If our universe is not infinite, what happens with the light beam (or photon) when it will travel through the whole universe? For example, observable universe according to wikipedia has diameter 93 billion light-years. What will happen with photon after 93 billion years if I generate it now? Will it return back to me? Or it will never reach the "edge" of the universe because the universe is expanding faster?
Of course, I assume that photon will no be absorbed :) because it is just a theoretical thinking. And return back I mean not exactly to the same point, but approximately within some range (let say 5% of the universe size).
Do I correctly understand that there are a few options for the case when the universe is finite (means "closed geometry"):
Photon will never return back because the universe will collapse before it (in case if there are no dark energy).
Photon will never return back because universe expanding faster than light speed.
Photon will come back because universe expanding slower than light. And what of these 3 options is most probable from a current scientists point of view?