Last night I watched the movie Deja Vu, which explores a time-travel scenario and the usual questions of whether we can change the past, and what happens if we do or even try. The film explicitly raises questions of ‘spirituality’, and one character even suggests that the past cannot be changed because ‘God has made up his mind about it already’. Yet the film is somewhat unique in raising the ethical issue of whether to intervene to change the past differently – if the past is still there, then (for example) the murder victim is still alive. Don’t we have an obligation or at the very least an opportunity to do something about it, to prevent something that, from that standpoint in time, has not yet happened?
Personally, I am not persuaded that some of the time-travel paradoxes explored in Doctor Who, Back to the Future and elsewhere are as problematic or as paradoxical as is claimed. After all, if time travel to the past is possible, then you can exist before you were born, and in two places at once, and so how is it more fundamentally problematic that you exist without ever having born (because you change history)?
It may simply be my lack of understanding of relativity and of quantum physics (although Richard Feynmann suggested that no one understands it, which makes me feel somewhat better), but I remain to be persuaded that the past continues to exist ‘somewhen’. Whatever may be implied by the fact that relativity treats time as thought it were another spatial dimension, it is no more obvious that we still exist in the past any more than that we still exist in the other points in space we used to occupy. So my guess is that time travel to the past is an impossibility. It will still be possible to sit near the event horizon of a black hole and get to the future faster than other people.
This leads me to conclude that, in spite of the many points that I find plausible and thought-provoking, I am not persuaded by one aspect of James Gardner’s “Selfish Biocosm” hypothesis (outlined in his book The Intelligent Universe), namely that our universe might be folded back around on itself and thus self-originating. Nevertheless, it is interesting to consider an alternative scenario in which universes that can support life are created through the life forms that inhabit such universes, so that they are self-replicating and have an ‘evolutionary advantage’. What if universes like ours result from physics experiments by intelligent life forms inhabiting universes like ours, trying to see whether it is possible to create a baby universe? It would be ironic if, like many biological species, universes reproduce through a process that results in the extinction of those instrumental in the process.