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Photon In A Gravitation Field

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Posted by Jim Bergquist on January 25, 2001 06:41:48 UTC

I agree with everything that you said except the part where the photon possesses potential energy. The gravitational field, whatever that is, receives the energy lost by the photon.

I do not know how far you have thought this through, but one can find some rather interesting trajectories for the photon if one assumes a simple model using E=hν as the energy of the photon, m=hν/c^2 as its gravitational mass and V=-GMm/r as the potential energy. You will also find that the event horizon is at r=GM/c^2. This is the radius for circular orbits of the photon. Photons within this distance tend to spiral inward while those outside tend to escape. There appear to be exceptions depending on the direction of propagation. One can derive an expression for the energy of the photon as a function of distance and energy at the event horizon or infinity, say. I prefer to view this model as qualitative rather than truely quantitative because the gravitational field near the event horizon is not well know. The correct model would probably include relativistic corrections to the gravitiational field.

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