I know massive objects can curve light, can we capture the image of past Earth by lights from Earth that curved by massive objects?


Light can be made to do this around black holes, sort of. At a certain distance from a black hole you have what's called a photon sphere. At this distance, determined by the mass of the black hole, photons travel in orbits because of the space-time curvature.

So to answer your question, maybe.

Firstly, a massive entity would need to be located at some point in space in order to influence the photons into an orbit - okay yes, possible. Secondly, this massive object would need to have a mechanism of instantaneously disappearing from space-time in order for the photos to tangentially come out of orbit and back towards earth.

I read on a previous question on Physics.SE that there is no such solution to the Einstein Field Equations which allows for a massive object to just disappear - the closest thing would be for the density distribution of the object to change but I can't say if that would yield the result you are asking about.

Rob Jeffries mentioned that images do exist which suggest that photons experience such a change in trajectory - this could happen on paths which are very close to a photon sphere-like one, but deviate enough from it to allow photos to escape.

  • 2
    $\begingroup$ I am not sure this is correct at all and have seen a number of images suggesting that photons can follow trajectories that come close to a black hole and end up on a trajectory back towards the object that emitted them. A vanishingly small fraction of photons may be following these paths, but that is a different answer to no. Perhaps you could provide some proof or references. $\endgroup$
    – ProfRob
    Oct 9 '15 at 17:36
  • $\begingroup$ No references to add to this, unfortunately. Answer edited to reflect this. $\endgroup$
    – Phizzy
    Oct 12 '15 at 10:34

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