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Gravity's Force

  1. Jan 8, 2009 #1
    If gravity is a force, then the moment the object producing gravity is taken away, it should result in gravity taken away instantaneously.
    However, why does Einstein say that Newton's classical mechanics are incorrect and that in fact he decided to propose spacetime and not follow what Newton has claimed hundreds of years ago?
  2. jcsd
  3. Jan 8, 2009 #2
    Gravity travels at the speed of light. If you take the object producing gravity away, you stop feeling its gravity as soon as you stop seeing it. I don't see any reason why a force would need to act instantaneously. In quantum mechanics, for example, forces are transmitted by special kinds of particles, which travel at the speed of light.

    Einstein said Newton's laws were incorrect because they didn't perfectly fit into his theory, which seemed more elegant. His own results explained gravity in a different way which felt more consistent. It turns out he was right, because GR explains the perihelion shift of Mercury, curvature of light (double the Newtonian value), time dilation in gravitational fields (measured in experiments) and quite a few other things.
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