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Is the past uniquely defined?

  1. May 2, 2012 #1
    Quantum mechanics provides indeterminism to our world. If we were to go back in time and let history takes it toll once again, we are very unlikely to end up with the same history as we have now. That is, the future is not unique. There is a clear consensus about this in the scientific world, and I have no problems or questions about it.

    Now, it is the rules of quantum mechanics that lead to this non-unique future, simply because these rules doesn't produce a unique outcome. These rules also applies in reverse, that is, if we want to figure out the past, rather than the future. So, even if we had all the knowledge of the present world at out disposal, we wouldn't be able to figure out the (unique) past. Rather, we would find many possible histories, all with the potential to lead to today. I now ask the question; is the past uniquely defined any more than the future is? We all agree pretty well about the events of the past, which suggest that the past very well may be unique. But how does the past protect itself against the fuzziness of quantum mechanics? In what way is the past uniquely defined, when the future aren't?

    Do any consensus about this "reverse determinism" exist? Thank you
  2. jcsd
  3. May 2, 2012 #2
    That's quite an interesting question..
    Although I wouldn't really know where to start out, I'm gonna keep my eye on this thread.
  4. May 2, 2012 #3


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    There are many phenomena that exhibit broken time reversal symmetry. I think that in itself should answer this question.

  5. May 2, 2012 #4


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    There are significantly fewer past states than future states. You can think of it as consequence of entropy increase, or you can think of it as what defines the arrow of time. Either way, past is much better determined than the future is. But there is absolutely no reason to believe that history is unique. It certainly isn't on microscopic level, and probably isn't on macroscopic either.
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