Maybe interstellar travel is basically impossible but there might be very long lived civilizations that propagate to others stars when one comes near by. Imagin

Maybe interstellar travel is basically impossible but there might be very long lived civilizations that propagate to others stars when one comes near by. Imagine what happens when both stars are populated by different long lived civilizations and they start to get near each other. I would love to read a good book speculating about such an event.