I have sort of been working on a story that relates to travelling backwards in time. It's a bit of an extrapolation of Star Trek matter transporters.

Imagine if you had the ability to transport a whole ship to a point in the universe that can be seen by a powerful telescope and arrive at that point instantly. If that point is distant enough then you have travelled back in time, as we all know that light has a fixed speed and the light from distant stars and galaxies may have taken many many years to reach us. So if you could transport to that light source, as we see it in the present, then you have travelled backwards in time the same amount of time that it has taken for that light to reach us. The problem with this method is that it cannot be reversed because if you transported back to the solar system by fixing it's co-ordinates from your new location, then you will travel backwards in time again.

Faster than light travel has certain problems that have not yet been solved, such as the crushing G-forces you would experience at such speeds.

Look, I know Star Trek is a flawed series with many scientific errors and fallacies but if that one bit of technology could be worked out and extrapolated in the way I described, it would open up the stars to us.