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I Great Circles and....Coriolis??

  1. Jun 2, 2016 #1

    Not sure how to categorize/title this question. I was looking at the Coriolis Effect and was considering the straight-line motion of an object wrt the background stars/masses and this question occurred to me:

    Except for the fact that they are travelling nowhere near fast enough to trace out a great circle, an object on the surface of the earth wants to travel in a great circle. If there was no atmosphere and I had an anti-gravity object that I could suspend just above the earth's surface, the object would trace out a great circle, similar to a satellite. The moment I let it go it would be at the maximum latitude (northern hemisphere) of a great circle and it would drift south towards the equator. Then it would spend an equal amount of time in the Southern Hemisphere, and it would meet me back where it started after 24 hours.(EDIT: 24 hours at the equator. Longer the further north or south you go)

    Is this correct? If it is then, surely, every elemental mass δm at the surface of the earth is trying to move in a great circle about the center of the earth. But because the crust is solid it can't. i.e. the crust is providing an opposing force towards the north(or south). How does this force play out? Does it add to the bulge at the equator in addition to the centrifugal bulge? How does this affect the atmosphere (since it can move) - do all gases in the atmosphere try to move towards the equator and so is the atmospheric pressure there greater?

  2. jcsd
  3. Jun 2, 2016 #2


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    Science Advisor

    No, it sounds more like a partial explanation of the equatorial bulge in the inertial frame, where there is no centrifugal force.
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