I remember reading a sci-fi book awhile back, probably early 2000's, but can't for the life of me find the book again or remember the title.
Humans are already in space and they come upon a beacon of some sorts, it's human, but from the future and the date is in a format that the current timeline doesn't understand so they don't know how far from the future it's from. They've been trying to figure out why stars keep popping up in places that weren't there before, and it turns out that the future is sending stars back through black holes because of the Galaxy's rotation or something, needing to correct it.
One of the main characters meets his future self in an elevator and future him is called Glassman or something, because he's transparent or something, and effectively immortal. He explains to his past self that his (future?) Ex wife discovers how to prevent people from aging/DNA damage in regards to the hayflick limit, etc, and that he cheats on her and they divorce or something. He tells him not to do that, and then tells him that he won't remember their conversation, except for a subconscious thought not to cheat on his wife.
Anybody have any clue what the book is??