Extraterrestrial civilizations on free-floating planets
extraterrestrial civilizations would ride free-floating planets to reach and colonize planets orbiting stars. Upon their close approach to planetary systems, the extraterrestrials could transfer from their free-floating planets to selected Oort-cloud objects of the planetary systems that would carry them inwards and towards the major planets of the planetary systems. Or, the planetary systems could capture such free-floating planets. Then, the extraterrestrials would colonize the planetary systems.
This is a scenario new to me but it makes a kind of sense. There should be a sci-fi novel in it somewhere.
At present, somewhere in space, hundreds of light years away from Earth or closer than that, migrating intelligent biological species or post-biological beings with artificial intelligence may be riding free-floating planets and looking for a new home.
“Post-biological beings with artificial intelligence?” Uh-oh.