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Our Moon Could Become a Planet

Posted by CowboyNeal on Fri Aug 18, 2006 05:55 AM
from the size-does-matter dept.
Space Science
anthemaniac writes "Earth's moon is drifting away from us more than an inch every year. In a few billion years, if the system survives, the moon would be reclassified as a planet under the new IAU definition. You gotta wonder if the astronomers who dreamed this definition up had thought of that."
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[+] IAU Proposes 3 New Planets 316 comments
IZ Reloaded writes "Sources tell SPACE.com that the International Astronomical Union is preparing to include three new entries to the current list of planets in our solar system. From the article: The asteroid Ceres, which is round, would be recast as a dwarf planet in the new scheme. Pluto would remain a planet and its moon Charon would be reclassified as a planet. Both would be called "plutons," however, to distinguish them from the eight "classical" planets. A far-out Pluto-sized object known as 2003 UB313 would also be called a pluton."
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  • Because *somebody* has to say it... (Score:5, Funny)

    by Anonymous Coward on Friday August 18 2006, @05:57AM (#15933383)

    That's no moon!

  • In a few billion years... (Score:5, Informative)

    by advocate_one (662832) on Friday August 18 2006, @06:00AM (#15933388)
    both the Earth and Moon will have been swallowed up by the Sun when it becomes a red giant...

  • It'll last our time (Score:5, Informative)

    by MathFox (686808) on Friday August 18 2006, @06:00AM (#15933389)
    "The sun will turn in a red giant before the moon gets far enough away to be classified as a planet"
  • In a billion years propably the defintion of planet will have a few thousand updates.
    The problem will fix itself in time I guess.

    • Re: (Score:3, Insightful)

      by Flibz (716178)
      Plus the human race will have rendered the Earth uninhabitable by then so there'll be nobody to care...

  • Hmm (Score:4, Insightful)

    by Klaidas (981300) on Friday August 18 2006, @06:07AM (#15933415) Homepage
    No-one knows if the humans will survive that long, maybe there will be no-one to rename it.

    • Re:Hmm (Score:5, Insightful)

      by kalirion (728907) on Friday August 18 2006, @08:00AM (#15933880)
      No-one knows if the humans will survive that long, maybe there will be no-one to rename it.

      A billion years? If our descendents exist by that time, they won't be considered human by our current definitions. I think it's a safe bet that the only way humans as we know them today could survive that long would be by either time-traveling or becoming a part of some aliens' (or dolphins') "Save the Humans" project.

  • It's not a moon... (Score:5, Funny)

    by aadvancedGIR (959466) on Friday August 18 2006, @06:08AM (#15933423)
    ...oh well, forget it, it's still a moon.

    Reminds me of that old joke telling that a quick computation on the evolution of this distance placed the moon 4 meters away from the earth 65 million years ago and thus explained why the dinausors died. ...at least the tallest ones.

  • This is going to complicate things. (Score:4, Funny)

    by gklinger (571901) on Friday August 18 2006, @06:10AM (#15933432) Homepage
    So basically my 100 millionths offspring's offspring is going to have a hell of a job making a solar system model for their fifth grade science project? Yikes! Up to now their only concern was how they were going to pay off my credit card debt.


    Seriously though, the International Astronomical Union better give this a second thought. I may be woefully ignornant on the subjecct but I really don't see why sticking with the current definition is a problem. I wish the article gave more information as to why they're 'fixing' that which doesn't appear broken.

    • Re:This is going to complicate things. (Score:5, Insightful)

      by terevos (148651) on Friday August 18 2006, @06:26AM (#15933479)
      I may be woefully ignornant on the subjecct but I really don't see why sticking with the current definition is a problem.


      Could you tell me what the 'current' definition is?

      The problem was that there wasn't a definition before. More of just an accepted method of measurement. And it was arbitrary. I think it was generally based off of 'anything as big or bigger than pluto is a planet'. That's not scientific at all. The new definition is great. It relies on science to determine the status of 'planet' rather than something arbitrary picked out of the sky to satisfy what people had learned in grade school.

      • Re:This is going to complicate things. (Score:4, Insightful)

        by gklinger (571901) on Friday August 18 2006, @06:45AM (#15933538) Homepage
        Heretofore a planet was (loosely) defined as a large mass in orbit around a star. In our solar system the primary tenet of planethood was that the object orbited the Sun rather than orbiting a body which orbited the Sun. There are other conditions, of course, because not everything that orbits the Sun is a planet but it's a good place to start. Simply put though, if an object doesn't meet the criteria of a) orbiting the sun and b) being of a certain size or larger it doesn't make the cut. If the IAU dispenses with or at least loosens those two historical criteria the solar system will suddenly be filled with planets and confusion (at least amongst the non-astronomer crowd) will ensue. That's the real problem. I think there is more to think about than simple semantics.

      • Re:This is going to complicate things. (Score:4, Funny)

        by Pike (52876) on Friday August 18 2006, @09:02AM (#15934251) Homepage Journal
        Could you tell me what the 'current' definition is?


        Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and that new one.

  • Many things will happen ... (Score:4, Insightful)

    by Ihlosi (895663) on Friday August 18 2006, @06:22AM (#15933470)
    ... when hell freezes over.



    In a few billion years, if the system survives,



    If we manage to figure out a way to move Earth away from the sun before it goes red giant, it will most likely involve leaving any unnecessary baggage (like orbiting balls of rock) behind.

  • Few Billion Years? (Score:5, Insightful)

    by the_crowing (992960) on Friday August 18 2006, @06:27AM (#15933483)
    I really don't think humans will last another thousand years (with the way we're poluting the environment and declaring war on each other plus the rising threat of nuclear weapons) let alone another few billion years. And provided we do last that long, I'm sure the standards for classifying planets will have changed hundreds of more times by then.

    • Re:Few Billion Years? (Score:4, Interesting)

      by Control Group (105494) on Friday August 18 2006, @09:20AM (#15934399) Homepage
      I think you're confusing the term "humans" with "human civilization as we are familiar with it."

      The odds of current civilization lasting another thousand years may be low, for the reasons you cite. The odds, however, of us successfully wiping out so much of the population that humans are no longer a viable species within the next thousand years are, in my opinion, fantastically low. We breed too fast, we're spread over 30% of the planet's total area, and we're highly adaptable to changing conditions.

      Frankly, I fully expect some descendant species of humans to be living here pretty much right up until the planet is inside the sun.

  • Taking the long view? (Score:5, Funny)

    by Rob T Firefly (844560) on Friday August 18 2006, @07:38AM (#15933767) Homepage Journal
    People are already arguing over things that may happen in a few billion years? I don't even buy green bananas!

  • Earth's rotational inertia is limited (Score:5, Interesting)

    by vincecate (741268) on Friday August 18 2006, @07:41AM (#15933778) Journal
    The energy to lift the Moon's orbit comes from the rotational energy of the Earth, which is limited. As the Moon gets higher the Earth rotates slower. There may not be enough energy to lift the Moon high enough to qualifty.

  • Seven years ago, to be exact (Score:4, Funny)

    by Megane (129182) on Friday August 18 2006, @07:50AM (#15933825)

    Remember when that radioactive waste dump on the moon blew up and sent big chunks of it all over the place? Yeah, that was some kind of fireworks. Good thing it was on our side of the planet when it happened or we'd have missed all the fun.

    Too bad about that moon base that was on one of the smaller chunks. That thing really hauled ass. Oh well, so it goes.

  • Earth won't still be rotating by then (Score:4, Insightful)

    by codemaster2b (901536) on Friday August 18 2006, @08:26AM (#15934011)
    A few billion years? Why should they care?

    It was projected that in a matter of millions of years, the moon will cause the earth to stop rotating altogether. Without rotation, do you seriously think we will inhabit this planet?

    For that matter, in a matter of millions of years, we should have developed a technology for making the earth rotate as fast as we wish, and moving the moon back where we want it to be. All it requires is enough rocket-power by even today's standards.

  • Planetary System rather than Planet/Moon (Score:4, Insightful)

    by scruffy (29773) on Friday August 18 2006, @08:35AM (#15934072)
    I'd prefer to think of the Earth and the Moon as a single planetary system, consisting of two planets (both easily satisfying the big enough/round enough definition). For simplicity and consistency, we can call the system Earth just like old times.

    Ditto for Pluto and Charon.

  • Both a planet and a moon (Score:4, Interesting)

    by mrogers (85392) on Friday August 18 2006, @08:44AM (#15934140) Homepage
    Why can't something be both a planet and a moon? As far as I understand it, the new IAU definition of a planet is something that's in orbit around a star, is not a star, and is large enough for gravity to make it roughly spherical. A moon is something that's in orbit around a planet. So you could argue that our Moon is already a planet (it's in orbit around the Sun as well as the Earth). The same would apply to many other large moons in the solar system.

  • Not a bad situation at all (Score:5, Interesting)

    by 9x320 (987156) on Friday August 18 2006, @09:08AM (#15934306)
    If the moon going further away from the Earth causes the barycenter of Earth to drift outside its surface, then the Earth will be orbiting a point outside itself, with its orbit becoming greater the farther the barycenter drifts, until it peaks at one point. This is similar to Pluto constantly orbiting a point outside itself, as illustrated in this NASA chart [wikipedia.org] hosted by Wikipedia. I think that when a moon begins to have that effect, it should be classified as a planet.

    Currently, the Earth's barycenter is three-fourths of the way to its surface, causing it to sort of wobble, rather than fully orbit an invisible point. This is like an analogy: This is like a Chippendale stripper doing a pelvic thrust, rather than running around in a circle.

    Earth's orbit around the sun currently makes the sun wobble in a barely perceptible fashion. Jupiter's orbit around the sun, however, causes the sun to orbit a point about 7% above its surface. I think that there should be a new class of planets for the purposes of describing a planet that makes a star orbit itself in this manner.

    Clearly, all brown dwarfs orbiting a star would also have a similar or greater effect. The best way to describe it, in my opinion, would be by merely affixing "co-orbital" to describe a planet altering the sun's orbit in this fashion, or a brown dwarf orbiting a star doing this.

    If this causes a planet to be "co-orbital" for only part of its orbit, or a natural satellite to be a planet for part of its orbit, in some eccentric situations, that's fine with me. There's one other issue with the new definition that makes me uncertain, though. EL61 is a "minor planet" that has a very oblong shape caused by its own orbit around the sun. If it were in a slower, closer orbit, its own gravity would almost certainly be enough to warp it into a nearly spherical shape. Should EL61 be considered a planet, despite its problem?

    • Re:So what? (Score:5, Insightful)

      by Fyz (581804) on Friday August 18 2006, @06:20AM (#15933453)
      If you'd bothered to RTFA, you'd find that the moon would be reclassified as a planet when the systems center of gravity no longer resides inside the Earth.

      I would gladly send my kid to this elementary school if they could prove that they could teach concepts like orbital decay and barycenters to to nine-year-olds.

      • Re:So what? (Score:5, Funny)

        by BecomingLumberg (949374) on Friday August 18 2006, @06:37AM (#15933515)
        "I would gladly send my kid to this elementary school if they could prove that they could teach concepts like orbital decay and barycenters to to nine-year-olds."

        I would only send my kid there if they LEARNED it. I have a feeling they most nine-year-olds would be picking boogers during that class.

      • Re:So what? (Score:5, Insightful)

        by Mr2cents (323101) on Friday August 18 2006, @07:02AM (#15933597)
        I already consider the moon-earth as a bi-planetary system. What's the big deal with these definitions, anyway? No matter where you draw the line, there will always be cases where there will be discussion. Like the criterium that the object has to be "nealy spherical" because of it's own gravity. Lots of planetoids are somewhere on this vague border.

        Comets, asteroids, planets, stars, they all have grey areas between them.

    • Re:Gosh. How shocking. (Score:5, Informative)

      by Anonymous Coward on Friday August 18 2006, @07:04AM (#15933606)
      Wrong, wrong, wrong! Just RTFA. The moon does not have to escape the Earth's gravitational pull in order to be re-classified as a planet. The only thing that would be necessary (according to the new definition of a planet) is that the Moon moves further away from the Earth, just enough so that the barycenter of the Earth-Moon system is above the surface of the Earth. The Moon would still orbit the Earth. Obviously, the moderators who gave a +5 Insightful to your comment have not read the article either.

      • Re:Gosh. How shocking. (Score:5, Insightful)

        by MindStalker (22827) <jlarsen@NOSpam.fsu.edu> on Friday August 18 2006, @07:55AM (#15933846) Journal
        This is called a Twin Planet. And no it would nolonger orbit the earth the earth, the "moon" would orbit eachother at a common point. Either way, I see no reason that once we have this designation of moon vs planet why we should be so beholden of "our" moon that we can't accept it nolonger being a moon. We shouldn't change the definition just to fit some popular idea.

    • Re:And what's the problem? (Score:5, Insightful)

      by jolyonr (560227) on Friday August 18 2006, @07:07AM (#15933615) Homepage
      Please stop giving +1 Insightfuls to people who either a) haven't read the article or b) haven't undestood it. The moon could be reclassified as a planet EVEN IF IT STILL ORBITS THE EARTH. It depends on whether the center of gravity of the pair is inside the earth or not.

    • Re:sea levels (Score:5, Informative)

      by Don_dumb (927108) on Friday August 18 2006, @07:56AM (#15933850)
      the farther away the moon is, the lower the seas
      Are you sure?
      It was my understanding that the moon affects the level of the tides, not the mean sea level, which is far more a product of the Earths gravity and dependant sea water pressure/density.

      and this should compensate for the ice melting.. although I always wonder what's the big deal, since icebergs are 90% submerged anyway, and ice takes more space than water (cause of the air bubbles)
      Yes all those scientists must have missed that one, eh?, I am glad there are informed people like you in world to set them straight.
      You are assuming that all the ice is in the seas, which it is NOT. A large amount sits on land in the form of Ice Shelves, there is enough to cover an entire contient (Antarctica) as well as most of Greenland and Canada, not to mention all the ice in Glaciers. As all this melts (and there is enough in Antarctia to contain 90% of the worlds fresh water) it wil flow into the sea and the sea level will rise, that is 'the big deal'.

      But don't worry I am sure Mr President will give you a big pay rise for that wonderfully dismissive comment on the effects of climate change.
    • Do you people even bother to check the stories and the claims made in the before posting?

      Maybe you should RTFA. The SPACE.com story is talking about in a few billion years, when the barycentre of the Earth-Moon system has moved above the surface of the earth. That would make the Earth and the Moon double planets. In a few billion years. The IAU FAQ you quoted was more concerned about right now.

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