Can Wormholes Be Used For Time Travel?

Question posed by Amy. Before reading this post, you might like to find out if wormholes exist, how wormholes work, and where all the wormholes are.

If you could make a wormhole it would, by definition, have two parts to it- an entrance and an exit, if you like. If your wormhole’s parts were fairly close to each other and you had some method of moving at least one of them, you could send it off on a journey as close to light speed as you can (or for a bit of a holiday very close to something with a very strong gravitational field, like a black hole).

When the other half of your wormhole comes back from its jaunt, due to the effects of relativity it will have aged less than the one that, as far as you’re concerned, stayed where it was: your wormhole’s exit has moved through time more slowly than than its entrance, which means that if you now fly through its entrance you’d come out of the exit before you went in.

So yes, in theory you could use a wormhole to travel backwards in time, but no further back than the time you originally built the wormhole. The further and faster your wormhole exit’s initial journey, the greater difference between the two mouths of your wormhole (in terms of time), and hence the further back in time you could travel.

But…

There’s always a ‘but’.

It is thought that a wormhole set up in this way would cause a radiation feedback loop, in which virtual particles are released from the wormhole’s exit and then go back in through the entrance, whereupon they are sent back and exit the exit again, and then go back in through the entrance… destroying the wormhole before any information can be passed through.

If you’re having trouble thinking about why this might happen, imagine the feedback loop between a microphone and a speaker: the screeching noise is caused by sound from the speaker being picked up by the microphone and then being amplified and re-emitted by the speaker, which is then picked up by the microphone, amplified again and then re-emitted by the speaker… and so on until, if the volume isn’t turned down or the microphone moved, the speaker is destroyed.

With the wormhole, due to the time-dilation involved, this would happen instantly, preventing the wormhole from ever being used.

There are some, however, who disagree with this line of thought.

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