Composition|five billion years from now}}, but in the forecast it is indicated to happen in only three. Maybe this is Randall taking liberties to show what happens during this phase, which would not fit into a four-billion-year forecast. Alternatively it just indicates how uncertain these kinds of forecasts are, or a statement that we may not know for certain that it will take five not three billion years, nor what toll other influences (such as attacking aliens) might take on the Sun.

In any case, the fourth panel shows the temperature at Earth's position inside the red giant Sun. The color of the panel indicates that we are inside the Sun. The temperature is 71,488,106 degrees Fahrenheit (39,715,597 degrees Celsius). The current temperature of the center of the Sun is "only" 27 million degrees Fahrenheit (15 million degrees Celsius), and although that may rise by a factor of ten during {{w|Stellar nucleosynthesis|helium fusion}}, that will only be at the very core and not out in the solar atmosphere reaching out to Earth. Here the temperature would only be of the order of thousands of degrees Fahrenheit, since the Sun's outer temperature decreases as it increases its diameter. So this panel's temperature also makes little sense by current understanding. It may involve some ambiguities regarding what the forecast means; the edge of the red giant Sun is predicted to be somewhere near the current orbit of Earth, but the position of the Earth could change. The most likely prediction at the moment is for Earth to move outward but, if the planet is engulfed by the Sun, it would spiral inward, and at some point fall apart. So in some sense "here" for the forecast could become a position deep inside the Sun, where core temperatures could reach 100 million Kelvin. The temperatures shown are unreasonably precise; they probably should have only two or at most three significant figures, if not for the running theme of escalating levels of prescience (enough to predict a future attack by flying saucers, etc).

The red giant phase lasts only half a million years, so a billion years after the Sun has been a red giant its outer atmosphere will definitely have disappeared, leaving only a dim, cool {{w|white dwarf}} to cool down. Given Randall's version of this time schedule, then it will have had about a billion years to cool down, but would still likely be the brightest object in the sky as seen from where the Earth once was. It is not shown in the last panel, where we just see other stars of the Galaxy. The temperature is down to that of the {{w|Cosmic microwave background|background radiation}}. Today this radiation has a temperature of 2.72548 kelvin = -270.4245 °C = -454.7641 °F. That is a few degrees F colder than what is shown in the comic, which states the temperature is -452 °F = 4.26 kelvin. This higher temperature may have been chosen to reflect that even the light from other stars would increase the actual temperature.

In the last panel with trillions of years, we jump right past the Sun's red giant phase to a panel looking much like the one after five billion years with only other stars, one of the original stars being no longer visible. Over the next three trillion years the stars become fewer and dimmer as they run out of fuel, while fewer new ones form to continue the cycles of star-formation. After four trillion years the background temperature decreases one degree to -453 °F as the universe keeps expanding and the wavelength of the radiation does the same, thus decreasing its temperature.

The title text is a play on comments referring to fast-changing weather on a more ordinary human timescale, such as Mark Twain's quip, "If you don't like the weather in New England now, just wait a few minutes."

A ten-day forecast was used in [[1245: 10-Day Forecast]]. In [[1379: 4.5 Degrees]], Randall looked at the weather over long periods of time as well. in [[1643: Degrees]] he addressed Celsius vs. Fahrenheit for measuring temperature.

===Image using Celsius===

There is a different user-made version for the picture, using [[3001|Celsius]] instead of Fahrenheit, [[:File:five_day_forecast_Celsius.png|in this image link]]. (For a version that also uses Kelvin, [[:File:five_day_forecast_Celsius+Kelvin.png|click here]].)

==Transcript==
:[A grid with six rows of five columns, where each row is labeled to the left. For each of the 30 squares a temperature is given in Fahrenheit at the top left. The rest of the square represents the weather as in a weather forecast (or some other relevant items for the comic), mainly in bright colors. Below are the six labels given above each of their five weather symbols with temperature given below these symbols description.]

:'''Your 5-day forecast'''
:[A bright yellow sun.]
:38°F
:[A grey cloud.]
:41°F
:[A grey cloud with six lines of blue raindrops below.]
:36°F
:[A grey cloud in front of a yellow sun.]
:40°F
:[A bright yellow sun.]
:44°F

:'''Your 5-month forecast'''
:[A bright yellow sun.]
:38°F
:[A green Christmas tree with red presents beneath it.]
:29°F
:[A grey cloud with four snowflakes below.]
:21°F
:[A grey cloud with four snowflakes below.]
:24°F
:[A grey cloud.]
:35°F

:'''Your 5-year forecast'''
:[A bright yellow sun.]
:38°F
:[A grey cloud.]
:25°F
:[A bright yellow sun.]
:36°F
:[A grey cloud with six lines of blue raindrops below.]
:37°F
:[A bright yellow sun.]
:41°F

:'''Your 5-million-year forecast'''
:[A bright yellow sun.]
:38°F
:[A bright yellow sun.]
:52°F
:[A grey cloud.]
:40°F
:[Two red flying saucers (with bright domes) are shooting energy beams downwards. One of the beams seems to impact with something at the bottom of the panel, which then explodes. Two plumes of smoke rises up from below, drifting to the right.]
:275°F
:[A grey cloud in front of a yellow sun.]
:40°F

:'''Your 5-billion-year forecast'''
:[A bright yellow sun.]
:38°F
:[A larger orange sun.]
:105°F
:[A very large red sun.]
:371°F
:[A pale yellow panel with no drawing.]
:71,488,106°F
:[A night sky with many bright stars.]
:-452°F

:'''Your 5-trillion-year forecast'''
:[A bright yellow sun.]
:38°F
:[A night sky with many bright stars.]
:-452°F
:[A night sky with many stars.]
:-452°F
:[A night sky with fewer not so bright stars.]
:-452°F
:[A night sky with few dim stars.]
:-453°F

{{comic discussion}}

[[Category:Comics with inverted brightness]]
[[Category:Comics with color]]
[[Category:Science]]
[[Category:Space]]
[[Category:Astronomy]]
[[Category:Weather]]
[[Category:Aliens]]
[[Category:Christmas]]

Talk:3075: Anachronym Challenge

2025-04-18T20:50:51Z

172.70.58.50:

Shouldn't "Anachronym" be "Anachronism"? The listed items aren't archaic acronyms. [[Special:Contributions/162.158.63.83|162.158.63.83]] 17:30, 11 April 2025 (UTC)
:No, "-nym" means name, so this is names that are outdated [[Special:Contributions/104.23.190.60|104.23.190.60]] 17:36, 11 April 2025 (UTC)
:: (The OP) Ah, I see now. An anachronym is a term used in an anachronistic way (like tin foil which isn't made of tin anymore), where an anacronym is an word that started as an acronym but is now treated as a word (people no longer think of it as an acronym). Neither term being in common parlance, and being only one letter different, my search for a definition got them confused.[[Special:Contributions/172.70.35.94|172.70.35.94]] 00:20, 12 April 2025 (UTC)

I'm not sure why he should be paying with paper money. He can easily pay by credit card ... using virtual debit card on his phone. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 17:46, 11 April 2025 (UTC)
: Paper money might not be made from paper anymore - at least, it isn't in NZ, where I live. [[Special:Contributions/172.69.0.130|172.69.0.130]] 17:53, 11 April 2025 (UTC)
::I think “paper money” is about paper no longer being made from papyrus. US bank notes are printed on rag paper, which is indeed a kind of paper despite containing little or no wood pulp.--[[User:Seakingsoyuz|Seakingsoyuz]] ([[User talk:Seakingsoyuz|talk]]) 18:20, 11 April 2025 (UTC)
:::Agreed. Rag paper is not just "a kind of paper", it's the original kind of paper (papyrus is not paper in any usual sense, because it is not made from pulped fibers). When paper was invented in China, it was made from rag fibers, and it was still made like that when it was first produced in Europe.
:: I don't think 'paper money' should be designated as being made of paper here. Everyone knows that paper money doesn't feel or act like paper. It's incredibly hard to rip. [[User:DollarStoreBa'al|DollarStoreBa'al]] ([[User talk:DollarStoreBa'al|talk]]) 18:27, 11 April 2025 (UTC)
::: Being Canadian, I thought the reference here was to what's described at Wikipedia as [https://en.wikipedia.org/wiki/Polymer_banknote Polymer banknotes]. --[[Special:Contributions/162.158.127.25|162.158.127.25]] 18:28, 12 April 2025 (UTC)
:The "card" in credit card seems to come from Latin and Greek for a piece of paper or papyrus. So a credit card, now made of plastic, metal, semiconductors, etc. might be considered an anachronym. [[Special:Contributions/162.158.41.95|162.158.41.95]] 19:20, 11 April 2025 (UTC)
:I don't think anybody's made sense of or convincingly explained the title text. Paper money actually is basically made of paper. Maybe that's the joke and why it's in the title text. Is there anywhere teaching that paper money isn't made of paper? Maybe it used to be made of the same paper we use for writing on, like IOUs. [[Special:Contributions/162.158.158.93|162.158.158.93]] 21:23, 14 April 2025 (UTC)
:: Not in the UK ... the notes are not made with any version of paper now. (see also Canada & New Zealand above.) [[User:The Yeti|The Yeti]] ([[User talk:The Yeti|talk]]) 20:38, 17 April 2025 (UTC)
:I think I figured it out. The article focuses heavily on actual production, but Randall doesn't mean that the original products no longer exist, he means that they aren't what stores are selling. Thinking on this I realized that paper money is like that too -- it's no longer backed by gold or silver. I added a sentence to the article to say this using the concept "fake" like "imitation porcelain". [[Special:Contributions/162.158.159.135|162.158.159.135]] 21:36, 14 April 2025 (UTC)
:The same person (me) wrote both of these posts but the IP addresses are changed by the server. [[Special:Contributions/162.158.158.16|162.158.158.16]] 21:40, 14 April 2025 (UTC)
::It's not the server, it's the Cloudflare gateway. Don't worry about it. Even if it wasn't the Cloudflare gateway's IP that you were getting, there's a good chance that your ''actual'' IP, via your actual ISP, is not static enough to be guaranteed the same from one post to another. If you want to state your continuation (and not get a named account to do so...) just say "Hi, it's IP <1.2.3.4> again..." or whatever you need to do. But (as with me) you seem not to have a driving wish for continuity of self so... don't worry about it. Ok? [[Special:Contributions/172.69.79.165|172.69.79.165]] 23:21, 14 April 2025 (UTC)
:After thinking on this further I am no longer convinced by this explanation either. It's possible.[[Special:Contributions/162.158.158.16|162.158.158.16]] 21:40, 14 April 2025 (UTC)
:He could pay with any form of contactless, given that pretty much everybody seems to touch whatever they're paying with against the sensor.[[Special:Contributions/172.70.162.58|172.70.162.58]] 13:24, 16 April 2025 (UTC)

Adults who "enjoy" rubber ducks include programmers: https://en.wikipedia.org/wiki/Rubber_duck_debugging [[Special:Contributions/172.71.95.27|172.71.95.27]] 18:40, 11 April 2025 (UTC)

The word money came from words that meant coin. The word coin evidently came from wedge shaped. Not quite anachronym, though somewhat anachronism. [[Special:Contributions/162.158.41.95|162.158.41.95]] 19:11, 11 April 2025 (UTC)

Surprised "lead pencil" didn't make the list [[Special:Contributions/172.68.12.109|172.68.12.109]] 19:13, 11 April 2025 (UTC)
:Not quite the same category. The core of wooden pencils never contained lead, that was always a misnomer by people who didn't know it was actually carbon. [[User:ChaoticNeutralCzech|ChaoticNeutralCzech]] ([[User talk:ChaoticNeutralCzech|talk]]) 08:07, 14 April 2025 (UTC)
::I thought soft metals like lead did work for writing with though, functioning similarly to the graphite in a pencil but possibly needing a rougher surface like chalk does. I'm surprised the name isn't from actual use as I had informally learned it was. I think I tested it by writing with lead solder. In ancient Rome people would write on rougher slate, not sure what they used to write on the slate with though. [[Special:Contributions/162.158.159.36|162.158.159.36]] 21:20, 14 April 2025 (UTC)

Duck Tape is no longer made from ducks! [[User:IIVQ|IIVQ]] ([[User talk:IIVQ|talk]]) 19:30, 11 April 2025 (UTC)

:It Actually got its name from being made from "duck fabric," a kind of heavy very tightly woven cotton fabric. Then there was confusion by a brand putting a picture of a duck on the label, and people using it to join segments of heating ducts together, making people falsely think it was originally called "duct tape," with duck being a fanciful brand name. Originally though it was developed for the military in WW1 to seal ammunition boxes in a waterproof way, but due to widespread improvised uses by soldiers, post war they decided to market it to civilians.--[[Special:Contributions/172.71.255.102|172.71.255.102]] 17:11, 14 April 2025 (UTC)
::What your thinking about is "fabric tape" or "gaffer's tape". What people call "duck tape" is actually called "duct tape," as in the tape you would use on air ducting. Many people misheard and dropped the final "t", and of course the Duck brand didn't help. --[[User:Mblumber|Mblumber]] ([[User talk:Mblumber|talk]]) 21:32, 14 April 2025 (UTC)
:::With both terms "duck tape" and "duct tape", there's valid (if false) etymologies. Being somewhat waterproof (the fabric being at least water-resistant and the adhesive being good even on damp surfaces) it being a "duck" material is fairly relatable. With it having a degree of air-tightness and some degree of heat-resistance, it's also trivially useful for sealing ambient-temperature ducting gaps (though you really need the metal-foil types for ducts with high or variable temperature airflows passing through them). [[Special:Contributions/172.69.79.165|172.69.79.165]] 23:21, 14 April 2025 (UTC)
::::Doing further research, the "duck" naming came first, due to it being made using duck fabric. Though there was some tape using it beforehand, it seems it first became widespread with something close to what we know today in WWII, intended for sealing ammunition boxes, but saw widespread other use by soldiers. Afterwards it was sold in hardware stores for household repairs, and made to be more heat tolerant to be good for use on heating ducts, also colored to match the tin typically used to make the ducts, and people started calling it "duct tape" in the 50's. Later, in the 70's, a company decided to market their brand by bringing back the original "duck" name, with a cartoon duck logo, though many people didn't realize that was the original name of that kind of tape, and thought they were just making a pun on "duct."--[[Special:Contributions/172.69.6.77|172.69.6.77]] 00:55, 15 April 2025 (UTC)
:::::Duck/duct is one of my go-to examples of folk etymology and misplaced language-snobbery. "''Actually'', it's..." type behaviour concerning "duct" tape has historically been in the direction of "duck is the misnomer, based on mishearing". And thats wrong. It was duck,but people thought it couldn't be duck because why the hell would it be duck, what the hell does duck mean when it's tape? OHHHH! It must be duct because people tape ducts with it. But no. It was duck. It became duct. It became duck again. It ''was'' all these things, because the only true arbiter of correct usage is common usage...but saying (knowingly, with an air of superiority) that it was originally duct is fundamentally incorrect. [[User:Yorkshire Pudding|Yorkshire Pudding]] ([[User talk:Yorkshire Pudding|talk]]) 22:06, 15 April 2025 (UTC)

"digital money" shouldn't be listed as what "paper money" is actually made out of. Nobody would say "I'm paying with paper money" if they are paying with some digital currency. The anachronism is "paper money" being actually made of linen or whatever hi-tech fibers. [[Special:Contributions/172.70.254.211|172.70.254.211]] 19:49, 11 April 2025 (UTC) anonymous user
:Not even ''fibers''. Sheet-polymers (with loads of complex embedded and pressed-in features) are becoming the new go-to for banknotes, in a number of countries. [[Special:Contributions/172.68.205.135|172.68.205.135]] 23:24, 11 April 2025 (UTC)

My wife suggests that this is much easier if you are tech shopping: Apple, Mouse, Spam, Phish, Cookies.[[Special:Contributions/162.158.78.225|162.158.78.225]] 20:03, 11 April 2025 (UTC)
:"Click mouse to accept cookie" meme - featuring rodent and confection. https://i.pinimg.com/originals/06/e6/7d/06e67d6ee5a2afa112bf548463e97125.jpg [[Special:Contributions/172.70.35.94|172.70.35.94]] 00:20, 12 April 2025 (UTC)
:That's not in the same category since computer mice were never ''made of'' actual mice{{cn}}. Anyway, I'm sure there are some examples in tech: '''compressed air''' (gas duster) cans do not actually contain nitrogen or oxygen but a mixture of hydrocarbon gases that can be liquified at pressures obtainable in a cheap can to drastically increase the volume ratio, but I can imagine people might have used actual pressurized air containers for dusting at some point (though likely not commercially). [[User:ChaoticNeutralCzech|ChaoticNeutralCzech]] ([[User talk:ChaoticNeutralCzech|talk]]) 08:07, 14 April 2025 (UTC)

Not sure why "sidewalk chalk" on there and who decides that calcium carbonate is allowed to be called chalk, but calcium sulphate is not. --[[Special:Contributions/108.162.216.196|108.162.216.196]] 05:25, 12 April 2025 (UTC)
:I came here wondering why it was on the list, but for a different reason: It's never been made from sidewalks. Yes, I actually needed to read the list to clear up the misconception. --[[Special:Contributions/162.158.127.25|162.158.127.25]] 18:28, 12 April 2025 (UTC)
::Because, other than the use we give it as "thing you write on blackboards with", chalk is originally a stone made of relatively loose calciulm carbonate (limestone mostly made from foraminifers), which is what was used to write on slate blackboards before we started making them out of pressed gypsum. --[[Special:Contributions/172.64.238.130|172.64.238.130]]
::Calcium carbonate chalk is still produced (mostly for mathematicians). Search for "Hagoromo Fulltouch." {{unsigned ip|172.71.190.234|15:47, 17 April 2025}}

You can still buy solid cast-iron irons. Although I doubt anyone actually uses them for smoothing clothes, more for decoration. [[User:SDSpivey|SDSpivey]] ([[User talk:SDSpivey|talk]]) 16:23, 14 April 2025 (UTC)
: If you can still buy _new_ ones update the article! People likely use the old ones in traditional communities though. [[Special:Contributions/162.158.159.36|162.158.159.36]] 21:20, 14 April 2025 (UTC)

When I typed started typing "silverware made" into Google, it suggested "silverware real silver", which brought up a very ad-heavy results page. A few of them were re-selling vintage silverware, but most seemed to be offering "new" designs. I had to scroll down several pages before I found stuff that looked even like a catalog, rather than an ad for one particular possible purchase.

But since it seems like a competitive market, and I wasn't patient enough to look for an informational marketing page, I don't feel comfortable picking one (or several) particular ads as the citation.

Perhaps someone else does. Or perhaps a screenshot archived somewhere. [[User:JimJJewett|JimJJewett]] ([[User talk:JimJJewett|talk]]) 18:09, 14 April 2025 (UTC)
:Since when are ads considered reliable sources? --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 19:24, 14 April 2025 (UTC)
::Since they indicate what's popular, what's commonly seen and commonly used. [[User:Yorkshire Pudding|Yorkshire Pudding]] ([[User talk:Yorkshire Pudding|talk]]) 09:38, 16 April 2025 (UTC)

;Steel
{{w|Stainless steel}} ''does'' contain Fe, so "iron" ain't ''that'' "wrong". [[Special:Contributions/172.70.35.95|172.70.35.95]] 05:48, 12 April 2025 (UTC)
:We have long made a distinction between "iron" and "steel", not to mention that, while stainless steel has about 1% carbon by weight (give or take: sometime more, sometimes less), since carbon is over 4 times lighter than iron, that makes about 4% (and up to 10%) of the atoms carbon, not to mention that, to be stainless, it has to either have a by weight composition of either over 10% chromium or over 8% nickel, which are almost the same weight as iron (a difference of around 5%, lower for chromium, higher for nickel). Given that the average stainless steel has a 18% by weight of chromium, adding that with the carbon means that only 3 out of 4 atoms are iron, and if you have copper and tin or copper and tin in that same ratio, it would long have surpassed the line to be called "bronze" or "brass", respectively. "Having iron atoms" is not the same as "made of iron", mainly when it originally was indeed made out of (wrought) iron. --[[Special:Contributions/188.114.111.245|188.114.111.245]]
::99% is a way higher percentage than say, the amount of nickel in nickels ($0.05 coins): 25% ({{w|Nickel (United States coin)|US}}) or 2% ({{w|Nickel (Canadian coin)|Canadian}}). The latter might qualify for this list because it actually used to be made of near-pure nickel, while the US coin's composition never changed since the first (1866) version that became known as the "nickel". [[User:ChaoticNeutralCzech|ChaoticNeutralCzech]] ([[User talk:ChaoticNeutralCzech|talk]]) 11:48, 14 April 2025 (UTC)
::Steel (stainless or otherwise) does not occur naturally. It has to be made. By humans. Out of iron. So in this case 'having iron atoms' DOES mean 'made of (as a synonym of 'from') iron'. [[Special:Contributions/172.70.86.129|172.70.86.129]] 04:11, 14 April 2025 (UTC)
::Bronze contains mostly copper. So I assume you would call it copper, too. --[[Special:Contributions/162.158.130.67|162.158.130.67]] 11:15, 14 April 2025 (UTC)

"Cutlery" specifically refers to metallic implements with a cutting edge. Knives, scissors, and swords are cutlery; Spoons and forks are not cutlery. Table knives, forks, and spoons, collectively are "flatware". [[Special:Contributions/162.158.164.155|162.158.164.155]] 10:01, 12 April 2025 (UTC)
:I was really hoping to re-edit that element, anyway. The comic says "silverware" which can relate to cutlery/other food-implements or to the plates or candlesticks or even ''trophies''. Someone assumed that meant cutlery(+dining implements in general). As well as other improvable writing about the assumption they went with. [[Special:Contributions/172.70.58.49|172.70.58.49]] 22:58, 12 April 2025 (UTC)
:I assume the confusion comes from the respecive British and American terms for a collection of forks, knives, and spoons. British English calls these things "cutlery" even if they don't have a cutting edge. American English commonly refers to these as "silverware," especially when made with stainless steel, although I have also heard the term "plastic silverware" or "wooden silverware" when "flatware" would probably have been a more accurate generic term. [[Special:Contributions/172.70.163.35|172.70.163.35]] 18:09, 13 April 2025 (UTC) (an American expat)
::While its etymology indicates cutting edges, is "cutlery" actually ''used'' to mean "bladed items" anywhere? In UK English, it exclusively means eating irons, and is the standard, unremarkable, everyday term. In the places that don't refer to their knives, forks and spoons collectively as "cutlery", do they really use the word at all? [[User:Yorkshire Pudding|Yorkshire Pudding]] ([[User talk:Yorkshire Pudding|talk]]) 09:34, 16 April 2025 (UTC)

;Paper
I just want to point out that paper made from cotton fibers instead of wood pulp ''is still paper''. You can buy it in the store. There are non-paper banknotes now, but not in the U.S., and I'd be surprised if polymer banknotes were ever called "paper money". [[User:LtPowers|LtPowers]] ([[User talk:LtPowers|talk]]) 12:35, 12 April 2025 (UTC)
:Be surprised. That's what they're usually called in Canada. --[[Special:Contributions/162.158.127.164|162.158.127.164]] 18:29, 12 April 2025 (UTC)
::And anywhere with polymer bills. "Paper money" = bills. Still, it's true that cotton-linen paper is still paper, so is hemp paper and any other paper made from cellulose fibers (paper can be categorized by cellulose source, average fiber length, thickness, impurities and papermaking method). You can even make paper out of old clothes made from vegetable textiles (like blue jeans, cotton T-shirts or hemp pants). As a weird side note, there are non-cellulose papers, like silk paper, but they are made in the same way as regular paper (which is not how plymer bills are made, to my understanding)--[[Special:Contributions/188.114.111.245|188.114.111.245]]
:::Yeah, I've always heard of it as "paper money" --[[User:Xnerkcd|xnerkcd]] ([[User talk:Xnerkcd|talk]]) 07:10, 13 April 2025 (UTC)
::::I have a different comment on the "money" section, namely that the thin. flat, wrinkleable stuff nowadays are not (at least not in the US) "promissory notes", and they haven't been since the Silver Certificates went out of circulation. No one makes any promises about them, other than that they are legal for paying debts. The stuff nowadays would be better called "fiat money", or perhaps someone else can offer a better term.
:::::{{wiktionary|folding#Noun|"Folding"}}? [[Special:Contributions/172.70.58.50|172.70.58.50]] 20:50, 18 April 2025 (UTC)

Ironing boards obviously came from use of irons. As irons aren't iron anymore, ironing board is also anachronistic. Quite often aluminium foil is refered to as 'silver foil', which is both not true (not made of silver), but also true (silver colour). And then there are people who still open 'tin cans' (but not). [[User:The Yeti|The Yeti]] ([[User talk:The Yeti|talk]]) 20:38, 17 April 2025 (UTC)

2500: Global Temperature Over My Lifetime

2025-04-13T18:05:45Z

172.70.58.50: /* Transcript */ Needed that, too... (Certainly still needs improvement/refinements.)

{{comic
| number = 2500
| date = August 9, 2021
| title = Global Temperature Over My Lifetime
| image = global temperature over my lifetime.png
| titletext = I was really impressed by the accuracy of some of the report's predictions about fossil fuel consumption. Then I realized, oh, right, of course.
}}

==Explanation==
This is Randall Munroe in his role as a meticulous, conscientious presenter of scientific data. The activities shown in Randall's lifeline, whether learning to ride a bike or even getting married, pale into insignificance when the consequences of unprecedented global average temperature rise are understood and accepted. In particular, he shows that back in 1982, two years before Randall was born, Exxon wrote an internal report predicting the rise of global temperatures due to fossil fuel use, and 40 years later their prediction (shown as the X in a circle at the top-right) is being shown to be right on track. Unfortunately, that report was hidden and not seen until much later, and the world has been slow to respond with the urgency needed to reverse the damage being done to the planet.

The Wikipedia article {{w|global temperature record}} has some telling graphs to supplement Randall's. This one: {{w|File:20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg|Global Average Temperature}} is the global average temperature change for the modern era, since data started being collected regularly in 1850. This one: {{w|File:2000_Year_Temperature_Comparison.png|2000 Year Temperature Comparison}} reconstructs 2000 years of temperatures.

And this comic is a small segment of another comic: [[1732: Earth Temperature Timeline]].

The comic itself links to [https://www.documentcloud.org/documents/2805576-1982-Exxon-Memo-to-Management-About-CO2 the referenced Exxon document about CO2 emissions].

The comic was published on the same day that the {{w|Intergovernmental_Panel_on_Climate_Change|U.N. Intergovernmental Panel on Climate Change}} released its [https://www.ipcc.ch/report/ar6/wg1/ 2021 Assessment Report]

One of the entries is ''I somehow graduate despite spending most of my time playing Mario Kart.'' ''{{w|Mario Kart}}'' is a popular video game series developed by {{w|Nintendo}}, and has been a [[:Category:Mario Kart|recurring theme]] on xkcd. Hewing close to the comic's timeline, [[127: The Fast and the Furious]], which contains an early ''Mario Kart'' joke, was released in July 2006.

The title text refers to the fact that Exxon, being a fossil fuel company, is likely to make better predictions on fossil fuel use as they are involved in fossil fuel production themselves.

==Transcript==
:[Graph of temperature over time, titled:]
:"Global average temperature
:Over my lifetime
:[smaller text]
:(60-month running June average, NOAA NCEI time series)"

:[The X axis is in years, going from 1980 to a little after 2020. Each decade is marked.]

:[The Y axis is in °C, with the "20th century average" at the bottom, up to +1°C (from the average), labelled every 0.2°C.]

:[Certain points and periods on the graph are marked and contain descriptions of events and actions that occurred in Randall's life.]

; November 1982 : Exxon International report predicts that fossil fuel use will raise global temperatures to about 1°C above their normal levels within 40 years
; October 1984 : I’m born in Easton, PA
; Summer 1991 : I learn to ride a bike
; Spring 1992 : My elementary school celebrates Earth Day and I learn about the greenhouse effect
; 1993-1996 : I get very into ''Star Wars'' and ''Animorphs''
; Fall 1996 : I stand around awkwardly at my first middle school dance
; Spring 2002 : I get accepted into college
; Spring 2006 : I somehow graduate despite spending most of my time playing Mario Kart
; Summer 2006 : I see ''An Inconvenient Truth'' in the theater and feel anxious
; Fall 2011 : I get married
; Summer 2012 : I read headlines about a global warning “pause” and hope that maybe things aren’t so bad
; 2013-2021 : I read more about climate science and get steadily more alarmed
; Spring 2016 : I read the 1982 Exxon report
; June 2020 : Global 60-month average reaches +0.94°C, Easton, PA is 2°C hotter than normal for the fifth year in a row
; Today : ''(no description)''
; 2022 (near future) : [Large X within a circle] 1982 Exxon Prediction

{{comic discussion}}

[[Category:Climate change]]
[[Category:Comics featuring Randall Munroe]]
[[Category:Mario Kart]]
[[Category:Star Wars]]
[[Category:Animorphs]]

2566: Decorative Constants

2025-04-08T19:00:10Z

172.70.58.50: /* Explanation */ oops, emphasised the wrong word

{{comic
| number = 2566
| date = January 10, 2022
| title = Decorative Constants
| image = decorative_constants.png
| titletext = Arguably, the '1/2' in the drag equation is purely decorative, since drag coefficients are already unitless and could just as easily be half as big. Some derivations give more justification for the extra 1/2 than others, but one textbook just calls it 'a traditional tribute to Euler and Bernoulli.'
}}

==Explanation==
This is another one of [[Randall|Randall's]] [[:Category:Tips|Tips]], this time a Math Tip. Randall gives an example of a complex-looking equation labeled 4-15:
T = 𝔻m0(rout − rin)μ̅
But since 𝔻 and μ̅ are "decorative", the equation can be reduced to:
T = m0(rout − rin)
Here, T is the net rate, m0 the unit mass, and (rout − rin) the flow balance.

The decorative symbols can be interpreted as constants 𝔻 = μ̅ = 1, in which case the implied operations of multiplication and exponentiation make sense. The 𝔻 is double-struck ("blackboard bold", thus in the comic only the vertical line is double). Mathematicians, who are always searching for more symbols{{citation needed}}, have taken to distinguishing things represented by the same letter by using different fonts, such as 𝑑, 𝐝, 𝒅, 𝐷, 𝐃, 𝑫, 𝒹, 𝒟, 𝖉, 𝕯, ∂, 𝕕, and 𝔻. The double-struck font is easier to write on a blackboard than a proper bold letter and often represents a set, such as ℝ for the set of real numbers or ℂ for the set of complex numbers. 𝔻 can represent the unit disk in the complex plane, the set of decimal fractions, or the set of split-complex numbers.

μ is the Greek lowercase mu and has many uses in mathematics and science. Here it has a bar, μ̅, which could indicate a number of things, including the complex conjugate. Intriguingly, μ is the symbol in statistics for the population mean, and the overbar represents the sample mean, so this could represent a random variable which is the average of a sample of means μi of different populations in some larger ensemble of populations. Using a special version both of D and μ to even further spice up the formula all leads up to the math tip.

Other examples of well known equations that are profound but look simple include:
*''E'' = ''mc''2 ({{w|Special Relativity}}),

*''PV'' = ''nRT'' (the {{w|Ideal Gas Law}}),

*''F'' = ''ma'' ({{w|Newton's Second Law}}),

*''V'' = ''IR'' ({{w|Ohm's Law}}),

*''Gμν'' + Λ ''gμν'' = ''κTμν'' ({{w|Einstein field equations}}), and

*''eπi+1'' = ''0'' ({{w|Euler's Identity}}).

Of these, only Einstein field equations have been spiced up with decorative indices (which actually hide a system of ten nonlinear partial differential equations). Euler's identity is massaged to include both 0 and 1 (since including both the additive and multiplicative identities is "more profound") since the interpretation of ''eiπ'' = ''-1'' is otherwise not necessarily intuitive; using the ratio of a circle's circumference to its '''radius''' (𝜏) rather than its diameter results in ''ei𝜏 = 1'' which can be interpreted as a statement that "one trip around the circle leaves you back where you started".

In the title text, Randall mentions the {{w|Drag equation}}, which is attributed to {{w|Lord Rayleigh}}. In {{w|fluid dynamics}}, the drag equation is a formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid. The equation is ''F''d = ½''ρu''2''c''d''A''. Here ''F''d is the drag force, ρ the mass density of the fluid, u the relative flow velocity, ''c''d the {{w|drag coefficient}} and A is the area.

Randall jokes that the factor of ½ in the equation is meaningless and purely decorative, since the drag coefficients, ''c''d, are already unitless and could just as easily be half as big thus leaving out the ½ in front of the equation. The ½ is thus just an example of a "decorative constant." The usual reason for including the factor of ½ is that it is part of the formula for kinetic energy that appears in the derivation of the drag equation, i.e. ½''ρu''2. However, modern treatments are so condensed that this factor of ½ is often smuggled in with no explanation.

Since we can choose the constants to be whatever we want, it could be possible to absorb the ½ into the drag coefficient ''c''d, but that does not mean it is unmotivated, since it comes from the kinetic energy. Still, Randall quotes Frank White's ''[https://www.amazon.co.uk/Fluid-Mechanics-Frank-White/dp/007119911X Fluid Mechanics''] textbook, [https://books.google.com/books?id=wGweAQAAIAAJ&q=traditional%20tribute&redir_esc=y which two times] calls it "a traditional tribute to Euler and Bernoulli." According to White, the factor of ½ rather comes from the calculation of the projected area of the object being dragged. Randall has brought up this point before, in his book, "[[How To]]".

The line from White probably refers to renowned mathematicians {{w|Leonhard Euler}} and {{w|Daniel Bernoulli}}. Euler who is held to be one of the greatest mathematicians in history worked directly with Daniel and was a friend of the {{w|Bernoulli family}}, that produced eight mathematically gifted academics. Bernoulli is known for modifying the definition of ''vis viva'' (what we now call kinetic energy) from ''mv''2 to ½''mv''2, as motivated by the derivation from the impulse equation. In 1741, he wrote
:[Define ''vis viva''] esse ½ ''mvv'' = ∫''pdx''.
That is, "define ''vis viva'' to be ½ ''mv''2 = ∫''p''d''x''," where ''p'' is the force (from ''pressione'') and d''x'' is the differential of position (infinitesimal displacement). Today, this equation says that the kinetic energy imparted to an object at rest equals the work done on it. In the drag equation ½ ρu2 represents the dynamic pressure due to the kinetic energy of the fluid, and hence the 1/2 makes sense to keep in the equation, and could thus easily be argued not to represent a decorative constant.

The title text is pretty much word-for-word a repeat from Randall's book ''[[How To]]''. In Chapter 11: ''How to Play Football'', he misuses the drag equation, and mentions this fact in more depth, in a footnote.

==Transcript==
:[A small panel only with text. Written as an excerpt from a mathematical text book. Begins with a number for an equation, then follows the equation written in larger letters and symbols. And below are explanations of each term in the equation. The μ has a bar over the top and the D has a double vertical line.]
:Eq. 4-15
:<big>T = 𝔻m0(rout - rin)μ̅</big>
:T: Net rate
:m0: Unit mass
:(rout-rin): Flow balance 
:𝔻, μ̅: Decorative

:[Caption below the panel:]
:Math tip: If one of your equations ever looks too simple, try adding some purely decorative constants.

==Trivia==
This was the first comic that came out after the [[Countdown in header text]] started.

{{comic discussion}}

[[Category:Tips]]
[[Category:Math]]
[[Category:Comics featuring real people]]