Using light as time, Centauri is in three positions of time all at once. From Sol, -1 (observed). From Sol, +1 (unobserved). From Sol, 0 (unobserved). Any space and time travel to Centauri system will always be -1 (space-time), via +1 (space-time), to 0. (space-time). Any time travel in the whole of space will be -1, via +1, to 0 . . . solely excepting, I think, "entropy". The time dimension of -1 (past) is always pre-existing. The time dimension of +1 (future) is always pre-existing. The time dimension of 0 is always pre-existing as the result third dimensional universe. The past is the future = 0 (3-d). The future is the past = 0 (3-d).