Travelling to a time in the past is, as far as we know, not possible. However, Einstein postulated a faster-than-light effect known as 'spooky action at a distance'. The problem is, how do you test for such an effect? That test may now be here. If all goes well, hopefully by September 15th, John Cramer will have experimented with a beam of laser light which has been split in two
to test Einstein's idea.
While he is only testing the quantum entanglement portion, changing one light beam and having the same change made in the other beam, his experiment might show that a change made in one beam shows up in the other beam
before he actually makes the change.
An interesting sidenote is that the money for this project was raised not from the scientific community but from the public at large. His fans have sent him the money necessary to purchase the equipment to test Einstein's idea.