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Thread: Question about rotation & flow of liquid(s) on an astronomical body.

  1. #1
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    Question Question about rotation & flow of liquid(s) on an astronomical body.

    The slower the rotation causes surface liquid(s) to rush toward the poles. Yes?

    The higher the rotation causes surface liquid(s) to rush toward the equator. Right?

    Does this mean the further back in time we go the more Earth's water was going toward, to the equator?

    This means the water is going, hyperslowly, towards the poles with each passing day yes?

    So, if Venus were Earthlike & had oceans, its rotation would cause its oceans to rush & bunch towards the poles?

    Mars's rotation is virtually identical to Earth's. So if Mars were Earthlike & had oceans, how would the oceans be flowing relative to Mars's poles & equator?

    Unlike Earth, Venus & Mars have no stable axial tilt yes? So, how would that factor into the flow of water & oceans on Mars & Venus relative to their equators & poles were they Earthlike?

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    Quote Originally Posted by Bad Ronald View Post
    The slower the rotation causes surface liquid(s) to rush toward the poles. Yes?
    I don't think that's the right phrasing. It's more like the water would distribute itself more evenly. If there's little rotation, then there is little equatorial bulge. I don't see how you'd call that "bunching" of stuff at the poles.
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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    Quote Originally Posted by 01101001 View Post
    I don't think that's the right phrasing. It's more like the water would distribute itself more evenly. If there's little rotation, then there is little equatorial bulge. I don't see how you'd call that "bunching" of stuff at the poles.
    True. Bad choice of words.

    Water, or other liquid, flows towards the poles under slower, or slowing, rotation, yes?

    Under faster, or accelerating, rotation, water or other liquid flows toward the equator, right?

    Bunching was a sloppy word to use.

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    But as the water flows to the equator it creates a bulge. This bulge has greater mass so feels a greater restoring force due to gravity. Eventually a stable (but dynamic) equilibrium is set up where the centrifugal force balances with the gravitational force. So the flow, in effect, stops. Or at least is neutralised by a counter flow. On Venus you'd see a very small equatorial bulge of water, on Earth you see a larger one. In essence these effects are a tug of water between gravity trying for a perfect sphere and centrifugal force trying to throw everything out perpendicular to the axis of rotation.

    Edit: If the rotation is accelerating then the equatorial bulge (or oblateness) increases - but for each speed of rotation there is a stable point at which the forces balance.
    Last edited by Shaula; 2010-May-10 at 09:19 PM. Reason: Added comment on accelerating rotation

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    Quote Originally Posted by Bad Ronald View Post
    Water, or other liquid, flows towards the poles under slower, or slowing, rotation, yes?
    Over the long run of spin down, there is a slow net gain around the poles, and a net loss from around the equator.

    But all the fluid matter doesn't wind up around the poles, nor does it rush, if that's where you're going, as it seemed in your opening.

    Also, I don't see how the Earth's equator would have been getting a net increase unless the rotation was speeding up (unless you want to consider new fluids arriving from afar).

    Unlike Earth, Venus & Mars have no stable axial tilt yes? So, how would that factor into the flow of water & oceans on Mars & Venus relative to their equators & poles were they Earthlike?
    I don't see the tilt of the axis being a big issue as to where the bulge is relative to the axis. The direction the axis points may wander around, but that wandering takes the whole non-rigid planet with it, including the equatorial bulge. The axis is the line which is spun about.
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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