No comparison between ghosts (or apparitions) and time travel (to the past): the question of time travel only consists in if is possible travel to the past, but there is no evidence that there are time travelers. However the question of ghosts is backwards: there is evidence that apparitions both living and deceased even inert objects, so the question is what is the nature of such apparitions. Some cases seem to indicate that the apparitions are spirits of the deceased, ie ghosts, because they have the appearance of a deceased and provide new information for the witness, in other cases it appeared seems to be a residue of the past which is again received by the witness...