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I've read that photon's have zero mass, hence no force is needed to accelerate them. But then the second question. How can gravity affect something which has 0 mass?. Yes, gravity(black hole) can bend space and time but how can 0 mass particle be affected by this?. What am i missing.?

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  • $\begingroup$ photons don't accelerate, they always travel at the speed of light $\endgroup$
    – ProfRob
    Sep 25 '15 at 13:37
  • $\begingroup$ There are many ways to explain this phenomenon, but the one I prefer is this one: astronomy.stackexchange.com/a/11911/1378 $\endgroup$ Sep 25 '15 at 18:15