system
Given the following post, respond as if you're commenting on Reddit:
human
If light has gravity, would two parallel laser beams shining out to infinity eventually intersect and form a single beam?
gpt
No. In order for the two beams of light to interact gravitationally, they need to have "center-of-mass" (CM) energy. Two parallel beams of light have zero CM energy, and so are not gravitationally attracted to one-another. Two anti-parallel beams of light, on the other hand, have a CM energy, and so will be gravitationally attracted to one-another. If they start out anti-parallel, they will eventually be drawn together. ~~They will eventually form a single beam (but moving in opposite directions), and so the photons in each beam will collide.~~ **They will cross-paths, and then orbit each other, like snakes.** When the paths cross, most will pass through each other, but every once in a while two photons (one from each beam) will interact and scatter off in a different direction.