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New Model Solves Grandfather Paradox

Posted by Zonk on from the i'm-my-own-grandpa dept.

goldfishy writes "If you went back in time and met your teenage parents, you could not split them up and prevent your birth - even if you wanted to, a new quantum model has stated. Researchers speculate that time travel can occur within a kind of feedback loop where backwards movement is possible, but only in a way that is 'complementary' to the present. In theory, you could go back in time and meet your infant father but you could not kill him." From the article: "Quantum behaviour is governed by probabilities. Before something has actually been observed, there are a number of possibilities regarding its state. But once its state has been measured those possibilities shrink to one - uncertainty is eliminated."

4 of 887 comments (clear)

  1. That's great! by cytoman · · Score: 5, Insightful

    This means that you cannot be killed when you go back in time, nor can you kill or destroy anything! That's just perfect!!

    Go back in time and be able to observe, only... no ability to interact with anyone either... it should be kinda like ghosts... we go back in time and observe and be like ghosts in the sense that we cannot interact and change anything that has already happened but only observe!

    Imagine the possibilities of history classes of the future... maybe there are already a lot of ghosts watching us right now... the future students studying history!!

    1. Re:That's great! by Lemmy+Caution · · Score: 5, Insightful

      Here's an interesting twist: I can change the past in a way that changes the future, if I do so in a way that I don't know now. I could, for example, buy some shares of a stock that I know will rise a hundred-fold in value, but make sure that I don't get the money until after the moment I depart current time. Since I don't know that I don't have an envelope worth millions of dollars hidden, with a mechanism that will inform me of it, say, a week after my time-travel tip, it does not contradict what is known about the present that I become a millionaire a week from now.

  2. No no no! by jerald_hams · · Score: 5, Insightful

    "Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious."

    That's not clear at all. If I went back in time and killed the baby George W Bush, it's like he would disappear in the middle of a speech. Rather the entire course of history branching from that moment would be changed, so that in the "present" no one would ever know GW had existed.

    -Alex

  3. Lame! by khasim · · Score: 5, Insightful
    Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious.
    Ummm, if you prevented their births, they wouldn't exist to "fade into the ether".

    It could be happening all the time and you wouldn't be aware of it (by definition).
    And now a team of physicists from the US and Austria says this situation can only be the case if there are physical constraints acting to protect the present from changes in the past.
    Sounds like bad fiction to me.
    The researchers say these constraints exist because of the weird laws of quantum mechanics even though, traditionally, they don't account for a backwards movement in time.
    Sounds like the techno-babble "justification" in the bad fiction.
    So, if you know the present, you cannot change it.
    And the easiest way to not change it is for time travel to be impossible.
    If, for example, you know your father is alive today, the laws of the quantum universe state that there is no possibility of him being killed in the past.
    If, for example, you knew a picture would be taken, you could reflect light from your body and appear in that picture, thereby altering the future.

    So, travelling back in time, you cannot reflect light, and, by the same token, you cannot absorbe light.

    And it just moves up from there for all other physical effects. Nothing touched, no air breathed, no light disturbed, nothing.

    So, how would you even know you were in the past?