We don’t need hyperexotic negative energy to travel to the stars, we just need to live a lot longer, and we need our friends and family to live longer too so we can comeback and see them again.
I kind of disagree here. 50 thousand years — it doesn't matter if people are biologically alive. You, your friends, family, society, relationships — would all be very, very different when you come back. If you just meant "see friends and family", yeah technically you could see each other I guess. Practically, might as well be an alien.
50,000 years later you sync memories if there has no been trickle of communication in that time between you and your instances