Question about photons traveling on same path

[stever]

There are no implications, because we can't tell anything except if we assume isotropy (for clock synchronization and in all our laws of physics), we get the simplest equations. Personally, I take this as a definiiton of physically meaningful isotropy. If our universe was observably anisotropic, that would mean that assuming isotropy leads to excess complications. Note, isotropy of two way light speed is measurable, so if you assume anisotropy it has to be of a very special type.

I understand your last sentence.
Einstein was complaining about the math complexity for general relativity. perhaps math simplicity can be a false prophet? I don't use math much and I feel more at ease with anisotropy than isotropy with regard to light speeds, as it seems closer to a pre-SR way of seeing. what really puzzles me is time dilation, mass increase and length contraction and what makes them real. maybe I'll look into it some time.

Anyway, I don't have enough time for physics. Thanks for everyones help.