explain xkcd - User contributions [en]

2684: Road Space Comparison

2022-10-13T06:35:39Z

172.69.62.71: /* Transcript */

{{comic
| number = 2684
| date = October 12, 2022
| title = Road Space Comparison
| image = road_space_comparison_2x.png
| imagesize = 740x1157px
| noexpand = true
| titletext = I wonder how hard it would be to ride an electric scooter in a hamster ball.
}}

==Explanation==
{{incomplete|Created by a CHAD WALKABLE CITIES ENJOYER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
The comic is a parody of a common comparison done in arguments for walkable cities - the amount of usable space taken up by cars and car-centric infrastructure that could be eliminated for other useful public amenities. The first of these may be from 1978[https://www.fietsersbond.nl/nieuws/van-wie-is-de-ruimte/].

The first 4 images are common, real-life comparisons involving people walking, people on bicycles, public transport and cars, which distinctly show how that the alternatives to cars take up significantly less space than cars do for the same number of people. However, from this point the comic becomes more and more absurd in its comparisons.

The 5th one shows 50 people on a tandem cycle. This would obviously be impractical in a city due to the tandem's sheer length and would not be able to work with fewer people due to its sheer mass. The longest tandem bicycle holds 52 people<ref>https://www.active.com/articles/bicycle-built-for-52-pedals-into-guinness-book</ref>.

The 6th one involves 20 people driving 40 cars, with each person driving 2 cars at a time by straddling them in the middle. Besides being unwieldy and impractical, it would also be extremely dangerous as the cars could go out of control at any time. Perhaps the cars would be a paired mix of left-hand-drive and right-hand-drive models, although with enough push-rods/levers (to also reach the traditional foot controls, and also gearsticks unless ''fully'' automatic) this might not be as important. However, even if the cars were perfectly safe to drive, it would be unsafe to drive them on most roads; roads with only one lane per direction are common, everywhere from city streets to exit ramps, and attempts to drive a pair of cars down such a road side by side are unlikely to end well.

(Of course, worse than any of these petty safety concerns is the fact that each person takes up twice as much road space, making most infrastructure a bit less efficient.)

The 7th one has 30 cars riding on 6 buses by stacking them on top of each other. Assuming the same people-per-car/bus from the earlier examples, this arrangement would have about 345 people riding on the same road! (Unless, of course, the busses are carrying 30 cars ''instead of'' their normal passengers.) In addition, people getting out of the cars when they reach their destination would be a problem for most cars in this arrangement due to them being stacked under other cars or surrounded by them. And as in the previous example, it would be impossible to safely drive anywhere without two clear lanes...and the body count would be considerably higher.

The 8th panel has 50 people in hamster balls. Randall has shown his interest in human sized [[:Category:Hamster Ball|hamster ball]] transportation before, and indeed this would be an enjoyable way to traverse a road, provided no other hamster balls try to drive into you and knock you off the road. The image shows 39 hamster balls, implying that roughly one in four has a passenger; under these constraints, they appear to be slightly more efficient than cars.

The 9th panel has 40 tiny cars pulling a big one. Such feats of strengths are a common sight while setting world records, so maybe this is a world record attempt by the cars in question. It is unknown how many people fit in the big car; judging by its size, it likely fits more than a single bus and less than three.

The 10th panel is a 50 person variation on the classic {{w|wolf, goat and cabbage problem}} (which has also been [[2348: Boat Puzzle|referenced before]] by Randall) except this one involves 30 goats, 20 cabbages and 10 wolves trying to cross the now-flooded road with a single boat. It is not known how many people (or cabbages for that matter) the boat fits, but since humans significantly outnumber the goats, cabbages and wolves, it doesn't seem like too much of a problem.

The title text proposes a problem related to another alternative form of transport – the electric scooter. Randall wonders how well an electric scooter would function when run inside the hamster ball. This would probably function like some sort of spherical {{w|monowheel}}.

==Transcript==
[Overhead views of many traffic scenarios are shown, with the last one being part of a river with road on either side.]
{|class="wikitable" style="marginauto"
|+Road space comparision
|-
!50 people walking!!50 people riding bikes!!50 people riding a bus!!50 people in 33 cars!!50 people on one tandem bicycle
|-
|[A picture of 50 people walking on the left lane of a road.]||[A picture of 50 bicycles with people on them on the left lane of a road.]||[A picture of a single bus.]||[A picture of 33 cars filling the road.]||[A picture of 50 people on one long tandem bicycle.]
|-
!20 people driving 40 cars!!30 cars riding on 6 buses!!50 people in human-sized hamster balls!!One giant car pulled by 40 smaller ones!!50 people with 30 goats, 20 cabbages, and 10 wolves
|-
|[A picture of 40 cars with 20 people between them with one leg in each side window.]||[A picture of 30 cars stacked as to fit on 6 buses.]||[39 hamster balls, each containing a person.]||[A large car connected to 40 normal cars by rope.]||[A picture of a road separated by a river. In said river is a dock and boat, and on the side closest to us are 50 people, 30 goats, 20 cabbages, and 10 wolves.]
|-
|}
{{comic discussion}}
[[Category:Hamster Ball]]
[[Category:Animals]]
[[Category:Food]]

Talk:2666: Universe Price Tiers

2022-08-31T23:41:00Z

172.69.62.71:

We seem to be in Universe Standard, based on the cosmic speed limit
[[User:Victor|Victor]] ([[User talk:Victor|talk]]) 22:03, 31 August 2022 (UTC)

Is the price per user (human)? Or payed by the "god" who runs the universe?
The interpretation would change quite a bit. If per user, some could travel fast while others would not see ads and could even be immortal.
If per universe, would the concept of ads disappear?
[[User:Victor|Victor]] ([[User talk:Victor|talk]]) 22:25, 31 August 2022 (UTC)

General comment, I think each line of the table should have a separate one-line or one-paragraph explanation, rather than squishing it into one column of a table which mostly reproduces the comic text. i.e. we don't need the table in the explanation, although it works fine in the transcript imo. [[Special:Contributions/172.69.62.71|172.69.62.71]] 23:40, 31 August 2022 (UTC)edit: a word

Talk:2666: Universe Price Tiers

2022-08-31T23:40:16Z

172.69.62.71:

We seem to be in Universe Standard, based on the cosmic speed limit
[[User:Victor|Victor]] ([[User talk:Victor|talk]]) 22:03, 31 August 2022 (UTC)

Is the price per user (human)? Or payed by the "god" who runs the universe?
The interpretation would change quite a bit. If per user, some could travel fast while others would not see ads and could even be immortal.
If per universe, would the concept of ads disappear?
[[User:Victor|Victor]] ([[User talk:Victor|talk]]) 22:25, 31 August 2022 (UTC)

General comment, I think each line of the table should have a one-to-one or one-paragraph explanation, rather than squishing it into one column of a table which mostly reproduces the comic text. i.e. we don't need the table in the explanation, although it works fine in the transcript imo. [[Special:Contributions/172.69.62.71|172.69.62.71]] 23:40, 31 August 2022 (UTC)

2624: Voyager Wires

2022-08-21T02:43:20Z

172.69.62.71: /* Explanation */

{{comic
| number = 2624
| date = May 25, 2022
| title = Voyager Wires
| image = voyager_wires.png
| titletext = Also, they're getting increasingly worried that someone will accidentally hit the 'retract' button, and that the end of the cable thrashing around as it winds up could devastate the Earth's surface.
}}

==Explanation==
{{incomplete|Created by a WIRE CUT BECAUSE OF BUDG- are you there houston? it's me v----ger, you'll never guess what I found! Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic claims that the {{w|Voyager program|Voyager probe}}s communicate with NASA though ridiculously long copper wires. These wires would have to be continuously lengthened as the probes travel away from Earth. Supposedly, because of "high copper prices and budget constraints," they may not be able to afford to lengthen the wires much longer. If this occurred, they would have to either cut the wires or let them break, which would prevent any further communication with the probes. In reality [https://voyager.jpl.nasa.gov/mission/status/ they use radio waves], not long copper wires, so this will not actually happen.

If copper wires were dragged by the Voyager probes, assuming a 1 mm² thick cable, 550 tons of copper would be needed per hour and it would add 1 million Ohm per hour to the cable resistance. At [https://www.moneymetals.com/copper-prices $8,560/ton], this would cost $41 billion dollars/year, which would be nearly twice [https://www.planetary.org/space-policy/nasas-fy-2022-budget NASA's entire annual budget].

The resulting wire would slow down the probes by drag unless the wire itself was actively suspended (i.e. accelerated) continuously as it was fed. The wire could not be used for any other mechanical purpose such as a {{w|Space elevator|space elevator}} for this reason.

Since the Earth spins, the wires would also spool around the Earth, slowing the probes down even further. [https://what-if.xkcd.com/157/ Clearly, this is not a good idea.] This problem might be avoided if the wires reached earth at one of the poles. Or perhaps they could go to an airplane that flies around earth at exactly 15 degrees of longitude per hour, with periodic air-to-air refueling, so that it is always on the side of the earth facing the probe.

Because the Voyager probes aren't in the plane of the earth's orbit around the sun, the Earth would not, in its rotation around the sun, drag these copper wires through the sun. If it did, the wires would melt.{{Citation needed}}

The title text references the phenomenon seen with self-retracting cables, such as are commonly found on vacuum cleaners, where the free end of the cable, where the plug is, oscillates more and more wildly as the cable approaches full retraction, leading to the danger of a painful rap on the hand if it is not withdrawn in time. A planet-sized impact of this kind could cause severe damage.

A few days before this comic was released, [https://voyager.jpl.nasa.gov/news/details.php?article_id=124 NASA had reported] receiving corrupted data from the Voyager 1 probe. The fact that they are receiving any data at all means that the attitude control system must be working (or else the antenna would not point at Earth), but they continue to investigate how that data could be corrupted after that point.

;Spoiler alert
The consequence of a cable between a craft in space and a planetary location being suddenly retracted was recently imagined in the first episode of the Apple TV+ series ''{{w|Foundation (TV series)|Foundation}}'', wherein a {{w|space elevator}} tether was severed. [https://www.youtube.com/watch?v=huRmvG3zRpg It didn't end well for anyone other than the terrorists] who won the freedom of thousands of inhabited worlds which had formerly suffered under the jackbooted oppression of {{w|Trantor}}'s fascist galactic Empire regime.

Another illustration in fiction of a severed space elevator is in Red Mars, part of the {{w|Mars Trilogy}} by Kim Stanley Robinson.

==Transcript==
:[In the bottom right corner is a space probe, with large satellite dish and long antenna. Behind it runs a long wire, that makes three loops before it is connected to North America on the Earth in the top left corner. To the left of the Earth there is a second wire, which goes off-panel to the left.]

:[Caption below the panel:]
:Sad news: Due to high copper prices and budget constraints, NASA may finally have to cut the wires that they've been spooling out to communicate with Voyager 1 and 2.

{{comic discussion}}

[[Category:Space probes]]

641: Free

2022-06-14T06:12:17Z

172.69.62.71: /* Trivia */

{{comic
| number = 641
| date = September 25, 2009
| title = Free
| image = free.png
| titletext = Asbestos is bad; definitely get the one on the right. Wait -- this one over here has no swine flu! Now I can't decide.
}}

==Explanation==
{{w|Asbestos}} is a fibrous material most commonly known and used for its heat-resistant properties. It was commonly used in housing insulation until its astonishingly destructive effects on human lungs were discovered. The use of asbestos in housing is now banned, but asbestos is still quite common in laboratory hot pads, as well as in concrete industrial buildings where the risk of it getting into the air is minimal.

The comic depicts a common advertising trick taken to an absurd extreme; quite clearly all of the cereal products depicted are asbestos-free, but most have opted not to advertise that fact (if it even occurred to them at all) because it should be obvious. A more realistic example can be found in {{w|Confectionery|confectionery}} products, wherein the term "{{w|fat}} free" might be applied when it's clear that {{w|sugar}}, {{w|gelatin}}, and other ingredients involved in the product are in no way related to, or contain, fat. Note that in some countries, like Germany for example, this practice is actually not allowed, since it counts as "misleading advertising".

While the suggestive implication might be that competitive products do not declare as asbestos free because they cannot truthfully say this, the irony may be that the "asbestos-free" disclaimer could also cause a customer to ''distrust'' the product on the grounds of {{w|Damning with faint praise|damning by faint praise}}—if the best thing they can say about a product is that it doesn't contain a toxic building material, do we really want to know what actually ''is'' in this stuff?

The claim in the title text—that a rival product has no {{w|swine flu}}—is equally superfluous, as any food product containing disease-causing viruses would be subject to recalls, severe fines, and quite a few people losing their jobs; the fact that the product is actually on a supermarket shelf implies that it already has a stellar reputation for not causing serious illness.{{Citation needed}} The use of it here could also be a reference to [[574: Swine Flu]].

The competing claims, however, sets up the ''hopefully'' false risks involved in whether to choose the one with definitely no asbestos (but possibly contains swine flu) or the other that definitely has no swine flu (but may include asbestos).

* GenCo probably stands for {{w|Generic brand|Generic}} or General Company and may be a reference to {{w|General Mills}}

* [http://ghostbusters.wikia.com/wiki/Stay_Puft_Marshmallows Stay Puft] is also the company that produces marshmallows in the movie franchise [[wikipedia:Ghostbusters_%28franchise%29| Ghostbusters]].

* [http://redfarmnyc.com/ RedFarm] is a Chinese restaurant in NYC.

Misleading advertising is also the subject of the previous comic [[624: Branding]], and of subsequent comics [[870: Advertising]] and [[993: Brand Identity]].

==Trivia==

* This comic is the namesake of a [https://tvtropes.org/pmwiki/pmwiki.php/Main/AsbestosFreeCereal trope], as well as being the page image for the trope's entry.

==Transcript==
:[A shelf holds 3 boxes of cereal. Each box shows a bowl of cereal.]
:GenCo Ⓞat Cereal
:StayPuft Oat Cereal
:RedFarm Oat Cereal (with additional text in a star) Asbestos-free!
:I hate whatever marketer first realized you could do this.

{{comic discussion}}

1227: The Pace of Modern Life

2022-05-21T01:36:26Z

172.69.62.71: Undo revision 270776 by Explain xkcd server admin (talk)

{{comic
| number = 1227
| date = June 19, 2013
| title = The Pace of Modern Life
| image = the pace of modern life.png
| titletext = 'Unfortunately, the notion of marriage which prevails ... at the present time ... regards the institution as simply a convenient arrangement or formal contract ... This disregard of the sanctity of marriage and contempt for its restrictions is one of the most alarming tendencies of the present age.' --John Harvey Kellogg, Ladies' guide in health and disease (1883)
}}

==Explanation==
The debate as to whether or not the pace of modern life is detrimental to society, culture, and the human experience in general has been going on for longer than we may realize. Presently, the debate has focused on technology such as smartphones, tablets, and other portable electronics; however, many of the same arguments were made against {{w|newspaper}}s, magazines, telegraphs, telephones, and even written correspondence 100 years ago.

People often tend to think of older times as better. The people complaining compare their present time to the time they lived in before, that is, a couple of decades ago, and this has been happening for over a century (at least). This comic makes a point that the older times people refer to, were also criticized in exactly the same fashion. Since the same criticism is applied to each generation by the generation before that one, every generation thinks that the one they were born in is the good one. This is presentism as explained by Randall in [[24: Godel, Escher, Kurt Halsey]].

The comic begins and ends with very similar arguments, perhaps emphasizing how these debates cycle and repeat over time. The comic does not directly state whether these opinions and criticisms were justified or simple fallacies. There is a desire to consider our present existence as good and reasonable and that society has been improving over time. The difficulty lies in considering the possibility that each generation was perhaps correct in their criticism.

On reading all of these quotes, one may find these quotes redundant and tiresome to read. Readers may find themselves skimming the text and skipping several quotes once they get the overall idea. This could be a self-referential point demonstrating that the writing style of older times was less convenient than the oft-criticized brief modern style.

Some parts of all that long texts are in bold, others not. Here is the summary for only this bold text, picturing just our ''Modern World'':

:The art of letter-writing is fast dying out. We fire off a multitude of rapid and short notes, instead of sitting down to have a good talk over a real sheet of paper.
:In olden times it was different. Men now live think and work at express speed. Sulkily read as they travel leaving them no time to talk with the friend who may share the compartment with them.
:The age of leisure is dead, and the art of conversation is dying. A craving for literary nips. There never was an age in which so many people were able to write badly.
:The art of pure line engraving is dying out. We live at too fast a rate nothing is left to the imagination and human faculty dwindle away amid the million inventions that have been introduced to render its exercise unnecessary.
:Thirty pages is now too much. Fifteen pages further condensed a summary of the summary.
:Those who are dipping into so many subjects and gathering information in a summary and superficial form lose the habit of settling down to great works.
:Hurried reading can never be good reading. Mental and nervous degeneration among a growing class of people, a brain incapable of normal working in a large measure due to the hurry and excitement of modern life, almost instantaneous communication between remote points of the globe.
:Teach the children how to play instead of shutting them in badly ventilated schoolrooms, increased demand made by the conditions of modern life upon the brain.
:We talk across a continent, telegraph across an ocean, we take even our pleasures sadly and make a task of our play.
:The managers of sensational newspapers create perverted tastes and develop vicious tendencies.
:To take sufficient time for our meals seems frequently impossible, may I be permitted to say a word in favour of a very worthy and valuable old friend of mine, Mr. Long walk? I am afraid that this good gentleman is in danger of getting neglected, if not forgotten.
:People talk as they ride bicycles–at a rush–without pausing to consider their surroundings the profession of letters is so little understood, tendency among the children of today to rebel against restraint. Our modern family gathering, silent, each individual with his head buried in his favourite magazine, deal openly with situations which no person would have dared to mention in general society forty years ago.
:A hundred years ago it took so long and cost so much to send a letter that it seemed worth while to put some time and thought into writing it. A brief letter to-day may be followed by another next week–a "line" now by another to-morrow.

The style of the comic is very similar to that of [[1311: 2014]], which was released half a year later.

The title text shows that the meaning of the institute of marriage debate has likewise been going on for quite some time.

==Transcript==
:'''The art of letter-writing is fast dying out.''' When a letter cost nine pence, it seemed but fair to try to make it worth nine pence ... Now, however, we think we are too busy for such old-fashioned correspondence. '''We fire off a multitude of rapid and short notes, instead of sitting down to have a good talk over a real sheet of paper.'''
::''The Sunday Magazine''
:::1871

:It is, unfortunately, one of the chief characteristics of modern business to be always in a hurry. '''In olden times it was different.'''
::''The Medical Record''
:::1884

:With the advent of cheap newspapers and superior means of locomotion... The dreamy quiet old days are over... '''For men now live think and work at express speed.''' They have their ''Mercury'' or ''Post'' laid on their breakfast table in the early morning, and if they are too hurried to snatch from it the news during that meal, they carry it off, to be '''sulkily read as they travel ... leaving them no time to talk with the friend who may share the compartment with them'''... The hurry and bustle of modern life ... lacks the quiet and repose of the period when our forefathers, the day's work done, took their ease...
::William Smith, Morley: ''Ancient and Modern''
:::1886

:Conversation is said to be a lost art ... Good talk presupposes leisure, both for preparation and enjoyment. '''The age of leisure is dead, and the art of conversation is dying.'''
::''Frank Leslie's popular Monthly'', Volume 29
:::1890

:Intellectual laziness and the hurry of the age have produced '''a craving for literary nips.''' The torpid brain ... has grown too weak for sustained thought.
:'''There never was an age in which so many people were able to write badly.'''
::Israel Zangwill, ''The Bachelors' Club''
:::1891

:'''The art of pure line engraving is dying out. We live at too fast a rate to allow for the preparation of such plates as our fathers appreciated.''' If a picture catches the public fancy, the public must have an etched or a photogravured copy of it within a month or two of its appearance, the days when engravers were wont to spend two or three years over a single plate are for ever gone.
::''Journal of the Institute of Jamaica'', Volume 1
:::1892

:So much is exhibited to the eye that '''nothing is left to the imagination'''. It sometimes seems almost possible that the modern world might be choked by its own riches, '''and human faculty dwindle away amid the million inventions that have been introduced to render its exercise unnecessary.'''
:The articles in the ''Quarterlies'' extend to thirty or more pages, but '''thirty pages is now too much''' so we witness a further condensing process and, we have the ''Fortnightly'' and the ''Contemporary'' which reduce thirty pages to '''fifteen pages''' so that you may read a larger number of articles in a shorter time and in a shorter form. As if this last condensing process were not enough the condensed articles of these periodicals are '''further condensed''' by the daily papers, which will give you a '''summary of the summary''' of all that has been written about everything.
:'''Those who are dipping into so many subjects and gathering information in a summary and superficial form lose the habit of settling down to great works.'''
:Ephemeral literature is driving out the great classics of the present and the past ... '''hurried reading can never be good reading.'''
::G. J. Goschen, ''First Annual Address to the Students'', Toynbee Hall. London
:::1894

:The existence of '''mental and nervous degeneration among a growing class of people''', especially in large cities, is an obvious phenomenon ... the mania for stimulants ... diseases of the mind are almost as numerous as the diseases of the body... This intellectual condition is characterized by '''a brain incapable of normal working ... in a large measure due to the hurry and excitement of modern life''', with its facilities for rapid locomotion and '''almost instantaneous communication between remote points of the globe'''...
::''The Churchman'', Volume 71
:::1895

:If we '''teach the children how to play''' and encourage them in their sports ... '''instead of shutting them in badly ventilated schoolrooms''', the next generation will be more joyous and will be healthier than the present one.
::''Public Opinion: A Comprehensive Summary of the Press Throughout the World'', Volume 18
:::1895

:The cause of the ... increase in nervous disease is '''increased demand made by the conditions of modern life upon the brain'''. Everything is done in a hurry. '''We talk across a continent, telegraph across an ocean''', take a trip to Chicago for an hour's talk... '''We take even our pleasures sadly and make a task of our play''' ... what wonder if the pressure is almost more than our nerves can bear.
::G. Shrady (from P.C. Knapp)
::"Are nervous diseases increasing?" ''Medical Record''
:::1896

:'''The managers of sensational newspapers''' ... do not try to educate their readers and make them better, but tend to '''create perverted tastes and develop vicious tendencies.''' The owners of these papers seem to have but one purpose, and that is to increase their circulation.
::''Medical Brief'', Volume 26
:::1898

:'''To take sufficient time for our meals seems frequently impossible''' on account of the demands on our time made by our business... We act on the apparent belief that all of our business is so pressing that we must jump on the quickest car home, eat our dinner in the most hurried way, make the closest connection for a car returning ...
::Louis John Rettger. ''Studies in Advanced Physiology''
:::1898

:In these days of increasing rapid artificial locomotion, '''may I be permitted to say a word in favour of a very worthy and valuable old friend of mine, Mr. Long Walk?'''
:'''I am afraid that this good gentleman is in danger of getting neglected, if not forgotten.''' We live in days of water trips and land trips, excursions by sea, road and rail-bicycles and tricycles, tram cars and motor cars .... but in my humble opinion, good honest walking exercise for health beats all other kinds of locomotion into a cocked hat.
::T. Thatcher, "A plea for a long walk",
::''The Publishers Circular''
:::1902

:The art of conversation is almost a lost one. '''People talk as they ride bicycles–at a rush–without pausing to consider their surroundings''' ... what has been generally understood as cultured society is rapidly deteriorating into baseness and voluntary ignorance. '''The profession of letters is so little understood''', and so far from being seriously appreciated, that ... Newspapers are full, not of thoughtful honestly expressed public opinion on the affairs of the nation, but of vapid personalities interesting to none save gossips and busy bodies.
::Marie Corelli,
::''Free opinions, freely expressed''
:::1905

:There is a great '''tendency among the children of today to rebel against restraint''', not only that placed upon them by the will of the parent. But against any restraint or limitation of what they consider their rights ... this fact has filled well minded people with great apprehensions for the future.
::Rev. Henry Hussmann,
::''The authority of parents''
:::1906

:'''Our modern family gathering, silent''' around the fire, '''each individual with his head buried in his favourite magazine''', is the somewhat natural outcome of the banishment of colloquy from the school ...
::''The Journal of Education'', Volume 29
:::1907

:Plays in theatres at the present time present spectacles and '''deal openly with situations which no person would have dared to mention in general society forty years ago'''... The current representations of '''nude men and women in the daily journals''' and the illustrated magazines would have excluded such periodicals from all respectable families two decades ago... Those who have been divorced ... forty and fifty years ago lost at once and irrevocably their standing in society, while to-day they continue in all their social relationships, hardly changed...
::Editorial, ''The Watchman'', Boston
:::1908

:We write millions more letters than did our grandfathers, but the increase in volume has brought with it an automatic artificial machine-like ring ... an examination of a file of old letters reveals not only a remarkable grasp of details. But a '''fitness and courtliness too often totally lacking''' in the mechanical curt cut and dried letters of to-day.
::Forrest Crissey, ''Handbook of Modern Business Correspondence''
:::1908

:'''A hundred years ago it took so long and cost so much to send a letter that it seemed worth while to put some time and thought into writing it.''' Now the quickness and the cheapness of the post seem to justify the feeling that '''a brief letter to-day may be followed by another next week–a "line" now by another to-morrow.'''
::Percy Holmes Boynton, ''Principles of Composition''
:::1915

{{comic discussion}}

[[Category:Language]]

23: T-shirts

2022-05-21T01:31:43Z

172.69.62.71: Undo revision 270771 by Explain xkcd server admin (talk)

{{comic
| number = 23
| date = October 26, 2005
| title = T-shirts
| image = t-shirts.jpg
| titletext = It's depressing how many of these are real shirts
}}

==Explanation==

This comic satirizes the plethora of "snarky" phrase T-shirts that exist today. In the top-left, the character wears a typical (and real) snark shirt, "I see dumb people" (suggesting that the wearer thinks everyone else is dumb, while being a parody of the phrase "I see dead people" from the movie ''{{w|The Sixth Sense}}''). Other shirts shown also suggest that the wearer is better than everyone else, and perhaps the shirts increasingly suggest that the wearer is anti-social moving from top to bottom. Near the bottom of the screen, the T-shirts no longer attempt to be witty and simply have straightforward phrases like "go away" and "die". These are exaggerations of the message that the other more-realistic shirts broadcast.

The final three shirts are also exaggerated shirts that suggest [[Randall]]'s view that people who wear snarky shirts are overcompensating for the fact that they are already alone or perhaps putting up a tough exterior to conceal their sadness that no one would talk to them anyway. Most notably "maybe if this T-shirt is witty enough, someone will finally love me" sums up what Randall thinks snarky shirts really say. There are shirts with this or a similar message, although it is unclear whether they were created before this comic or as a tribute to this comic.

In the title text, Randall says that it's depressing how many of the shirts in the comic actually exist in real life, further underlining the point that these shirts are overly arrogant, to the point where one might believe that Randall made them up. This highlights the inadequacy of substance within these T-shirts and the terror they invoke in Randall's mind.

==Transcript==
:[A collection of phrases on T-shirts. The first and the last on actual black T-shirts worn by the same person, whose facial expression is more sad on the last one.]
:I see dumb people
:As a matter of fact the world <big>does</big> revolve around me
:I can only please one person per day / today is not your day.
:You know what your problem is? You're stupid.
:Get a clue
:Do I <u>look</u> like a people person?
:Your village called / they want their idiot back
:Go away
:I hate you all
:Die.
:Help.
:Maybe if this T-shirt is witty enough, someone will finally love me.
:Oh God I'm so alone.

==Trivia==
*This was the 24th comic originally posted to [[LiveJournal]].
**The previous was [[22: Barrel - Part 3]].
**The next was [[37: Hyphen]].
*Original title: "Wednesday's Drawing"
*Original [[Randall]] quote: "I saw the 'problem' t-shirt (upper right) on campus a few days ago and suddenly felt so sad."
*This comic was posted on [[xkcd]] when the web site opened on Sunday the 1st of January 2006.
**It was posted along [[:Category:First day on xkcd|with all 41 comics]] posted before that on LiveJournal as well as a few others.
**The latter explaining why the numbers of these 41 LiveJournal comics ranges from 1-44.
*One of the original drawings drawn on [[:Category:Checkered paper|checkered paper]].
*This is one of the few, early comics that contains a non-[[stick figure]] character.
*The last phrase of the comic was made into an actual T-shirt called "[https://store.xkcd.com/products/witty Witty]" sold at the xkcd store (as "maybe if this shirt is witty enough, someone will finally love me").
*Real shirts are: 'I see dumb people', 'As a matter of fact, the world '''does''' revolve around me', 'You know what your problem is? You're stupid.', 'I can only please one person per day//This is not your day.', 'Do I LOOK like a people person?', 'Get a clue', 'Your village called//They want their idiot back', 'Go away', 'Die.', 'Help', and 'Maybe if this t-shirt was witty enough, someone will finally love me.'
*'I hate you all' doesn't exist, but 'Hate you all' and 'I hate you' does. 'Oh god//I'm so alone' also doesn't exist, but 'Oh god I'm gonna die alone' and 'Oh god I am so alone in my world' does.

{{comic discussion}}

[[Category:Comics posted on livejournal| 24]]
[[Category:First day on xkcd]]
[[Category:Checkered paper]]
[[Category:Sarcasm]]
[[Category:Comics with xkcd store products]]

1958: Self-Driving Issues

2022-05-21T01:01:15Z

172.69.62.71: Undo revision 270751 by Explain xkcd server admin (talk)

{{comic
| number = 1958
| date = February 21, 2018
| title = Self-Driving Issues
| image = self_driving_issues.png
| titletext = If most people turn into murderers all of a sudden, we'll need to push out a firmware update or something.
}}

==Explanation==

[[Cueball]] explains being worried about {{w|autonomous car|self-driving cars}}, noting that it may be possible to fool the sensory systems of the vehicles. This is a common concern with {{w|AI}}s; since they think analytically and have little to no capability for abstract thought, they can be fooled by things a human would immediately realize is deceptive.

However, Cueball quickly assumes that his argument actually doesn't hold up when comparing AI drivers to human drivers, as both rely on the same guidance framework. Human drivers follow signs and road markings, and must obey the laws of the road just as an AI must. Therefore, an attack on the road infrastructure could impact both AIs and humans. However, humans and AIs are not equally vulnerable. For example, a fake sign or a fake child could appear to a human as an obvious fake but fool an AI. A creative attacker could put up a sign with CAPTCHA-like text that would be readable by humans but not by an AI.

Cueball further wonders why, in this case, nobody tries to fool human drivers as they might try to fool an AI, but [[White Hat]] and [[Megan]] point out that most {{w|Road traffic safety|road safety systems}} benefit from humans not actively trying to maliciously sabotage them simply to cause accidents.{{Citation needed}}

The title text continues the line of reasoning, noting that if most people did suddenly become murderers, the AI might be needed to be upgraded in order to deal with the presumable increase in people trying to cause car crashes by fooling the AI - a somewhat narrowly-focused solution given that a world full of murderers would probably have many more problems than that. As Megan sees humans as a 'component' of the road safety system, it might also be suggesting a firmware update for the buggy people who have all become murderers, one that would fix their murderous ways. We are not currently at a point where we can create and apply instantaneous firmware updates for large populations; even combining all the behavioral modification tools at our disposal -- {{w|psychiatry}}, {{w|cognitive behavioral therapy}}, {{w|hypnosis}}, {{w|mind-altering drugs}}, {{w|prison}}, {{w|CRISPR}}, etc. -- is not enough to perform such a massive undertaking, as far as we know. The update might be about the car's firmware since it can used to disable the brakes and thus causing or preventing many deaths.

==Transcript==
:[Cueball is speaking while standing alone in a slim panel.]
:Cueball: I worry about self-driving car safety features.

:[In a frame-less panel it turns out that Cueball is standing between White Hat and Megan, holding his arms out towards each of them, while he continues to speak.]
:Cueball: What's to stop someone from painting fake lines on the road, or dropping a cutout of a pedestrian onto a highway, to make cars swerve and crash?

:[Zoom in on Cueball's head as he continues to contemplate the situation holding a hand to his chin, while looking in White Hat's direction. Megan replies from off-panel behind him.]
:Cueball: Except... those things would also work on human drivers. What's stopping people '''''now? '''''
:Megan (off-panel): Yeah, causing car crashes isn't hard.

:[Zoom back out to show all three of them again.]
:White Hat: I guess it's just that most people aren't murderers?
:Cueball: Oh, right. I always forget.
:Megan: An underappreciated component of our road safety system.

==Trivia==
The [[title text]] was published with a typo: "murderers" was misspelled as "muderers."

The theme of human fear and overreaction to the advent of more or less autonomous robots also features in [[1955: Robots]].

Self-driving cars is a [[:Category:Self-driving cars|recurring subject]] on xkcd.

A variation on the idea that humans are mentally "buggy" is suggested in [[258: Conspiracy Theories]], though in that case divine intervention is requested to implement the "firmware upgrade".

This comic appeared one day after the Electronic Frontier Foundation co-released a report titled [https://www.eff.org/deeplinks/2018/02/malicious-use-artificial-intelligence-forecasting-prevention-and-mitigation The Malicious Use of Artificial Intelligence: Forecasting, Prevention, and Mitigation]. The report cites subversions and mitigations of AI such as ones used in self-driving cars. However, the report tends toward overly technical means of subversion. Randall spoofs the tenor of the report through his mundane subversions and over-the-top mitigations.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Megan]]
[[Category:Self-driving cars]]
[[Category:Sabotage]]

1323: Protocol

2022-05-21T01:00:21Z

172.69.62.71: Undo revision 270750 by Explain xkcd server admin (talk)

{{comic
| number = 1323
| date = January 29, 2014
| title = Protocol
| image = protocol.png
| titletext = Changing the names would be easier, but if you're not comfortable lying, try only making friends with people named Alice, Bob, Carol, etc.
}}

==Explanation==
{{w|Alice_and_Bob|Alice, Bob, and Eve}} are role names traditionally used in describing cryptographic protocols. Rather than talking about "Person A", "Person B", "Person C", names beginning with each letter are used instead, and giving them different genders let pronouns be used to shorten discussions. For example: "Person A sends Person B a message encoded with Person B's public key" is much easier to parse when written as "Alice sends Bob a message encoded with his public key." Eve is short for "eavesdropper" - a person trying to find out what's being said in the conversations between the other people. The classic situation involves Alice wanting to send a secret message to Bob, while Eve (the eavesdropper), attempts to read the message, ideally without Alice or Bob ever finding out. Additional participants such as Carol (Person C) can be added if necessary. The list of names has become very standardised over time as described at {{w|Alice and Bob}}.

The joke here is that any computer scientist, hearing the names used, will think that they are listening to a cryptography problem. By changing the names in a story to these role names, you can induce them to listen carefully to boring stories. The fewer the interesting details, the more it sounds like a general problem, so very boring stories are actually the easiest.

The title text shows a more radical approach to the problem, for people who do not feel comfortable about lying. In this approach, you only make friends with people who have the appropriate names already.

The comic title also can be interpreted in two ways. First, the computer scientist thinks the conversation is about an encryption protocol. Second, the way the conversation is carried resembles a protocol used by many data communication systems, where one side sends data while the other sends back an [http://en.wikipedia.org/wiki/Acknowledgement_(data_networks) acknowledgement] upon receiving the data. In this case, the data are the lines of the boring story.

In comic [[177: Alice and Bob]] these names are used in the same context. Instead of Alice and Bob being perfectly innocent people who just want to communicate in private, Bob is actually having an affair with Alice. Eve —his former partner— cracked the encryption to see what the message contained. Thus, this comic seems to continue the Alice/Bob romance, jealous-Eve plot, with Eve apparently confronting Alice over her text message to Bob.

==Transcript==
:[Cueball is telling a story to a Computer Scientist who is seated at his desk.]
:Cueball: Alice sends a message to Bob saying to meet her somewhere.
:Computer Scientist: Uh huh.
:Cueball: But Eve sees it, too, and goes to the place.
:Computer Scientist: With you so far.
:Cueball: Bob is delayed, and Alice and Eve meet.
:Computer Scientist: Yeah?
:CAPTION: I've discovered a way to get computer scientists to listen to any boring story.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Computers]]
[[Category:Cryptography]]
[[Category:Multiple Cueballs]]

1791: Telescopes: Refractor vs Reflector

2022-05-21T00:59:44Z

172.69.62.71: Undo revision 270749 by Explain xkcd server admin (talk)

{{comic
| number = 1791
| date = January 27, 2017
| title = Telescopes: Refractor vs Reflector
| image = telescopes_refractor_vs_reflector.png
| titletext = On the other hand, the refractor's limited light-gathering means it's unable to make out shadow people or the dark god Chernabog.
}}

==Explanation==
This comic compares two major types of {{w|optical telescope|optical telescopes}}: The {{w|refracting telescope}} and the {{w|reflecting telescope}}. A refracting telescope produces an image with a series of lenses. A reflecting telescope uses mirrors. (A third type, the {{w|catadioptric system}} telescope, uses both mirrors ''and'' lenses. It is not shown here.)

It first looks like the comic is simply trying to show that refracting has many flaws, such as expense, size and visibility (see more [[#The real problems with refracting telescopes|details below]]). However, the punchline invalidates these complaints with the (apparently major) flaw listed with the reflecting telescope: '''It can't see space vampires'''.

The unstated reason for this is that {{w|vampires}}, {{w|Vampire#Apotropaics|according to some cultures}}, cannot be seen in a mirror. As {{w|Space Vampires}} (like earth vampires) are widely believed to be {{w|Vampire#Origins_of_vampire_beliefs|made up}} and thus unlikely to interest most [[1644: Stargazing|stargazers]],{{Citation needed}} this complaint is superfluous, and the reflecting telescope effectively has no flaws in comparison to the refracting telescope. There are other problems, though, with reflecting telescopes see [[#The real problems with reflecting telescope|details below]]. (Also there was a big problem in the [[#Trivia|original version of this comic]]).

Frequently, however, the right-angle transition at the base of the refractor telescope is done with a prism (an "image erector"). This uses the optical principle of total internal reflection. If mirror-non-appearance of vampires is due to the interaction of evil with silver, a refractor using a prism could still see vampires. On this theory, however, the reflector could too, since modern astronomical mirrors are coated with aluminum, not silver.

The title text expands on the seeing of supernatural beings, as another negative point is added to the refracting telescope; it apparently can't see {{w|Shadow person|Shadow People}} or the Slavic god {{w|Chernobog|Chernabog}} (sometimes spelled Chernobog), both of which are important although clearly not as important to the telescope's merit as seeing vampires since the fact is only mentioned in the title text. So of course the refracting telescope is still the best. Of course also neither the {{w|Shadow_person#History_and_folklore|shadow people}} nor {{w|Chernobog#Folklore|the god}} exists{{Citation needed}} so this would likewise be a moot point.

In reality, "shadow people" are a psychological phenomenon wherein humans ascribe human shapes and movements to shadows in dark spaces. Chernobog is a 12th century Slavic deity, whose name translates to ''black god''. His most famous appearance in modern media was in the 1940 Disney movie {{w|Fantasia (1940 film)|''Fantasia''}} (and Disney merchandise is also almost the only place that his name is spelled as Randall spelled it, with an "a" in the middle). Because shadows are dark and the god is also dark, they cannot be seen by the refracting telescope due to the reduced light-gathering which has already been mentioned as a drawback in the main comic.

Telescopes have been the subject of [[:Category:Telescopes|many comics]] on xkcd. Recently one about space telescope was released [[1730: Starshade]] and before that a large "private" telescope was shown in [[1522: Astronomy]].

===The real problems with refracting telescopes===
The basic performance of a telescope is determined by its size: a wider telescope catches more light, making it easier to see faint objects, while a longer telescope is better for high magnification viewing. For looking at stars, the width is actually more important. No matter how much you zoom, a star is too far away to make bigger, but with a big aperture, you can see stars too faint for the naked eye. Planets benefit more from magnification, and distant galaxies need both.

In both respects, it's much easier to make a big reflector telescope than a big refractor one. Since a lens can only be held in place by its edge, the center of a large lens sags due to gravity, distorting the images it produces. This means most refractor telescopes make do with narrow apertures only a couple of inches across. Reflector telescopes are sometimes called "light buckets" because they can have extremely big openings that can catch light from even very faint stars. In addition, because it has a mirror at one end, the reflector telescope is, in effect, twice as long as it appears - a refractor just cannot compete.

Refracting telescopes were only gradually overtaken by reflecting telescopes, however. In the age of {{W|great refractors}}, the largest telescopes in the world were refractors. Reflectors at the time had mirrors surfaced in {{W|speculum metal}} that began to tarnish only months after application, negatively affecting telescope performance. This problem was resolved when it became possible to surface a mirror in silver, but the problems with refractive lenses persist. Because of this, the {{w|List of largest optical telescopes historically|largest optical telescopes ever built}} are reflectors, rather than refractors. In addition, a {{w|liquid mirror telescope}} uses a very cheap, but potentially very large mirror - with the drawback that the telescope can only look straight upwards.

'''Randall's points:'''
*More expensive
**Grinding a high quality lens is more expensive than producing an equivalent mirror - {{w|Crown glass (optics)|crown glass}}, which is needed for good quality telescope lenses, is expensive.
*Less compact
**In theory, a refractor ''could'' be made compact, but the image quality would be awful, because the lens would have to be extremely fat. The longer the telescope is, the less dramatic the focusing needs to be.
*{{w|Chromatic aberration}}:
**In optics, chromatic aberration is an effect resulting from dispersion in which there is a failure of a lens to focus all colors to the same convergence point, producing a rainbow effect around the image familiar to people who wear glasses, and with prisms. It occurs because lenses have different refractive indices for different wavelengths of light. Each colour is therefore focused slightly differently by the lens. Mirrors don't have chromatic aberration, since the light is reflected off the front of the mirror. The {{w|achromatic lens}} can reverse this effect, but it's expensive and its size is limited. Nevertheless, before telescope mirrors were perfected in the early 20th century, the best telescopes were achromatic refractors.
***Note that this effect has also been mentioned in relation to photography by [[Black Hat]] in [[1014: Car Problems]], in a completely different context, but shows this is an issue Randall has considered before.
*Reduced light-gathering
**Apart from generally needing to be smaller than reflector telescopes a further problem comes from glass defects, striae or small air bubbles trapped within the glass. In addition, glass is opaque to certain wavelengths, and even visible light is dimmed by reflection and absorption when it crosses the air-glass interfaces and passes through the glass itself. All of this reduce the light gathered.

'''Other problems not mentioned by Randall:'''
*Suspending a lens
**Another important difference (and a big reason why large refracting telescopes don't exist) is that the lens of a refracting telescope has to be supported by the edges, so that light can pass through it. As a result there comes a point where it is no longer feasible to mount a large lens in a telescope due to its weight and the need to support it from the edges. In contrast the mirror of a reflecting telescope is supported from behind, and any support structures for the primary mirror are not in the path of the light. As a result, substantially larger mirrors can be easily mounted and supported. As an additional benefit this behind-the-mirror support has led to the creation of {{w|Adaptive_Optics|Adaptive Optics}}, a technique (which is impossible for refracting telescopes) that allows some of the atmosphere's distortions to be corrected for.
*A mirror can be segmented to make a larger reflecting surface out of smaller (and hence easier to build/mount/support) mirrors. By using a {{w|Segmented_mirror|segmented mirror}} it is possible to build an effective aperture much larger than what could be built even from a single mirror, which is itself much larger than the largest possible lens that might be built for a refracting telescope.

===The real problems with reflecting telescope===
It is worth noting that (apart from the vampire problem) a reflecting telescope also has disadvantages compared to a refracting telescope:
*The main disadvantage is that in almost all reflecting telescope designs the focal point is directly in front of the mirror, i.e. in between the mirror and the target of interest.
**As a result a {{w|Secondary_mirror|secondary mirror}} is commonly used to direct the focal point somewhere outside of the field of view. However, this secondary mirror (and the struts that support it) will still block part of the field of view - although the focus of the telescope means that the secondary mirror is not visible when looking at distant objects, it will result in diffraction patterns that also hinder the image quality. In fact, this is the source of the {{w|Diffraction_spike|diffraction spikes}} around stars which are commonly seen in astronomical images.
*** {{w|Off-axis reflecting telescope|Off-axis telescopes}} avoid the problem of diffraction from in-path obstructions, they also require larger footprints and more complicated mirror shapes compared to their on-axis counterparts.
*A reflecting telescope is also harder to maintain:
**The mirrors need to be very precisely aligned (this is called {{w|collimation}}), and this can be a laborious process. They may also need re-polishing.
**The telescope is open at one end, allowing dust and dirt to enter.
*A reflecting telescope is not very portable. This is why {{w|Birdwatching|bird-spotters}} use small refractor telescopes as an easy way to get a closer view of birds.

Despite this disadvantage, reflecting telescopes are used almost exclusively in modern astronomy because of practical limitations in making large refracting telescopes. Very few amateur astronomers use refracting telescopes - nowadays, they mostly exist to con people looking for Christmas presents in department stores (just because a telescope promises 100x zoom doesn't mean the image quality is any good!)

On the other hand, reflecting telescopes help astronomers gaze at Beige Gorgons (mentioned in [[2360: Common Star Types|comic 2360: Common Star Types]]).

==Transcript==
:[A one panel comic showing two different telescope designs next to each other with labels above them and a bullet list of points below them. The left drawing will be described first then the right.]

:[Left:]
:<big>Refractor</big>

:[A slim telescope design is shown. At the top the light enters shown in a light yellow shade between two thin parallel light gray lines that just fits inside the opening of the telescope which is slightly wider at the top than at the lens sitting a short way into the opening. The lens causes the light to focus just where the telescope again changes dimensions, and the light enters a small opening at the bottom of the long pipe of the telescope. Here the yellow light is a point as the two gray lines cross each other at that point. The light then broadens slightly again and the thin yellow light cone hits a mirror at the bottom of the telescope and is reflected to the left and out through the eyepiece. Below are the following points:]
:*More expensive
:*Less compact
:*Chromatic aberration
:*Reduced light-gathering

:[Right:]
:<big>Reflector</big>

:[A much broader (more than 150% of the first) but also much shorter (66%) telescope design is shown. At the top the light enters shown in a light yellow shade between two thin parallel light gray lines that still just fits inside the opening of the telescope. On it's way down to the bottom of the telescope the light passes by a small mirror turned down towards the bottom. When the hits the curved bottom mirror light is focus on it's way back back and a small light cone hits the small mirror mentioned before sitting almost at the top of the telescope. This mirror reflects the light to the left into an even thinner light cone that goes out through the eyepiece located near the top of the telescope. Below is the following point:]
:*Can't see space vampires

==Trivia==
In an '''[http://www.explainxkcd.com/wiki/images/archive/b/b2/20170127171253%21telescopes_refractor_vs_reflector.png earlier version]''' of this comic, the eyepiece of the refracting telescope included a mirror, often used with refractors to give an upright image and more comfortable access for the observer. This would of course invalidate the only advantage it has (vampire-visibility) over reflecting telescopes.

[[Randall]] later corrected this so the '''[http://www.explainxkcd.com/wiki/images/b/b2/telescopes_refractor_vs_reflector.png current/final version]''' shows the light going straight out of the end.

An {{w|amici roof prism}} is sometimes used instead of a mirror with refractors, because it does not only deliver an upright image, but also one that is not a mirror image. In a prism, there is only total reflection, which, as opposed to a metal mirror, would probably work on vampires.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Telescopes]]
[[Category:Rankings]]
[[Category:Science]]
[[Category:Astronomy]]
[[Category:Space]]
[[Category:Religion]]

2294: Coronavirus Charts

2022-05-21T00:59:20Z

172.69.62.71: Undo revision 270748 by Explain xkcd server admin (talk)

{{comic
| number = 2294
| date = April 15, 2020
| title = Coronavirus Charts
| image = coronavirus_charts.png
| titletext = Adding data for South Korea but with their cases scaled to match the population of Japan and the land area of Australia, and vice versa.
}}

==Explanation==
This comic is the 19th comic in a row (not counting the [[2288: Collector's Edition|April Fools' comic]]) in a [[:Category:COVID-19|series of comics]] related to the {{w|COVID-19 pandemic}}.

During the current outbreak of COVID-19, there have been many graphs used by health officials and others to show trends in infection and death rates. Their x-axis is usually time. The curves might represent different countries or different mitigation strategies. But
health officials and media have struggled to decide what to put on the y-axis. Because testing strategies and reporting are so variable across even small regions, their data does not reflect comparable guesses at the true number of cases. So they produce graphs of confirmed cases, confirmed plus suspected cases, deaths, hospitalizations, any of the above per capita, day-to-day changes in any of the above, and [https://fivethirtyeight.com/features/new-york-coronavirus-curve share of test results that are positive for different areas of New York].

This graph, however, while sharing similarities with actual data and graphs is completely useless. This is due to the bizarre data-points being used, as well as the unhelpful graph axes. The caption of the comic notes as much, perhaps indicating that this comic is intended to satirize the useful, but exceptionally detailed graphs that are currently in use. Some of these graphs have a semilog scale, like this graph - but generally the y-axis is the log scale and the x-axis is not. Sometimes the other graphs compare things of vastly different sizes - as demonstrated by showing both the USA and New York. Sometimes they scale the data to population, as referenced by the title text.

In addition, the selection of geographic areas used here is incomprehensible. Two of the lines represent countries (USA and Italy), and another represents part of one of those countries (New York City area). The New York City area may have been chosen because it has a very large number of cases, more than some countries. However, a fourth line combines Norway and Sweden -- two countries which are culturally, economically, and geographically similar [https://theconversation.com/coronavirus-why-the-nordics-are-our-best-bet-for-comparing-strategies-135344 but have imposed very different strategies] regarding closing businesses and schools. Combining Norway and Sweden obscures any differences attributable to their different policies regarding the virus. A fifth line represents not a geographical area but the ''ratio'' between France and Spain, making an already meaningless graph even less comprehensible.

The title text adds a further ambiguity: Usually, there are only two items being compared in a "vice versa" (e.g. "Would you rather have live in a city with the land size of San Francisco and the population density of Tokyo, or vice versa?" when comparing two other cities with those measurements); here there are ''three'', leading to either ambiguity (''possibly'' two South Korea lines, each based on one of two complementary sets of cross-demographic refactoring), or six lines being embodied in that "vice versa".

'''Other metrics used'''

X-axis:
*Negative test results: Negative [https://covidtracking.com/ test results] would refer to people who were tested for COVID-19, but who do not have the disease (or were not able to confirm having the disease). If there are any places reluctant to test, in order to artificially suppress the unpopular number of positives, this measure would similarly be unreasonably low. It might therefore be an important key measure, used as just one component of a meta-measurement, to regrade or even highlight such practices. At least until the figures are freshly massaged by instead overtesting people with a low probability of being infected.
* per Google search for "COVID": Meanwhile, [https://trends.google.com/trends/explore?date=today%203-m&q=covid Google search results for "COVID"] are search hits for that word. There is no relation between these two, and furthermore, it does not make sense for this to be graphed on a {{w|logarithmic scale}}.
* As mentioned above, the x-axis for most charts is time, as it is valuable to know how the virus or deaths are spreading over time. Negative test results should grow over time, but may not grow uniformly depending on availability of tests, and some may later be invalidated as testing methodologies are refined. Given that and depending on the trends in Google searches for COVID, it's entirely possible for multiple points in time to map to the same value of ''x'' (although none of the curves shown here do, Scenario 4 from [[2289: Scenario 4]] did).

Y-axis:
*[https://www.worldometers.info/coronavirus/worldwide-graphs/#daily-deaths Coronavirus deaths today]: Deaths from the coronavirus "today" are constantly reported by the media, and could be a helpful metric in seeing whether the virus is spreading or not, if deaths "today" are compared to deaths yesterday and previous days.
*[https://www.worldometers.info/coronavirus/worldwide-graphs/#total-cases Total cases] one week ago: This is a much larger number than deaths and will completely dominate the sum. Cases one week ago might have some predictive value for deaths today or in the near future, but adding them together double-counts many cases.
*{{w|Per capita}}: This is a measure of the amount per person, and is useful for averaging out numbers based on population size. For example, the United States have the most publicly-reported COVID-19 cases and deaths, but also has the third-largest population of all countries, so using per capita numbers tells a different story.

Title text: While adding data for South Korea might be helpful (as it shows an Asian country, compared to just Europe and the US), it is only logical to scale the data to the population of another country (e.g. Japan) if you're actually comparing the two countries (i.e. does Japan have more or fewer cases per capita than South Korea). Scaling cases based on land area is much less useful; it's true that countries with lots of {{w|land area}}, like Australia, do have lower population densities, which affects the spread of disease, but most of the people in Australia live in higher-density cities on the coast, so the actual change is not that great.

==Transcript==
{{incomplete transcript|Needs description of the shapes of all curves. Do NOT delete this tag too soon.}}

[A graph is drawn.]
:[A curve labeled "United States" starts about halfway up the vertical axis, rises almost to the top, and then levels off about a third of the way along the horizontal axis.]
:[4 other curves are also shown, labeled "New York City area", "Italy", "Norway + Sweden" and "Ratio between France and Spain".]
:Y-axis label: Coronavirus deaths today plus total cases one week ago per capita
:X-axis label: Negative test results per Google search for "COVID" (log scale)
:Caption: I'm a huge fan of weird graphs, but even I admit some of these coronavirus charts are less than helpful.

{{comic discussion}}
[[Category:COVID-19]]
[[Category:Charts]]
[[Category:Line graphs]]

468: Fetishes

2022-05-04T01:55:39Z

172.69.62.71: Undo revision 236427 by X. K. C. D. (talk)

<div style="display: none">crap</div>
{{comic
| number = 468
| date = August 27, 2008
| title = Fetishes
| image = fetishes.png
| titletext = They eventually resolved this self-reference, but Cantor's 'everything-in-the-fetish-book-twice' parties finally sunk the idea.
}}

==Explanation==
{{w|Bertrand Russell}} and {{w|Alfred North Whitehead}} co-wrote the ''{{w|Principia Mathematica}}'', with the intention of cataloging all of mathematics and ridding it of contradiction and self-reference. {{w|Kurt Gödel}} later showed that such a system is impossible, and that {{w|Gödel's incompleteness theorems|any system of axioms (complex enough to represent arithmetic) is incomplete}}.

This comic, however, presents an alternate universe scenario: here, Russell and Whitehead are pursuing the more salacious (but no less comprehensive) task of compiling a list of all sexual fetishes. This seems to be going fine until they ask Gödel for his fetishes; Gödel says that he is turned on by "anything not on your list." This creates a paradox - Russell and Whitehead now have no way to complete their list, because Gödel's fetishes cannot be included without putting them on the list, which would immediately invalidate them. In fact, this is precisely {{w|Russell's Paradox}}, discovered by Bertrand Russell himself.

The title text references {{w|Georg Cantor}}, the inventor of {{w|set theory}}, and adds a second, similar paradox: if you have a fetish for doing everything in the book twice, then that belongs in the book - but then, you must also have a fetish for doing ''that'' twice, so you have to put that in the book too; this process will keep adding fetishes to the book ''ad infinitum'', again making the task impossible to complete.

There is a [http://www.visualcomplexity.com/vc/project_details.cfm?id=319&index=319&domain= fetish roadmap] ([http://web.archive.org/web/20070630175441/http://www.deviantdesires.com/map/mappics/map06sm.jpg archive.org]) by Katharine Gates, author of Deviant Desires and DeviantDesires.com.

An earlier comic also refers to Kurt Gödel: [[24: Godel, Escher, Kurt Halsey]].

==Transcript==
:[Caption above the panel:]
:Author Katharine Gates recently attempted to make a chart of all sexual fetishes.
:Little did she know that Russell and Whitehead had already failed at this same task.

:[Russell, with long hair, and Whitehead are standing with Gödel (the last two are both Cueball-like), Russell holding a clipboard and smoking a pipe.
:Gödel is holding his chin with his right hand as he ponders the question.]

:Russell: Hey, Gödel — we're compiling a comprehensive list of fetishes. What turns you on?
:Gödel: Anything not on your list.
:Russell: Uh…hm.

{{comic discussion}}
[[Category:Comics featuring real people]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Sex]]
[[Category:Logic]]
[[Category:Recursion]]

218: Nintendo Surgeon

2022-05-04T01:55:19Z

172.69.62.71: Undo revision 235999 by X. K. C. D. (talk)

{{comic
| number =218
| date =February 2, 2007
| title =Nintendo Surgeon
| image =nintendo_surgeon.png
| titletext =Scary thought #138: Raptors coming down the waterslide behind me.
}}

==Explanation==
The {{w|Nintendo Entertainment System}}, released in North America in 1985, helped revitalize the video-game industry after the {{w|North American video game crash of 1983|video-game crash}} of 1983, with such games as the ''{{w|Super Mario Bros.}}'' series, ''{{w|The Legend of Zelda (game)|The Legend of Zelda}},'' the ''{{w|Mega Man}}'' series, ''{{w|Castlevania}},'' and ''{{w|Metroid (game)|Metroid}}'' helping it stand alone as what is still considered by many people today, the greatest video-game console of all time.

However, it was notorious for glitching games upon start-up, due in no small part to the unusual shape of the game console, which required one to open the door, push the game cartridge inside, push down to lock it in place, and push the power button. The console was deliberately designed this way so that it wouldn't look like a regular video-game console (and wouldn't be associated with the still-fresh stigma of the video-game crash only two years previous), but it caused no end of pain for people wanting to play the games. It would work fine for about two years, but after that "cartridge tilt" would become a problem as either the game's or the console's electric contacts could become misaligned.

A ubiquitous fix for this problem among gamers was to take the cartridge out, blow into it, and put it back inside, all to clean out any dust inside the cartridge that would make "cartridge tilt" worse and occur more frequently. This was not a recommended solution by Nintendo of America, and didn't always work, but it worked frequently enough to enter gamer culture, and even today, people who had the NES as children remember having to do that.

The NES was 22 years old as of the date this comic was written. Someone who was 10 years old when they got their Nintendo for Christmas could ''very well'' be old enough in 2007 to have attained their doctorate degree, and so this comic hearkens back to the aforementioned cartridge fix by suggesting that a heart surgeon might try that on a real-life heart patient. And like the introduction states, that ''is'' a scary thought.

The title text is one of many xkcd references to the terrifying ''[[velociraptor|Velociraptor]]'' predator from the dinosaur movie ''{{w|Jurassic Park}}.''

==Transcript==
:Scary Thought #137: The NES came out over two decades ago. Those kids are all grown-ups now.
:[Two surgeons are in an operating room, leaning over a patient.]
:First Surgeon: He's going into cardiac arrest. Stand by for defibrillation.
:Second Surgeon: Wait. First let's try taking out the heart, blowing into the ventricles, and putting it back in.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Medicine]]
[[Category:Velociraptors]]
[[Category:Video games]]
[[Category:Comics to make one feel old]]

2614: 2

2022-05-04T01:54:49Z

172.69.62.71:

<div style="display: none">crap crap </div><noinclude>:''This page refers to the comic named "2". For comic #2, see [[2: Petit Trees (sketch)]].''</noinclude>
{{notice|'''WARNING:''' The vast majority of ExplainXKCD's pages are currently vandalized. The script has been stopped, but many pages are still vandalized. {{#expr: {{LATESTCOMIC}} - {{PAGESINCAT:All comics|R}}}} out of {{LATESTCOMIC}} ({{#expr: 100 - ({{PAGESINCAT:All comics|R}} / {{LATESTCOMIC}} * 100 round 0)}}%) are vandalized, leaving only {{PAGESINCAT:All comics|R}} ({{#expr: ({{PAGESINCAT:All comics|R}} / {{LATESTCOMIC}} * 100 round 0)}}%).<br>''<u>Users:</u>'' You can help combat this! Click on "random page" and revert the latest edit, if it is vandalistic.}}
{{comic
| number = 2614
| date = May 2, 2022
| title = 2
| image = 2.png
| titletext = It's like sigma summation notation, except instead of summing the argument over all values of i, you 2 the argument over all values of 2.
}}

==Explanation==
{{incomplete|Created by A VERY JEALOUS NUMBER ₃½ⁿ₇₇₇ⅥⅣ₆⁸⁴⁴½⅔⅜ↆ↉↉∂, WHO DEMANDS TO HAVE THEIR OWN WEBCOMIC NEXT - Please change this comment when editing this page. The titletext needs to be worked in there, but I think I got everything else in some sort of order, pending general improvements. Do NOT delete this tag too soon.}}

This demonstrates the different ways in which the number 2 can be typeset in various scientific fields. Whilst these typefaces are used with any number, using the number 2 in this instance provides a clear illustration of where adding numbers can signify either a feature of a concept (such as the number of electrons in an atom) or a mathematical operation on it (such as raising a value to it's second power).

The dotted box represents any character (presumably a letter or bigram of letters). All the other notation consists only of the digit 2, in various fashions with occasional additional punctuation, and labelled as to what the 'purpose' might normally be of any particular element(s) as indicated, with respect to the general term, in the following fashions:
;Regular Math
:Precedes the term. "2x" indicates two times the value of ''x'' in normal {{w|algebra|algebraic}} use that should be familiar for many people. {{Citation needed}}
;Physics
:A preceding superscript. "<sup>2</sup>H" would indicate the particular {{w|isotope}} of Hydrogen with the atomic weight of two, i.e. deuterium, which is most often encountered when working with the atomic level of matter where the total number of neutrons and protons in the atom is important. It can also represent tetration, which is iterated exponentiation.
;Chemical Physics
:A preceding subscript, "<sub>2</sub>He" indicates the atomic number of an atom, which is the number of protons it contains, and thus a guide to the number of electrons its unionised form usually has and hence meaningful in its potential chemical interactions with other atoms. This should be invariant for any particular named element, but is usually given simultaneously with the presuperscripted mass number where it can be indicative of the applicable nuclear physics. {{w|Chemical Physics}} is a subdiscipline of physics and chemistry and **must never** be confused with {{w|Physical Chemistry}}. It can also represent pentation, which is iterated tetration.
;Regular Math or Footnotes
:A trailing superscript is typical of a {{w|Exponentiation|power value}}, in this case "x²" would be ''x'' multiplied by a second copy of itself, and a fairly typical mathematical standard.
:Additionally, superscripted numbers are one common way to mark words in a line of text in a way to refer to a {{w|Note (typography)|footnote}}, typically placed at the bottom of the page, with additional information that would not be appropriate or easily comprehendable to edit into the main text itself. The ambiguity between footnotes and exponents was used in [[1184: Circumference Formula]]
;Chemistry
:A trailing subscript is used in chemistry to indicate a multiple of the element (or group of elements, in brackets) in a {{w|chemical formula}}. "H<sub>2</sub>O" indicates two hydrogen atoms bond with a single oxygen atom in a molecule of water.
;Matrices! ("2,2")
:Extending the trailing subscript with a comma-separated value usually indicates a multidimensional array (e.g. establishing a 2-by-2 square of numbers, or this particular position in such an array), which is in the realms of {{w|Matrix (mathematics)|matrix mathematics}}. This is a little bit beyond 'everyday algebra' for many people, as seemingly indicated by the exclamation of the mere mention of matrices!
;The Physicists Are At It Again ("2;2")
:This label encompasses a mark that turns the prior comma into a semicolon, as part of the trailing subscript. This is a common notation for the {{w|Covariant derivative}} of a tensor field, which is commonly used in the mathematics of general relativity.
;Either High School Math Function or Incomprehensible Group Theory
:The number 2 in parentheses that follow a term would normally be the argument to a {{w|Function (mathematics)|function}}, e.g. "f(2)", which means that you should take the value (in this case 2) and find the result if manipulated by the predefined function ''f''. It is generally taught as part of algebraic mathematics already described, i.e. at {{w|Secondary school|High School}}.
:In {{w|group theory}}, however, the number 2 in parentheses could indicate a cyclic subgroup or ideal generated by two or a special case of cycle notation for elements of symmetry groups used to mean an element that keeps 2 fixed. This may be somewhat beyond high-school level.{{citation needed}}
;Oh no. Whatever this is, it's cursed.
:A symbol centered underneath another symbol is normally reserved for doing summations, where the big symbol is Σ, or some other operation applied to a sequence of numbers.
:It does not make sense to have a single number there, as indicated in the alt text. As with [[2529: Unsolved Math Problems|other things]] in Randall's comic universe, the explanation for this particular anomaly is that it is 'Cursed'. The usage mentioned in the alt text is an operation (Σ, summation) over a variable usually indicated by a letter such as i, where the operation is performed over all values of the variable, i.e. you Σ the argument over all values of i. In the "2" case, the alt text says you "you 2 the argument over all values of 2", i.e. the Σ operation has been replaced by the "2" operation and the i variable has been replaced by the "2" variable. 2 is usually not an operation, though the definition of 2 under {{w|Church_encoding#Church_numerals|church encoding}} is a function that takes in and produces functions. However, 2 is not a variable (and definitely not both at the same time).
:: Things being cursed is a common trope within recent XKCD comics which have mentioned items including [[2332:_Cursed_Chair|Cursed chairs]] and [[Category:Cursed_Connectors]]. This notation is one of the few occasions where the supernatural have demonstrable implications on science and mathematics for those foolhardy enough to use it.

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

:[An apparent generalisation of a scientific expression consisting of a dotted rectangular 'box' outline, left empty, and various commonly-themed symbology around it:]

:[as normal text, to the left of all the rest:] 2
:[superscript to the immediate left of the box:] 2
:[subscript also to the immediate left of the box:] 2
:[superscript to the immediate right of the box:] 2
:[subscript also to the immediate right of the box:] 2;2 [i.e. separated by a semicolon]
:[as normal text, to the right of almost all the rest:] (2) [i.e. enclosed in standard parentheses]
:[smaller subscript, centered immediately beneath the 2 within the parentheses:] 2

:[Further details are drawn in grey tone, around or near various of the elements of the expression:]
;[Captions above the numbers]
:[with an arrow pointing to the leftmost 2:] Regular Math
:[with an arrow pointing to the leftwards superscript 2:] Physics
:[with an arrow pointing to the rightwards superscript 2:] Regular math or footnotes
:[with an arrow pointing to the parenthetical 2 at the right:] Either high school math functions or incomprehensible group theory

;[Captions below the numbers]
:[with an arrow pointing to the leftwards subscript 2:] Chemical Physics
:[with an arrow pointing to just the rightwards subscript 2:] Chemistry
:[with an arrow pointing to a distorted grey ring snaking around only the comma of the semicolon and the following 2 of the rightmost subscript:] Matrices!
:[with an arrow pointing to a larger grey ring that passes fully around the whole semicolon and final 2 of the rightmost subscript:] The physicists are at it again
:[with an arrow pointing to the small 2 placed below the parenthetical 2:] Oh no. Whatever this is, it's cursed.

{{comic discussion}}
[[Category:Math]]
[[Category:Physics]]
[[Category:Chemistry]]
[[Category:Comics featuring Cursed Items]]