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GR explanation of Newtonian Phenomena

  1. Apr 11, 2008 #1
    1. How would a general relativist explain why an object falls towards the earth?

    2. Is it correct to say that it is not the apple that falls towards the earth but it is the earth that accelerates towards the apple? Why is this ok to say?
  2. jcsd
  3. Apr 11, 2008 #2


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    The apple follows a geodesic path through space-time. One way o describing the mathematical characteristics of this path is to say that it satisfies the principle of extremal aging.

    see for instance http://www.bun.kyoto-u.ac.jp/~suchii/extrem.aging.html [Broken]

    and look for past PF posts with this keyword.

    2) The question is really irrelevant in GR - it doesn't matter which viewpoint you use.
    Last edited by a moderator: May 3, 2017
  4. Apr 11, 2008 #3


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  5. May 26, 2008 #4
    Science does not explain, it describes. To say that it explains leads one into a logical circle.
    What accelerates is actually doing the acceleration is a coordinate dependant statement. Once you choose a coordinate system you can state whose coordinates in that system represents an accelerating object. Here I speak of 3-acceleration since the 4-acceleration of each object, i.e. earth and apple, is zero.

  6. May 27, 2008 #5


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    Since the OP is no longer with us, there seems no point in keeping this thread open.
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