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How would a man on earth appear from outer space

  1. Jun 10, 2009 #1

    I was reading a general physics book and wondered how would a man on earth appear to somebody watching from outer space.
    Say for example a man on earth just drops a ball from his hand, will it appear to somebody watching from outer space, as if the ball is released tangent to the spin of the earth?

    I hope my question makes sense!

    Another question, why don't we feel the pseudo force due to the earth's rotation on its axis? or is it too weak?
  2. jcsd
  3. Jun 10, 2009 #2
    We do feel pseudo forces. That's why tornados and hurricanes (but not toilets) spin different directions in different hemispheres (because of the fictitious Coriolis force) and why the earth is kinda like a squashed sphere not a perfect sphere (centrifigal force). In general these fictitious forces emerge when we assume we are in a stationary reference frame but actually are in a rotating one (see http://en.wikipedia.org/wiki/Rotating_reference_frame). However, how we look to a person in space is ENTIRELY dependent on what the reference frame of the person is. For example, if the person was in geosynchronous orbit they wouldn't see anything odd.
  4. Jun 10, 2009 #3


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    It is too weak to be felt, in the presence of gravity. More precisely, it's about 300 times weaker than gravity (at the equator), and a human can't pick out that 1-in-300 difference. If there were no gravity, you'd probably be able to feel the centrifugal force, though; about 1.5-2 N on an average adult.
    Last edited: Jun 10, 2009
  5. Jun 10, 2009 #4


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    Hi vijay! :smile:
    Yes, if the Earth is dark (because it's night), but the ball is lit, then all the watcher will initially be able to see is the ball moving tangent to the spin of the earth, as you say. :smile:
  6. Jun 12, 2009 #5
    Thank you all for responding and confirming the answers.
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