explain xkcd - User contributions [en]

Talk:2484: H-alpha

2021-07-05T13:10:44Z

172.68.110.116:

I think the first company that got really mad was Goodyear, because they're famous for using blimps.

- unsigned comment

===Additional detail===
A H(ydrogen)-Alpha filter is a special lens used for viewing the {{w|H-alpha|Hydrogen-Alpha}} wavelength of light through telescopic or photographic devices. It works by filtering out all wavelengths of light except the red spectral line associated with hydrogen. This is commonly used to see shape and structure of objects that emit said light (namely, our own sun, and various nebulae as mentioned in the text).

Many earlier designs for {{w|airship|airships}} (including the ill-fated {{w|LZ_129_Hindenburg|Hindenburg}}) used (highly flammable) hydrogen gas for lift due to both its lower cost and higher availability. After the Hindenburg disaster designers switched exclusively to helium or heated air for lift.
I
The Hindenberg was supposed to be using Helium, but the USA was the prime producer at that time and for some reason refused to supply Germany at the time. This forced the use of Hydrogen, with the regrettable result. Choice of exterior paint, the gas 'bag' design being too permeable and lack of earthing were also factors. [[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 20:27, 3 July 2021 (UTC)

{{w|MetLife|Metropolitan Life Insurance Company}} (AKA MetLife) is an insurance company that licensed the Peanuts characters, In particular, Snoopy in their advertising. They featured the {{w|Snoopy}} character in his alter-ego role of World War I Fighter Ace (which frequently fought with the Red Baron in the Charles Schulz comics) in both print and television ads between 1985 and 2016, and most notably pictured on some of their advertising blimps.

[[Special:Contributions/162.158.142.160|162.158.142.160]] 06:29, 3 July 2021 (UTC) Not the Red Baron

Many nebulae contain excited hydrogen atoms emitting the Hα wavelength, so a Hα filter is useful for removing other light such as light pollution, making nebulae stand out in photographs.

In most cases when a sun filter is mentioned, it's probably a white-light filter that only reduces the light intensity. A Hα filter is used to highlight the sun's chromosphere – the layer above the sun's apparent "surface", the photosphere.

I'm not sure whether the same filters are actually used for photographing both the sun and nebulae.

[[Special:Contributions/162.158.183.220|162.158.183.220]] 11:52, 3 July 2021 (UTC)

I think someone should edit the summary to detail two points: One, that blimps are not the same as zeppelins. The latter has a rigid body and tanks of gas, rather than the former's balloon body. And two, airships such as the Hindenburg were never designed to be flown using hydrogen; it would have continued to use helium on that one fateful flight if it had not been for a trade embargo on Germany for the gas from its largest supplier, the United States.

I don't believe blimps have really ever been flown with hydrogen, but someone who knows better should add it.
[[Special:Contributions/172.69.142.62|172.69.142.62]] 20:02, 4 July 2021 (UTC)

About the Warning: i don't think that a filter has the ability, to hurt anyone. Therefore it should be rephrased, that the remaining sunlight will still hurt you eyes.
[[Special:Contributions/172.68.110.116|172.68.110.116]] 13:10, 5 July 2021 (UTC)

2480: No, The Other One

2021-06-24T05:19:00Z

172.68.110.116: /* Explanation */

{{comic
| number = 2480
| date = June 23, 2021
| title = No, The Other One
| image = no_the_other_one.png
| titletext = Key West, Virginia is not to be confused with Key, West Virginia.
}}

==Explanation==
{{incomplete|Created by HOUSTON. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

This is a map of the United States, showing cities or towns with the same name as other more famous cities. For example, the map has a dot for a place called Los Angeles in Texas, not to be confused with Los Angeles, California.

Few place names are unique, and there may be {{w|List of the most common U.S. place names|many places with the same name}}. However, names can become associated with specific places on a national level, where the best-known example is usually the biggest or otherwise the most significant. The name of this comic indicates the contextualization required to specify one of the less-famous exemplars of a given name. Someone might say they are from "Los Angeles" and would have to say "no, the other one" since the listener would assume they are from Los Angeles, California.

The [[title text]] references {{w|Key, West Virginia}} and {{w|Key West, Virginia}}, two places that, when spoken aloud, are only distinguishable by the pause (comma) location. Neither are to be confused with {{w|Key West|Key West, Florida}}.

{| class="wikitable"
|-
! Place name in comic
! Well-known place
! Notes
|-
| {{w|Albany, Georgia}}
| rowspan="3" | {{w|Albany,_New_York|Albany, New York}}
| rowspan="3" | Albany is the capital of New York state.
|-
| {{w|Albany, Minnesota}}


|-
| {{w|Albany, Wyoming}}

|-
| {{w|Alexandria,_Louisiana|Alexandria, Louisiana}}
| {{w|Alexandria,_Virginia|Alexandria, Virginia}}
| Alexandria, VA is known for being George Washington's hometown. It is not named after {{w|Alexandria|Alexandria, Egypt}}.
|-
| {{w|Anchorage, Kentucky}}
| {{w|Anchorage,_Alaska|Anchorage, Alaska}}
| Anchorage is Alaska's most populous city.
|-
| {{w|Atlanta,_Delaware|Atlanta, DE}}
| rowspan="6" | {{w|Atlanta|Atlanta, Georgia}}
| rowspan="6" | Atlanta is the capital of Georgia, a center of the civil rights movement in the 1950's and 60's, and a major air transportation hub.
|-
| {{w|Atlanta,_Michigan|Atlanta, MI}}

|-
| {{w|Atlanta,_Idaho|Atlanta, ID}}

|-
| {{w|Atlanta,_Nebraska|Atlanta, NE}}

|-
| {{w|Atlanta, Texas|Atlanta, TX}}
|
|
|-
| {{w|Atlanta, Wisconsin|Atlanta, WI}}
|
|
|-
| {{w|Atlantic City, Wyoming|Atlantic City, WY}}
| {{w|Atlantic City, New Jersey}}
| Atlantic City, NJ is a famous coastal resort town in New Jersey known for its casinos, boardwalk and beaches.
|-
| {{w|Austin, MN}}
| {{w|Austin, Texas}}
| Austin is the capital of the state of Texas, and the 11th largest city (by population) in the US.
|-
| {{w|Baton Rouge, South Carolina|Baton Rouge, SC}}
| {{w|Baton Rouge, Louisiana}}
| Baton Rouge is the capital of the state of Louisiana.
|-
| {{w|Beaumont, California|Beaumont, CA}}
| {{w|Beaumont, Texas|Beaumont, TX}}
| Beaumont is best known for the oil discovery that sparked the Texas oil boom of the early 1900s.
|-
| {{w|Beverly Hills, Illinois|Beverly Hills, IL}}
| rowspan="2" | {{w|Beverly Hills, California|Beverly Hills, CA}}
| rowspan="2" | Beverly Hills is a city in Los Angeles County, CA and is home to many celebrities, luxury hotels, and the Rodeo Drive shopping district.
|-
| {{w|Beverly Hills, Texas|Beverly Hills, TX}}

|-
| {{w|Bloomington, Minnesota | Bloomington, MN}}
| {{w|Bloomington, Indiana | Bloomington, IN}}
| Bloomington is the location of Indiana University.
|-
| Boston, MO
| {{w|Boston|Boston, MA}}
| Boston is the capital of Massachusetts and the scene of several key events of the American Revolution.
|-
| Bowling Green, FL
| rowspan="2" | {{w|Bowling Green, Kentucky|Bowling Green, KY}}
| rowspan="2" | Bowling Green, KY is the largest city of this name, and the 3rd most populous city in Kentucky.
|-
| Bowling Green, OH
|-
| Bridgeport, WV
| {{w|Bridgeport, Connecticut|Bridgeport, CT}}
| Bridgeport is the most populous city in Connecticut and fifth most populous in {{w|New England}}.
|-
| Buffalo, TX
| rowspan="2" | {{w|Buffalo, New York|Buffalo, NY}}
| rowspan="2" |
|-
| Buffalo, WY
|-
| Cambridge, OH
| {{w|Cambridge, Massachusetts|Cambridge, MA}}
| Cambridge, Massachusetts is a city in the Boston metropolitan area known as the home of {{w|Harvard University}} and {{w|Massachusetts Institute of Technology}} among others.
|-
| Cedar Rapids, NE
| {{w|Cedar Rapids, Iowa|Cedar Rapids, IA}}
|
|-
| Charlestown, NY (?)
|
|
|-
| Cleveland, UT
| {{w|Cleveland|Cleveland, OH}}
|
|-
| Columbus, GA
| {{w|Columbus, Ohio|Columbus, OH}}
|
|-
| Dallas, GA
| rowspan="4" | {{w|Dallas|Dallas, TX}}
| rowspan="4" |
|-
| Dallas, NC
|-
| Dallas, OR
|-
| Dallas, SD
|-
| Dayton, NV
| {{w|Dayton, Ohio|Dayton, OH}}
|
|-
| Des Moines, NM
| rowspan="2" | {{w|Des Moines, Iowa|Des Moines, IA}}
| rowspan="2" |
|-
| Des Moines, WA
|-
| {{w|Detroit,_Alabama|Detroit, AL}}
| rowspan="2" | {{w|Detroit|Detroit, MI}}
| rowspan="2" | Detroit is best known as the center of the U.S. automobile industry.
|-
| Detroit, KS
|-
| Disney, OK
|
|
|-
| Fayetteville, TN
|
|
|-
| Gettysburg, OH
| rowspan="2" | {{w|Gettysburg, Pennsylvania|Gettysburg, PA}}
| rowspan="2" |
|-
| Gettysburg, SD
|-
| Grand Rapids, MN
| {{w|Grand Rapids|Grand Rapids, MI}}
| The second most populous city in the state of Michigan
|-
| {{w|Houston,_Alaska|Houston, AK}}
| rowspan="6" | {{w|Houston|Houston, TX}}
| rowspan="6" | Houston is the most populous city in Texas and the fourth-most populous in the United States.
|-
| {{w|Houston,_Alabama|Houston, AL}}
|-
| Houston, FL
|-
| Houston, IN
|-
| Houston, MO
|-
| Houston, OH
|-
| Indianapolis, IA
| {{w|Indianapolis|Indianapolis, IN}}
|
|-
| {{w|Jackson,_Alabama|Jackson, AL}}
| {{w|Jackson,_Mississippi|Jackson, MS}}
| Jackson is the capital of Mississippi, but there are {{w|Jackson|many other}} states with Jacksons. This one is likely particularly notable due to its proximity to Jackson, MS.
|-
| {{w|Jamestown,_California|Jamestown, CA}}
| rowspan="2" | {{w|Jamestown,_Virginia|Jamestown, VA}}
| rowspan="2" | Jamestown was the first permanent English settlement in the Americas.
|-
| Jamestown, ND
|-
| Jersey Shore, PA
|
|
|-
| Key West, VA
|
|
|-
| Knoxville, IA
|
|
|-
| Las Vegas, NM
|
|
|-
| {{w|Lincoln,_California|Lincoln, CA}}
| rowspan="4" | {{w|Lincoln,_Nebraska|Lincoln, NE}}
| rowspan="4" | Lincoln is the capital of Nebraska.
|-
| Lincoln, IL
|-
| Lincoln, MT
|-
| Lincoln, RI
|-
| Lisbon, ME
| rowspan="2" | {{w|Lisbon,_Portugal|Lisbon, Portugal}}
| rowspan="2" | Lisbon is the capital of Portugal, in Europe
|-
| Lisbon, NH
|-
| Long Beach, NJ
|
|
|-
| Los Angeles, TX
|
|
|-
| {{w|Louisville, Colorado|Louisville, CO}}
| {{w|Louisville, Kentucky|Louisville, KY}}
| Louisville is the largest city in Kentucky
|-
| Manhattan, KS
| rowspan="2" |
| rowspan="2" |
|-
| Manhattan, MT
|-
| Memphis, NE
|
|
|-
| {{w|Mesa,_California|Mesa, CA}}
| rowspan="2" | {{w|Mesa,_Arizona|Mesa, AZ}}
| rowspan="2" | Mesa is a suburb of Phoenix, and the largest suburban city by population in the United States.
|-
| Mesa, CO
|-
| {{w|Miami,_Arizona|Miami, AZ}}
| rowspan="2" | {{w|Miami|Miami, FL}}
| rowspan="2" | Miami is the seventh largest city in the United States and a major tourism hub.
|-
| Miami, TX
|-
| Mountain View, HI
| Mountain View, CA
|
|-
| {{w|Nashville,_Arkansas|Nashville, AR}}
| {{w|Nashville,_Tennessee|Nashville, TN}}
| Nashville is the capital of Tennessee and a major center for the country music industry.
|-
| New England, ND
|
|
|-
| New Haven, KY
| {{w|New Haven, Connecticut|New Haven, CT}}
| New Haven is the second largest city in Connecticut, and is known for its distinctive {{w|New Haven-style pizza|pizza}}. It also home to {{w|Yale University}}
|-
| New York, TX
|
|
|-
| Newark, DE
|
|
|-
| North Pole, NY
| {{w|North_Pole|North Pole}}
| North pole is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface.
|-
| Oakland, OR
|
|
|-
| Orlando, OK
|
|
|-
| Ottawa, KS
| {{w|Ottawa| Ottawa, Ontario, Canada}}
| Ottawa is the capital of Canada
|-
| Pasadena, MD
| rowspan="2" | {{w| Pasadena, CA}}
| rowspan="2" | Pasadena, California is the home of {{w|California Institute of Technology}} and the NASA {{w|Jet Propulsion Laboratory}}
|-
| Pasadena, TX
|-
| {{w|Peoria,_Arizona|Peoria, AZ}}
| {{w|Peoria, Illinois|Peoria, IL}}
| Peoria is known for being considered an "Average American Town", in the phrase {{w|Will_it_play_in_Peoria%3F|"Will it play in Peoria?"}} It is actually smaller than Peoria, AZ.
|-
| Philadelphia, MS
| rowspan="2" |
| rowspan="2" |
|-
| Philadelphia, NY
|-
| Phoenix, MD (?)
| rowspan="2" |
| rowspan="2" |
|-
| Phoenix, OR
|-
| {{w|Plano,_Illinois|Plano, IL}}
| {{w|Plano,_Texas|Plano, TX}}
| Plano is part of the {{w|Dallas–Fort_Worth_metroplex|Dallas-Fort Worth metroplex}}, and the home of many corporate headquarters.
|-
| {{w|Plymouth,_California|Plymouth, CA}}
| rowspan="2" | {{w|Plymouth,_Massachusetts|Plymouth, MA}}
| rowspan="2" | Plymouth was the site of the colony founded in 1620 by the Mayflower Pilgrims.
|-
| Plymouth, IN
|-
| {{w|Portland,_Maine|Portland, ME}}
| {{w|Portland,_Oregon|Portland, OR}}
| Portland, OR was {{w|Portland,_Oregon#Establishment|named after}} Portland, ME
|-
| Princeton, ID
| rowspan="2" | {{w|Princeton, New Jersey}}
| rowspan="2" | Princeton, NJ is famous for being the home of the eponymous {{w|Princeton University}} and the {{w|Institute for Advanced Study}}
|-
| Princeton, MA
|-
| {{w|Richmond, Vermont}}
| {{w|Richmond, Virginia}}
| The Virginian Richmond was named after {{w|Richmond,_London|the suburb of London, UK}} due to an observed similarity of the river. London's Richmond was named for the palace built there by Henry VII, itself named after the {{w|Richmond,_North_Yorkshire|market town}} and castle in the north of England that was a childhood home. That was in turn named for the {{w|Richemont,_Seine-Maritime|Normandy}} area from which the noble family came who were gifted this land for their part of the Norman Conquest of England in the 11th century. There are more than fifty settlements called Richmond across the world, directly or indirectly taking their names from one or other of the English 'originals'.
|-
| Roswell, GA
|
|
|-
| Saint Louis, MI
| rowspan="2" |
| rowspan="2" |
|-
| Saint Louis, OK
|-
| Salem, CT
|
|
|-
| San Diego, TX
|
|
|-
| Santa Fe, TX
|
|
|-
| Savannah, MO
|
|
|-
| South Bend, TX
|
|
|-
| Texas, NY
| State of Texas
| Located in Mexico township, NY. North of the village of Mexico. No plans for a wall.
|-
| Vienna, ME
| {{w|Vienna, Austria}}
| Vienna ist the capitol and largest city of Austria
|-
| Washington, NC
|
|
|-
| White House, TN
|
|
|}

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

{{comic discussion}}
[[Category:US maps]]

2465: Dimensional Chess

2021-05-21T14:51:47Z

172.68.110.116: Making the number of dimensions more clear

{{comic
| number = 2465
| date = May 19, 2021
| title = Dimensional Chess
| image = dimensional_chess.png
| titletext = In Dimensional Chess, every move is annotated '?!'.
}}

==Explanation==
{{incomplete|Created by a N-DIMENSIONAL CHESSBOARD. Needs an explanation of what is seen on the board, both including the pieces that are visible on the higher dimensional boards as well as the empty squares seen on some positions. Do NOT delete this tag too soon.}}

Being good at {{w|chess}} is often regarded as a sign of high intelligence. A skilled player must be able to consider possibilities several moves in advance, which can be represented as an exponentially growing tree of possibilities. The {{w|branching factor}} of chess, the approximate number of legal moves available at any given time, is about thirty-five, although most players (human and computer) will use heuristics to prune the trees to regard only likely or promising moves. Expanding the playing field by generalizing to {{w|three-dimensional chess}} (or beyond) will increase the branching factor even further, and so someone who is able to competently play three-dimensional chess could be regarded as even more intelligent than someone who can only play two-dimensional chess. Making chess into an N-dimensional game thus makes it arbitrarily more difficult, even before Randall's addition of non-uniform dimensionality of the board.

Regarding Randall's rule that "every row has one more dimension than the one behind it," it is easiest to see how this is applied with the first two rows on each end. The first row on each end is a like a row on a traditional two-dimensional chess board (albeit played with three-dimensional pieces): you can go from left to right, or forward into the next row. The second row then becomes a two-dimensional row of a three-dimensional space: you can go left to right, forward to back, and now top to bottom. Note that there are seven spaces (represented by "shelves") from top to bottom, as opposed to the typical eight rows from left to right/front to back. This is likely to make sure there is symmetry between how many additional spaces are on top versus on the bottom (three, in this case). Moving another row would presumably add movement in some other direction to make it more complicated/interesting. This escalates until somehow the middle two rows require moving pieces in ''five'' dimensions (the middle two rows are four-dimensional rows + moving to other rows as fifth dimension), despite humans can only experience three spatial dimensions. This could potentially be accomplished via playing on a computer.

There are eight squares on the first row, 56 on the second row and presumably 504 on the third and 1512 on the fourth, thus making the total number of squares 4160 rather than the 64 of a traditional chess board. The drawing shows apparently five squares (or boxes) stacked on the third row and if this is also formed symmetrically, there are four hidden out of sight. The middle rows are already quite convoluted but it seems as if Randall drew three boxes along this dimension. Due to this dimensionality increase, there is plenty of free space in the middle board, drastically changing the game dynamics such that shadowing plays very little role and that movement is very unrestricted.

The title text refers to the practice of writing down what happens throughout the game, so that it is possible to review how the game progressed later. Recording moves in this fashion is required in most tournament situations. There are several common forms of {{w|Chess notation}} used for this purpose, and as well as indicating the moves, players may add annotations indicating their opinions about whether a particular move was good, bad, or peculiar. According to the title text, every annotation is followed by "?!"—which indicates a questionable move, of dubious value but not obviously a blunder either. The joke is that the variable-dimensional game is so complicated that any move will answer this description.

Note that "in dimensional chess" may be a pun on "N-dimensional chess."

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

:[A chessboard is depicted in the middle of a stack of boards. All pieces visible on the middle board are in their starting positions, except the white knight from a2 at d1 and the black pawn from g2 at e2. There are three boards each above and below the original, missing columns a and h. On columns c & f on each board, there are clear cubes with a small pedestal on each square. Columns d & e are similar, except with multiple cubes on each square. No chess pieces are visible, except for a white piece -- not clearly visible, but implicitly the white king's knight -- on the second board above the middle on b2 and a black pawn on the top board on f3. Below the chessboards is a caption]
:[Caption below the panel]:
:The problem with ''N-''dimensional chess is that ''N'' is a constant across the board. In my new variant, every row has one more dimension than the one behind it.

{{comic discussion}}
[[Category:Chess]]