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The Grandfather Paradox Avoided

July 23, 2010

Not Pictured: Professor Lloyd

It’s become a cliche in sci-fi: When traveling into the past, never meet your past self! You would create a paradox! An alternate reality! The end of time and space as we know it!

But one quantum physicist, along with Spock, is saying that’s all bull.

Scientists are able to ‘teleport’ quantum states from one place to another. But what about through time? Christopher Seth Lloyd and his team at MIT say that using the same principles and a further strange quantum effect known as ‘postselection‘, it should be possible to do the same backwards in time.  Paradox free. Says Lloyd, “It is possible for particles (and, in principle, people) to tunnel from the future to the past.”

“You could think of it as postselection affecting the history of the particle, sending the state back in time.” says Dr Richard Low, a quantum computing scientist from the University of Bristol and whose name I can’t connect to BTTF at all. The Telegraph continues:

Unlike previous theories of teleportation, this apparently avoids the “grandfather paradox” – or, to Back to the Future fans, the Marty McFly problem. If you go back and change time, and accidentally end up killing your own grandparent, you create a paradox – you will not be born, so you cannot go back and affect time. Even with subatomic particles, this is still a problem: upon travelling back in time, the particle could somehow destroy its earlier self or move it, thus preventing it from travelling.

However, because of the probabilistic nature of quantum mechanics, Prof Lloyd’s method seems to avoid this. Anything caused by the time travel must have had a finite probability of happening anyway, so paradoxical impossibilities are out.

So it’s possible, in theory, to travel back in your own timeline, but you’d go back and take your previous self’s place. You can’t meet your past self because you ARE your past self. It’s more like Quantum Leap than Back to the Future. It even smells a bit of immortality. Every time you get close to death, you go into the local Quantum Lap to zip back to the starting point to hop on this crazy ride all over again.

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One Comment leave one →
  1. November 17, 2010 4:06 pm

    There’s also a theory that time travel would involve jumping into a parallel universe (one stemmed off of your own from the past) in which you could kill someone that would prevent you from being born, and it does; but only in that dimension. The you from the alternate time line would still exist – Maybe! This would also suggest that you from other alternate time lines went to other alternate time lines and did what you did, possibly killing the you that you recognize yourself to be. If not, you still have the problem of returning to the correct time line (you could get there and only one quantum difference exists, but you wouldn’t know!).

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