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Hello, I have a question regarding wormholes and quantum entanglement. I know that, theoretically, if one was to take two ends of a wormhole and keep one stationary while one moves around, it would be possible to travel back in time. Could this be duplicated practically by using entangled particles - due to the fact that they are connected instantly much like the two ends of a wormhole? In this experiment, one would keep one particle stationary while moving the other one in a particle accelerator or something like that, to observe the time dilation effects between them (hopefully resulting in some form of backwards time travel effects, like the case with the wormholes). What is your opinion on this? And is it right to compare wormholes to entangled particles because of their similar characteristics (with regard to connecting different points in space - or different particles separated by space) instantly? Thank you for your help!
Question Date: 2011-03-26
Answer 1:

It's actually not possible to send signals or communicate a-causally with entangled particles. The important point to understand is that in order to entangle two particles, they must initially be in the same location. Even though the entangled particles may later be separated over large distances and the collapse may occur instantaneously, because the particles couldn't travel to their current locations faster than the speed of light,entanglement can't be used to send signals any faster than by sending regular light signals. In particular, entangled particles definitely can't be used to send signals back in time.

To understand this, it's useful to think about how entangled particles are actually created and used. Researchers commonly create entangled photons in labs, then send them down long optical fibers traveling in separate directions and can perform entanglement measurements over widely separated distances. However, because the entangled photons traveled at the speed of light down the optical fibers, the entangled communication can't be any faster than if an ordinary light signal was simply sent down the optical fibers.

Regarding wormholes, entangled particles aren't really a good analogy,since they can't cause any sort of a-causality. You might be interested to learn about something called Topological Censorship. Roughly, it states that unless an observer falls into a black hole (or comes out of a white hole, but that's really pathological), they can't even measure if their universe has a wormhole. If you're interested in learning more about Topological Censorship, you might be interested in reading the article

article

Answer 2:

This question is unanswerable in the light of what we currently know: wormholes have never been observed to exist, so it's entirely up for speculation what their properties might be. The entire concept of wormholes flies in the face of relativity, no matter what you do, it would violate causality in some fashion. Anything involving wormholes therefore involves physics of the sort that is currently totally unknown. This is why quantum entanglement is so surprising, because it, too, seems to fly in the face of relativity.



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