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Our Moon Could Become a Planet

Posted by ryuzaki0 on 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."

9 of 438 comments (clear)

  1. In a few billion years... by advocate_one · · Score: 4, Informative

    both the Earth and Moon will have been swallowed up by the Sun when it becomes a red giant...

    --
    Donald 'Duck' Dunn: We had a band powerful enough to turn goat piss into gasoline.
    1. Re:In a few billion years... by durgaprasad_j · · Score: 5, Informative

      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

    2. Re:In a few billion years... by SamSim · · Score: 3, Informative

      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.

      --
      qntm.org
  2. It'll last our time by MathFox · · Score: 4, Informative

    "The sun will turn in a red giant before the moon gets far enough away to be classified as a planet"

    --
    extern warranty;
    main()
    {
    (void)warranty;
    }
  3. Re:Gosh. How shocking. by Anonymous Coward · · Score: 5, Informative

    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.

  4. Re:sea levels by Don_dumb · · Score: 4, Informative
    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.
    --
    If this were really happening, what would you think?
  5. Re:Fatal Flaw in IAU Definition by kalidasa · · Score: 3, Informative

    That's not how the definition works - if a coorbital body has the barycenter of its minor orbit with its companion body outside either body, it's a planet. If it is too small to ignite fusion and orbits a star, it's a planet, regardless of whether the barycenter of the planet-star system is inside the surface of the star.

  6. Re:Do the math... by LiquidCoooled · · Score: 5, Informative

    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".

    --
    liqbase :: faster than paper
  7. Re:Sun or Earth? by 2short · · Score: 4, Informative

    "Of Time and Space and Other Things"

    Which was a collection of essays on various interesting science stuff, though I don't know if any of it was published seperately.