explain xkcd - User contributions [en]

482: Height

2022-05-04T01:17:16Z

Ionre: Undo revision 236673 by X. K. C. D. (talk)

{{comic
| number = 482
| date = September 29, 2008
| title = Height
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = height.png
| titletext = Interestingly, on a true vertical log plot, I think the Eiffel Tower's sides would really be straight lines.
}}
{{TOC}}

==Explanation==
''Height'' uses a {{w|logarithmic scale}} to depict the contents of the {{w|universe}} at progressively smaller distances from Earth (less high above the Earth), starting at the highest possible "point," the edge of the {{w|observable universe}}, going all the way down to the grass beneath our feet. The comic is a direct companion piece to [[485: Depth]], also released on a Monday the week after this one. ''Depth'' similarly uses the logarithmic scale to depict the Earth at progressively greater magnification (going "deeper" down), from Earth's surface (the grass) to the interior of a single proton.

The very top (edge) of the observable universe is described as being 46 billion {{w|light years}} above the Earth. The universe is "only" about {{w|Age of the universe|13.8 billion years old}}, so the {{w|cosmic background radiation}} that reaches the Earth today has also only traveled 13.8 billion light years. However, during that time, {{w|Metric expansion of space|the universe has expanded}}, so the galaxies that formed from that spot where this background radiation was emitted 13.8 billion years ago would now be 46 billion light years away. This has led to many {{w|Observable_universe#Misconceptions_on_its_size|misconceptions regarding the size}}, the most typical being that the radius of the observable universe is "only" 13.8 billion light years. See this video, ''[https://www.youtube.com/watch?v=QXfhGxZFcVE How Do You Measure the Size of the Universe?]'', for a great explanation of the 46 billion light years.

To the right of the text, [[Black Hat]] stands atop the comic, having just dropped a cat off the edge head first; he is clearly going to test if the cat will land on its feet, being a jerk per his usual character. It will take some time, though, before the cat reaches Earth....

As one scrolls down, the depicted distances become less compressed, until arriving at the surface of Earth, all the while approaching a 1:1 scale with real-life distances. As shown in [[1162: Log Scale]], if [[Randall]] didn't do this, the comic would be much, MUCH longer.

In this comic, most objects that are grounded on Earth are scaled logarithmically on the vertical axes and linearly on the horizontal axes (some are scaled linearly on both axes). Displaying objects in this manner noticeably distorts their shape; the Great Pyramid, for instance, looks not like a pyramid but like a bullet.

Outside of the Earth's atmosphere, the objects are placed at their actual distances from Earth on the log scale, but their shapes are not subjected to the logarithmic scaling of Earth objects, instead appearing as they would be seen (otherwise, round objects like the sun would appear more egg shaped, with the flatter side facing upward). However, objects are still much larger or much smaller than they would be in real life, in order to allow them to be properly seen.

In the title text, Randall muses on how the inwardly-curved sides of the {{w|Eiffel Tower}} might actually become perfectly straightened when subjected to this logarithmic distortion. Although it is shown to bulge in the comic proper, this may be a consequence of Randall's rough art style rather than any reflection of his beliefs. The actual shape of the Tower approximates an {{w|Exponential function|exponential curve}}, which would indeed give a straight line on a log scale, although it was actually designed by {{w|Gustave Eiffel}} to minimize wind resistance rather than to be mathematically exact (the design is so perfect that the amount the Tower sways in the wind is less than the amount it is distorted due to thermal expansion of the sunlit side).

===Objects===
All objects are sorted from bottom to top by their maximum distance from earth for objects in a solar orbit, and their current distance for others.

{| class="wikitable"
|-
! Distance
! Object
! Description
|-
| 435 ×1024m
| Black Hat and cat
| Black Hat dropping a cat off the top of the comic, presumably to determine whether it will land on its feet.
|-
| 435 ×1024m
| colspan="2" align="center" style="background: #ffdead;" | Top of {{w|observable universe}}
|-
| 11.3 ×1024m
| {{w|Hubble Deep Field}} objects
| Objects of extremely distant galaxies found in a long-exposure photograph by of the Hubble telescope, 12 billion light-years away. The rightmost object is probably intended to be a quasar, schematically shown from the side.
|-
| 9.46 ×1024m
| colspan="2" align="center" style="background: #ffdead;" | One billion light years
|-
| 3.1 ×1024m
| {{w|Quasar}}
| A supermassive black hole at the center of some young, distant galaxies, the energy released by stuff as it falls into them makes them the brightest known objects, the black hole eventually gets too big so the huge amounts of energy can't escape, but while they're active, they outshine entire clusters of galaxies.
|-
| 2.36 ×1024m
| {{w|Great Attractor}}
| An unusual concentration of intergalactic mass. (It could also just be [[502: Dark Flow|Your Mom]]).
|-
| 425 ×1021m
| {{w|Antennae Galaxies}} (colliding)
| A pair of colliding galaxies.
|-
| 23.6 ×1021m
| {{w|Andromeda Galaxy}}
| A sibling to our Milky Way. It is the nearest spiral galaxy to ours.
|-
| 23.6 ×1021m
| Holy crap lots of space
| There is a lot of {{w|Void (astronomy)|nearly empty space between galaxies}}.
|-
| 9.46 ×1021m
| colspan="2" align="center" style="background: #ffdead;" | One million light years
|-
| 2.38 ×1021m
| [http://knowyourmeme.com/memes/cat-on-a-keyboard-in-space Cat on a keyboard in space]
| An internet meme featuring a picture of a cat sitting on a musical keyboard, superimposed on an image of space.
|-
| 1.56 ×1021m
| {{w|Magellanic Clouds}}
| These clouds are a pair of nearby dwarf galaxies.
|-
| 263 ×1018m
| Edge of Galaxy
| The edge of the {{w|Milky Way}} galaxy, the galaxy in which we reside.
|-
| 245 ×1018m
| {{w|Galactic Center}}
| The center of the Milky Way galaxy.
|-
| 61.5 ×1018m
| {{w|Crab Nebula}}
| Nebula are supernova remnants.
|-
| 14.2 ×1018m
| {{w|Horsehead Nebula}}
| A dark nebula that is part of the Orion Constellation.
|-
| 12.7 ×1018m
| {{w|Orion Nebula}}
| A nebula that is part of the Orion Constellation, just south of Orion's Belt.
|-
| 8.14 ×1018m
| {{w|Rigel}}
| The brightest star in the Orion Constellation, it is actually a triple star system known alternatively as Beta Orionis.
|-
| 6.08 ×1018m
| {{w|Betelgeuse}}
| The star Betelgeuse is displayed along with the location of {{w|Ford_Prefect (character)|Ford Prefect}} on his home planet, which orbits Betelgeuse. Ford Prefect is a fictional character from the science fiction parody {{w|The Hitchhiker's Guide to the Galaxy}}.
|-
| 4.20 ×1018m
| {{w|Pleiades}}
| The Pleiades also have a derogatory remark (for those who do not know how to recognize them), as per [[66: Abusive Astronomy]]. This is probably because they are Randall's favorite astronomical entity as is stated at the very bottom of the [http://www.xkcd.com/about/ about] page on xkcd.
|-
| 2.90 ×1018m
| The [http://en.memory-alpha.org/wiki/Romulan_Neutral_Zone Romulan Neutral Zone]
| This marks the edge of the {{w|Star Trek}} Federation.
|-
| 931 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | The first radio broadcast was in January 1910. Since radio waves travel at the speed of light, and this was published in September 2008, the radio waves traveled about 98.5 light years. See {{w|Contact (1997 film)}} for a depiction of this. This is also referenced in [[1212: Interstellar Memes]].
|-
| 350 ×1015m
| {{w|Arcturus}}
| An orange giant star that is part of the Boötes constellation.
|-
| 320 ×1015m
| {{w|Pollux}}
| One of the most distinct stars in the Gemini Constellation, it is large Orange Giant with an apparent visual magnitude of 1.1
|-
| 242 ×1015m
| The edge of {{w|Federation Sector 0-0-1}}
| The sector of space assigned to Earth in {{w|Star Trek}}.
|-
| 224 ×1015m
| {{w|Iraq and weapons of mass destruction|"missing WMDs"}}
| A reference to the alleged weapons of mass destruction that were used as a pretense to mobilize the world population against Iraq and start the Iraq war.
|-
| 81.3 ×1015m
| {{w|Sirius}}
|Also known as Alpha Canis Majoris or the Dog Star, it is actually a binary system of stars consisting of a main sequence white star and a small white dwarf.
|-
| 56.6 ×1015m
| {{w|Barnard's Star}}
| Barnard's Star is a very small red dwarf that is of great interest to astronomers as an achievement in the SIM ({{w|Space Interferometry Mission}}) to find a celestial object out of solar system that is as small as 3 earth masses.
|-
| 41.3 ×1015m
| {{w|Alpha Centauri}}
| Alpha Centauri is the closest star system to our planet.
|-
| 30.9 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | One {{w|parsec}} (= 3.26 light-years).
|-
| 9.46 ×1015m
| colspan="2" align="center" style="background: #ffdead;" | One {{w|light-year}}.
|-
| 15.0 ×1015m
| {{w|Oort cloud}}
| A halo of ice balls surrounding our solar system, but missing the {{w|Kuiper belt}} between Neptune and the Oort cloud. The Oort cloud is only theorized to exist, with no confirmed direct observations, so Randall has written a question mark (?) next to this region of the graph.
|-
| 350 ×1012m
| {{w|Bupkis}}
| Yiddish for "nothing." Only a handful of objects are known to orbit between the Kuiper Belt and the Oort Cloud.
|-
| 55.0 ×1012m
| A comet that will destroy the Earth in late 2063.
| To coincide with the latest biblically-based prophesy for the [http://www.askelm.com/prophecy/p971105.htm end of the world].
|-
| 19.5 ×1012m
| {{w|Voyager 1}}
| An early space probe. Distance correct as of 20th Nov 2014, click [http://voyager.jpl.nasa.gov/where/ here] to see NASA's live distance counter.
|-
| 16.7 ×1012m
| {{w|Pioneer 10}}
| Listed distance is an estimate based on {{w|Pioneer_10#Current_status|this information}}.
|-
| 17.7 ×1012m
| {{w|Pioneer 11}}
| By the similarity in appearance to Pioneer 10, this unlabeled probe must be Pioneer 11. Listed distance is an estimate based on {{w|Pioneer_11#Current_status|this information}}.
|-
| 14.5 ×1012m
| {{w|Eris (dwarf planet)|Eris}}
| One of a pair of {{w|Trans-Neptunian object}}s now classified as {{w|dwarf planet}}s. The "All hail Discordia!" after Eris is a reference to {{w|Discordianism}}, a somewhat tongue-in-cheek religion based around the goddess Eris. The distance is the maximum distance from Earth.
|-
| 7.50 ×1012m
| {{w|Pluto}}
| One of a pair of {{w|Trans-Neptunian object}}s now classified as {{w|dwarf planet}}s. Pluto was originally classified as the 9th planet of the Solar system. Many people were appalled when it was suddenly degraded to dwarf planet. Obviously Randall does not think much of these people, thus the comment: ''Not a planet. Neener neener''. The distance is the maximum distance of Pluto from Earth.
|-
| 4.70 ×1012m
| {{w|Neptune}}
| Neptune is displayed here with its moons. Neptune is the eighth and final planet in our solar system.
|-
| 3.20 ×1012m
| {{w|Uranus}}
| Uranus is displayed here with its moons. Uranus is the seventh planet in our solar system.
|-
| 1.67 ×1012m
| {{w|Saturn}}
| Saturn is displayed along with its moons. One of Saturn's moons, most likely {{w|Enceladus}}, is labeled as a potential location to find life. Enceladus was known in 2008 to have a possible subsurface ocean and active geysers, and a paper co-authored by well-known planetary scientist Caroline Porco in Astrobiology during that year (when the comic was published) spelt out the case for searching for life there (McKay et al. 2008 "The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume," Astrobiology 8(5):909-919). In 2015, the {{w|Cassini probe}} sampled material thought to be from Enceladus' geysers, and scientists have found evidence that its subsurface ocean closely resembles a particular kind of deep sea hydrothermal environment on Earth known to harbor life.

A more distant possibility is that Randall is referencing Saturn's largest (and much more well known moons) {{w|Titan (moon)|Titan}}, the only known moon to have an atmosphere and lakes. It was long predicted that there may be bodies of liquid on the surface filled with liquid methane and ethane (Titan is too cold for liquid water and life as we know it, but ethane and methane remain a liquid at those temperatures). There is some speculation that exotic forms of life based on extremely cold exotic chemistries may form in such conditions, with liquid hydrocarbons playing the role of the solvent (the role water plays in terrestrial life).
|-
| 928 ×109m
| {{w|Jupiter}}
| Jupiter is displayed along with its moons. One of Jupiter's moons, {{w|Europa (moon)|Europa}}, is labeled as a potential location to find life. Europa may be covered by a deep ocean of water found under a layer of ice many kilometers thick. Some hypothesize that life could have formed in such oceans.
|-
| 222 ×109m
| Asteroids
| The {{w|Asteroid|Asteroid belt}} contains a spaceship from {{w|Asteroids (video game)}}
|-
| 133 ×109m
| {{w|Mars}}
| Note the path, reflecting the fact that their distances from Earth vary as the planets move in their orbits with a maximum distance of 401 million km and a minimum of 54.6 million km.
|-
| 114 ×109m
| {{w|Venus}}
| Note the path, reflecting the fact that their distances from Earth vary as the planets move in their orbits with a maximum distance of 261 million km and a minimum of 37.7 million km.
|-
| 138 ×109m
| {{w|Mercury}}
| Mercury is the innermost planet in our solar system. The distance shown is the maximum distance from Earth.
|-
| 149 ×109m
| {{w|Sun}}
| The Sun is the star at the center of our solar system, around which the Earth and the other planets orbit.
|-
| 16.3 ×109m
| {{w|Discovery One}}
| The Discovery One from {{w|2001: A Space Odyssey}}, referring to the quote "open the pod bay door, HAL." Also may be a reference to [[375: Pod Bay Doors]].
|-
| 9.43 ×109m
| Planet Express
| The spaceplane is most likely the Planet Express from {{w|Futurama}}, where Fry once discussed "a big heaping bowl of salt."
|-
| 400 ×106m
| Human Altitude Record
| Achieved by the team of {{w|Apollo 13}} approximately 100 km higher than the remaining Apollo missions.
|-
| 384 ×106m
| {{w|Moon}}
| The Moon is the Earth's only natural satellite.
|-
| 90.4 ×106m
| {{w|Snoop Dogg}}
| A tongue-in-cheek reference to a rapper notorious for smoking marijuana, shown as having the second-highest altitude record. Someone who is taking drugs is said to be getting high.
|-
| 60.5 ×106m
| {{w|Space elevator}}
| A proposed method of transporting cargo or people into orbit, consisting of a large mass beyond geosynchronous orbit, a station at the geosynchronous point, a cable connecting it to the Earth, and a climber that can scale the cable. Space elevators are also seen in [[697: Tensile vs. Shear Strength]] and [[536: Space Elevators]].
|-
| 42.1 ×106m
| colspan="2" align="center" style="background: #ffdead;" | {{w|Geosynchronous orbit|Geosynchronous Orbit}}
|-
| 20.2 ×106m
| {{w|GPS (satellite)|GPS Satellites}}
| GPS satellites are used for global positioning.
|-
| 3.94 ×106m
| {{w|Lunar Lander}}
| The quote is a reference to {{w|Contact (1997 film)}}, where the main character Ellie Arroway after witnessing a celestial light show up close says "Poetry! They should've sent a poet."
|-
| 800 ×103m
| {{w|Space debris|Space Junk}}
| There is a large quantity of defunct objects in orbit around the Earth. Amongst other things, this includes old satellites, rocket stages, and fragments from collisions or disintegration. Space junk is also referenced in [[1242: Scary Names]] under the title {{w|Kessler syndrome}}.
|-
| 422.5 ×103m
| {{w|International Space Station}}
| The ISS (International Space Station) is a multinational effort to put a research vessel in space. It is currently the largest artificial object in Earth's orbit, as well as the location of the longest continuous human presence in space.
|-
| 100 ×103m
| colspan="2" align="center" style="background: #ffdead;" | The {{w|Edge of space|official edge of space}} as defined by the {{w|Kármán line}}.
|-
| 76.0 ×103m
| {{w|Meteors}}
| Meteors are chunks of rock (usually asteroids) that burn up in the atmosphere, producing the bright light associated with them. If they are large enough to hit the ground, they become meteorites, which is why Munroe labeled them only in the upper atmosphere.
|-
| 25.0 ×103m
| {{w|High-altitude balloon|High-altitude balloons}}
| Unmanned balloons, typically filled with helium or hydrogen. The current altitude record was set in 2002 by a balloon named BU60-1 that reached 53,000m.
|-
| 16.1 ×103m
| colspan="2" align="center" style="background: #ffdead;" | 1/10 ATM = 0.1 {{w|Atmospheric pressure|atmosphere of pressure}}
|-
| 12.0 ×103m
| {{w|Airliner|Airliners}}
| This is a typical cruising altitude of jet aircraft, equating to roughly 40,000 feet. (Aircraft altitude tends to be specified in feet rather than metres (yay!?))
|-
| 8.84 ×103m
| {{w|Mount Everest}}
| The Earth's highest mountain, located in the {{w|Himalayas|Himalayan mountain range}} in South Asia.
|-
| 8.00 ×103m
| {{w|Cory Doctorow}}
| Cory Doctorow is a [[:Category:Comics featuring Cory Doctorow|recurring theme]] in xkcd. He was first seen in a balloon in [[239: Blagofaire]].
|-
| 6.34 ×103m
| {{w|Space Shuttle Columbia disaster}}
| The {{w|Space Shuttle Columbia}} and its seven-member crew were lost when it disintegrated at [http://books.google.co.uk/books?id=6v16AgAAQBAJ&lpg=PA7&ots=LDKQ3nsNHs&dq=shuttle%20columbia%20altitude&pg=PA7#v=onepage&q=shuttle%20columbia%20altitude&f=false approximately 63,400m] in 2003. This number is inconsistent with the height of the graph by a factor of 10 (probably a mistype by Randall).
|-
| 6.00 ×103m
| {{w|Helicopter}}
| Though the record for helicopter altitude (without payload) is 12,442m, normal flying is usually performed much lower. In the US, 6000m is into {{w|Class A airspace}}, which is restricted and requires flight under {{w|Instrument Flight Rules}}.
|-
| 6.00 ×103m
| {{w|Cloud}}
| Though not actually labeled, there are a couple of clouds shown. While different cloud types vary in height, 6000m is roughly in the middle of the height range for [http://weatherfaqs.org.uk/node/21 clouds in temperate regions].
|-
| 5.49 ×103m
| colspan="2" align="center" style="background: #ffdead;" | 1/2 ATM = 0.5 {{w|Atmospheric pressure|atmosphere of pressure}}
|-
| 1.78 ×103m
| [[Cueball]]
| Apparently still using Python as shown in comic [[353: Python]].
|-
| 800 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 800 meters
|-
| 800 ×100m
| {{w|Burj Khalifa|Burj Dubai}}
| Now known as the Burj Khalifa, it is the tallest building in the world. This was also a main feature in [[1110: Click and Drag]].
|-
| 500 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 500 meters
|-
| 400 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 400 meters
|-
| 325 ×100m
| {{w|Eiffel Tower}}
| A famous landmark in Paris, France.
|-
| 300 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 300 meters
|-
| 200 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 200 meters
|-
| 150 ×100m
| Kite
| Kite string is commonly sold in large spools; a nice thick spool will probably hold 150 meters. Kites are a [[:Category:Kites|recurring theme]] in xkcd; for instance, see [[235: Kite]].
|-
| 140 ×100m
| {{w|Great Pyramid of Giza}}
| One of the Seven Wonders of the Ancient World. It is located in Egypt.
|-
| 120 ×100m
| {{w|Pop fly}}
| In {{w|Baseball}}, a 'Pop Fly' is when the batter mis-hits the baseball, which then follows a tall arc deep into the infield where it's easy picking for the other team to catch on its way down. The highest recorded pop fly, not including those that landed in foul territory, was 172 meters.
|-
| 115 ×100m
| {{w|Redwood Tree|Redwood trees}}
| The tallest trees in the world. At 115.61 m (379.3 ft), {{w|Hyperion (tree)|Hyperion}}, a Coast Redwood, holds the record for the tallest tree in the world.
|-
| 100 ×100m
| colspan="2" align="center" style="background: #ffdead;" | 100 meters
|-
| 20.0 ×100m
| {{w|Oak}}
| While oaks may grow to be in excess of 40m in height, heights of around 20m are more typical. The person in the tree saying, "Hey, squirrels!" is a reference to [[167: Nihilism]].
|-
| 16.4 ×100m
| Tallest stilts
| The tallest {{w|stilts}} recorded by the Guinness Book of World Records (as of November 2006) were 16.4 meters, or nearly 54 feet. See also [http://www.explainxkcd.com/wiki/images/8/89/1608_1038x1095y_Hamsterball_and_stilts_room.png these tall stilts] from [[1608: Hoverboard]].
|-
| 13.0 ×100m
| {{w|Brachiosaurus|Brachiosaur}}
| A large genus of dinosaur.
|-
| 8.00 ×100m
| {{w|Giraffe}}
| The tallest living terrestrial animal, with fully grown adults reaching in excess of 5 m. While labeled 8m in the comic, the [http://www.big-animals.com/the-giraffe-the-worlds-tallest-animal/ record] for height is reported at 5.8m. Giraffes have been used by Randall for measuring heights, most prominently in the [[what if?]] ''{{what if|44|High Throw}}''.
|-
| 1.70 ×100m
| {{w|Human height|Folks}}
| Determining an average height of the world population is fraught with complications, but as a ballpark figure, 1.7m is fairly accurate.
|}

==Transcript==
:'''Top of observable universe'''
:[Black Hat is standing on top, throwing a black kitty down.]
:Black Cat: Mrowl!
:[Map of the universe from observable universe to Earth. Each area of item is labeled. Labels left to right, up to down:]
:(46 billion light years up)
::Hubble Deep Field Objects
:-One billion light years-
::Great Attractor
::Antennae Galaxies (colliding)
::Andromeda
::Holy crap lots of space
:-One million light years-
::Magellanic Clouds
::Edge of galaxy
::Galactic center
::Crab Nebula
::Orion Nebula
::Horsehead Nebula
::Romulan neutral zone
::The Pleiades, duh!
::Rigel
::Betelgeuse
::Ford Prefect
:[Three arrows are pointing up above three lines with the following label:]
:-Expanding shell of radio transmissions-
::[Above a dotted line:]
::Edge of federation sector 0-0-1
::Pollux
::Arcturus
::Missing WMDs
::Sirius
::Barnard's Star
::Alpha Centauri
:-One parsec-
:-One light year-
::Oort Cloud (?)
::Bupkis
::Comet which will destroy Earth in late 2063
::Pioneer 10
::Voyager I
::Eris (All hail Discordia!)
::Pluto (Not a planet. Neener neener.)
::Neptune
::Uranus
::Saturn
::[Two arrows point to two moons, one next to each of the planets above and below.]
::<-- Life -->
::Jupiter
::Asteroids
::Mars
::Venus
::Sun
::Mercury
::Spaceship Planet Express: Hey, a heaping bowl of salt!
::Spaceship Discovery One: Open the fridge door, Hal.
::Moon
::Human altitude record (Apollo 13)
::2nd place: Snoop Dogg
::Space elevator - One of these days, promise!
::Geosynchronous Orbit
::GPS satellites
::Lunar lander: In retrospect, they shouldn't have sent a poet. I have no idea how to land.
::International Space Station
::Space junk
:-Official edge of space (100 km)-
::Meteors
:-1/10 ATM-
::High altitude balloons
::Airliners
::Shuttle Columbia lost
:-1/2 ATM-
::Cory Doctrow
::Everest
::Helicopters (6000 m)
::Cueball: Woo Python!
::[A vertical scale is drawn along the right side of the picture, starting at 1 km and getting progressivly smaller and smaller.]
:1 km
:-800 m-
::Burj Dubai (~800 m)
:500
:400
::Eiffel Tower (325 m)
:200
::Kites
::Great Pyramid (140 m)
::Pop fly
::Redwood (115 m)
:100m
::Oak (20 m)
::A person in the oak: Hey squirrels!
::Tallest stilts
::Brachiosaur (13 m)
::Giraffe (8 m)
::[Megan and Cueball holding the kite are labeled:]
::Folks
:'''The observable universe, from top to bottom'''
::~On a log scale~
::Sizes are not to scale, but heights above the Earth's surface are accurate on a log scale. (That is, each step up is double the height.)

==Trivia==
*A print version of this comic is available in the [https://store.xkcd.com/products/height-poster xkcd store].

{{comic discussion}}

[[Category:Charts]]
[[Category:Large drawings]]
[[Category:Illustrations of scale]]
[[Category:Comics with inverted brightness]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Cory Doctorow]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Space probes]]
[[Category:Astronomy]]
[[Category:Space]]
[[Category:Elevators]] 
[[Category:Baseball]]
[[Category:Animals]]
[[Category:Dinosaurs]]
[[Category:Giraffes]]
[[Category:Squirrels]] 
[[Category:Programming]] 
[[Category:Kites]]
[[Category:Star Trek]]
[[Category:Comics with xkcd store products]]

2578: Sword Pull

2022-05-04T01:16:39Z

Ionre: Undo revision 236781 by X. K. C. D. (talk)

{{comic
| number = 2578
| date = February 7, 2022
| title = Sword Pull
| image = sword_pull.png
| titletext = Merlin really shouldn't leave his dirt bike lying around.
}}

==Explanation==
A surprised [[Cueball]] walks up to a stone where apparently a sword is stuck in almost to the hilt, embedded in a stone much like a particularly well-known fable in the legends of {{w|King Arthur}}. This may mean this sword is called {{w|Excalibur}}. Usually, the narrative is that the one who can free the significant sword becomes king of England (or, technically, Britain), see for instance Disney's ''{{w|The Sword in the Stone (1963 film)|The Sword in the Stone}}'' — or the scene as featured in [[1521: Sword in the Stone]], where [[Megan]] decides to return the sword back into the stone after reading about {{w|England}} on Wikipedia. (It has been commented that the one who managed to embed the sword in the stone in the first place may have had the greater skill and/or strength.)

Cueball rises to the challenge and stands atop the stone, for leverage, and pulls hard to yank it almost out of the stone. With a surprise even greater than before, he finds that the pulling of the sword merely starts a motor within the stone and, almost immediately, the whole assemblage starts moving to the right with Cueball still standing upon it. Having failed to fully remove the sword from the stone, after he releases it the sword is retracted back to its original position inside the now moving stone.

The title text implies that the sword is actually the {{w|rope start|rope starter}} for Merlin's {{w|dirt bike}}. {{w|Merlin}}, a wizard, is typically known as King Arthur's mystical advisor. The title text mentions that Merlin really should not just let his dirt bike lie around, indicating that this is a common occurrence and has caused problems before. Since rocks are usually not dirt bikes in disguise,{{citation needed}} [[Randall]] may be describing this literally, as in a stone-bike that travels through the dirt, as it appears to represent in the last panel.

Some similarly-sized stones, namely {{w|Sailing stones|sailing stones}}, do move spontaneously with up to 0.3 km/h in precise conditions. However, the stone in the comic appears to be moving at a higher speed, and sailing stones require no rope starting.{{citation needed}}

==Transcript==
:[Cueball walks towards a large stone on the ground from which the hilt of a sword is protruding. The ground he walks on is uneven, with small plants growing and small stones lying on the ground.]
:Cueball: ??

:[Cueball stands on the stone and attempts to pull the sword out of the stone using both hands and leaning a bit back away from the sword.]

:[Cueball manages to pull the sword partially out of the stone, still using both hands, and now he is almost standing in full height, but still leaning a bit back. Both he and the sword is vibrating from the effort, as indicated by several sets of two lines around the sword and Cueball's arms. The pull gives off a loud sound, and also a buzzing sound comes because of the pull. And three small lines above the right part of the stone indicated that other sounds are coming from the stone]
:Pull: <big><big>''Yank!''</big></big>
:Sword: ''Zzz<big>z</big>z''
:Stone: Put put put
:Stone: Brrrrr<big>rr</big>

:[Cueball is still holding on to the sword, with the tip still inside the stone. But he is not pulling anymore and is now looking down on the stone beneath him. There are now several lines from both sides of the stone indicating noises coming from the stone, which now is written on both sides of Cueball on the stone.]
:Cueball: ?? ??
:Stone:Rrr<big>r<big>rrrrrrrr</big></big>rr

:[Cueball has released the sword which has then returned to the original position deep in the stone. The stone is now clearly moving to the right of the panel, with Cueball on top of it. He is looking behind him and holding his arms out to the side to keep his balance. The patch where the stone lay to start is dark. Four large lines behind the stone indicates how it is moving. The stone is already partially outside the right edge of the panel. The sound from the stone is floating behind the stone as it moves to the right]
:Stone: Rrrr<big>rrrrrr<big>r</big>rr</big>

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Fiction]]

2132: Percentage Styles

2022-05-04T01:16:05Z

Ionre: Undo revision 236801 by X. K. C. D. (talk)

{{comic
| number = 2132
| date = April 3, 2019
| title = Percentage Styles
| image = percentage_styles.png
| titletext = In a tribute to classical Latin, I started pronouncing it 'per-kent.' Eventually my friends had to resort to spritzing me with a water bottle like a cat to train me out of it.
}}

==Explanation==
On March 29, 2019, The {{w|AP Stylebook}} changed a long-standing rule that forbade press writers from using the percent sign (%) when writing percentages. This had long been a controversial rule, leading to much debate over the preferable way to write percentages, before the Associated Press finally conceded the point.

The comic lists the best to worst ways in which you can write out phrases that are phonetically the same as "65%". They go from the common "65%" and "65 percent" to "65 per cent," which is not common in Randall's area and time, to the eccentric "sixty-five%" and "65 per¢" (using the cent currency symbol) which are not used in normal writing and would stand out like a sore thumb when read. The middle option, "65 per cent", was common in older literature, along with "65 per cent.", using "cent." as an abbreviation for "centum", which is Latin for "hundred". ("per" in Latin translates to "through", "for", and several other English prepositions.) The entire string would translate to "65 for every hundred." "Per cent" is more widely used in British English than in American English today.

A small gap between the ends of the bar and the best and worst options may suggest the existence of even better and worse options not listed in this comic, such as "6ty5/¢".

Other abbreviations not mentioned in the comic include "pct.", "pct" or "pc". See {{w|Percentage}}.

The title text references the ambiguity of {{w|hard and soft C}} in English. In Classical Latin, "C" is always pronounced like "K". However, in English, most "C"s before E, I and Y (including "percent") are soft, and pronounced like "S". In academia, [http://www.covingtoninnovations.com/mc/latinpro.pdf Latin students are taught the Classical Latin pronunciations of words], rather than the pronunciation used by the Catholic church. Some students of Latin may adopt the Latin pronunciation of English words derived from Latin. Such people may tend more to pronounce, even when not the correct choice, "celtic" like "keltic" (this ''is'' the correct choice, except for the {{w|Boston Celtics|basketball team}}), "caesar" like "kaiser", or "cent" like "kent" (although since this involves obviously saying something others aren't going to understand unless they took the same classes, it might as well be "per kentum").

People sometimes train a cat out of a bad behavior, such as scratching upholstery, by spritzing the cat with water when the cat does the undesired behavior. In this case, Randall's friends found him so annoying they trained him out saying "per kent" by spraying him with water every time he pronounced it that way. Training people this way was previously a punchline in [[220: Philosophy]], while training a cat this way was previously a punchline in [[1786: Trash]].

===Styles and their acceptability===
;65%
:This is the standard way of writing percentages. Randall's approval acceptability is 98%.
;65 percent
:This one has no space, it is more common in American English. Rating: 97 percent
;65 per cent
:This one has a space, it is more common in British English. Rating: 86 per cent
;Sixty-five%
:This one writes out the number, but not the percent sign. Rating: Sixty%
;65 per¢
:This one uses the cent symbol in place of the word cent, which is incorrect in this context, as ''cent'' here does not refer to a currency. Rating: 2 per¢

==Transcript==
:Percentage styles in order of acceptability
:[A long vertical line is shown with five dots on it.]
:[Label at the top:]
:Best
:[Dot labels from top to bottom:]

:65%
:[very short distance]
:65 percent
:[at roughly quarter scale]
:65 per cent
:[at roughly half scale]
:Sixty-five%
:[at the end]
:65 per¢

[[Category:Charts]]

{{comic discussion}}

2223: Screen Time

2022-05-04T01:12:43Z

Ionre: Undo revision 236796 by X. K. C. D. (talk)

{{comic
| number = 2223
| date = November 1, 2019
| title = Screen Time
| image = screen_time.png
| titletext = These new Bluetooth socks are great, but it's troubling to learn that I average almost 14 hours of Shoe Time a day.
}}

==Explanation==
[[Cueball]] is reading the report from a smartphone app showing the average time each day that he was NOT looking at his phone during the hours he was awake this last week. This is a reversal of the more expected behavior for a {{w|screen time|screen-time}} app, which would normally report the amount of time spent looking at the screen. The point is that as mobile phone usage becomes more prevalent, it may be easier to comprehend to report non-screen time.

People in the US spent an average of 24 hours of non-work/education screen time per week in 2015, compared to 10 hours of active leisure, according to one estimate.[[https://www.brookings.edu/blog/social-mobility-memos/2016/09/13/how-free-time-became-screen-time/ How free time became screen time]] Averaged per day that comes to 3.4 hours screen time and 1.4 hours active leisure.

Screen time may be associated with various undesirable conditions, such as mental health difficulties like depression, decreased activity, reduced sleep quality and quantity.

In Cueball's particular case, if we assume that he is awake 17 hours a day (the average for most people in USA), then his non-screen time average of 2 hours 48 minutes means that he spent more than 84% of his awake time last week looking at a screen. This means that while his 6% improvement is positive, he still has quite a significant habit. His previous non-screen-time would have been 2 hours 38 minutes, so he has managed to shave 10 minutes off. Increased screen time often comes at the expense of decreased sleep time, so it may not be fair to assume a constant amount of sleep.<ref>[[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5279707 Digital media use in the 2 h before bedtime is associated with sleep variables in university students]]</ref><ref>[[https://www.sciencedirect.com/science/article/abs/pii/S1389945717303507 Decreases in self-reported sleep duration among U.S. adolescents 2009–2015 and association with new media screen time]]</ref>

Ironically, in order for Cueball to use the app, he has to be looking at his mobile screen. The increasing use of mobile devices in modern society has been a cause for concern, with many people arguing this leads to addiction, other health risks, or people simply not talking to each other.

The title text parodies the idea of a screen time app by describing a "shoe time" app, which would track the amount of time a person spends wearing shoes. It's unclear what the practical use for this would be, as there is little controversy about the prevalence of shoes in our society. Possibly an app that tracks the amount of time wearing ''specific'' shoes could be useful; for example, a person suffering medical problems from wearing the wrong footwear could track the amount of time they spend wearing particular shoes, and correlate this with their health to figure out which ones are causing problems.

Possibly, the point being made is that use of phones have become so constant in our lives that using them for many hours a day is as unremarkable as using shoes for many hours a day. Or, since it's the socks that are Bluetooth-enabled, they may be reporting negatively about almost constant obstruction by shoes, whereas the socks would prefer to report a much lower "Shoe Time" score.

Some cultures have the custom of taking shoes off when in the house, so those people would boast lower (and presumably more favorable) "Shoe Time" scores. It may also be a reference to the "{{w|shoe phone}}" on the television show ''{{w|Get Smart}}''. (If {{w|Maxwell Smart}} wore these socks, they could track his phone usage, because his phone was in his shoe).

==Transcript==
:[Cueball is looking down at his phone. The text is what he reads on the screen, as shown by a zigzag line emanating from a starburst at the top of the phone.]
:Phone: Screen time report:
:Phone: While awake, you averaged 2H 48M per day looking at things other than your phone. That's up 6% from last week!

:[Caption below the panel]
:At some point, it starts making more sense to track '''''non'''''-screen time.

{{comic discussion}}

[[Category: Comics featuring Cueball]]
[[Category:Smartphones]]
[[Category:Screen Time]]

1936: Desert Golfing

2022-05-04T01:11:47Z

Ionre: Undo revision 232636 by X. K. C. D. (talk)

{{comic
| number = 1936
| date = January 1, 2018
| title = Desert Golfing
| image = desert_golfing.png
| titletext = I just want to stay up long enough to watch the ball drop into the hole number 2018.
}}

==Explanation==
A common joke surrounding the turn of the New Year is to make a comment about "next year" on New Year's Eve or "last year" on New Year's Day. While technically correct, some people may derive a snarky humor from making observations about the span of years when the reality has been more along a span of days or even, as in this comic, only a few hours.

In this, the second of two [[:Category:New Year|New Year comics]] in a row, with this one being released on New Year's Day 2018, [[Cueball]] observes that he has [[1475|technically]] "been playing ''{{w|Desert Golfing}}'' nonstop since late 2017". Desert Golfing is a game that takes place in an endless side-scrolling desert, where the player can shoot a golf ball using a one finger swipe to determine direction and power. The entirety of the "golf course" is made of sand, making the physics of the golf ball more difficult to predict and control, as if from a bunker. After reaching a hole, the game automatically generates a completely random new course, making the game go on forever, and the score is purely dependent on how long you play the game.

Although Cueball's statement could be taken to mean he has devoted his waking hours to the game, the clock on the wall reveals both the truth of his comment and that he is not exaggerating. While he has only been playing the game for two and a half hours, give or take, those two-and-a-half hours started at about 11:10 PM on December 31st, meaning that it is presently January 1st and he has indeed been playing the game "nonstop since late 2017" (assuming he has not taken a break to eat or use the facilities).

Someone off-panel acknowledges the joke by saying that he should "take a break in 2018", and Cueball declares it is his New Year's resolution to go to bed. This is not a typical New Year's resolution, as most resolutions are about something you need to change in your life from last year, and going to bed (or at least sleeping) is not something you would have been able to avoid for a whole year.{{fact}} This may also be making a joke about how quickly many New Year's resolutions are broken, as Cueball has singularly failed to stick to his. New Year's resolutions have been mentioned before, the first time in [[1154: Resolution]], where the tradition of {{w|New Year's resolutions}} is the entire joke.

The title text states that the only reason Cueball has stayed up to play Desert Golfing is to watch the ball drop into hole number 2018 — this is a pun on the {{w|Times Square Ball}}, a pyrotechnical device in New York City that lights up spectacularly as soon as the new year begins. Because the event is televised on many news channels, "watching The Ball drop" is now a common way to count down the seconds to the new year. Cueball takes this literally, and tries to drop his (golf) ball to signify the beginning of 2018.

==Transcript==
:[An analog clock showing 11:12 hangs on the wall left above of Cueball who is sitting on a couch leaning on the left armrest, feet up on the couch. He holds a smartphone horizontally and the screen is clearly brown. Above him is a large brown bubble showing the content of the screen, thus showing that he is playing Desert Golfing. The sky is light brown, the sand below is dark brown, the golf ball is white and is followed by a white line showing its trajectory towards the gray flag stick with a yellow flag on it, which is to the right of the screen. The hole is just before the flag stick, an indentation in the sand.]

:[The clock is now showing 12:00 and Cueball is sitting straight upright on the couch, the screen display above him shows that he continues to play, but now on a new golf hole with different contours. The trajectory of the ball is much more complicated than before, and it seems he has had to play a very special loop shot to get out of a deep pit.]

:[The clock is showing 12:34 as Cueball once again sits as in the first panel, but now towards the right armrest and he is almost lying down with his head on the rest. Once again the screen is visible above him and it is shown that the hole has changed again.]

:[The clock is showing 1:47 when Cueball, now sitting up against the right armrest, finally speaks while continuing to play, with the brown screen visible, as he holds it on his knees, but the screen display is not shown. An off-panel voice answers him from the right.]
:Cueball: Technically, I've been playing ''Desert Golfing'' nonstop since late 2017.
:Off-panel voice: Might want to take a break sometime in 2018.
:Cueball: Yeah, my New Year's resolution is to go to bed.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics with color]]
[[Category:Comics featuring Cueball]]
[[Category:Sport]]
[[Category:Video games]]

1261: Shake That

2022-05-04T01:09:25Z

Ionre: Undo revision 233380 by X. K. C. D. (talk)

{{comic
| number = 1261
| date = September 6, 2013
| title = Shake That
| image = shake that.png
| titletext = How do I work it? IT'S ALREADY WORKING!
}}

==Explanation==
Visiting a club, [[Megan]] is exhorted by a phrase used in several songs, to "shake what your mama gave you", a crude euphemism typically used to encourage shaking one's body parts, referring to any of the sexually appealing anatomical parts of the dancer. Taking this exhortation extremely literally, Megan proceeds to locate a mug presumably given to her by her "mama" labeled "World's greatest daughter" and shakes it.

The phrase "shake what your mama gave ya" was in use as early as 1992, when it was the title of a song by {{w|Poison Clan}}, a southern hip-hop group that was influential from 1990–1995. Another version by Stik-E & Da Hoodz was released in 1995 by Phat Wax records. The line gained a wider audience when it was sampled by {{w|Fatboy Slim}} in the similarly titled "Ya Mama" on his 2000 album ''{{w|Halfway Between the Gutter and the Stars}}''. More recently the line was featured in the {{w|Lil Jon}} single "Stick That Thang Out". In fitting with the general thematic composition of such a song, a large part of which revolves around either goading a woman to, or describing one who is dancing seductively in a nightclub - this line asks a girl to dance, thereby swaying her hips & buttocks, or breasts, the most common male 'fetishes' — making them more conspicuous in the usually dim ambiance because of the phase lag with the rest of the body, which may be attributed to non-rigidity of the elastic structures — for purposes of her male audience's gratification (whether it be solicited or voyeuristic).

The title text refers to another lyrical cliche, "work it", which typically refers to "working" one's body; again, generally seductively. The action may be considered work either from the point of mechanical work, or as a reference to a professional dancer. This naturally leads Megan to further confusion (as indicated by the title text) when taken literally, as she responds "it's already working!" It is not entirely clear if she is again referring to the mug, or simply another generic object not displayed in the comic.

[[1291: Shoot for the Moon]] may be a continuation of this, due to Megan misunderstanding common saying or references.

==Transcript==
:[Megan stands in a disco, surrounded by dancing figures. She looks confused.]
:PA system: Shake what your mama gave you
:Megan: ???
:[Megan walks out of the club door.]
:[We see a mug on a table, labelled "World's Greatest Daughter".]
:[Megan shakes the mug.]

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Comics with color]]
[[Category:Language]]
[[Category:Music]]

152: Hamster Ball

2022-05-04T01:08:33Z

Ionre: Undo revision 233302 by X. K. C. D. (talk)

{{comic
| number = 152
| date = September 3, 2006
| title = Hamster Ball
| image = hamster_ball.png
| titletext = Reportedly, double-walled inflatable balls like this exist somewhere. Now to find that place.
}}

==Explanation==
The comic starts with a {{w|genie}}, who, having been freed from a magical lamp, grants the owner three wishes; this isn't unusual, since the {{w|Genie in popular culture|idea of a genie}} who does this is a very {{tvtropes|GenieInABottle|common trope}} in the fantasy genre.

[[Cueball]] asks for a human-sized {{w|hamster ball}}, and when he gets it, he starts to roll around in it, obviously entertained.
The genie then asks what he would like for his {{tvtropes|ThreeWishes|other two wishes}}, to which, having already being granted his heart's desire, he states that he wouldn't need the other wishes for anything.

The title text refers to the activity of {{w|Zorbing}}. Later, [[Randall]] found out where to get one and went on a [[211: Hamster Ball Heist|hamster ball heist]], and hamster balls have been a [http://www.explainxkcd.com/wiki/index.php/Category:Hamster_Ball recurring theme] on xkcd since this comic, and 14 years later it received a direct sequel [[2331: Hamster Ball 2]].

This comic is referenced in [[1975: Right Click]], where one of the things the ADVENT.EXE wishing well allows you to wish for is a human-sized hamster ball. Doing so redirects you to this page.

Genies (or magic lamps) are mentioned in at least four other comics:
*[[532: Piano]]
*[[879: Lamp]]
*[[1391: Darkness]]
*[[2193: Well-Ordering Principle]]

In the first two, Randall manages to use the concept to make penis-related jokes. 
In the fourth, the issue of number of wishes is discussed, from the perspective of wanting more than three wishes. The issue of wishing for more wishes is also the subject of [[1086: Eyelash Wish Log]], so it is not always enough with one or even three wishes!

==Transcript==
:[Cueball stands by a genie, whose lower body becomes smoke and trails down to an old-fashioned lamp.]
:Genie: You have awakened me from the lamp. You may have three wishes. What does your heart desire?
:Cueball: I'd like a human-sized hamster ball.

:[A hamster ball appears; Cueball is inside it, arms outstretched.]
:Cueball: Sweet!

:[Cueball steps to left; the ball rolls that way.]

:[He does the same thing to his right.]

:[Cueball comes to rest in the centre of the panel.]

:Genie: And your other wishes?
:Cueball: Why would I need other wishes?

==Trivia==
*For some unknown reason, this comic was the second of only a handful of comics to be [[:Category:Sunday comics|released on a Sunday]].
**The Monday release was then skipped, and the next comic came out Wednesday. So this was in principle supposed to be a Monday release.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Hamster Ball]]
[[Category:Comics sharing name|Hamster Ball]]