I have a question on my mind for some time and I would be grateful if someone could help me figure out the answer. So, let's consider an imaginary experiment: two mirrors in space, far away from any gravitational effect, parallel to each other, and 2 beams of light falling at a small incidental angle on one of the mirrors, such that the beams travel reciprocal parallel great distances. The question is would they attract to each-other, and get closer together? From the mirrors’ frame, the classical gravitational law would predict that they do, due to their mass m=hυ/c^2…
