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Gravitation ?

  1. Jul 3, 2008 #1
    1. "Gravitation" is a general term describing the attractive influence that all objects with mass exert on each other.
    2. The photon is massless,has no electric charge and does not decay spontaneously in empty space.

    My question is why does gravity affect particles without mass (like photons) ?
  2. jcsd
  3. Jul 3, 2008 #2
    You have been misled by Newton for too long.
    Newton's most important contribution to science was his mathematical definition of how motion changes with time. He showed that the force causing apples to fall is the same force that drives planetary motions and produces tides. However, Newton was puzzled by the fact that gravity seemed to operate instantaneously at a distance. He admitted he could only describe it without understanding how it worked. Not until Einstein's general theory of relativity was gravity changed from a "force" to the movement of matter along the shortest space in a curved spacetime. The Sun bends spacetime, and spacetime tells planets how to move. For Newton, both space and time were absolute. Space was a fixed, infinite, unmoving metric against which absolute motions could be measured. Newton also believed the universe was pervaded by a single absolute time that could be symbolized by an imaginary clock off somewhere in space. Einstein changed all this with his relativity theories, and once wrote, "Newton, forgive me."
    Last edited: Jul 3, 2008
  4. Jul 3, 2008 #3


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    Very well said, kahooman. I make only one addition for the beneift of the OP:
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