What happens to photons that are traveling away from the universe -never to return?
Do they have no interreaction with it ?
Do they cease to exist on the basis that all existence implies a relationship? (you know the old question about the tree in the forest that nobody sees fall or maybe even the sound of one hand clapping )
Or are they still in a relationship with their "mother" universe even though they will never interreact directly again?
Could they bump into a "virtual" particle ?(I "understand" that these are particles that spontaneously pop out of the vacuum)
Apologies in advance for any elementary misunderstandings.