Scientists create matter from pure light, proving the Breit-Wheeler effect
I have had this mental question about 'what time is it when photons collide'.  Given that a photon could have been travelling for a million years colliding with one that has only been travelling for a microsecond, and from the photon perspective there is no passage of time and no distance.I then kept reading things that tell me photons don't interact, which saddened me because I like the question.  This now appears to not be the case, is there a specific condition under which photons can interact like this?