The Real Rules for Time Travelers

By Miss Cellania in Science & Tech on Feb 3, 2010 at 11:13 am

This article at Discover Magazine has nothing to do with the science fiction stories we are so familiar with. Author Sean Carroll looks at time travel as a physicist. He says if time travel were possible (and it might be), there would be no paradox, because we cannot change what has already happened. Ever. Then it gets weird.

Imagine that we have been appointed Guardian of the Gate, and our job is to keep vigilant watch over who passes through. One day, as we are standing off to the side, we see a person walk out of the rear side of the gate, emerging from one day in the future. That’s no surprise; it just means that you will see that person enter the front side of the gate tomorrow. But as you keep watch, you notice that he simply loiters around for one day, and when precisely 24 hours have passed, the traveler walks calmly through the front of the gate. Nobody ever approached from elsewhere. That 24-hour period constitutes the entire life span of this time traveler. He experiences the same thing over and over again, although he doesn’t realize it himself, since he does not accumulate new memories along the way. Every trip through the gate is precisely the same to him. That may strike you as weird or unlikely, but there is nothing paradoxical or logically inconsistent about it.

Link -via Digg

(image credit: Biwa Studios)


Email This Post
Tweet This Post 
Share This Post on Facebook

Tags: , ,


Neat stuff from the NeatoShop:


  1. Splint Chesthair
    Feb 3rd, 2010 at 2:46 pm

    I’ve always thought birth and death were just biological mechanisms for time travel and just like Dr. Sam Beckett, the process messes with our memories. Oh boy!

  2. felixthecat
    Feb 3rd, 2010 at 3:54 pm

    Alfred Bester’s “The Men Who Killed Mohammed” had a different notion, one that involved parallel universes. Go back in time, strangle the baby Hitler in his crib, and return to the present. But the present returned to is not the original present, but a parallel one in which WWII never occurred.

  3. vmos
    Feb 3rd, 2010 at 5:13 pm

    “you can’t create a paradox because it’s impossible to change the past because time travel doesn’t work like that”

    BALONEY

  4. kim
    Feb 3rd, 2010 at 6:13 pm

    I have asked to see the future, and did see it, therefore the future traveled back to me. This makes a certain sense.

  5. allexx
    Feb 3rd, 2010 at 7:53 pm

    The problem with this theory is that there is no past that can be changed. So if you can travel to say 2013, you can’t come back to 2012. Also the person in the story only has a 24 hour life span….He would’nt be a man then. Its not a life span, its a 24hr moment in time. Is it past or present humm?

  6. AshleyZ
    Feb 3rd, 2010 at 10:31 pm

    The quoted story sure looks paradoxical to me. Suppose the time traveler who exited the gate had a beard that was 1 mm long. In the 24 hours he loiters near the gate, it might grow to 2 mm. But clearly he can’t be the same man who exited the gate, since the man going in had a 2 mm beard but the man coming out only had a 1 mm beard. I think the author must have forgotten to mention one of his assumptions.

  7. Necronomic Recovery
    Feb 4th, 2010 at 9:31 am

    I’ve long maintained that you can’t change the past.

    Say your friend dies in a car crash. You travel back in time to save him. Your friend says thanks as you head back to your future.
    From your friend’s point of view, he carries on his life until he reaches the point in time where you jump back in time to save. Except you don’t. Because he didn’t die.
    So if he didn’t die, you never had to go back in time. And if you never went back in time, then who saved him from being killed in a car crash? Paradox.

    (I suppose your friend could manipulate you into time travelling back to save him or just outright ask you to but this contradicts the original reason. Your friend was, as far as you were concerned originally, dead.)

    So the only leeway I can see for changing the past is if the exact circumstances are not know. The outcome can never change but the details can.


Keep track of the comments with Comment RSS

Don't Miss: New Stuff | Bestsellers | The Cute Store
                   Funny T-Shirts

Need a gift? Get unforgettable gifts for:
Geeks | Pranksters | Kids | Hipsters | Shutterbugs

Lijit Search

Old school? Bookmark us! RSS Feed Twitter Facebook Page