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Why the Word 'Planet' Will Never Be Defined 141

eldavojohn writes "What makes a planet a planet? Slashdot covered the great debate about whether or not Pluto qualified and now has up an article explaining why we'll never have the term 'planet' defined to a point that everyone can agree on. Divisions in the scientific community currently stand over whether or not it has to be in orbit around a star, the dynamics of the body in question and apparently the country you come from plays a part in it too. Some feel the United States is the dominant deciding factor on the definition but the IAU has not turned to democratizing the definition yet." From the article: "In the broadest terms, a planet could be thought of as anything from an 800-kilometer-wide (500-mile-wide) round rock orbiting a dead star to a colossal gas ball floating alone in space."
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Why the Word 'Planet' Will Never Be Defined

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  • Background info (Score:1, Informative)

    by Anonymous Coward
    This [] article has some good background info. Also see the article on the redefinition [].
    • Re: (Score:1, Funny)

      by Anonymous Coward
      why hasn't this been moderated up??
      • Too easy. It's almost like saying look here [] for more info. It's one click away from being the same thing, and arguably more informative, since I'm providing more than two links.

        P.S. Thanks for not going the "MOD PARENT UP" route.

  • by Nijika ( 525558 ) on Tuesday November 21, 2006 @02:05PM (#16934970) Homepage Journal
    Floating mass of sh*t bigger than the moon that isn't on fire, but that is orbiting some floating mass of sh*t that is, in fact, on fire.
    • Re: (Score:2, Funny)

      by Anonymous Coward
      So your mom pacing around a burning trash can would be a planet but the rest of her skinnier homeless friends wouldn't be? That isn't fair.
      • Re: (Score:1, Funny)

        by Anonymous Coward
        Last night his mom and I became a "double planet" for awhile.
    • Re: (Score:2, Funny)

      by Anonymous Coward
      Floating mass of sh*t bigger than the moon that isn't on fire, but that is orbiting some floating mass of sh*t that is, in fact, on fire.

      Respectfully, Sir, your definition is full of floating sh*t.

    • Re: (Score:2, Funny)

      by Anonymous Coward
      Floating mass of sh*t bigger than the moon that isn't on fire, but that is orbiting some floating mass of sh*t that is, in fact, on fire.

      Define "Moon".
    • So if the mass of sh*t we live on all live on suddenly stops orbiting the mass of sh*t that is on fire it stops being a planet??
      • Re: (Score:3, Insightful)

        by geoffspear ( 692508 )
        If the Earth suddenly stops orbiting the Sun, I can confidently say that no one will care about the defintion of "planet" anymore. But since I can't imagine a situation in which we suddenly stopped being in orbit around the Sun that doesn't involve the planet soon afterwards being sucked into the Sun and crushed, I'd say "yes".
      • If I'd be serious for a moment here, yes, actually that sounds sensible to me as for large random spherical objects drifting around in space. Why not?
    • Re: (Score:3, Interesting)

      by ozbird ( 127571 )
      Define "on fire". For example, white dwarves that orbit a star (e.g. Type Ia supernova progenitors) are hot, but not "on fire" ("burning" nuclear fuel); are they "planets"?
    • For a moment I thought the Death Star could be clasified as a planet but then recalled that it's only 120 kilometers in diameter which is much smaller than the moon...
  • democratic? (Score:3, Insightful)

    by SillyNickName4me ( 760022 ) <> on Tuesday November 21, 2006 @02:06PM (#16935022) Homepage
    Some feel the United States is the dominant deciding factor on the definition but the IAU has not turned to democratizing the definition yet."

    Lets see now.. democratically deciding a definition? hmm...

    At any rate, the USA being the dominant deciding factor might make some sense seeing how they also invest a lot into the actual science part of this, but if the IAU did turn to democratize the decision, then the USA can't be the deciding factor seeing how they are a mere 4% of the world population....

    • Lets see now.. democratically deciding a definition? hmm...
      I think the closest we've ever come is wiktionary [].
    • Re:democratic? (Score:4, Insightful)

      by vertinox ( 846076 ) on Tuesday November 21, 2006 @03:49PM (#16937620)
      Lets see now.. democratically deciding a definition? hmm...

      To be fair, all definitions are democratically decided even if no one votes on them.

      If tomorrow everyone on the earth decided to call what we use to call the color blue as the color red... Then tomorrow the sky would be red.

      If tomorrow everyone decided that a yard (or meter or what have you) is not 3 feet but now four and we adjusted all our documentation and measurement tools to reflect this then it would be so.

      Heck... We could even call the Antarctic hot and the Sahara cold as long as we all agreed that the term hot meant one would "burn" to death of hypothermia and you would "freeze" to death of heat exhaustion.

      Really... Definitions themselves do not imply or detail facts.

      Calling something a moon or a planet does not change its behavior or physical properties, but it does change how we as humans relate to said objects and property behaviors.

      Of course we don't go around changing things willy nilly because it is hard to get everyone to agree all at the same time. Although... Come to think of it... Since we are not all speaking English on this world of ours, we might not be really agreeing as much as we think.

      Sometimes terms in other languages used for the same object or property, doesn't have the same exact meaning as another languages word for the same thing.
      • Re: (Score:3, Insightful)

        If I say that whatever everyone else calls blue is in fact called red, then I made a definition. The fact that noone other then me might use it doesn't change that. While the usefullness of a definition often depends on how well accepted it is within the target audience, definitions themselves do not depend on that.

        • If I say that whatever everyone else calls blue is in fact called red, then I made a definition.

          Fair enough.

          But if you disagree with the everyone else in the world, then you risk them defining you as insane.

          Although, without insanity, life would be very boring.
          • But if you disagree with the everyone else in the world, then you risk them defining you as insane.

            It seems they do that anyway.
    • Democracy in USA has been lobbied to death. If you want special treatment for SUVs so they don't get nailed by regulations, go talk nicely to DoE/EPA.

      If you want the moon to be a planet, and greased the right palms, you could probably swing it.

  • by StressGuy ( 472374 ) on Tuesday November 21, 2006 @02:11PM (#16935128)
    actually called an "Air Biscut"....never heard it described as a planet before, but, I suppose if it really were that colassal....
  • by PsyQo ( 1020321 )
    I would define a Planet as: A relative of Captain Planet
  • by Channard ( 693317 ) on Tuesday November 21, 2006 @02:12PM (#16935178) Journal
    'A series of gaming sites ran by counter strike kiddies who think that half life 2 is going to be better than far cry.'. Not sure I quite get that 100%, but you can't argue with the wisdom of the internet.
  • Oh really? (Score:5, Funny)

    by spellraiser ( 764337 ) on Tuesday November 21, 2006 @02:15PM (#16935266) Journal

    #define PLANET

    Don't see what's so hard about that ...

    • Re: (Score:3, Funny)

      by PseudoQuant ( 916182 )
      Unfortunately, your method is error prone and dependent on header order. See, I just undid your definition:

      #undef PLANET

  • They say that Pluto's
    Not quite a planet.
    These KBOs
    Are goofy, dammit.
    Burma Shave.
  • Original Meaning (Score:5, Insightful)

    by scottennis ( 225462 ) on Tuesday November 21, 2006 @02:17PM (#16935326) Homepage
    From Wikipedia:

    In ancient times, Grecian astronomers noted how certain lights moved across the sky in relation to the other stars. These objects were believed to orbit the Earth, which was considered to be stationary. The "wandering" lights were called planets, a Greek term meaning "wanderer".


    Why not just stick to this original definition? If it "wanders" among the stationary celestial lights and casts light visible to the naked eye, it's a planet.

    Everything else can be labeled SAO "speculative astronomical object."
    • Re: (Score:1, Insightful)

      by Anonymous Coward
      Why not just stick to this original definition? If it "wanders" among the stationary celestial lights and casts light visible to the naked eye, it's a planet.

      Your definition of planet includes commets, which the Greeks didn't count as planets. To answer your question, the problem with the original definition is it doesn't let people claim they discovered a planet. That's the whole reason silly things like Pluto are counted as planets, because finding another KBO isn't going to make your name go down in
    • So the Earth is not a planet?
      • From the classical definition: does the Earth look like a wandering light in the sky? No, so the Earth is not a planet. Neither is Neptune. What they are are spherical objects orbiting the center of mass of local solar system, as well as the center of the galaxy, and the center of mass of the Local Group, etc. Call them "spherobs" or somesuch if you *must* have a simple word.

        That's it! From another classical source: "Earth is a class M spherob".
    • by mcmonkey ( 96054 )

      Why not just stick to this original definition? If it "wanders" among the stationary celestial lights and casts light visible to the naked eye, it's a planet.

      Why not? First, everything in the sky "wanders," perhaps not at a rate comparable to the motion of the planets, but for whatever arbitrary set of objects you call "stationary celestial lights" everything else moves.

      Second, your definition would rename everything we think of as a planet to non-planet, and rename stars, galaxies, and other objects p

    • This would mean that Neptune, Uranus and Pluto would no longer be planets as they are not visible with the naked eye. What do you call Neptune then? A large asteroid?
  • by dannys42 ( 61725 ) on Tuesday November 21, 2006 @02:18PM (#16935342)
    Anything equal to or greater than the size of Marvin's brain.
  • Why is this so hard? (Score:5, Interesting)

    by Thraxen ( 455388 ) on Tuesday November 21, 2006 @02:22PM (#16935442)
    I don't get the problem? First, start off with the idea that a planet must be orbiting a star... similar to how moons are defined as orbiting a planet. Even if they are orbiting a pulsar (dead star) they are still planets, but not if they are orbiting a failed star (brown dwarf). If you find a brown dwarf with satellites call that something else. Then the article mentions the possibility of having planet sized objects orbiting each other the same way binary stars orbit one another. OK, make that a seperate category. After that just define the mass need to be called a planet and be done with it. I'm sure there are plenty of other scenarios out there that need to be defined, but the basic rules don't seem difficult to set up.
    • Re: (Score:3, Interesting)

      by greginnj ( 891863 )
      Here's why: []

      Basically, you can have an item in a multi-star system -- is it in a stable orbit around one of them, or is it just doing a few loop-de-loops on its way through? Can it orbit 2, 3, ..., n stars at once? s/980122c.html [] With multiple star systems with large interstellar distances, its orbit could be millions of years -- by which time the stars have changed relative position, in which case 'stable orbit' l
    • by sco08y ( 615665 )
      start off with the idea that a planet must be orbiting a star

      So if you knock it out of orbit (somehow...) it changes into "not a planet"?

      A sibling post raised a similar point, so we're both arguing that where it happens to be shouldn't affect the definition. It defies our (well, my at least) intuitive understanding of the word to determine a body's identity by where it happens to be.

      But you're on the right track, I think. What if we determined it based on something more essential, like how it was formed? So
    • by waveclaw ( 43274 )
      Technically, planets are orbited by satellites and there is but one Moon, the largest narual satellite of the Earth.

      I don't get the problem? First, start off with the idea that a planet must be orbiting a star... similar to how moons are defined as orbiting a planet

      And I do stress technically. In Chemistry, physics and even lowely IT humans use specialized jargon and words with precise definitions. It's like a network protocol, if you going to exchange information about something it would be nice to have
  • We need to simplify these definitions for the greater good of humanity...

    Here's my suggestion...

    satellite = thing
    planet = thing+
    star = thing ++
    comet/asteroid = thing-
    spacedust = thing--
    • Why not just call everything a satellite? Everything is affected by the gravity of something else. If you simplify it to say that all objects are satellites, but some of those satellites have satellites, you replace an ever complicated system with one simple word. Now, you'd have satellite classifications which could get complicated as well, but if it's well thought out, you should be able to tell by the classification what type of object it is.

      star(Sun) = satellite
      Earth = satellite
      Moon = satellite
  • If you don't like the IAU decision, file an appeal with the Intergalactic Circuit Court.

    Unfortunately, as we do not have the minimum 9 planets required to qualify as a class A solar system, we will have to wait for a trial date with a municipal court first.

  • by Ant P. ( 974313 ) on Tuesday November 21, 2006 @02:37PM (#16935834) Homepage
    "Anything which is roughly spherical under its own gravity, in a more-or-less circular orbit around the sun, and its orbital path isn't shared with an object larger than itself."
    • by 2short ( 466733 )
      So Ceres is a planet, though I don't know if you consider that a problem. Also, one could envision a couple as-yet undiscovered Oort cloud objects in the same fairly circular orbit and whichever is a tiny bit bigger is a planet and the other is not, and that would be unsatisfying.
      • I liked this definition too, until I found out there would be 50-something things in the solar system that would therefore count as a planet.
    • The problem is that "roughly" and "more-or-less" or not rigorous, so that definition will cause endless arguments about whether or not an object is "roughly spherical" and whether or not it's object is "more-or-less" circular.
    • Any liquid in space will be roughly spherical under its own gravity. Congratulations constellation urinous: you're now a collection of planets.

      Earth only has a "more-or-less circular orbit" right now, but it's not always that way [], so we wouldn't be on a planet anymore.

      I'm not sure what you mean by "orbital path isn't shared," but that would seem to discount binary planets, among other things.
  • How about "It is a planet if Galactus would consume it" ?
  • The definition of the word "planet" will matter in the future when it comes to mining in "hey, you have to pay a different amount of tax when you're mining a planet vs. an asteroid vs. a planetoidy thing."
    • In that case the legislators will use a different definition than others: for example, a tomato counts as a vegetable for taxation purposes even though it's botanically a fruit.
  • Why define it? (Score:5, Insightful)

    by Dirtside ( 91468 ) on Tuesday November 21, 2006 @02:40PM (#16935902) Journal
    The real question is, why do we need a precise, "official" definition of "planet"? Astronomers and other scientists aren't going to make scientific decisions based on it -- it's not like it matters whether Pluto is officially a planet according to the IAU when an astronomer decides to study Pluto. "Oh, the IAU says it's not a planet, therefore it's not interesting enough to study."

    In general, the whole point of category words like "planet" is so that I can point at an object and say, "That's a planet," and you immediately have some basic information about it, because we agree on what "planet" means. But if we're scientists, studying it (or deciding whether to study it), then we need a whole lot more info. Gas giant? Small, terrestrial rock? Iceball? Distance from star? Eccentricity of orbit? Etc. "Planet" doesn't tell you any of that.

    Ultimately, the main reason to specify an "official" definition of "planet" is for the sake of deciding whether and how we want to encourage space travel, exploration, astronomy, and related sciences. To give an extreme example, if the definition of "planet" included any solid body primarily orbiting a star, there'd be millions of planets in every star system, and saying that NASA's going to go explore a planet would be meaningless. The public wouldn't care and wouldn't go out of its way to support it.

    At the other extreme, limiting the planets to rocky or gaseous bodies at least the size of Mercury, orbiting a star, and having a very low orbital eccentricity, means that when you discover a body that only misses ONE of those criteria, the definition seems arbitrary and people will just ignore it. Imagine if we find a trans-Neptunian object that's the size of Mars, and is a rocky, terrestrial body like Mars, but merely has an eccentric orbit? Very few laypeople would accept that that's not a planet, mostly because laypeople's perception of a stellar body is based on its physical characteristics, not its orbital ones. If Earth was somehow flung out into space, orbiting nothing, it'd stop being a planet? (Well, we'd all be dead, but that's another issue.)
    • Re:Why define it? (Score:4, Insightful)

      by nine-times ( 778537 ) <> on Tuesday November 21, 2006 @03:20PM (#16936920) Homepage

      The real question is, why do we need a precise, "official" definition of "planet"?

      Yes, exactly. The word "planet", as used today, describes a specific collection of bodies in our own solar system. It was devised by ancient astronomers to describe the lights in the sky that didn't follow the normal pattern of stars. Stars go in circles, planets go back and forth. The word has taken on a new meaning as our understanding of celestial bodies has grown, but now it's generally used to indicate that one of the collection of 9 specific bodies. Just as "sun" is used to indicate our star specifically, "planets" indicate specific bodies orbiting our sun.

      If we really need a more general definition that's more scientific than "largish body that orbits a star," for the sake of scientific accuracy, then come up with a new term. Take the word "far" for example. It's a general-use word, not a scientific one. We might use it when talking about scientific issues, like, "the nearest star to the sun is far away," but it doesn't have scientific accuracy. This doesn't mean that we need to define "far" as "greater than 1 light-year" and then try to force people to stop claiming that someplace on earth is "far". It means that, if you want a precise scientific term to indicate "greater than 1 light-year away", you need to come up with a new word which isn't "far".

    • Re: (Score:3, Insightful)

      by aitala ( 111068 )
      Why define it? Cause that's one of the things astronomers do... they define and classify objects. Its just gotten more complicated because of new objects in the Solar System and around other stars...

    • Agreed: put it this way. Geologists don't lie awake at night worrying about the definition of the word "continent".
    • by deblau ( 68023 )
      The real question is, why do we need a precise, "official" definition of "planet"?
      Because people use words to communicate, and important words should be more precise to improve communication.
  • by mpthompson ( 457482 ) on Tuesday November 21, 2006 @02:41PM (#16935914)
    ... so why not the IAU. Simply break planets down into different subclasses. Everyone knows that Earth is a Class M [] planet.

    There's already a helpful classification guide [] to help them get started.
  • by oneiros27 ( 46144 ) on Tuesday November 21, 2006 @02:44PM (#16935990) Homepage
    It's a problem with any discipline -- language is not exact.

    What qualifies as meat? Does seafood count as meat? Not for Catholics.

    What qualifies as a person? What about in utero? Maybe for manslaughter, but why not count that time for age restrictions?

    What qualifies as blue? Is cyan blue enough? It depends on what you're using the category for.

    Anyone who's tried to work on standardize terminology (eg, specialized thesauri, or even just a controlled vocabulary) will know that it is a long, exhasting process that takes years in some cases, and even then, is likely to change.

    Planets are not a classical category [], and will be subject to prototype effects [].
    • Re: (Score:3, Interesting)

      by zeromorph ( 1009305 )

      It's a problem with any discipline -- language is not exact.

      Language is as exact as needed for everyday interaction. But some disciplines decided that they need a less flexible (and in some respects less effective) but more rigid medium and so they decided to define the terms they use normatively. That's why we have logic, algebra and other formalisms. In jurisprudence and the humanities/arts it works different, but they nonetheless deviate from everyday language.

      Now we have to decide whether the term "

    • Re: (Score:3, Interesting)

      by radtea ( 464814 )
      Planets are not a classical category, and will be subject to prototype effects.

      The basic premise behind classical categories is in any case nonsensical, so is isn't clear what benefit there would be if planets fell into any of them.

      Physics has been steadily eroding the Aristotlian world view for centuries now, and the categories died with Einstein's unified description of space and time. Aristotle was an acute observer of the human condition, and his world view accurately captures a vast amount of folk-epi
  • Yeah, sure. (Score:1, Interesting)

    by Anonymous Coward
    And it has nothing to do with the fact Americans have discovered only one object (in Sol System) that COULD, by much stretching and wigging with the definition classify as planet (Pluto), but shouldn't really.

    And the fact that it's bleeding obvious to any European, (or unbiased American) that we have EIGHT planets, while it's (mostly) Americans who seem to be violently opposed to the idea of Pluto not being a planet is a mere coincidence.
  • planet := thing_in_space && !moon && !star && !comet && !black_hole && !white_dwarf && !satellite && !garbage && !deathstar

    Piece of cake.
  • Planet = anything that was suggested as possibly existing by Lowell, even if it turns out only to be a fraction of the predicted size, so as to distract the world from the fact he was convinced there was an advanced civilisation on Mars.
  • Uranus is huge but its not a planet! :-)
  • Just ask the Intellectual Property Lawyers from Magrathea... I bet they have a clear definition.

    A scientific definition may be hard to come by, however when the time comes a legal one sure won't be.
  • The real problem (Score:4, Informative)

    by edwardpickman ( 965122 ) on Tuesday November 21, 2006 @02:59PM (#16936402)
    There can't be one definition because there are three classes of planets. Gas giants, rocky planets and icy planets. The big argument is whether to include icy planets but icy planets are closer to earth than gas giants so how do you include one but not the other? The sensible definition to come up with three classes and require them to orbit the sun to exclude moons and to have sufficent gravity for a roughly round shape, the Earth isn't perfectly round. What it would leave us with is four rocky planets, four gas giants and a similar number of icy planets. The Oort cloud gets tougher. Since they still orbit the sun it might be wise to come up with a fourth definition of outer planets for any Oort Cloud objects. One excuse for eliminating Pluto was it's eliptical orbit but most planets have eliptical orbits so that factor gets arbitary. Splitting the definition avoids demoting any planets and allows for new objects including some that may not fit well with the current definition.
  • "...a colossal gas ball floating alone in space." Ugh, that reminds me, I have to call my uncle.
  • One of the reasons the IAU tackled this issue at the last conference was politics - because the report from the Planet working group was leaked, the IAU felt they had to 'do something' fast because 'the press was watching'. They managed to make an entire mess of the process, including creating the redefinition 'rules' in a matter of days, and basically confusing the entire voting process...

    I learned this from someone who was actually at the conference... and I was quite frankly appalled at they way they h
  • by j_f_chamblee ( 253315 ) on Tuesday November 21, 2006 @03:04PM (#16936520) Homepage Journal
    Richard Feynman had something to say about this debate, though somewhat obliquely. The parentheticals below are my own.

    "You can know the name of a bird (or a planet) in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird (or planet)... So let's look at the bird ( or planet) and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something."

    The point here is that scientific knowledge (whether it be social, biological, or physical) is about explaining how things work (understanding processes) or why they are the way they are (understanding variation). Debate over essentialist categories like "planet," "species," "nation-state," etc. are, as one other person in this discussion has already mentioned, problems of language.

    Interestingly, Wittgenstein [] might have a thing or two regarding this topic as well, especially in later work [].
    • You can know the name of a bird (or a planet) in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird (or planet)... So let's look at the bird ( or planet) and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something.

      Wikipedia gives me 5 names in 4 languages for the Malachite Kingfisher []:
      English: Malachite Kingfisher
      Latin: Alcedo cristata
      Afrikaans: Kuifkopvisvange

  • We see almost as much variation in types of stars, yet we have a very clear definition of what a star is. The key is the ability to classify them. Stars are easy to see and catalog, direct observation can be performed by anyone with a modest telescope, so a classification system is easy when you have a catalog of millions(billions?). We've directly seen about 10 "planets", we've detected through indirect means an additional ~190 "planets". We don't yet have the technology to observe directly. Until we do, w
  • The definition of "planet" is now based on a body's relationship to its surroundings, and as long as we're clear on that I don't see the problem. The same thing goes for "moon", "island", etc. Without water around it, it's not an island, it's a hill or a mountain.

    We can have other terms to describe bodies that don't relate to their surroundings, but it's a nice, concise way to describe a body as a part of a solar system.
  • I don't understand why we don't just call them all planets and then drop em into different classes of planets ala Star Trek. This way you can call them all planets still, pluto and whatnot will just fall into a different class of planet. What is the drawback to this? That we'll have more planets? big deal!
  • Just make the definition:

    Anything larger than (some arbitrary size larger than Pluto but smaller than Mercury). All objects identified as planets prior to 1950 shall still be considered to be planets, even if they do not otherwise fit this definition.

    That's the easy way of saying that Pluto shouldn't be a planet, but will be considered one anyway. I don't understand all the fuss. It's not like Pluto will have its feelings hurt or have a party one way or the other. Since I see more support for leaving
  • That is, an object that orbits the sun, is large enough to be round, and has "cleared the neighbourhood" of smaller objects.

    Most people seem to trip up on the last part. I think the idea is that an object shouldn't have any "rivals" in its orbit, for lack of a better word. I was browsing some astronomy sites a few months ago and found a good page on Sedna which had a discussion of what should be considered a planet. This is before the recent reclassifications but I think it illustrates what the IAU was thi
  • The term "planet" will never be officially defined because no one besides some obsessive-compulsive grammar nazis cares whether some dead rock floating through outer space should be called "planet" or "planetoid".

    Not a flamebait nor a troll, but the simple truth. Real scientists have better things to do than play around with semantics, and no one cares what the armchair astronomists say.

  • I love the smell of schadenfreude in the morning. :)
  • To help us navigate the goofily drawn line between planet and dog, perhaps it would be "civil" of us to just create the abstract notion of a "union of particles orbiting the sun". We could then define Pluto as one of those, and leave the religious issue of which such unions should be marryable to the word "planet" to the respective scientific faiths to sort out. I'm sure that with an appropriate number of masses it will all work out divinely.

  • The classification of living organisms is in constant flux. A century or so ago, there were two kingdoms: animalia and plantae. Parameciums were animals, mushrooms were plants.

    When I was in high school, there were three: animal, vegetable, and protista, it being felt that single-celled organisms really weren't typical animals. It may shock some--it certainly shocked cellular biologists when I was in grad school--to know that circa 1940-1950 there was serious consideration given to the concept that protozoan

  • Here's what the definition should be;

    Planet: Any planetary body that has an atmosphere that orbits that may or may not a star. If they exist, this could include rogue planets.

    Moon: Any planetary body that orbits a planet is considered a moon with one exception of similar asteroids as Phobos or Deimos.

    Asteroids, Comets, Etc: Any planetary body floating anywhere that do not have an atmosphere and primary made minerals of nearby other asteroids. Phobos and Deimos
  • As I figure the difference between "large rock orbiting the sun" and "larger rock orbiting the sun" will never be too important, why not define a planet by some standard of surface gravity, the point where it can hold gases without requiring the gases to be attracted to the body by some other force?
  • The IAU had a great draft which basically said if it orbited a star, and was roughly spherical under its own gravity, and wasn't itself undergoing nuclear fusion it was a planet. Nothing at all wrong with this definition. I couldn't give a shit if Pluto was called a planet or an Oreo. THAT definition was self consistent and just plain made sense.

    However a definition that makes a "Dwarf Planet" not a planet, and anything not orbiting our sun not a planet (despite the scientific community having talked and of

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