I thought of a thought experiment that had me questioning how time reversal works in quantum mechanics and the implications. The idea is this ... you are going forward in time when you decide to measure a particle. The particle then collapses to the observed state. Now if physics were to be the same in reverses time, then if we stop and reverse time then measure that very same particle again ... then I would imagine that since the wave function has collapsed we ought to measure the same thing. What this says to me is that given some time evolution in the + direction, if we measure a particle and it collapses the wave function, then if you reverse the arrow of time to go in the - direction we ought to get the same answer as before. The future/present effects the past. This means if we theoretically had a time machine and went back in time, we would have traveled into a different past.
Another implication of this thought experiment is that the future would be indistinguishable from the past and would hence forth be the same. I would imagine that this is consistent with the 2nd law of thermodynamics since physics dictates that entropy only increases ... going in the reverse direction of time to decrease entropy would violate the laws of physics. Has anyone else out there thought about this?
From my studies in quantum mechanics, I don't remember any postulates stating anything like this, but this all makes sense to me. Are there any theories out there that go along these lines?