• Question: Can you think of anyway, theoretically of course, that you can change the past without creating a paradox? ie grandfather paradox

    Asked by watsonjc06 to Carol, Ellie, John, Phil, Rebecca on 28 Jun 2012.
    • Photo: John Welford

      John Welford answered on 28 Jun 2012:


      I think the grandfather paradox only applies if you kill a member of your family when you go back in time – so that you cannot be born. There are various ideas that get around the paradox, such as joining a new timeline, in which you are never born, or that you are physically unable to kill your family member and they somehow survive.

      If you don’t kill anyone when you go back in time then I don’t think there is any paradox. In fact so many things in life as really inconsequential that you might not end up changing history that much at all.

      For example if you went back and disturbed Newton so that he didn’t discover gravity (caught the apple before it landed on his head or whatever) then I bet someone else would have discovered gravity instead. Things might be slightly different when you got back to the present, but I bet not that much, and how could you know whether it would be better or worse?

      It’s all theoretical but it can be fun to think about. What do you think?

    • Photo: Carol White

      Carol White answered on 6 Jul 2012:


      There’s a few solutions to time travel paradoxes. One famous one is the “multiple universes hypothesis” – where time has an infinite number of universes which make up the “multiverse”.

      If you travel back in time, you end up in a parallel universe. This means that if you went back and deliberately or accidentally killed your grandfather, the “grandfather paradox” wouldn’t happen because the grandfather would be the “wrong” one. The “real” grandfather is still in the original universe and so it couldn’t happen.

      What do you think?

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