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Homework Help: How do we argue that gravity is not a force due to curvature of space-time?

  1. Oct 22, 2008 #1
    1. The problem statement, all variables and given/known data
    How do we argue that gravity is not a force due to curvature of space-time?

    2. Relevant equations

    I'm new.. I don't even understand the eqn of tensor calculus.

    3. The attempt at a solution

    No force is needed for as massive objects follows the curvature of spacetime with their innate velocity? Just like the earth orbits around the sun because its velocity sustains it in the path of curvature caused by the sun?

    I'm writing an essay on this. and I need more points to elaborate on curvature.
    Thanks for all help given.
  2. jcsd
  3. Oct 22, 2008 #2
    Yea basically. The earth thinks its going in a straight line, but since the space around earth is curved by the sun, the earth follows a circular trajectory as a result. The key word "geodesic."
  4. Oct 23, 2008 #3
    What gives the earth its inherent/innate velocity to maintain its trajectory/geodisic movement instead of being attracted towards the sun?
    Does this velocity only apply to massive objects? what about smaller objects like humans, do we attract each other?
  5. Oct 24, 2008 #4
    well the earth is attracted towards the sun, or else it would fly out into space. It continues to move though because there is nothing to stop it (see, "newtons first law of motion").
    Yes, all objects attract all other things gravitationally, even humans. Even individual atoms attract others gravitationally, but the force is extraordinarily weak and it is really only noticeable in very large objects such as planets and stars.
  6. Oct 24, 2008 #5


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    A telling case could be made against gravity being interpreted as curvature of spacetime if there were a dependence of gravity on the material an object is made of instead of just it's mass. So a gold satellite would orbit differently from an aluminum satellite it would make it difficult to interpret as geometry. As far as we know so far, they don't. Look up the Eotvos experiment. Work in this direction is still going on. Look up Gravity Probe B. Work those into your essay.
  7. Oct 27, 2008 #6
    One point to note... My essay is to understandable to a layman and my tutor told me to focus more on the geometry/geodesic such that NO FORCE is required between masses.

    I was wondering how do I explain geodesics in a laymanized manner. sigh
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