# Thread: Wormholes and time travel

1. ## Wormholes and time travel

I understand (well, I eat paste, but I get the general idea) that in theory, if you could accelerate one of the mouths of a traversable wormhole, you could create a time machine because of relativistic time dilation. That makes sense.

Let us postulate that I have a wormhole (in my wardrobe) whose other mouth is connected to a planet (wintery, with talking animals) on the other side of the universe, in a system that moves at relativistic speeds to our own system so that time appears to pass faster there. (Would that mean that our side is the one that was accelerated to match the wardrobe's relative motion to the spot near the lamppost? Sounds like a nightmare to even begin figuring out how to make stargates stay in the same place on a planet...)

My question here is mostly that if you traverse the wormhole, how would you yourself experience that change in acceleration? Can you have one hand in Narnia and the rest of your body on the other side, making that hand age 20 times faster? (I think Niven wrote a story about this once, and it wasn't pretty...) How would the traversal work in general, keeping in mind that this is all highly theoretic in the first place?

As I said, I eat paste. Just some idle discussion to while away the time during a long car ride, and I was wondering if anyone here had any fun input or if I'm completely in the rough here...

2. Actually both ends of the wormhole would experience time at the normal rate (one second per second- apologies to Paul Beardsley, who has expressed a dislike for this expression in the past, if I recall correctly). So if you put your hand through the wormhole, your hand would age at the same rate as the rest of your body. This would be true for all kinds of wormholes; see this page
http://www.mmaidana.com.ar/tim.html
where a couple (Kip Thorne and his wife) hold hands through a wormhole, one end of which is travelling at relativistic speeds.

Only when you tried to travel back to Earth through normal space (or send a message, by radio for instance) would you notice that the frames of reference at each end of the hole do not match.

3. There is also the issue that to get a shift that you are looking for is not possible over the scale of a human body. As I understand it the lorentz contraction would prevent you from finding a situation where you're hand could age faster then the rest of you by 20 times without it being ripped off.

4. Excellent, thank you for that link!

5. Having read the article now, it doesn't really answer my question. In the article in question, the two are holding hands inside the wormhole. Nobody at any time has a hand in the other's frame of reference. I was wondering what exactly happens when one steps through one of the two mouths of the wormhole.
Last edited by jokergirl; 2012-Jun-18 at 11:16 AM.

6. Do you notice that your feet are aging slower then your head? They are in 2 different frames of reference. The frames are just nearly the same.

7. Then you already answered your own question while completely ignoring mine. What if they are very different?

8. No matter where you are, no matter how fast you are moving, your experience of time is always one second per second. If, for some reason, your feet were accelerated fast enough to be in a significantly different frame to your head, you would be torn apart.

The same would happen in a wormhole; if the space-time metric within the wormhole is sufficiently flat for Kip Thorne and his missus to hold hands without being torn apart, then stepping through the hole would not cause them to observe anything out of the ordinary. This is the big challenge with wormholes, by the way; a wormhole that doesn't rip you apart is the desirable kind, known as a traversable wormhole.

9. This page gives a very, very good idea of what it would be like to pass through a wormhole; in particular keep an eye on the different coloured cubes as they flip and turn themselves inside out.
http://www.spacetimetravel.org/wurml...mlochflug.html

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