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View Diary: Getting to Know Your Solar System (4): Earth (Vol. 1) (46 comments)

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  •  OK. So you're saying (3+ / 0-)
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    Troubadour, Wee Mama, Dragon5616

    the general tendancy for a planet's rotational system would naturally be to flip around.  But in the close planets, and in the far planets, other factors make them tend toward the sun-planet orbital plane.  Yes?

    And if Earth didn't have its moon it would be flipping too? btw I agree that such an irregular orbital pattern would degrade the probability of sustained life on Earth immensely).  

    But are you saying Mars flips around?  It spins in a pattern different from the one most of the planets spin in?  The natural (randomly rotating axial rotational pattern)?

    •  The general tendency of a solid object (3+ / 0-)
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      Wee Mama, Sneelock, Dragon5616

      that spins is to wobble and have the axis migrate over time.  If it's close to another large mass, that migration is dampened or eradicated altogether by tides.  In a gas giant, that other mass is the planet itself, because it's mostly gas - i.e.,  its own mass dampens rotational deviations.

      I should note these axial migrations occur over multi-million-year timeframes, not anything that would be of practical concern.

      The conundrum of stable democracy: Reform requires the consent of the corrupt.

      by Troubadour on Mon Sep 05, 2011 at 12:04:34 AM PDT

      [ Parent ]

      •  So the giant impact not only gave us the moon, (3+ / 0-)
        Recommended by:
        Troubadour, Sneelock, Dragon5616

        but also stability and perhaps the particular atmosphere we began with, and plate tectonics?

        If it takes such a big impact at the right angle to make a habitable planet, that would seem to lower the size of the pool of planets friendly to complex life.

        Is it true? Is it kind? Is it necessary? . . . and respect the dignity of every human being.

        by Wee Mama on Mon Sep 05, 2011 at 07:34:15 AM PDT

        [ Parent ]

        •  It's important not to over-generalize. (4+ / 0-)

          It took that impact to make Earth habitable to complex life.  Something else, in some other orbit, with a different mass and atmosphere, might be habitable all by itself, and still others might be habitable with the help of smaller moons.  A large gas giant moon might also be habitable under some conditions.

          The conundrum of stable democracy: Reform requires the consent of the corrupt.

          by Troubadour on Mon Sep 05, 2011 at 08:14:34 AM PDT

          [ Parent ]

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