“No one thinks they are from across the universe. Whatever they are—if they exist at all—they seem to be from a parallel dimension.”
I think they are inter-dimensional. But one cannot rule out entanglement as a mode of transportation from far distances. Or even being in two places at one time using entanglement. This might explain the “only partly physical” state when it happens.
We are but infants about possible physics. However they have already been here forever. Maybe longer than we have.
Very true.
They certainly might be capable of using a technology and a physics that permits them to cross vast distances in ways we are incapable of imagining.