Time travel doesn’t exist in the sense that most people/sci-fi writers want it to. But the incredible Sean Carroll, science blogger extraordinaire, leaves open the possibility of parallel universe time travel, the kind they use in the new Star Trek movie.
As I was watching the movie, the thought of parallel universes rocked my ethical foundations. I remember in my intro to philosophy course we discussed a thought experiment (I think by Derek Parfit) in which there’s this fabulous new technology that scans your body, molecule-by-molecule, disintegrates it, and transmits the information at the speed of light to another super-appliance, which builds you back up, at the exact molecular state you were at in the first location. Anyway, the point of the thought experiment is that the whole thing gets messed up if the first machine doesn’t disintegrate you, and all of a sudden there are two yous, with different perspectives and memories, and it gets you thinking about A) the special nature of subjective experience and B) how carelessly you gave yourself up for disintegration when you were sure that your molecular structure would instantiate somewhere else in the universe, when that doesn’t ensure a continuity of consciousness. It would just be like all of a sudden having a twin.
But it seems to me that parallel universes lessen the moral gravitas of large-scale civilian deaths, like the demolition of planet Vulcan. Because most planet-destroying events are relatively quick and painless for the inhabitants of the unfortunate planet. See Star Wars or the new Star Trek. It’s not comparable to a modern-day genocide in terms of suffering and indignation that the victims experience. What Earth genocides and sci-fi planet-destructions have in common: the intensely evil intent of the perpetrators, and the tragedy that a culture has been wiped from existence.
What the existence of a parallel universe does, however, is qualify that second part of the evil of planet-destruction. The destruction of planet X is not as tragic if in some parallel universe planet X has not been destroyed, and therefore the cultures and ways of life of the citizens of planet X (hereafter referred to as Xians) goes on.
Some assumptions I’m going off of:
- Our moral judgments aren’t limited by space, time, or the confines of our own universe.
One might object: It’s possible that events in parallel universes are so far removed from our reality - more like fiction than something happening on the other side of our planet – that they should cause us no grief or consolation. To that, I answer: we didn’t make it up. If parallel universes actually exist, then things might actually be flourishing or suffering. And that’s what we need to consider in our moral reasoning, not where/when the suffering/flourishing things are.
- It doesn’t matter if Xians can procreate and return to parallel universes in which they’ve been wiped out, it just matters that they exist in any universe.
If you agree that you don’t have to know a culture personally to be happy that its extinction, then you should also agree that you don’t have to be in the same universe as the Xians to be content that their way of life continues in some form.
This argument is limited to the cases in which we have two parallel universes, A and B, and in A a planet, X, is destroyed and in B, planet X is not destroyed. Even with an infinite number of parallel universes, it isn’t always the case that you get that case. It’s possible that planet X being destroyed is a necessary characteristic of any universe, and in which case we (and the Xians, I suppose) can at least take consolation in the fact that the Xians’ total annihilation was a cosmically necessary tragedy that couldn’t have gone any other way.