explain xkcd - User contributions [en]

2516: Hubble Tension

2021-09-16T22:51:49Z

Rhubbarb: /* Explanation */ highlighed the incomaparability of Ponytail and Dave's chosen units

{{comic
| number = 2516
| date = September 15, 2021
| title = Hubble Tension
| image = hubble_tension.png
| titletext = Oh, wait, I might've had it set to kph instead of mph. But that would make the discrepancy even wider!
}}

==Explanation==
{{incomplete|Created by Dave - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
[[Ponytail]] is telling [[Cueball]] about the {{w|expansion of the universe}} telling him that there are three main estimates of the rate of expansion, and that they all disagree. She then tells him of the two well known (and very complicated) methods, and finally the joke is that the third method is performed by a guy named Dave (who replies from off-panel), and he claims to measure the distances with a radar gun, as if the galaxies were speeding here on Earth.

The fact that most {{w|galaxies}} are receding from us, and that the distance to the galaxy is directly proportional to the speed (as measured by {{w|red-shift}}) was discovered in the 1920s by {{w|Edwin Hubble}} and others. This constant of proportionality is known as the {{w|Hubble Constant}}.

One way of measuring the Hubble Constant is to measure the distance to (relatively) nearby galaxies. Once distance is obtained, speed can be easily obtained by measuring the red-shift and thus the Hubble Constant calculated. Measuring the distance turns out to be fiendishly difficult because a distant bright star looks the same as a dim star that is closer, and localized movements can influence the speed of recession — though less significantly, for multiple reasons, the further away are the objects that you study.

In practice, astronomers have a number of ways of measuring distance that work at different scales, and they can be built upon to measure distance to far away galaxies. This is known as the {{w|Cosmic distance ladder}}.

The first rung is {{w|parallax}}. As the Earth orbits around the Sun, nearby stars appear to move slightly relative to distant stars; a star that moves by one second of arc is said to have a distance of 1 {{w|Parsec}} — about 3¼ light years or 30 trillion (3x1013) kilometers.

The next rung is {{w|Cepheid variables}}, which periodically brighten and dim. The frequency of variation is related to the absolute brightness of the star, and thus by comparing the absolute to the relative brightness (subject to the {{w|Inverse-square law}} where not otherwise obscured) the distance can be measured.

The final rung is {{w|Type Ia supernova}}, which occur when an accreting {{w|white dwarf}} exceeds 1.4 solar masses. Because the initial mass is always identical, the absolute brightness of the explosion is as well, so the distance can be similarly calculated.

Putting these together, the best measurement of the Hubble Constant is 73 km/s/Mparsec.

This is in conflict with the other main way of measuring the Hubble Constant, analyzing makeup of the {{w|Cosmic Microwave Background}} (CMB) radiation, which yields a value of 68 km/s/Mparsec. The difference is statistically significant, and well outside the error bounds of each measurement.

Since the CMB technique relies on our understanding and assumptions about the early universe, as well as on the cosmological effects of General Relativity on large scales, if this discrepancy proved real it could be the gateway to new discoveries in cosmology and gravity, as well as possibly shed light on the origin of the universe and a '{{w|Theory Of Everything}}'. Cosmologists got quite excited about this. It might also be that there was a previously unaccounted-for error in any of the rungs of the cosmological distance ladder, and that once that is fixed, the two results will be consistent.

The third method introduced in this comic is a guy named Dave who is trying to use a {{w|radar speed gun}} (as used by the police for detecting speeding cars) to try to measure the movement of astronomical bodies. A radar system works by sending electromagnetic radiation from the gun and then measuring the returned radiation to determine how far away or how fast a moderately distant object is moving. Because of the transmission and return times required (and the inverse-square law), a radar device will only be able to get information about the very closest objects, such as the Moon (a type of {{w|Earth–Moon–Earth communication|Moon bounce}}) and other objects orbiting the Earth (or ''perhaps'' the Sun), where the influence of being in orbit utterly dominates over any possible Hubble-shift. And that still needs powerful radar systems like the former {{w|Arecibo Telescope}} to be able to get any useful information that far away, a hand-held radar gun would not be able to 'lock on' across even those distances.

Going by back-calculating grossly 'idealized' universe models, as suggested by the other two estimates, a receding velocity of 85 miles per hour ('mph'; about 137 kilometers per hour, 'kph' or 'km/h') should be seen at a distance of roughly 1700-1850 light-years, on the order of the thickness of our galactic disc. Much too far to use a radar gun on, also much too close to exclude any significant galactic stellar motions. Much the same is true if the figure is actually 85 kph (1050-1130 ly), as suggested it might be in the title text. It is also dimensionally wrong, as it is quoted as a straight "distance per time", not "distance per time ''per distance''".

Aside from being practically incorrect, that value of 85 kph relates to around 53 mph, which might be the normally observed traffic speed on certain roads (especially if someone is conspicuously using a radar gun!) if by 'all directions' you effectively mean 'both directions' of traffic flow that Dave could possibly be measuring. Dave may have been referring to the kind of {{w|Ford Galaxy|Galaxy}} that he ''can'' more easily find out the velocity of.

The comic is likely making fun of the common internet phenomenon of amateur (wannabe?) scientists seeking to discredit established scientific facts by reporting the results of experiments made using everyday tools. Dave has probably heard of the fact that there is no agreement in the scientific measurements of the Hubble constant and decided to try to settle the controversy using the tools at his disposal, without remotely realizing that the margin of error required in the measurements is well outside the range of what can be used with conventional objects.

Dave might also lack an understanding of units of measure and dimensions. Ponytail describes the measurements of the rate of universal expansion, a speed that varies with distance, in km/s/Mparsec, having dimension 1/T or 1/time. Dave made his measurements in miles/hour or km/h, which have dimension L/T or length/time. These are not comparable with the official units. Dave does not appear to be aware of this (and Ponytail does not draw Cueball or Dave's attention to it).

==Transcript==
:[Cueball and Ponytail are walking to the right. Ponytail has her palm raised.]
:Ponytail: There are three main estimates of the universe's expansion rate and they all disagree.

:[They keeping walking to the right.]
:Ponytail: Measurements of star distances suggest the universe is expanding at 73 km/s/megaparsec.

:[They are still walking to the right.]
:Ponytail: Measurements of the cosmic microwave background suggest it's expanding at 68 km/s/megaparsec.

:[They continue walking to the right. Ponytail points towards Dave who replies from off-panel to the right.]
:Ponytail: And Dave, who has a radar gun, says it's expanding at 85 mph in all directions.
:Dave (off-panel): ''Those galaxies are really booking it!''
:Ponytail: Thanks, Dave.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]
[[Category:Physics]]

1970: Name Dominoes

2018-03-22T22:59:48Z

Rhubbarb: /* Explanation */ added names and Wikipedia references for the smaller and larger "dominoes".

{{comic
| number = 1970
| date = March 21, 2018
| title = Name Dominoes
| image = name_dominoes.png
| titletext = In competition, you can only play a name if you know who the person is. No fair saying "Frank ... Johnson. That sounds like a real person! Let me just Google him real quick."
}}

*A large version of the comic picture can be found [https://xkcd.com/1970/large/ here].
*A numbered version can be found [http://www.explainxkcd.com/wiki/images/7/73/1970-_Name_Dominoes_-_The_large_image_with_numbers.jpg here].

==Explanation==
{{incomplete|Created by Fats Domino: Table links should be checked and explanation and connections added. (Add a full transcript... "Done!" And good luck with that! "Thanks".) Do NOT delete this tag too soon. }}

{{w|Dominoes}} is a family of boardgames played with rectangular "domino" tiles. A domino tile is divided into two squares, each displaying a number. Under most rules, a domino tile is placed on the table adjacent to another tile, and the adjacent ends must match in some way (namely by the number displayed on the touching ends). Randall's "name dominoes" shows a set of domino tiles with people's names instead of numbers, and adjacent tiles are matched by whether the closest name is the same (such as how Chris Evans' family name matches Evan Taylor Jones' given name).

The title text spells out a rule that a player may only place a tile if they know who that person is. This is a variation of a rule in {{w|Scrabble}}, where a player loses a turn if their chosen word don't survive a dictionary challenge over the validity of the word. This rule implies that players are allowed to create new name dominoes tiles and that it is not a fixed set. In this case the player that is challenged has used the name Frank Johnson of which there are {{w|Frank Johnson|12 exact matches}} on Wikipedia along with six with a middle name and more. In a google search as of the day the comic came out the first hit was {{w|Frank Johnson (basketball)|Frank Johnson}} who is a retired American professional basketball player and coach. Randall has made several [[:Category:Basketball|references to basketball]] in his comics.

A large board is covered in rectangular "dominoes" (270), with each domino bearing the name of a "well-known" person or character (fictional). The dominoes are arranged as if a game of dominoes were being played, but instead of the game requiring the number of spots of adjacent dominoes to match up, this game requires adjacent ''names'' to match up. Because most people have two or more names, different matches are made at each end of a domino. Fun fact is that two of the people is "named after" the game: {{w|Fats Domino}} and {{w|Domino Harvey}}.

The match can be exact (e.g., "Kevin" on one domino adjacent to "Kevin" on another), homonymic (e.g., "Klein" adjacent to "Kline"), or nickname-based (e.g., "James" adjacent to "Jimmy", which in turn is adjacent to "Jim"). Sometimes last names are matched up with first names (e.g., "{{w|Elizabeth Warren}}" adjacent to "{{w|Warren Beatty}}"), and in some cases only a single name is used (e.g., "{{w|Columbo}}", "{{w|Drake_(musician)|Drake}}", "{{w|Garfield_(character)|Garfield}}", "{{w|Prince_(musician)|Prince}}"). Singular names are represented by a half-size square "domino" (or "{{w|Polyomino|monomino}}"), with a few exceptions: "{{w|Garnet_(Steven_Universe)|Garnet}}" has a full-size tile (a complex reference explained below), and "{{w|Batman}}" and "{{w|Superman}}" have full-size tiles and are placed as though they were two-part names: the first square of "Superman" is matched with "Super", and the second square is matched with the second square of "Batman" (as though both characters had the last name "Man"). Some people have three or more names (e.g., "{{w|Frank Lloyd Wright}}") and have a 3-square domino tile (or "straight {{w|Tromino|tromino}}", 50% longer than normal) which permits matching to a middle name (e.g. "Frank Lloyd Wright" is matched to "{{w|Lloyd Alexander}}" and "{{w|Harold Lloyd}}").

The names come from a wide variety of fields: scientists (e.g., {{w|Isaac Newton}}), historical figures ({{w|George Washington}}), musicians ({{w|Drake (musician)|Drake}}), politicians ({{w|John Kerry}}), actors ({{w|Kevin Costner}}), writers ({{w|Washington Irving}}), fashion designers ({{w|Oscar de la Renta}}), and so on. Most of the names are real people but a few are fictional characters, including some non-human characters like {{w|Garfield_(character)|Garfield}} and {{w|Grover#Super_Grover|Super Grover}}. In one case the nick name for a company is used: {{w|Ma Bell}} aka Bell System.

One notable reference beyond just the use of a name is in the bottom left, there is the connection [ {{w|William Safire}} ][ Garnet ][ {{w|Jack Ruby|Ruby, Jack}} ]. The connection seems to be based on the fact that {{w|Sapphire}}, {{w|Garnet}} and {{w|Ruby}} are all {{w|gemstones}}, which does not match the implied rules of the game. This tile is a reference to the character {{w|Garnet_(Steven_Universe)|Garnet}} in the cartoon {{w|Steven Universe}}, who is a "fusion" formed by two Gems: Ruby and Sapphire. Thus, the name "Garnet" is treated as though it was two names "Ruby" and "Sapphire", requiring a two-square tile despite having a one-word name. Randall has previously made references to this universe in [[1608: Hoverboard]]. (See [http://www.explainxkcd.com/wiki/images/3/39/1608_1031x1095y_Steven_Universe_family_and_ice_cream_prediction.png this] and [http://www.explainxkcd.com/wiki/images/f/fa/1608_1077x1109y_Darth_Vaders_talks_about_Steven_Universe_on_the_bridge_Megan_adjust_antenna.png this] image from that comic).

Additionally, Ayn Rand, Paul Ryan and Rand Paul have been mentioned before, in the title text of [[1277: Ayn Random]]. That idea may have been the prototype for this.

In at least one case it is not entirely clear who is being referred to: "John Kelly" most likely refers to Gen. {{w|John F. Kelly}}, Donald Trump's chief of staff, but the name is extremely common and could equally refer to {{w|John Kelly|any number of people}}.

==Table of names==
*Work in progress
**The number # refers to the numbers on this [http://www.explainxkcd.com/wiki/images/7/73/1970-_Name_Dominoes_-_The_large_image_with_numbers.jpg numbered picture].
***Read more on this page:
***[[1970: Name Dominoes/Numbered images]]
*Wiki links not tested as they were set in only from the name in the comic.
**Spell checking...

{| class="wikitable sortable"
!style="width:15%"|Domino
!style="width:45%"|Notability and notes
!style="width:15%"|Connections
!style="width:20%"|Mode
!style="width:5%"|#
|-
|{{w|Christian Campbell}}
|
|
|
|1
|-
|{{w|Neve Campbell}}
|American actress, known for starring in the movie series Scream.
|
|
|2
|-
|{{w|Joe McCarthy}}
|
|
|
|3
|-
|{{w|Eugene McCarthy}}
|
|
|
|4
|-
|{{w|Gene Vincent}}
|
|
|
|5
|-
|{{w|Gene Kelly}}
|
|
|
|6
|-
|{{w|Kate Hudson}}
|
|
|
|7
|-
|{{w|Rock Hudson}}
|
|
|
|8
|-
|{{w|Gordon Brown}}
|Former British Prime Minister
|
|
|9
|-
|{{w|James Brown}}
|
|
|
|10
|-
|{{w|Jon Brown}}
|
|
|
|11
|-
|{{w|John Howard}}
|Australian politician. Served as 25th Prime Minister of Australia from 1996-2007.
|
|
|12
|-
|{{w|Columbo}}
|Fictional character. Homicide detective from American TV show "Columbo"; portrayed by actor Peter Falk.
|
|
|13
|-
|{{w|Chris Columbus (filmmaker)|Chris Columbus}}
|Film director and screenwriter.
|Columbo Christopher Columbus Chris Hughes
|Last-Only (approximate) First-First (approximate) and Last-Last First-First
|14
|-
|{{w|Christopher Columbus}}
|Italian explorer. Credited with "discovering" the Americas in 1492 by leading voyages and establishing continued ties between Europe and the Americas.
|
|
|15
|-
|{{w|Naomi Campbell}}
|British model and actress.
|
|
|16
|-
|{{w|Joseph Campbell}}
|American author. Most known for his book The Hero with a Thousand Faces about the hero type found throughout world mythologies.
|
|
|17
|-
|{{w|Joseph Smith}}
|American religious leader; founder of Mormonism. Publisher of The Book of Mormon.
|
|
|18
|-
|{{w|Frank Vincent}}
|American actor.
|
|
|19
|-
|{{w|John Kelly}}
|White House Chief of Staff under President Donald Trump. Retired US Marine Corps general.
|
|
|20
|-
|{{w|Katherine Johnson}}
|African-American mathematician at NASA. Calculated trajectories, launch windows, and flight paths for NASA moon missions and the Space Shuttle.
|
|
|21
|-
|{{w|The Rock}}
|Nickname for Dwayne Johnson, a pro wrestler and actor.
|
|
|22
|-
|{{w|Chris Rock}}
|American comedian.
|
|
|23
|-
|{{w|Chris Isaac}}
|
|
|
|24
|-
|{{w|James Newton Howard}}
|
|
|
|25
|-
|{{w|John Wayne}}
|
|
|
|26
|-
|{{w|Howard Stern}}
|
|
|
|27
|-
|{{w|Howard Hunt}}
|
|
|
|28
|-
|{{w|Chris Hughes}}
|
|
|
|29
|-
|{{w|Naomi Watts}}
|
|
|
|30
|-
|{{w|Naomi Klein}}
|
|
|
|31
|-
|{{w|Kevin Kline}}
|
|
|
|32
|-
|{{w|Francis Bacon}}
|
|
|
|33
|-
|{{w|Francis Drake}}
|
|
|
|34
|-
|{{w|Lyndon Johnson}}
|
|
|
|35
|-
|{{w|Oscar the Grouch}}
|
|
|
|36
|-
|{{w|Oscar Isaac}}
|
|
|
|37
|-
|{{w|Isaac Hayes}}
|
|
|
|38
|-
|{{w|Isaac Newton}}
|Well-known 1600s physicist who created the three laws of motion.
|
|
|39
|-
|{{w|Wayne Newton}}
|
|
|
|40
|-
|{{w|Wayne Knight}}
|
|
|
|41
|-
|{{w|Helen Hunt}}
|
|
|
|42
|-
|{{w|Helen Hughes}}
|
|
|
|43
|-
|{{w|James Watt|James Watt (Steam)}}
|
|
|
|44
|-
|{{w|James G. Watt|James Watt (Interior)}}
|
|
|
|45
|-
|{{w|Kevin Costner}}
|
|
|
|46
|-
|{{w|Kevin Bacon}}
|
|
|
|47
|-
|{{w|Kevin Love}}
|
|
|
|48
|-
|{{w|Lisa Frank}}
|
|
|
|49
|-
|{{w|Frank Drake}}
|
|
|
|50
|-
|{{w|Drake}}
|
|
|
|51
|-
|{{w|Oscar de la Renta}}
|
|
|
|52
|-
|{{w|Oscar de la Hoya}}
|
|
|
|53
|-
|{{w|Sean Hayes (actor)|Sean Hayes}}
|
|
|
|54
|-
|{{w|Wallace Shawn}}
|
|
|
|55
|-
|{{w|Wayne Howard}}
|
|
|
|56
|-
|{{w|Wayne Brady}}
|
|
|
|57
|-
|{{w|James Brady}}
|
|
|
|58
|-
|{{w|Tom Brady}}
|
|
|
|59
|-
|{{w|Helen Thomas}}
|
|
|
|60
|-
|{{w|Tom Hanks}}
|
|
|
|61
|-
|{{w|Hank Aaron}}
|
|
|
|62
|-
|{{w|Aaron Carter}}
|
|
|
|63
|-
|{{w|Stephen James}}
|
|
|
|64
|-
|{{w|Will Smith}}
|
|
|
|65
|-
|{{w|Kevin Smith}}
|
|
|
|66
|-
|{{w|Kevin James}}
|
|
|
|67
|-
|{{w|Garfield (character)|Garfield}}
|A fictional cat and the star of the eponymous ''{{w|Garfield}}'' comic by {{w|Jim Davis (cartoonist)|Jim Davis}}. Previously appeared in [[78: Garfield]].
|
|
|68
|-
|{{w|James Garfield}}
|
|
|
|69
|-
|{{w|Warren Buffett}}
|
|
|
|70
|-
|{{w|Jimmy Buffett}}
|
|
|
|71
|-
|{{w|Warren Beatty}}
|
|
|
|72
|-
|{{w|Elizabeth Warren}}
|
|
|
|73
|-
|{{w|Earl Warren}}
|
|
|
|74
|-
|{{w|Elizabeth Kolbert}}
|
|
|
|75
|-
|{{w|Stephen Colbert}}
|
|
|
|76
|-
|{{w|George Wallace}}
|
|
|
|77
|-
|{{w|Charles Wallace}}
|
|
|
|78
|-
|{{w|James Monroe}}
|
|
|
|79
|-
|{{w|Marilyn Monroe}}
|
|
|
|80
|-
|{{w|Hank Williams}}
|
|
|
|81
|-
|{{w|William C. Williams}}
|
|
|
|82
|-
|{{w|Steve Harvey}}
|
|
|
|83
|-
|{{w|Domino Harvey}}
|
|
|
|84
|-
|{{w|Harvey Milk}}
|
|
|
|85
|-
|{{w|James Saint James}}
|
|
|
|86
|-
|{{w|Etta James|Etta James (1)}}
| Used again in 266
|
|
|87
|-
|{{w|Jim Jones}}
|
|
|
|88
|-
|{{w|James Earl Jones}}
|
|
|
|89
|-
|{{w|Charlie Parker}}
|
|
|
|90
|-
|{{w|Ray Parker Jr.}}
|
|
|
|91
|-
|{{w|Ray Charles}}
|
|
|
|92
|-
|{{w|Charles Manson}}
|
|
|
|93
|-
|{{w|Marilyn Manson}}
|
|
|
|94
|-
|{{w|Robin Williams}}
|
|
|
|95
|-
|{{w|Billy D. Williams}}
|American actor best known for playing {{w|Lando Calrissian}} in ''{{w|The Empire Strikes Back}}'' and ''{{w|Return of the Jedi}}''.
|
|
|96
|-
|{{w|Will Wright}}
|
|
|
|97
|-
|{{w|Fats Domino}}
|
|
|
|98
|-
|{{w|Bill Clinton}}
|
|
|
|99
|-
|{{w|Jimmy John}}
|
|
|
|100
|-
|{{w|Tom Jones}}
|
|
|
|101
|-
|{{w|Tommy John}}
|
|
|
|102
|-
|{{w|Quincy Jones}}
|
|
|
|103
|-
|{{w|James Earl Ray}}
|
|
|
|104
|-
|{{w|Man Ray}}
|
|
|
|105
|-
|{{w|Rachel Ray}}
|
|
|
|106
|-
|{{w|Ray Allen}}
|
|
|
|107
|-
|{{w|Tim Allen}}
|
|
|
|108
|-
|{{w|Tim Cook}}
|
|
|
|109
|-
|{{w|Tim Howard}}
|
|
|
|110
|-
|{{w|Robin Wright}}
|
|
|
|111
|-
|{{w|Wilbur Wright}}
|
|
|
|112
|-
|{{w|Fatty Arbuckle}}
|
|
|
|113
|-
|{{w|Fat Joe}}
|
|
|
|114
|-
|{{w|George Clinton}}
|
|
|
|115
|-
|{{w|John Kerry}}
|
|
|
|116
|-
|{{w|Kerry Washington}}
|
|
|
|117
|-
|{{w|John Irving}}
|
|
|
|118
|-
|{{w|John Quincy Adams}}
|
|
|
|119
|-
|{{w|John Adams}}
|
|
|
|120
|-
|{{w|Amy Adams}}
|
|
|
|121
|-
|{{w|Aimee Mann}}
|
|
|
|122
|-
|{{w|Superman}}
|
|
|
|123
|-
|{{w|Batman}}
|
|
|
|124
|-
|{{w|Ayn Rand}}
|
|
|
|125
|-
|{{w|Lily Allen}}
|
|
|
|126
|-
|{{w|Paul Allen}}
|
|
|
|127
|-
|{{w|Ron Howard}}
|
|
|
|128
|-
|{{w|Howard Hughes}}
|
|
|
|129
|-
|{{w|Joe Kennedy}}
|
|
|
|130
|-
|{{w|George Bush}}
|
|
|
|131
|-
|{{w|George Wasington}}
|
|
|
|132
|-
|{{w|Wasington Irving}}
|
|
|
|133
|-
|{{w|Martha Wasington}}
|
|
|
|134
|-
|{{w|Ma Rainey}}
|
|
|
|135
|-
|{{w|Jack Ma}}
|
|
|
|136
|-
|{{w|Super Grover}}
|
|
|
|137
|-
|{{w|Jack Black}}
|
|
|
|138
|-
|{{w|Rand Paul}}
|
|
|
|139
|-
|{{w|Paul Ryan}}
|
|
|
|140
|-
|{{w|Paul Simon}}
|
|
|
|141
|-
|{{w|Ron Paul}}
|
|
|
|142
|-
|{{w|John Hughes}}
|
|
|
|143
|-
|{{w|Langston Hughes}}
|
|
|
|144
|-
|{{w|John F. Kennedy}}
|
|
|
|145
|-
|{{w|Little Richard}}
|
|
|
|146
|-
|{{w|Rich Little}}
|
|
|
|147
|-
|{{w|Martha Stewart}}
|
|
|
|148
|-
|{{w|Yo Yo Ma}}
|
|
|
|149
|-
|{{w|Ma Bell}}
|Aka Bell System, the system of companies, led by the Bell Telephone Company and later by AT&T, which provided telephone services to much of the United States and Canada from 1877 to 1984.
|
|
|150
|-
|{{w|Grover Cleveland Alexander}}
|
|
|
|151
|-
|{{w|Grover Cleveland}}
|
|
|
|152
|-
|{{w|Jack White}}
|
|
|
|153
|-
|{{w|Jack Ryan}}
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|{{w|Little Prince}}
|One of the main characters of ''{{w|The Little Prince}}'', a novella by {{w|Antoine de Saint-Exupéry}}. The Little Prince has previously appeared in [[618: Asteroid]], as well as [http://what-if.xkcd.com/68 article 68] of ''[[what if?]]''.
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|A {{w|garnet}} is a gem stone and the two names around here are {{w|William Safire}} (almost {{w|Sapphire}}) and {{w|Jack Ruby}} as in {{w|Ruby}}. But it is not just used because they are all {{w|gemstones}}. It is instead a reference to the character {{w|Garnet_(Steven_Universe)|Garnet}} in the cartoon {{w|Steven Universe}}. She is a "fusion" formed by two gems: Ruby and Sapphire, hence the legal connection in the Name Dominoes... Randall has previously made references to this universe in [[1608: Hoverboard]]. (See [http://www.explainxkcd.com/wiki/images/3/39/1608_1031x1095y_Steven_Universe_family_and_ice_cream_prediction.png this] and [http://www.explainxkcd.com/wiki/images/f/fa/1608_1077x1109y_Darth_Vaders_talks_about_Steven_Universe_on_the_bridge_Megan_adjust_antenna.png this] image from that comic).
|{{w|William Safire}} {{w|Jack Ruby}}
|Last-Only (as a Sapphire gem stone) Last-Only (as a Ruby gem stone) Both used to fuse together to Garnet.
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|{{w|James Cook}}
|18th century British explorer, navigator, cartographer, and captain in the Royal Navy.
|Alistair Cooke Cokie Roberts Alistair Cookie James Fenimore Cooper
|Last-Last (approximate) Last-First (approximate) Last-Last (approximate) First-First
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|Name misspelled Alistiar Cooke in the comic.
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|{{w|Monsterpiece_Theater#Alistair_Cookie|Alistair Cookie}}
|A parody of Alistair Cooke "played" by Cookie Monster in the Sesame Street sketch "Monsterpiece Theatre" in the 1980s, a parody of the PBS series "Masterpiece Theatre".
|James Cook Alastair Reynolds
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|Used first time in 86
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==Transcript==
:[This comic a large grid with 270 black "domino" tiles. On each tile there is a name written with white text. The grid is arranged so that each touching side corresponds with the first or last name of another person (or at least there are some kind of relation between the names on the end of connecting tiles). Some of the domino tiles are rotated 90, 180 or 270 degrees so the text is either to be read down, up-side down or up. The names on the tiles are listed here below in approximate reading order, thus staring top left and moving over the grid from left to right and down. Each swipe left to right covers approximately tiles that are within a span of one standard tile in height. To be exact it lists the names in the order they were numbered in this [http://www.explainxkcd.com/wiki/images/7/73/1970-_Name_Dominoes_-_The_large_image_with_numbers.jpg image]. One name is used twice, Etta James.]
:Christian Campbell
:Neve Campbell
:Joe McCarthy
:Eugene McCarthy
:Gene Vincent
:Gene Kelly
:Kate Hudson
:Rock Hudson
:Gordon Brown
:James Brown
:Jon Brown
:John Howard
:Columbo
:Chris Columbus
:Christopher Columbus
:Naomi Campbell
:Joseph Campbell
:Joseph Smith
:Frank Vincent
:John Kelly
:Katherine Johnson
:The Rock
:Chris Rock
:Chris Isaac
:James Newton Howard
:John Wayne
:Howard Stern
:Howard Hunt
:Chris Hughes
:Naomi Watts
:Naomi Klein
:Kevin Kline
:Francis Bacon
:Francis Drake
:Lyndon Johnson
:Oscar the Grouch
:Oscar Isaac
:Isaac Hayes
:Isaac Newton
:Wayne Newton
:Wayne Knight
:Helen Hunt
:Helen Hughes
:James Watt (Steam)
:James Watt (Interior)
:Kevin Costner
:Kevin Bacon
:Kevin Love
:Lisa Frank
:Frank Drake
:Drake
:Oscar de la Renta
:Oscar de la Hoya
:Sean Hayes
:Wallace Shawn
:Wayne Howard
:Wayne Brady
:James Brady
:Tom Brady
:Helen Thomas
:Tom Hanks
:Hank Aaron
:Aaron Carter
:Stephen James
:Will Smith
:Kevin Smith
:Kein James
:Garfield
:James Garfield
:Warren Buffett
:Jimmy Buffett
:Warren Beatty
:Elizabeth Warren
:Earl Warren
:Eliabeth Kolbert
:Stephen Colbert
:George Wallace
:Charles Wallace
:James Monroe
:Marilyn Monroe
:Hank Williams
:William C. Williams
:Steve Harvey
:Domino Harvey
:Harvey Milk
:James Saint James
:Etta James
:Jim Jones
:James Earl Jones
:Charlie Parker
:Ray Parker Jr.
:Ray Charles
:Charles Manson
:Marilyn Manson
:Robin Williams
:Billy D. Williams
:Will Wright
:Fats Domino
:Bill Clinton
:Jimmy John
:Tom Jones
:Tommy John
:Quincy Jones
:James Earl Ray
:Man Ray
:Rachel Ray
:Ray Allen
:Tim Allen
:Tim Cook
:Tim Howard
:Robin Wright
:Wilbur Wright
:Fatty Arbuckle
:Fat Joe
:George Clinton
:John Kerry
:Kerry Washington
:John Irving
:John Quincy Adams
:John Adams
:Amy Adams
:Aimee Mann
:Superman
:Batman
:Ayn Rand
:Lily Allen
:Paul Allen
:Ron Howard
:Howard Hughes
:Joe Kennedy
:George Bush
:George Wasington
:Wasington Irving
:Martha Wasington
:Ma Rainey
:Jack Ma
:Super Grover
:Jack Black
:Rand Paul
:Paul Ryan
:Paul Simon
:Ron Paul
:John Hughes
:Langston Hughes
:John F. Kennedy
:Little Richard
:Rich Little
:Martha Stewart
:Yo Yo Ma
:Ma Bell
:Grover Cleveland Alexander
:Grover Cleveland
:Jack White
:Jack Ryan
:Debby Ryan
:Carly Simon
:Carly Hughes
:Charles Evans Hughes
:John Williams
:Little John
:Stuart Little
:Potter Stewart
:Kristen Stewart
:Kristen Bell
:Kristen Hooks
:Alexander Graham Bell
:Franklin Graham
:Lloyd Alexander
:Meg White
:Meg ryan
:Debbie Reynolds
:John Reynolds
:Carly Fiorina
:Grace Lee Boggs
:Wade Boggs
:William Safire
:Prince William
:Little Prince
:Harry Potter
:James Potter
:James Hook
:James Dean
:Aretha Franklin
:Frank Lloyd Wright
:Barry White
:Walter White
:Walt Whitman
:John Kelly
:Grace Lee
:Nancy Grace
:Garnet
:Prince
:Prince Felder
:Prince Harry
:Harry Styles
:John Dean
:Benjamin Franklin
:Harrold Lloyd
:Harrold Ford
:Betty White
:Meg Whitman
:Christine Todd Whitman
:Megyn Kelly
:Grace Kelly
:Grace Jones
:Jack Nicholson
:Jack Ruby
:Jack Russel
:Harry Fielder
:Harry Trueman
:Harry Jon Benjamin
:John Edward
:Benjamin Harrison
:Harrison Ford
:Henry Ford
:Betty Ford
:Betty Friedan
:Chris Christie
:Chris Pratt
:Maggie Grace
:Grace Hopper
:Russel Crowe
:Russ Smith
:John Smith
:Justin Long
:John Bel Edwards
:John Candy
:John Henry
:Henry James
:Bill James
:Chirs Cooper
:Chirs Hemsworth
:Chirs Evans
:Topher Grace
:Van Morrison
:Sheryl Crow
:Sheryl Sandberg
:Cameron Crow
:Long John Silver
:Olivia Newton John
:Huey long
:John Edwards
:Candy Crowley
:Alestier Crowley
:James Fenimore Cooper
:James Cook
:Robert Frost
:Bob Evans
:Evan Tayler Jones
:James Cameron
:Cam Newton
:Cameron Diaz
:Huey Newton
:Huey Lewis
:John Lewis
:Jenny Lewis
:Ryan Lewis
:Burt Reynolds
:Alistiar Cooke
:Alistair Cookie
:Cokie Roberts
:John Roberts
:Robert Johnson
:Robert E. Lee
:Tommy Lee
:Tommy Lee Jones
:Etta James
:John Oliver
:Ryan Reynolds
:Alastair Reynolds

{{comic discussion}}

[[Category:Large drawings]]

1938: Meltdown and Spectre

2018-01-08T10:23:59Z

Rhubbarb: /* Explanation */ added note on "driving through walls" and "quantum tunnelling"

{{comic
| number = 1938
| date = January 5, 2018
| title = Meltdown and Spectre
| image = meltdown_and_spectre.png
| titletext = New zero-day vulnerability: In addition to rowhammer, it turns out lots of servers are vulnerable to regular hammers, too.
}}

==Explanation==
{{incomplete|Looks good, but something seems to be missing. Could someone recheck this again? Do NOT delete this tag too soon.}}
This comic was inspired by the {{w|Meltdown (security vulnerability)|Meltdown}} and {{w|Spectre (security vulnerability)|Spectre}} bugs in certain processors. These vulnerabilites were disclosed to the public the week of this comic. The bugs made big news because they broke the "walls" between programs executing concurrently on the same computer, in some circumstances allowing malware to steal secrets from normal, bug-free programs.

{{w|Speculative execution}} is a technique used to speed up computer processors. Processors {{w|Instruction pipelining|handle instructions in a series of steps}}, like an assembly line. The processor works on several successive instructions, each at a different stage in the assembly line. It may start speculatively executing instructions that follow a particular result of a decision before the logic that makes that decision is finished. Once the decision is made, it keeps results from the selected path, and discards unnecessary processing. This allows it to keep doing useful work while some slower decision is made. [[Ponytail]] uses {{w|Tram|trolley (tram)}} tracks as an analogy for streams of instructions in a program.

The {{w|Trolley Problem}} is a thought experiment where an out-of-control trolley is heading to a switch which you control. Leaving the switch as-is will cause it to kill multiple people stuck on the tracks, but switching the track will cause it to kill one person; this creates the ethical dilemma of passively causing multiple deaths versus actively causing one. The Trolley Problem has gained significant memetic traction, helped in no small part by its frequent inclusion in “introduction to philosophy” type courses. Also, the problem has seen revitalized interest with the emergence of {{w|autonomous car}}s, which may be faced with what are essentially {{w|autonomous car#Moral issues|such choices}} in emergency situations.

The "quantum" aspect of this is that in some {{w|interpretations of quantum mechanics}}, quantum-level particles can be viewed as taking every possible path at once, with the result being the sum of all of them, a result popularized by the {{w|Copenhagen interpretation|common interpretation}} of {{w|Schrödinger's cat}}, where the cat is both dead and alive until some event results in one of the states being selected.

Meltdown and Spectre result from flawed implementations of speculative execution, where the effects of speculatively executed instructions are not completely discarded. The phantom trolley driving through walls is an analogy for the computer instructions being able to access protected areas. This may also be a reference to {{w|quantum tunnelling}}.

In many cases, contrary to what the comic implies, both paths are not taken simultaneously during speculative execution. A {{w|branch predictor}} may be used to select the most likely path, and the effects should be completely erased if the predicted path is incorrect. Both branch prediction and taking both paths (known as eager evaluation), are considered speculative execution and are affected by these bugs.

The {{w|Row Hammer}} problem had been known for many years before this cartoon. A {{w|Dynamic random-access memory|common form of computer memory}} is constructed from tiny capacitors organized in a two-dimensional grid of rows and columns. Capacitors store charge to represent information. By applying a pattern of memory access that rapidly changes a row of capacitors, you can cause charge to overflow to nearby rows and incorrectly change their states.

Ponytail mentions that we especially suck at building "shared computers" because Rowhammer, Spectre, and Meltdown all break down the security divisions built between programs and between users. A hacker running a separate program in a separate account shouldn't be able to access your secrets or change the behavior of your program, but these problems allow them to. This is particularly dangerous for time-sharing, servers, and {{w|Cloud computing|the cloud}}, where different programs, websites, or even companies can be sharing the same hardware.

[[Cueball]] took her explanation literally, and came to the conclusion that the cloud "is full of phantom trolleys armed with hammers". Instead of correcting him, Ponytail decides to accept his interpretation (perhaps because she found this idea to be kinda cool).

The title text humorously states that as well as row hammer, computer servers also can be harmed by regular hammers. A {{w|zero-day (computing)|zero-day}} vulnerability is an attack that takes advantage of a vulnerability that hasn't been published yet, and so is not patched in any vulnerable system. This would imply that the Rowhammer vulnerability is what inspired someone to try taking a hammer to a server. One might "patch" a server against this attack by plating it with stronger metal. (The fact that compromising IT systems is sometimes easier done physically than logically is also mentioned in [[538: Security]].)

==Transcript==
:[Cueball and Ponytail are walking.]
:Cueball: The Meltdown and Spectre exploits use "speculative execution?" What's that?
:Ponytail: You know the trolley problem? Well, for a while now, CPUs have basically been sending trolleys down '''''both''''' paths, quantum-style, while awaiting your choice. Then the unneeded "phantom" trolley disappears.

:[Ponytail framed alone, facing left. They have stopped walking.]
:Ponytail: The phantom trolley isn't supposed to touch anyone. But it turns out you can still use it to do stuff.
:Ponytail: And it can drive through walls.

:[Cueball and Ponytail are standing, facing each other.]
:Cueball: That sounds bad.
:Ponytail: Honestly, I've been assuming we were doomed ever since I learned about Rowhammer.

:Cueball: What's ''that''?
:Ponytail: If you toggle a row of memory cells on and off really fast, you can use electrical interference to flip nearby bits and—
:Cueball: Do we just suck at ... computers?
:Ponytail: Yup. Especially shared ones.

:[They resume walking to the right.]
:Cueball: So you're saying the cloud is full of phantom trolleys armed with hammers.
:Ponytail: ...Yes, that is exactly right.
:Cueball: Okay. I'll, uh... install updates?
:Ponytail: Good idea.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Computers]]

Talk:1684: Rainbow

2016-05-23T12:03:46Z

Rhubbarb: add Wikipedia link for rainbows

How do I find the official transcript?[[User:Transuranium|Transuranium]] ([[User talk:Transuranium|talk]]) 11:00, 23 May 2016 (UTC)Transuranium
:Most recent comics do not have official transcripts. {{User:17jiangz1/signature|11:13, 23 May 2016}}
::But now there is one here ;-) [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 11:38, 23 May 2016 (UTC)

Now that XKCD adopts the voice of God, it's time to write him off and move elsewhere. [[Special:Contributions/141.101.70.109|141.101.70.109]] 11:56, 23 May 2016 (UTC)

For the sake of doctrinal accuracy, God (assuming the comic is in fact referring to the Jewish God who set his war bow in the cloud after the Flood) never promised not to destroy the earth by fire. Christian theology (2 Peter 3:10) implies God fully intends to destroy the earth by fire - or at least by unprecedented universal nuclear fission. [[Special:Contributions/108.162.221.87|108.162.221.87]] 11:59, 23 May 2016 (UTC)

When the conditions are right, various types of [[wikipedia:Rainbow#Variations|multiple rainbow]] may be visible. [[User:Rhubbarb|Rhubbarb]] ([[User talk:Rhubbarb|talk]]) 12:03, 23 May 2016 (UTC)

1673: Timeline of Bicycle Design

2016-04-27T10:34:34Z

Rhubbarb: mention of Mandelbrot's DOB

{{comic
| number = 1673
| date = 27 April, 2016
| title = Timeline of Bicycle Design
| image = timeline of bicycle design.png
| titletext = I'll be honest--the 1950s were a rough time for cycling.
}}

==Explanation==
Randall created a 200 year history for bicycles as created by Gianluca Gimini in his project Velocipedia. Gimini asked people to draw free hand sketches of bicycles and rendered the results as real bikes.

https://www.behance.net/gallery/35437979/Velocipedia

The 1925 model is reminiscent of a {{w|fractal}}; {{w|Benoit Mandelbrot}} was born just before this date, in late 1924.

==Transcript==
{{incomplete transcript}}

{{comic discussion}}

1669: Planespotting

2016-04-20T08:13:42Z

Rhubbarb: minor: added link

{{comic
| number = 1669
| date = April 18, 2016
| title = Planespotting
| image = planespotting.png
| titletext = No, a hydroplane doesn't land on water--that's an aquaplane. A hydroplane is a plane that gets electric power from an onboard water reservoir with a tiny dam and turbines.
}}

==Explanation==
{{incomplete|So far mainly a list. Could be listed better either bullet or in a table.}}

[[Cueball]] and a [[:Category:Characters with Hats|man with a hat]] are out '''planespotting''', or {{w|Aircraft_spotting|aircraft spotting}}, a hobby where tracking the movement of aircraft allows plane fans to see as many different types of planes as possible. A knowledgeable spotter would just by the silhouette and maybe the engine sound of the plane be able to tell what type of plane it is. (And may be rather proud of the fact, if he or she can tell this before one of the other spotters...)

The plane in the comic is most likely a {{w|Bombardier Dash 8|Bombardier Q400}}, a twin-engine regional turboprop with a T-tail as depicted.

The man with the hat asks Cueball to identify the airplane flying overhead. Cueball (or [[Randall]] qua the caption), who "assumes" he knows a lot about planes gives a long, nonsensical answer, proving that he does not. As mentioned in the caption he never actually checked if what he thought he knew was fact or fiction. As it turns out it is mainly fiction, but of course with some reference to real planes or vehicles. (Due to the fact the characters are drawn in silhouette it is impossible to determine whether the character with the hat is [[Black Hat]] or [[White Hat]] or some other character).

*'''Boeing''': {{w|Boeing}} is a company that designs and builds aircraft, although not the Q400. It is one of the best known Aerospace companies in the world, so putting this in front is not a way of displaying any particular knowledge of planes.
*'''Q404''': The reference to Q404 is close to the Q400, which this likely is. [[404]] also refers to an error shown when a specific internet address or file is not found, or as in this case, the plane is not found!
*'''Twin-engine''': {{w|Category:Twin-engined_aircraft|Twin-engine}} refers to aircraft with two engines, so at least Cueball got that right.
*'''Quad band''': Communication equipment that can use 4 different radio frequency bands is called {{w|quad band}}.
*'''MiG''': {{w|MiG}} is a Russian manufacturer of military aircraft, formerly the Mikoyan-and-Gurevich Design Bureau.
*'''MIG-380''': a type of welding equipment ({{w|metal inert gas}}, 380V). On the other hand {{w|A380}} is an aircraft developed by {{w|Airbus}}
*'''Hybrid''': A {{w|hybrid vehicle}} is able to use more than one distinct power source. Boeing is currently working on a [http://www.boeing.com/aboutus/environment/environment_report_14/2.3_future_flight.html concept hybrid plane] capable of using both electricity and natural gas.
*'''Dual wield''': {{w|Dual wield}}ing is using two weapons, one in each hand. It is highly unlikely that the aircraft is dual-wielded by its pilot, and it is equally ridiculous to imagine that the plane is dual-wielding anything.
*'''Mk.''': "Mk." (or Mark) is usually used to specify a model number using a Roman numeral. "Mk" is also phonetically close to {{w|Mach_number|Mach}}, a multiple of the {{w|speed of sound}}, often used to describe the speed of {{w|Supersonic_speed|supersonic}} aircraft.
*'''IVII ''': IVII is not a standard number in the {{w|Roman_numerals|Roman numeral system}}, under standard rules it would be written like VI = 6. On the other hand, it could be a mishmash way of writing "42", (IV = 4, II = 2) which could then make it a reference to the {{w|Phrases_from_The_Hitchhiker's_Guide_to_the_Galaxy#Answer_to_the_Ultimate_Question_of_Life.2C_the_Universe.2C_and_Everything_.2842.29|Answer to Life, The Universe, and Everything}} according to {{w|Douglas Adams}}' {{w|The Hitchhiker's Guide to the Galaxy}}, something referenced before in xkcd, for instance in [[1608: Hoverboard]] if you got [http://www.explainxkcd.com/wiki/images/1/1c/42_coins.PNG 42 coins]. The correct way to say 42 in Roman numerals is XLII. The number could also be MI, or 1001, but this is unlikely.
*'''Turbodiesel''': {{w|Aircraft_diesel_engine|Diesel engines}} are only rarely used in aircraft because of their low power-to-weight ratio. {{w|Turbo-diesel|Turbo-diesel}} engines are much more common in cars and trucks. A {{w|Turboprop}} is indeed a kind of aircraft propeller.
*'''797''': The {{w|Boeing 797}} has never been produced, but a hoax design has been circulating the Internet since the mid-2000's.
*'''Hydroplane''': A hydroplane either refers to {{w|aquaplaning}}, a very undesirable activity of a wheeled vehicle crossing shallow water, or a type of {{w|hydroplane (boat)|boat}} for which hydroplaning is the desired mode of travel. The correct name for planes which can land on water is {{w|seaplane}}, {{w|flying boat}} or {{w|floatplane}}, depending on construction and use, however the term ''hydroplane'' had been used in this meaning in the past; also in many languages such aircraft are named ''hydro'' (or some spelling variant of this Greek prefix) + whatever stands for ''plane'', e.g. in Spanish, Italian, Portuguese, French, Czech, Slovak, Russian and others.

In the title text the concept of hydroplane is mixed up with other concepts, none of which has anything to do with airplanes:
*'''Aquaplane''': An aquaplane is a similar to a short {{w|surfboard}}, on which a person stands while the board is pulled by a speedboat. As noted with ''Hydroplane'' above, the term ''aquaplane'' is also used as a verb to describe the loss of traction of a wheeled vehicle at speed on a surface covered in shallow water. The correct name for a plane that lands on water (on purpose) is a {{w|seaplane}}.
*'''Dam and turbines''': Powering an aircraft with a miniature {{w|hydroelectric dam}} connected to an on-board reservoir is an absurdity. Hydroelectric plants derive power from the potential energy released by a mass of water as it falls. Because the plane is lifting the water reservoir in addition to its own weight, such a dam could never produce enough power. Ludicrously small hydroelectric power systems were previously considered in [[what if?]] "{{what if|91|Faucet Power}}". In 2008, Randall discussed the more reasonable physics problem of whether an airplane would be capable of [https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/ flight from a treadmill].

Only three weeks prior to this comic, [[1660: Captain Speaking]] was released only with a drawing of a plane in the air, where the captain eventually finds out that his plane is probably a Boeing...

==Transcript==
:[Cueball and a man with a hat is seen in silhouette standing on the ground looking towards the sky. A fixed wing aircraft can be seen in the sky, also in silhouette.]
:Man with hat: What's That Airplane?
:Cueball:Oh, that's a Boeing Q404 twin-engine quad-band MIG-380 hybrid dual-wield Mk. IVII Turbodiesel 797 Hydroplane.

:[Caption below the panel:]
:I've always assumed I'm one of those people who knows a lot about planes, but I've never actually checked.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Characters with Hats]]

1669: Planespotting

2016-04-20T08:08:19Z

Rhubbarb: added cross-reference for aquaplane used as a verb

{{comic
| number = 1669
| date = April 18, 2016
| title = Planespotting
| image = planespotting.png
| titletext = No, a hydroplane doesn't land on water--that's an aquaplane. A hydroplane is a plane that gets electric power from an onboard water reservoir with a tiny dam and turbines.
}}

==Explanation==
{{incomplete|So far mainly a list. Could be listed better either bullet or in a table.}}

[[Cueball]] and a [[:Category:Characters with Hats|man with a hat]] are out '''planespotting''', or {{w|Aircraft_spotting|aircraft spotting}}, a hobby where tracking the movement of aircraft allows plane fans to see as many different types of planes as possible. A knowledgeable spotter would just by the silhouette and maybe the engine sound of the plane be able to tell what type of plane it is. (And may be rather proud of the fact, if he or she can tell this before one of the other spotters...)

The plane in the comic is most likely a {{w|Bombardier Dash 8|Bombardier Q400}}, a twin-engine regional turboprop with a T-tail as depicted.

The man with the hat asks Cueball to identify the airplane flying overhead. Cueball (or [[Randall]] qua the caption), who "assumes" he knows a lot about planes gives a long, nonsensical answer, proving that he does not. As mentioned in the caption he never actually checked if what he thought he knew was fact or fiction. As it turns out it is mainly fiction, but of course with some reference to real planes or vehicles. (Due to the fact the characters are drawn in silhouette it is impossible to determine whether the character with the hat is [[Black Hat]] or [[White Hat]] or some other character).

*'''Boeing''': {{w|Boeing}} is a company that designs and builds aircraft, although not the Q400. It is one of the best known Aerospace companies in the world, so putting this in front is not a way of displaying any particular knowledge of planes.
*'''Q404''': The reference to Q404 is close to the Q400, which this likely is. [[404]] also refers to an error shown when a specific internet address or file is not found, or as in this case, the plane is not found!
*'''Twin-engine''': {{w|Category:Twin-engined_aircraft|Twin-engine}} refers to aircraft with two engines, so at least Cueball got that right.
*'''Quad band''': Communication equipment that can use 4 different radio frequency bands is called {{w|quad band}}.
*'''MiG''': {{w|MiG}} is a Russian manufacturer of military aircraft, formerly the Mikoyan-and-Gurevich Design Bureau.
*'''MIG-380''': a type of welding equipment ({{w|metal inert gas}}, 380V). On the other hand {{w|A380}} is an aircraft developed by {{w|Airbus}}
*'''Hybrid''': A {{w|hybrid vehicle}} is able to use more than one distinct power source. Boeing is currently working on a [http://www.boeing.com/aboutus/environment/environment_report_14/2.3_future_flight.html concept hybrid plane] capable of using both electricity and natural gas.
*'''Dual wield''': {{w|Dual wield}}ing is using two weapons, one in each hand. It is highly unlikely that the aircraft is dual-wielded by its pilot, and it is equally ridiculous to imagine that the plane is dual-wielding anything.
*'''Mk.''': "Mk." (or Mark) is usually used to specify a model number using a Roman numeral. "Mk" is also phonetically close to {{w|Mach_number|Mach}}, a multiple of the speed of sound, often used to describe the speed of {{w|Supersonic_speed|supersonic}} aircraft.
*'''IVII ''': IVII is not a standard number in the {{w|Roman_numerals|Roman numeral system}}, under standard rules it would be written like VI = 6. On the other hand, it could be a mishmash way of writing "42", (IV = 4, II = 2) which could then make it a reference to the {{w|Phrases_from_The_Hitchhiker's_Guide_to_the_Galaxy#Answer_to_the_Ultimate_Question_of_Life.2C_the_Universe.2C_and_Everything_.2842.29|Answer to Life, The Universe, and Everything}} according to {{w|Douglas Adams}}' {{w|The Hitchhiker's Guide to the Galaxy}}, something referenced before in xkcd, for instance in [[1608: Hoverboard]] if you got [http://www.explainxkcd.com/wiki/images/1/1c/42_coins.PNG 42 coins]. The correct way to say 42 in Roman numerals is XLII. The number could also be MI, or 1001, but this is unlikely.
*'''Turbodiesel''': {{w|Aircraft_diesel_engine|Diesel engines}} are only rarely used in aircraft because of their low power-to-weight ratio. {{w|Turbo-diesel|Turbo-diesel}} engines are much more common in cars and trucks. A {{w|Turboprop}} is indeed a kind of aircraft propeller.
*'''797''': The {{w|Boeing 797}} has never been produced, but a hoax design has been circulating the Internet since the mid-2000's.
*'''Hydroplane''': A hydroplane either refers to {{w|aquaplaning}}, a very undesirable activity of a wheeled vehicle crossing shallow water, or a type of {{w|hydroplane (boat)|boat}} for which hydroplaning is the desired mode of travel. The correct name for planes which can land on water is {{w|seaplane}}, {{w|flying boat}} or {{w|floatplane}}, depending on construction and use, however the term ''hydroplane'' had been used in this meaning in the past; also in many languages such aircraft are named ''hydro'' (or some spelling variant of this Greek prefix) + whatever stands for ''plane'', e.g. in Spanish, Italian, Portuguese, French, Czech, Slovak, Russian and others.

In the title text the concept of hydroplane is mixed up with other concepts, none of which has anything to do with airplanes:
*'''Aquaplane''': An aquaplane is a similar to a short {{w|surfboard}}, on which a person stands while the board is pulled by a speedboat. As noted with ''Hydroplane'' above, the term ''aquaplane'' is also used as a verb to describe the loss of traction of a wheeled vehicle at speed on a surface covered in shallow water. The correct name for a plane that lands on water (on purpose) is a {{w|seaplane}}.
*'''Dam and turbines''': Powering an aircraft with a miniature {{w|hydroelectric dam}} connected to an on-board reservoir is an absurdity. Hydroelectric plants derive power from the potential energy released by a mass of water as it falls. Because the plane is lifting the water reservoir in addition to its own weight, such a dam could never produce enough power. Ludicrously small hydroelectric power systems were previously considered in [[what if?]] "{{what if|91|Faucet Power}}". In 2008, Randall discussed the more reasonable physics problem of whether an airplane would be capable of [https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/ flight from a treadmill].

Only three weeks prior to this comic, [[1660: Captain Speaking]] was released only with a drawing of a plane in the air, where the captain eventually finds out that his plane is probably a Boeing...

==Transcript==
:[Cueball and a man with a hat is seen in silhouette standing on the ground looking towards the sky. A fixed wing aircraft can be seen in the sky, also in silhouette.]
:Man with hat: What's That Airplane?
:Cueball:Oh, that's a Boeing Q404 twin-engine quad-band MIG-380 hybrid dual-wield Mk. IVII Turbodiesel 797 Hydroplane.

:[Caption below the panel:]
:I've always assumed I'm one of those people who knows a lot about planes, but I've never actually checked.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Characters with Hats]]

1669: Planespotting

2016-04-20T07:58:55Z

Rhubbarb: added note on the phonetic similarity between Mk and Mach

{{comic
| number = 1669
| date = April 18, 2016
| title = Planespotting
| image = planespotting.png
| titletext = No, a hydroplane doesn't land on water--that's an aquaplane. A hydroplane is a plane that gets electric power from an onboard water reservoir with a tiny dam and turbines.
}}

==Explanation==
{{incomplete|So far mainly a list. Could be listed better either bullet or in a table.}}

[[Cueball]] and a [[:Category:Characters with Hats|man with a hat]] are out '''planespotting''', or {{w|Aircraft_spotting|aircraft spotting}}, a hobby where tracking the movement of aircraft allows plane fans to see as many different types of planes as possible. A knowledgeable spotter would just by the silhouette and maybe the engine sound of the plane be able to tell what type of plane it is. (And may be rather proud of the fact, if he or she can tell this before one of the other spotters...)

The plane in the comic is most likely a {{w|Bombardier Dash 8|Bombardier Q400}}, a twin-engine regional turboprop with a T-tail as depicted.

The man with the hat asks Cueball to identify the airplane flying overhead. Cueball (or [[Randall]] qua the caption), who "assumes" he knows a lot about planes gives a long, nonsensical answer, proving that he does not. As mentioned in the caption he never actually checked if what he thought he knew was fact or fiction. As it turns out it is mainly fiction, but of course with some reference to real planes or vehicles. (Due to the fact the characters are drawn in silhouette it is impossible to determine whether the character with the hat is [[Black Hat]] or [[White Hat]] or some other character).

*'''Boeing''': {{w|Boeing}} is a company that designs and builds aircraft, although not the Q400. It is one of the best known Aerospace companies in the world, so putting this in front is not a way of displaying any particular knowledge of planes.
*'''Q404''': The reference to Q404 is close to the Q400, which this likely is. [[404]] also refers to an error shown when a specific internet address or file is not found, or as in this case, the plane is not found!
*'''Twin-engine''': {{w|Category:Twin-engined_aircraft|Twin-engine}} refers to aircraft with two engines, so at least Cueball got that right.
*'''Quad band''': Communication equipment that can use 4 different radio frequency bands is called {{w|quad band}}.
*'''MiG''': {{w|MiG}} is a Russian manufacturer of military aircraft, formerly the Mikoyan-and-Gurevich Design Bureau.
*'''MIG-380''': a type of welding equipment ({{w|metal inert gas}}, 380V). On the other hand {{w|A380}} is an aircraft developed by {{w|Airbus}}
*'''Hybrid''': A {{w|hybrid vehicle}} is able to use more than one distinct power source. Boeing is currently working on a [http://www.boeing.com/aboutus/environment/environment_report_14/2.3_future_flight.html concept hybrid plane] capable of using both electricity and natural gas.
*'''Dual wield''': {{w|Dual wield}}ing is using two weapons, one in each hand. It is highly unlikely that the aircraft is dual-wielded by its pilot, and it is equally ridiculous to imagine that the plane is dual-wielding anything.
*'''Mk.''': "Mk." (or Mark) is usually used to specify a model number using a Roman numeral. "Mk" is also phonetically close to {{w|Mach_number|Mach}}, a multiple of the speed of sound, often used to describe the speed of {{w|Supersonic_speed|supersonic}} aircraft.
*'''IVII ''': IVII is not a standard number in the {{w|Roman_numerals|Roman numeral system}}, under standard rules it would be written like VI = 6. On the other hand, it could be a mishmash way of writing "42", (IV = 4, II = 2) which could then make it a reference to the {{w|Phrases_from_The_Hitchhiker's_Guide_to_the_Galaxy#Answer_to_the_Ultimate_Question_of_Life.2C_the_Universe.2C_and_Everything_.2842.29|Answer to Life, The Universe, and Everything}} according to {{w|Douglas Adams}}' {{w|The Hitchhiker's Guide to the Galaxy}}, something referenced before in xkcd, for instance in [[1608: Hoverboard]] if you got [http://www.explainxkcd.com/wiki/images/1/1c/42_coins.PNG 42 coins]. The correct way to say 42 in Roman numerals is XLII. The number could also be MI, or 1001, but this is unlikely.
*'''Turbodiesel''': {{w|Aircraft_diesel_engine|Diesel engines}} are only rarely used in aircraft because of their low power-to-weight ratio. {{w|Turbo-diesel|Turbo-diesel}} engines are much more common in cars and trucks. A {{w|Turboprop}} is indeed a kind of aircraft propeller.
*'''797''': The {{w|Boeing 797}} has never been produced, but a hoax design has been circulating the Internet since the mid-2000's.
*'''Hydroplane''': A hydroplane either refers to {{w|aquaplaning}}, a very undesirable activity of a wheeled vehicle crossing shallow water, or a type of {{w|hydroplane (boat)|boat}} for which hydroplaning is the desired mode of travel. The correct name for planes which can land on water is {{w|seaplane}}, {{w|flying boat}} or {{w|floatplane}}, depending on construction and use, however the term ''hydroplane'' had been used in this meaning in the past; also in many languages such aircraft are named ''hydro'' (or some spelling variant of this Greek prefix) + whatever stands for ''plane'', e.g. in Spanish, Italian, Portuguese, French, Czech, Slovak, Russian and others.

In the title text the concept of hydroplane is mixed up with other concepts, none of which has anything to do with airplanes:
*'''Aquaplane''': An aquaplane is a similar to a short {{w|surfboard}}, on which a person stands while the board is pulled by a speedboat. The correct name for a plane that lands on water (on purpose) is a {{w|seaplane}}.
*'''Dam and turbines''': Powering an aircraft with a miniature {{w|hydroelectric dam}} connected to an on-board reservoir is an absurdity. Hydroelectric plants derive power from the potential energy released by a mass of water as it falls. Because the plane is lifting the water reservoir in addition to its own weight, such a dam could never produce enough power. Ludicrously small hydroelectric power systems were previously considered in [[what if?]] "{{what if|91|Faucet Power}}". In 2008, Randall discussed the more reasonable physics problem of whether an airplane would be capable of [https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/ flight from a treadmill].

Only three weeks prior to this comic, [[1660: Captain Speaking]] was released only with a drawing of a plane in the air, where the captain eventually finds out that his plane is probably a Boeing...

==Transcript==
:[Cueball and a man with a hat is seen in silhouette standing on the ground looking towards the sky. A fixed wing aircraft can be seen in the sky, also in silhouette.]
:Man with hat: What's That Airplane?
:Cueball:Oh, that's a Boeing Q404 twin-engine quad-band MIG-380 hybrid dual-wield Mk. IVII Turbodiesel 797 Hydroplane.

:[Caption below the panel:]
:I've always assumed I'm one of those people who knows a lot about planes, but I've never actually checked.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Characters with Hats]]

1375: Astronaut Vandalism

2014-05-30T22:52:46Z

Rhubbarb: Partial undo and edit overenthusiastic cleanup (revision 68559); reverted deletions but retained the improved organisation

{{comic
| number = 1375
| date = May 30, 2014
| title = Astronaut Vandalism
| image = astronaut_vandalism.png
| titletext = That night, retired USAF pilots covertly replaced the '62' with '50'.
}}

==Explanation==
Signs like this normally show the distance to places on earth's surface. This sign also has an arrow pointing away from earth and towards "space", with a distance of 62 miles (100 km), due to "astronaut vandalism".

We think of Space as being so very far away. This comic puts into perspective that it's really a lot closer to get to Space than to many destinations we're used to getting to by car or airplane. We think of 62 miles as being an easy trip on the ground, but that same 62 miles is incredibly hard when going vertically, against the force of gravity. Distance-wise, however, it's the same.

The title text states that the distance to "space" was changed later from 62 miles (100 km) to 50 miles (80 km) by retired Air Force pilots. This indicates that the pilots wanted to reduce the altitude considered to be "space", so that their own high altitude flights could be considered space flights.

The {{W|U.S. Air Force|USAF}} will award {{W|astronaut wings}} to rated astronauts who fly higher than 50 miles, while the {{W|World Air Sports Federation}} (FAI) in the mid 1950s designated the 100-kilometer {{W|Karman Line}} (62 miles) as the official boundary between the {{W|Earth's atmosphere}} and {{W|outer space}}. So for some pilots in the 1960s it was enough to fly above 50 miles to earn the wings and eight pilots on the {{w|X-15|X-15 Program}} earned them like this. This explains why it was retired pilots who changed the sign - so their wings would still be valid.

There may be an Elvis aspect to this comic. The mileages are approximately consistent with the signs being in Tupelo, Mississippi, birthplace of Elvis Presley. Tupelo is about 100 miles from Graceland (Elvis' home) in Memphis, Tennessee. Tupelo is also a bit over a hundred miles from the International Rock-A-Billy Hall of Fame in Jackson, Tennessee. The mileages given by Google maps, however, don't exactly match the mileages on the sign in the comic. Instead of 98 & 115 (in the comic), Google maps gives 101 & 104.

Another possible explanation is a simple mixup. {{W|Winona, Mississippi}} is the hometown of astronaut {{W|Donald H. Peterson}}, who is a retired Air Force officer and pilot, and served as an astronaut in the early Shuttle program. From Winona, it is 115 miles to Memphis International Airport, and 98 miles to Jackson-Medgar Wiley Evers International Airport ([http://www.travelmath.com/nearest-airport/Winona,+MS source]). Thus, the sign would be reasonably located in Winona, albeit with an error, and Peterson would have vandalized it (and some visiting USAF buddy of his could change it back).

The road from Jackson to Memphis is I-55 (northwards); the distance (according to [https://maps.google.co.uk/maps?saddr=jackson&daddr=memphis&hl=en&sll=33.137551,-89.802246&sspn=8.955085,10.338135&geocode=FQXX7AEdluOf-ikhG3SQfysohjGgOPBB5M0TBw%3BFd5WGAIdLPah-ilFl0PqHn7VhzH-thpgFfOT0Q&t=h&mra=ls&z=8 Google Maps]) is 210 miles. That 98+115=213 may indicate that the location is 3 miles off I-55. There is a place called "Pace" near Cleveland which is around 79 miles from Winona. The "astronaut vandalism" may have been to prefix "Pace" with an "s" to form "sPace", and then to rotate the sign. The spacing on the signs in the cartoon is consistent with the idea that the "s" was added; it is a little cramped. The "P" of "space", "M" of "Memphis" and "J" of "Jackson" are perhaps a little larger than the other letters, indicating that those might have been the original initial majuscule letters.

Based purely on the mileages, it is most likely that the sign is located in or near Grenada, MS. This makes the mileages nearly correct when using US-51 as opposed to I-55 to get to Memphis and Jackson, and also is about 62 miles from Pace, MS via Mississippi Route 8. It is unlikely, however, that a sign in Grenada would include the mileage to such a small town as Pace from such a great distance. Cleveland would be a much more useful control city for motorists. Additionally, since the viewer is looking east, Pace would be behind the viewer. Assuming the one doing the vandalism did more than simply turn and add a letter to the sign, it is possible that they also detached it from the southbound-side of the pole (where it could be viewed pointing to the west) and reattached it to the eastbound side, as shown here.

==Transcript==
:[A signpost with three arrows.]
:[Arrow pointing up:]
:Space 62
:[Arrow pointing right:]
:Jackson 115
:[Arrow pointing left:]
:Memphis 98

==Trivia==
*See [http://www.slate.com/articles/news_and_politics/explainer/2004/09/where_does_space_begin.html Slate: Where does space begin?] for more background.
*This comic was published on the same day that Version 2 of the {{w|Dragon (spacecraft)|Dragon spaceship}} was unveiled.
*The Memphis mileage may be a reference to {{W|Windows 98}}, which was internally codenamed Memphis whilst in development at {{W|Microsoft}}.

{{comic discussion}}

1375: Astronaut Vandalism

2014-05-30T13:00:40Z

Rhubbarb: Interstate 55 not Route 55

{{comic
| number = 1375
| date = May 30, 2014
| title = Astronaut Vandalism
| image = astronaut_vandalism.png
| titletext = That night, retired USAF pilots covertly replaced the '62' with '50'.
}}

==Explanation==
Signs like this normally show the distance to places on earth's surface. This sign also has an arrow pointing away from earth and towards "space", with a distance of 62 miles (100 km), due to "astronaut vandalism". The title text states that the distance to "space" was changed later from 62 miles (100 km) to 50 miles (80 km) by retired Air Force pilots. This indicates that the pilots wanted to reduce the altitude considered to be "space", so that their own high altitude flights could be considered space flights.

The {{W|U.S. Air Force}} will award {{W|astronaut wings}} to rated officers who fly higher than 62 miles as {{W|World Air Sports Federation}} (FAI) in the mid 1950s designated the 100-kilometer {{W|Karman Line}} (62 miles) as the official boundary between the {{W|Earth's atmosphere}} and {{W|outer space}}. In the 1960s, however, after the FAI defined space at 100 km, it was enough to fly above 50 miles to earn the wings and seven pilots earned them like this. This explain why it was retired pilots who changed the sign - so their wings would still be valid.

Useful summary: [http://www.slate.com/articles/news_and_politics/explainer/2004/09/where_does_space_begin.html Slate: Where does space begin?]

This comic was published on the same day that Version 2 of the [http://en.wikipedia.org/wiki/Dragon_(spacecraft) Dragon spaceship] was unveiled.

There may be an Elvis aspect to this comic. The mileages are approximately consistent with the signs being in Tupelo, Mississippi, birthplace of Elvis Presley. Tupelo is about 100 miles from Graceland (Elvis' home) in Memphis, Tennessee. Tupelo is also a bit over a hundred miles from the International Rock-A-Billy Hall of Fame in Jackson, Tennessee. The mileages given by Google maps, however, don't exactly match the mileages on the sign in the comic. Instead of 98 & 115 (in the comic), Google maps gives 101 & 104.

Another possible explanation is a simple mixup. {{W|Winona, Mississippi}} is the hometown of astronaut {{W|Donald H. Peterson}}, who is a retired Air Force officer and pilot, and served as an astronaut in the early Shuttle program. From Winona, it is 115 miles to Memphis International Airport, and 98 miles to Jackson-Medgar Wiley Evers International Airport ([http://www.travelmath.com/nearest-airport/Winona,+MS source]). Thus, the sign would be reasonably located in Winona, albeit with an error, and Peterson would have vandalized it (and some visiting USAF buddy of his could change it back).

The road from Jackson to Memphis is I-55 (northwards); the distance (according to [https://maps.google.co.uk/maps?saddr=jackson&daddr=memphis&hl=en&sll=33.137551,-89.802246&sspn=8.955085,10.338135&geocode=FQXX7AEdluOf-ikhG3SQfysohjGgOPBB5M0TBw%3BFd5WGAIdLPah-ilFl0PqHn7VhzH-thpgFfOT0Q&t=h&mra=ls&z=8 Google Maps]) is 210 miles. That 98+115=213 may indicate that the location is 3 miles off I-55. There is a place called "Pace" near Cleveland which is around 79 miles from Winona. The "astronaut vandalism" may have been to prefix "Pace" with an "s" to form "sPace", and then to rotate the sign. The spacing on the signs in the cartoon is consistent with the idea that the "s" was added; it is a little cramped. The "P" of "space", "M" of "Memphis" and "J" of "Jackson" are perhaps a little larger than the other letters, indicating that those might have been the original initial majuscule letters.

The Memphis mileage may be a reference to {{W|Windows 98}}, which was internally codenamed Memphis whilst in development at {{W|Microsoft}}.

==Transcript==
:[A signpost with three arrows.]
:[Arrow pointing up:]
:Space 62
:[Arrow pointing right:]
:Jackson 115
:[Arrow pointing left:]
:Memphis 98

{{comic discussion}}

1375: Astronaut Vandalism

2014-05-30T12:52:11Z

Rhubbarb: A PLACE called PACE

{{comic
| number = 1375
| date = May 30, 2014
| title = Astronaut Vandalism
| image = astronaut_vandalism.png
| titletext = That night, retired USAF pilots covertly replaced the '62' with '50'.
}}

==Explanation==
Signs like this normally show the distance to places on earth's surface. This sign also has an arrow pointing away from earth and towards "space", with a distance of 62 miles (100 km), due to "astronaut vandalism". The title text states that the distance to "space" was changed later from 62 miles (100 km) to 50 miles (80 km) by retired Air Force pilots. This indicates that the pilots wanted to reduce the altitude considered to be "space", so that their own high altitude flights could be considered space flights.

The {{W|U.S. Air Force}} will award {{W|astronaut wings}} to rated officers who fly higher than 62 miles as {{W|World Air Sports Federation}} (FAI) in the mid 1950s designated the 100-kilometer {{W|Karman Line}} (62 miles) as the official boundary between the {{W|Earth's atmosphere}} and {{W|outer space}}. In the 1960s, however, after the FAI defined space at 100 km, it was enough to fly above 50 miles to earn the wings and seven pilots earned them like this. This explain why it was retired pilots who changed the sign - so their wings would still be valid.

Useful summary: [http://www.slate.com/articles/news_and_politics/explainer/2004/09/where_does_space_begin.html Slate: Where does space begin?]

This comic was published on the same day that Version 2 of the [http://en.wikipedia.org/wiki/Dragon_(spacecraft) Dragon spaceship] was unveiled.

There may be an Elvis aspect to this comic. The mileages are approximately consistent with the signs being in Tupelo, Mississippi, birthplace of Elvis Presley. Tupelo is about 100 miles from Graceland (Elvis' home) in Memphis, Tennessee. Tupelo is also a bit over a hundred miles from the International Rock-A-Billy Hall of Fame in Jackson, Tennessee. The mileages given by Google maps, however, don't exactly match the mileages on the sign in the comic. Instead of 98 & 115 (in the comic), Google maps gives 101 & 104.

Another possible explanation is a simple mixup. {{W|Winona, Mississippi}} is the hometown of astronaut {{W|Donald H. Peterson}}, who is a retired Air Force officer and pilot, and served as an astronaut in the early Shuttle program. From Winona, it is 115 miles to Memphis International Airport, and 98 miles to Jackson-Medgar Wiley Evers International Airport ([http://www.travelmath.com/nearest-airport/Winona,+MS source]). Thus, the sign would be reasonably located in Winona, albeit with an error, and Peterson would have vandalized it (and some visiting USAF buddy of his could change it back).

The road from Jackson to Memphis is Route 55 (northwards); the distance (according to [https://maps.google.co.uk/maps?saddr=jackson&daddr=memphis&hl=en&sll=33.137551,-89.802246&sspn=8.955085,10.338135&geocode=FQXX7AEdluOf-ikhG3SQfysohjGgOPBB5M0TBw%3BFd5WGAIdLPah-ilFl0PqHn7VhzH-thpgFfOT0Q&t=h&mra=ls&z=8 Google Maps]) is 210 miles. That 98+115=213 may indicate that the location is 3 miles off Route 55. There is a place called "Pace" near Cleveland which is around 79 miles from Winona. The "astronaut vandalism" may have been to prefix "Pace" with an "s" to form "sPace", and then to rotate the sign. The spacing on the signs in the cartoon is consistent with the idea that the "s" was added; it is a little cramped. The "P" of "space", "M" of "Memphis" and "J" of "Jackson" are perhaps a little larger than the other letters, indicating that those might have been the original initial majuscule letters.

The Memphis mileage may be a reference to {{W|Windows 98}}, which was internally codenamed Memphis whilst in development at {{W|Microsoft}}.

==Transcript==
:[A signpost with three arrows.]
:[Arrow pointing up:]
:Space 62
:[Arrow pointing right:]
:Jackson 115
:[Arrow pointing left:]
:Memphis 98

{{comic discussion}}