Editing 3063: Planet Definitions

{{comic
| number    = 3063
| date      = March 14, 2025
| title     = Planet Definitions
| image     = planet_definitions_2x.png
| imagesize = 653x1435px
| noexpand  = true
| titletext = Under the 'has cleared its orbital neighborhood' and 'fuses hydrogen into helium' definitions, thanks to human activities Earth technically no longer qualifies as a planet but DOES count as a star.
}}

==Explanation==
{{incomplete|A table might be better to format the explanation.}}

This comic addresses the {{w|IAU definition of planet|controversy of whether of Pluto is a planet}} and explores many definitions, most of them humorous/nonsensical, of what a planet could be.

;Traditionalist: <u>{{w|Pluto}} is a planet</u> (9 planets)
:In modern times, there was {{w|IAU definition of planet#Background|no formal definition of a "planet"}} prior to 2006.  However, it was generally accepted as a colloquialism that there were nine planets around the {{w|Sun}}, Pluto included, primarily starting with Pluto's discovery in 1930, based upon that time's scientific consensus that there ought to be another planet to account for peculiarities in the the orbits of the other outer planets. As more sophisticated methods of mapping the {{w|Solar System}} were developed and {{w|Eris (dwarf planet)|Eris}} was discovered to be even more massive than Pluto (which may not have been as significant as the theories that lead to its discovery suggested) it became clear to astronomers that a more standardized definition was needed. In 2006 the International Astronomical Union (IAU) published their formal redefinition of a "planet" to require a planet to be gravitationally dominant within its orbit, disqualifying Pluto (and Eris) which is now considered a "dwarf planet." This has been subject to push back from countless people, including [https://arxiv.org/abs/2110.15285 some planetary scientists], but in mostly nostalgic laypeople dissatisfied with Pluto being "demoted" or otherwise relegated when schoolchildren and adults alike have 'known' that there are nine planets for the most part of the last century (and [[988: Tradition|tradition]] has previously been refered to as whatever was current during "Baby Boomers' childhoods").
:Ironically, some of the latest study of the outer solar-system includes the possibility of yet ''another'' {{w|Planet Nine}}, but only time will tell if such an object exists and whether it would cross the IAU's current threshold or even require the threshold itself to be reassessed once more.

;Modern: <u>Pluto is not a planet</u> (8 planets)
:When the IAU redefined what a planet is in 2006, Pluto no longer qualifies as a planet. (since it wasn't able to clear its neighborhood around its orbit) Using the modern, and recently official, definition of a planet, only eight celestial objects qualified.

;Expansive: <u>Dwarf planets are planets</u> (17+ planets)
:It is likely that since the term "dwarf planet" contained "planet" in its name, Randall considered those as also planets under this category. 
:It is also likely that the number of planets includes the ones that are considered planets and the ones that are considered to have compacted into fully solid bodies, {{w|Dwarf planet#Most likely dwarf planets| as defined by Grundy ''et al.'',}} those being {{w|Ceres (dwarf planet)|Ceres}}, Pluto, Eris, {{w|Makemake}}, {{w|Haumea}}, {{w|Gonggong (dwarf planet)|Gonggong}}, {{w|Quaoar}}, {{w|Orcus (dwarf planet|Orcus}} and {{w|Sedna (dwarf planet)|Sedna}}.
:The basis for this viewpoint is the possible alternative re-evaluation that the IAU could have adopted, in that all newly discovered things ''like'' Pluto (being considered a planet) should therefore be considered a planet. Indeed, Ceres had been observed some time before Pluto and had been called a planet (or a "minor planet") within both scientific and public realms.

;Ultratraditionalist: <u>Only the classical planets are planets</u> (5 planets)
:The {{w|classical planets}} are objects found and considered by the Greek astronomers in classical antiquity to be considered planets. Their definition of "planet" considered visible objects that move across the sky relative to the fixed stars, the original word itself being translated as "wanderer". There are seven classical planets, but if one were to only consider the ones that fall under the IAU's definition of a planet (this being ''less'' traditional), then there would only be five. (The Sun and the {{w|Moon}} would be disqualified.)
:Being (mostly) true to the spirit of the historic naming convention, this would be a conservative but 'valid' version of the criterion.

;Condescending: <u>Only giant planets are planets; the rest are big {{w|asteroid}}s</u> (4 planets)
:This definition may refer to the {{w|giant planets}}, planets much larger than the {{w|Earth}}. Only the four outer (IAU-defined) planets fall under this definition.
:Relegation of anything smaller, including our own planet, is an extreme attitude, but most of the initial [[:Category:Exoplanets|exoplanets]] discovered were, by practical necessity in their detection, also only of the "giant planet" mind.

;Simplistic: <u>Anything gravitationally round is a planet</u> (37+ planets)
:Using the Wikipedia {{w|list of gravitationally rounded objects of the Solar System}}, there are 37 objects listed. That includes the Sun, 8 planets, 9 dwarf planets and 19 {{w|Natural satellite|moon}}s, but falls short of also highlighting all of the smallest visible objects (as per Universalist, below).
:This definition is essentially ''part'' of the actual current definition of a planet, leaving out the main factor that specifically disqualifies Pluto.

;Grounded: <u>Only objects a spaceship has landed on are planets</u> (10 planets)
:This list includes objects in the Solar System that a spacecraft has {{w|List of landings on extraterrestrial bodies| performed a soft landing on}}.  The list includes {{w|Venus}}, Earth, {{w|Mars}}, the Moon, {{w|Titan (moon)|Titan}}, {{w|433 Eros|Eros}}, {{w|25143 Itokawa|Itokawa}}, {{w|162173 Ryugu|Ryugu}} and {{w|101955 Bennu|Bennu}}. Notably, {{w|comet}} {{w|Philae (Spacecraft)| landings}} are not included in the list.
:The justification for this seeks to be that we must 'touch' the object before we consider it as worthy of being classified as more than a mere blob (or dot) in space.

;Regolithic: <u>Anything covered in dirt and ice and stuff is a planet</u> (infinite)
:This list excludes the {{w|Gas Giant}}s and the {{w|Ice Giant}}s. The list would likely include dwarf planets, asteroids, moons and comets. This is effectively the opposite of the "condescending" definition: every object in the solar system is included in one definition or the other (except for the Sun, which inhabits ).
:This is also an extension on the prior classicication. In this case ''could'' we meaningfully touch the object, with predominatingly atmospheric bodies being not considered so.

;Lunar: <u>You can't be a planet if you don't have a moon</u> (12+ objects)
:Only some objects in the solar system have known and acknowledged moons orbiting them. The value given may be {{w|List of natural satellites| the number of planets and dwarf planets}} that have moons, when excluding  {{w|Haumea}} for not reaching {{w|hydrostatic equilibrium}} despite having moons.  The Sun is excluded because its satellites are not moons, because ... oh, look, a Squirrel!
:Adopting this definition would suggest that a planetary body is not worthy of the name if it doesn't (with no matter for what reason) demonstrably have the means to dominate its local area by being the overwhelming focus of all adjacent bodies' own orbits.

;Solipsistic: <u>Earth is the only planet</u> (1 planet)
:{{w|Solipsism}} is the idea that only one's own mind is sure to exist. Randall extrapolated this idea to mean that only one's own planet that they are standing on is sure to exist.
:This projects (and relies upon) a more philosophical and/or semiotic assesment than any scientific one.

;Judgemental: <u>Only the prettiest ones are planets</u> (6 planets)
:This list is likely formulated from Randall's own perception of the prettiest planets in the Solar System. Strangely, seven objects are highlighted:
:* Earth
:* Jupiter
:* One of Jupiter's moons (unclear)
:* Saturn
:* One of Saturn's moons (unclear, possibly Titan)
:* Neptune's moon (probably Triton)
:* Pluto
:The subjectivity of this version of the definition makes it unlikely that a consensus of this form could be established.

;Empiricist: <u>Only worlds that I, author of this table, have personally seen are planets</u> (12 planets)
:This list may refer to the celestial objects in the Solar System that have been made visible at night, probably using with an optical telescope (a hobbyist one, perhaps Randall's, or from time borrowed on a major institutional installation). Jupiter's {{w|Galilean moons|four largest moons}} are [https://web.archive.org/web/20201112024151/http://denisdutton.com/jupiter_moons.htm technically visible to the naked eye] but hard to distinguish due to Jupiter's brightness, while Neptune is considered too faint to see (even if you know where to look). It may also be the case that Randall has never taken the time to look for Neptune while using a telescope. Apparently Randall has seen Uranus, which technically [https://www.skyatnightmagazine.com/advice/skills/how-see-uranus-in-night-sky Uranus ''is'' visible to the naked eye] under the very best viewing conditions, but these conditions are rare and it again requires knowing exactly where to look.
:The omission of the Sun from the list of worlds that Randall has personally seen is interesting. Yes, people are not supposed to stare at the Sun,{{citation needed}} but it is not too uncommon to accidentally look in its direction for a split-second before instinctively closing one's eyes and turning one's head away.
:As a different form of subjectivity, the value of this grouping's criteria is questionable, but not uncommon in other 'softer' sciences.

;Marine biologist: <u>Only objects with oceans are planets</u> (6+ planets)
:This list includes Earth, {{w|Europa (moon)|Europa}}, {{w|Ganymede (moon)|Ganymede}}, {{w|Callisto (moon)|Callisto}}, Titan, and {{w|Enceladus}}. Most of these have had the presence of significant water identified from the way local magnetic/electric fields are detected, but see the following item.
:There is a resemblance, here, to a loose understanding of what a "world" is, i.e. one that possesses various distinct 'terrains' beyond mere dry (and possibly considered featureless) rock. A marine biologist would, of course consider a marine (if not pellagic or bathyspheric) environment to be an essential element of any world.

;Maritime: <u>Only objects with ''surface'' oceans are planets</u> (2 planets)
:In the comic, only Earth and a Saturnian moon (likely to be Titan) are highlighted. Earth is the only body known in the solar system to have liquid water on the surface significant enough to be called an ocean. Titan's cold and dense atmosphere notably maintains surface 'seas' of methane and nitrogen, where other moons (given as additonal in the prior item) seem to have their liquid water beneath either whole-surface ice caps or otherwise deep under the surface.
:From the narrower point of view of a sailor, for example, there is no benefit in considering water hidden away far beneath the surface, and it might as well not be there. Whereas it's possible that a well-prepared mariner could eventually sail the strange seas of Titan, as easily (or easier) as an airman might {{w|Dragonfly (Titan space probe)|fly through its skies}}.

;Universalist: <u>They're all planets</u> (infinite)
:This list claims that all objects are planets, all drawn items (as also would presuming all undrawn/undrawable items) being marked as such, including the Sun.
:Giving up on any thought of exclusivity, this unconventional view willingly inducts all visible objects into consideration.

;Existentialist: <u>What if {{w|outer space|space}} ''itself'' is a planet???</u> (Duude)
:This list is different from the list above as it claims that all of space, rather than only the objects existing in space, are planets. The interjection ''Duude'' expresses one's amazement at this 'revelation' and replaces the number count— and is sometimes stereotyped to imply the speaker is high on marijuana or other drugs popular with the 1960s hippie counterculture.
:The strange stretch of imagination, as prompted by some narcotic or other, abandons all pretense at sensibly sorting everything into "planet" or "not planet", as not only is everything a planet, but so is the nothing ''between'' these titular planets.

;Spiteful: <u>''Only'' Pluto is a planet</u> (1 planet)
:This list is a malicious play on the demotion of Pluto by demoting all other planets except Pluto instead, leaving Pluto as the only planet in the solar system.
:This is the taxonomic equivalent of refusing to play and taking your ball home to spite those who you think don't deserve it.

;(title text) {{w|Star}}: <u>Earth is a star</u> (2 stars)
:In May 1934, Mark Oliphant, Paul Harteck and Ernest Rutherford at the Cavendish Laboratory, published an intentional deuterium fusion experiment, and made the discovery of both tritium and helium-3. This is widely considered the first experimental demonstration of fusion. Randall considers that this makes Earth fall into the category of a star due to the human-induced ability for Earth to fuse hydrogen into helium using nuclear fusion.
:By changing not only the definition, but the term being defined, this drifts yet further from any consensus view on the original question and into a typical punchline absurdity.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[A table with 3 columns, and 17 rows below the the header row, labelled "Definition", "# of planets" and "Solar system".]
:[In each row, the first column has a single word, in bold, then a descriptive sentence. The second column has a digit or other 'value'. The third column is a not-to-scale drawing of the Solar system, featuring the Sun, various 'planetary' bodies and an apparently selective sample of moons/asteroids, as follows: The Sun, Mercury, Venus, Earth + The Moon, Mars + two moons (Phobos and Deimos), a small selection of Asteroid Belt bodies (Ceres in the midst of other, smaller, examples), Jupiter + four moons (likely Io, Europa, Ganymede and Callisto), a ringed Saturn + usually one moon (probably Titan) or two (possibly Enceladus or Iapetus, as required), Uranus + four or five moons (likely to be Miranda, Ariel, Umbriel, Titania and Oberon, but one of these (shown upon the face of Uranus) only appears in some iterations of the base image), Neptune + one moon (probably Triton), Pluto + one moon (Charon), four more plutoid/Kuiper Belt objeccts (too little context to identify, but possibly Haumea, Makemake, Gonggong and Eris, in distance order), the first two of them with distinct moons indicated (entirely dependent upon which main objects they are).]
:[Each row's illustrated solar system has indivudal combinations of green highlights applied to the otherwise repeated diagram.]
:[Row 1: Definition:] Traditionalist: Pluto is a planet [Number:] 9 [Highlit: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto]
:[Row 2: Definition:] Modern: Pluto is not a planet [Number:] 8 [Highlit: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune]
:[Row 3: Definition:] Expansive: Dwarf planets are planets [Number:] 17+ [Highlit: Mercury, Venus, Earth, Mars, Ceres (in Asteroid Belt), Jupiter, Saturn, Uranus, Neptune, Pluto and the further main bodies]
:[Row 4: Definition:] Ultratraditionalist: Only the classical planets are planets [Number:] 5 [Highlit: Mercury, Venus, Mars, Jupiter, Saturn]
:[Row 5: Definition:] Condescending: Only giant planets are planets; the rest are big asteroids. [Number:] 4 [Highlit: Jupiter, Saturn, Uranus, Neptune]
:[Row 6: Definition:] Simplistic: Anything gravitationally round is a planet [Number:] 37+ [Highlit: The Sun, Mercury, Venus, Earth, The Moon, Mars, Ceres (without other asteroids), Jupiter + moons, Saturn with Titan, Uranus and its moons, Neptune with its moon, Pluto and the four further dwarf planets]
:[Row 7: Definition:] Grounded: Only objects a spaceship has landed on are planets [Number:] 10 [Highlit: Venus, Earth, The Moon, Mars, five (non-Ceriese) asteroids and Titan]
:[Row 8: Definition:] Regolithic: Anything covered in dirt and ice and stuff is a planet [Number:] [infinity symbol] [Highlit: Mercury, Venus, Earth, The Moon, Mars, Ceres with all other asteroids depicted in the Asteroid Belt, the moons of Jupiter, the sole moon! of Saturn, the moons of Uranus, the moon of Neptune, Pluto with  Charon, and all remaining dwarf planets with their moons]
:[Row 9: Definition:] Lunar: You can't be a planet if you don't have a moon [Number:] 12+ [Highlit: Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and three of the other dwarf planets in the Kuiper belt, including one with no obviously drawn moon]
:[Row 10: Definition:] Solipsitic: Earth is the only planet [Number:] 1 [Highlit: The Earth]
:[Row 11: Definition:] Judgemental: Only the prettiest ones are planets [Number:] 6 [Highlit: The Earth, Jupiter with one of its moons (not identified), Saturn, one of ''two'' Saturnian moons in this image and Pluto]
:[Row 12: Definition:] Empiricist: Only worlds that I, author of this table, have personally seen are planets [Number:] 12 [Highlit: Mercury, Venus, The Earth, The Moon, Mars, Jupiter with its four moons, Saturn and Uranus]
:[Row 13: Definition:] Marine biologist: Only objects with oceans are planets [Number:] 6+ [Highlit: The Earth, three Jovian moons, the two illustrated Saturnian moons]
:[Row 14: Definition:] Maritime: Only objects with [next word in italics] surface oceans are planets [Number:] 2 [Highlit: The Earth and Titan]
:[Row 15: Definition:] Universalist: They're all planets [Number:] [infinity symbol] [Highlit: All drawn objects, including The Sun and all other objects including all the moons/asteroids]
:[Row 16: Definition:] Existantialist: What if space [next word in italics] itself is a planet??? [Word, in italics:] Duude [Highlit: The whole third column cell]
:[Row 17: Definition:] Spiteful: [next word in italics] Only Pluto is a planet [Number:] 1 [Highlit: Pluto]

==Trivia==
*In the [https://www.explainxkcd.com/wiki/images/archive/6/66/20250314195557%21planet_definitions_2x.png original version of the comic], there were two errors that would alter be fixed. The "Traditionalist" definition highlighted Neptune's satellite {{w|Triton (moon)|Triton}} instead of Pluto. The images of the Solar System for the "Traditionalist" and "Modern" definitions were swapped, resulting in Pluto being incorrectly highlighted in "Modern" and omitted in "Traditionalist.

*The "Judgemental" definition has seven colored objects instead of the labelled six. This mistake has never been fixed.

{{comic discussion}}

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