A thought experiment (borrowed from wikipedia, as discussed by Todd and myself down in San Diego):

Take a modified Schroedinger’s Cat Box, which has in it a weapon set to trigger if a particular quantum particle is spin-down upon measurement (assume that the particle is equally likely to be spin-up or spin-down) – and place yourself inside.  Every ten seconds, another particle is measured; if it comes out spin-down, the weapon fires and you die.

If you believe in the Many Worlds Interpretation (MWI) of quantum mechanics, then entering the Box might be a way to have your consciousness “travel” into low-probability outcome universes.  MWI means each possible state is actually a parallel universe, and the observer happens to be in one of them measuring one possible state.  (This might sound crazy to you, but other possible interpretations, like the Copenhagen Interpretation, require the act of observation to force reality into a particular state, which I consider to be just as crazy, physics-ly speaking.)

I believe that I observe reality from the seat of my consciousness, my “self”, where I consider myself to be.  Even those of us (ahem) who believe in no free will still must consider the seat of their sensory centers, and can call that the “self” for the purposes of this discussion.  So the question becomes: what happens to the “self” in this experiment?  You do the experiment, and every 10 seconds, it is 50% as likely as previous that you survived.  Each time you die, you won’t make any further observations.  But each time you live, you will observe that you survived.  There will always be a smaller but nonzero number of universes in which “you” survived and made that observation.

And then the question that Todd and I posed to ourselves: is there moral value here?  By running the experiment, you “kill” the spin-down self after 10 seconds.  Even if you ended up in the spin-up universe, what is the relationship between you-up and you-down?  Should it matter?

Nobody really understands quantum mechanics, which is sometimes really disturbing.  Thinking about this idea in one sense makes things even more disturbing, but in another good way, helps me think about the high-minded issues that bother me (some not particularly related to quantum mechanics!)