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Our Moon Could Become a Planet 438

Posted by CowboyNeal
from the size-does-matter dept.
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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Our Moon Could Become a Planet

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  • by Anonymous Coward on Friday August 18, 2006 @06:57AM (#15933383)

    That's no moon!

  • by advocate_one (662832) on Friday August 18, 2006 @07:00AM (#15933388)
    both the Earth and Moon will have been swallowed up by the Sun when it becomes a red giant...
    • by LiquidCoooled (634315) on Friday August 18, 2006 @07:09AM (#15933429) Homepage Journal
      ...and we will still be waiting to play Duke Nukem forever on our Vista machines.
      • Re: (Score:3, Funny)

        by jtobin (988724)
        Nah, we'll all be using Slackware with 2.6 kernel (released a few weeks earlier).
    • by durgaprasad_j (888320) on Friday August 18, 2006 @08:08AM (#15933624)
      In about 5 billion years, when the Sun is a red giant, it will be so large that it will consume Mercury and Venus. Models predict that the Sun will expand out to about 99% of the distance to the Earth's present orbit (1 astronomical unit, or AU). However by that time the orbit of the Earth will expand to about 1.7 AUs due to mass loss by the Sun. Our planet will thus escape envelopment. -- Reference http://en.wikipedia.org/wiki/Star [wikipedia.org]
    • by SamSim (630795) on Friday August 18, 2006 @08:11AM (#15933636) Homepage Journal
      Actually, probably not. Even where it is right now, Earth is almost on the boundary line between being swallowed and escaping (Venus is definitely gone, Mars definitely isn't). But as the Sun expands it will also become more luminous, which means the solar wind will increase. Over billions of years this will push Earth into a wider, safer orbit. It'll still get roasted to a crisp, but probably survive as a planet.
    • Re: (Score:3, Funny)

      by ortholattice (175065)
      It won't be billions of years, it will be in 1999 when there will be a nuclear explosion on the far side of the moon. Then it will travel throughout the galaxy, on the way picking up a hot alien called Maya as its science advisor.
    • It will happen in a few million years, not billion. Google the math:
      distance of barycenter from center of Earth: 2,900 miles
      radius of Earth: 3,960 miles
      distance of barycenter from Earth's surface: 1,060 miles
      same, expressed in inches: 67,161,600 inches
      speed of lunar creep away from Earth: 1.6 inches / year
      Time until the barycenter is on the surface: 41,976,000 years.

      That is pretty dang short in the context of astronomy. Or even in the context of geology. I think it would be truly short-sighted (I

      • Re:Do the math... (Score:5, Informative)

        by LiquidCoooled (634315) on Friday August 18, 2006 @11:10AM (#15934764) Homepage Journal
        Consider 2 bodies of equal mass seperated by a distance of X.
        The Centre of mass is right in the centre of the space between them.

        The distance X increases by 1 unit, does the centre of mass also increase by 1 unit?

        Adjust this equation to put it into earth/lunar context and you will understand why scientists don't just "google the math".
  • It'll last our time (Score:5, Informative)

    by MathFox (686808) on Friday August 18, 2006 @07:00AM (#15933389)
    "The sun will turn in a red giant before the moon gets far enough away to be classified as a planet"
  • by Ghost Hedgehog (814914) on Friday August 18, 2006 @07:01AM (#15933395) Homepage Journal
    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 @07:07AM (#15933415)
    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 @09:00AM (#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.
  • by aadvancedGIR (959466) on Friday August 18, 2006 @07:08AM (#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.
  • by gklinger (571901) on Friday August 18, 2006 @07:10AM (#15933432)
    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.

    • by terevos (148651) on Friday August 18, 2006 @07:26AM (#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.
      • by gklinger (571901) on Friday August 18, 2006 @07:45AM (#15933538)
        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.
        • Your proposed definition is indeed a good starting point. Coincidentally, that's the same starting point of the new proposed definition, so I guess you agree with it, then?

          The problem is that any consistent, non-arbitrary definition will result in either 1) removing Pluto's planetary status, which people don't seem to like for some reason, or 2) adding a lot more "planets" to the solar system.

          The new definition is (in summary) that a planet is anything that orbits primarily the sun and is large enough
      • by Pike (52876) on Friday August 18, 2006 @10:02AM (#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.
  • ok (Score:3, Interesting)

    by joe 155 (937621) on Friday August 18, 2006 @07:14AM (#15933441) Journal
    I know a lot of the other comments about this are just saying that our system probably won't be around or that of course it won't be a moon because it's not in orbit, but what I think is more interesting is about the definition of a planet which they seem intent on creating...

    Pluto may oir may not be a planet, but who cares? Don't change the definition because it doesn't change anything and it alters what we have traditionally though of it as and causes confusion with no real benifit. As to the three new planets which might come about because of this I think we should treat them with scepticism, I'm not completely against change if there will be an imporvement to understanding but I feel these things are not really in the spirit of being "planets" (I know that sounds crazy but you probably know what I mean...)
    • Who cares? (Score:3, Insightful)

      Obviously, people care tremendously, which is why we ended up with this half-assed bandaid of a definition - which is an attempt to use a single word to describe three wildly divergent phenomena in a way that makes scientific sense and will pass muster with every pseudoscientist who thinks they have a right to an opinion on the matter.

      The brutal truth is that there are at least three types of bodies that orbit the sun - rocky planets, gas giants, and bodies made up primarily of ices like Pluto and his frien
  • by Ihlosi (895663) on Friday August 18, 2006 @07:22AM (#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 @07:27AM (#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.
    • by Control Group (105494) on Friday August 18, 2006 @10:20AM (#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.
    • Re: (Score:3, Funny)

      by mgblst (80109)
      Don't worry, when things get really bad the Stark program will get underway to ensure that some of survive.
  • Wait a minute... (Score:3, Interesting)

    by Jugalator (259273) on Friday August 18, 2006 @07:37AM (#15933512) Journal
    But here's the thing. Earth's Moon was born in a catastrophic collision more than 4 billion years ago.

    So is this established fact now? I thought the that was far from proven, and even a quite debated theory.
    But maybe the impact hypothesis has gained traction in the science community since I heard of this?
  • by SirBruce (679714) on Friday August 18, 2006 @08:19AM (#15933671) Homepage
    The problem is they're saying if a "moon" is orbiting a barycenter that's not inside another planet, then it's not orbiting that planet and becomes a planet itself. For this reason, they argue Charon is a planet, rather than a moon.

    The problem is that barycenter of Jupiter's orbit around the Sun is also outside the Sun. Therefore, by the same logic, Jupiter wouldn't be a planet.

    Bruce
  • by Rob T Firefly (844560) on Friday August 18, 2006 @08:38AM (#15933767) Homepage Journal
    People are already arguing over things that may happen in a few billion years? I don't even buy green bananas!
  • by vincecate (741268) on Friday August 18, 2006 @08:41AM (#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.
    • There may not be enough energy to lift the Moon high enough to qualifty.

      Good point. You must be the Vincent Cate I remember from s.s.[hp]

      If Ceres is reclassified as a planet I wonder if this would make it more attractive for a manned mission. An astronaut could be the next Armstrong (first to walk on another planet orbiting the sun) for much less than the cost of landing on Mars.

      That is assuming that the Moon doesn't get reclassified. If that happens Neil, Buzz and Mike have a party.

  • by Megane (129182) on Friday August 18, 2006 @08:50AM (#15933825) Homepage

    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.

  • At first I thought TFA said a few million years and I started getting worried, then I reread it and now I'm ok. Whew, that was a close one!

  • If the astronomers who thought of the new classification system really give a shit about reclassifying something that will happen in a FEW BILLION YEARS.

    If we are even still on Earth in the year 3,000,000,2006 - that is.
  • Surely the reason why the Moon is considered a satellite of the Earth, rather than the Earth and Moon being considered a binary system, is because the centre of mass of the combined system is within the volume of one of the bodies {in this case, the Earth}? If the C. of M. was somewhere in the space between the two bodies, then they would constitute a binary system. Since the Earth weighs about 82 times as much as the moon, and the radius of the Earth is about 6.4 megametres, for the C. of M. to be just
  • by codemaster2b (901536) on Friday August 18, 2006 @09:26AM (#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.
  • by scruffy (29773) on Friday August 18, 2006 @09:35AM (#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.

  • by wmaster (987425) on Friday August 18, 2006 @09:36AM (#15934076) Homepage
    I am hopefully looking forward to this "Golden Age" in just a few billions of years, when our biggest problem definitely will be the fact, that the moon would be reclassified as a planet under the new IAU definition. ;-) Greetings, Chris
  • by mrogers (85392) on Friday August 18, 2006 @09:44AM (#15934140)
    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.
  • by 9x320 (987156) on Friday August 18, 2006 @10:08AM (#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?
  • "So what planet are you from?"

    "I am from planet Moon."

    "What?"

    "@#)$*(@#($&*(, I told you LAST TIME What's on second!!!! Graaaah!"
  • by AF Webster (996337) on Friday August 18, 2006 @03:49PM (#15936817)
    Moving away at its current speed, it would have taken 10bn years to move from the Roche limit to its current position. (In rough figures: 4*(10^8)m / (0.04m/year) = 10^10years)

    But the moon is drifting away due to tidal effects. So it would have been drifting faster in the past. Taking that into account, the MAXIMUM possible time the Moon could have been orbiting earth is less than 1.5bn years.

    So how come many scientists think the Earth-Moon system is 4.5bn years old? Maybe they just haven't done the math.

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