No paradox for time travellers

[Stacy Dohm]

No paradox for time travellers

THE laws of physics seem to permit time travel, and with it, paradoxical situations such as the possibility that people could go back in time to prevent their own birth. But it turns out that such paradoxes may be ruled out by the weirdness inherent in laws of quantum physics.
Some solutions to the equations of Einstein's general theory of relativity lead to situations in which space-time curves back on itself, theoretically allowing travellers to loop back in time and meet younger versions of themselves. Because such time travel sets up paradoxes, many researchers suspect that some physical constraints must make time travel impossible. Now, physicists Daniel Greenberger of the City University of New York and Karl Svozil of the Vienna University of Technology in Austria have shown that the most basic features of quantum theory may ensure that time travellers could never alter the past, even if they are able to go back in time.
The constraint arises from a quantum object's ability to behave like a wave. Quantum objects split their existence into multiple component waves, each following a distinct path through space-time. Ultimately, an object is usually most likely to end up in places where its component waves recombine, or "interfere", constructively, with the peaks and troughs of the waves lined up, say. The object is unlikely to be in places where the components interfere destructively, and cancel each other out.
Quantum theory allows time travel because nothing prevents the waves from going back in time. When Greenberger and Svozil analysed what happens when these component waves flow into the past, they found that the paradoxes implied by Einstein's equations never arise. Waves that travel back in time interfere destructively, thus preventing anything from happening differently from that which has already taken place (www.arxiv.org/quant-ph/0506027). "If you travel into the past quantum mechanically, you would only see those alternatives consistent with the world you left behind you," says Greenberger.
“The most basic features of quantum theory may ensure that time travellers could never alter the past”
"This is a very nice idea," says physicist Avshalom Elitzur of the Weizmann Institute in Rehovot, Israel, who also suggests that further work in the area could help to clarify the nature of time itself. "Time is a very mysterious thing."
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[Keith Ranville]

I believe in Paradox,

If John F. Kennedy wasn't shot we would be living in a alternate time in space like 9/11 if it never happened, just think if a event could be un-naturally prevented this would creat a paradox. If a such a large paradox was contrude this would effect -people's psyce   

[4th Horseman of the Apocalypse]

I believe in paradoxes, too, there are probably millions of different realities that one can exist in, we just happen to be stuck in one of the more miserable ones! 

[Keith Ranville]

who knows 4th Horseman of the Apocalypse,

These amazing Amercan blunders may have humanized America if it was meant to be maybe different strokes, other nations may have gotten jealous. Like I was ones told everything happens for a reason? to bad in this case it feels like for all the wrong reasons? This is where Deju Vu comes in, when one would say do I know you in a better life.

     

[Stellaraxe]

I used to believe that everything happens for a reason, however, I realize now that there are too many variables for life to simply exist on a linear trek.  Who knows is there is a single all seeing per looking out for us when it comes to time travel?

[Keith Ranville]

Well I had a premonition of a car crash, a girl that was at my house at a get togather, and I went out of my way to persuade her to stick around and her friends figured I was up to getting with her? She decided to stick around I said I had a awfal feelling if you were to go.

Later in the evening the car that this girl friend I met and that she was suposed to be in flip and the seat where this girlfriend I barely knew was to be sitting in,  the roof was crushed in? Thank god there were only injuries from this none alcohol related accident.

A what if story,

[Thanos]

That actually falls under the category of precognition.  However, perhaps in another universe, she took the ride in the car and terrible things happened.

[Robert0326]

Stacy,

So if I were to go back in time and kill my grandfather (grandfather paradox) when he was still a child I would still be born?  I don't see how that would be possible.

[Vanessa Korias]

I don't think time travel for the purpose of altering reality is possible at all. More than likely, you would be creating a second reality where your grandfather was killed, you weren't born, while the first reality still exists somewhere.

[Volitzer]

What about temporal repossessions ??