excuse my lack of understanding! Is there anything in physics which directly suggests that if FLT was possible, you would travel back in time? does anything forbid the possibility that instead you gradually change your time reference to keep causality? With the example of a very fast train, a light is turned on in the centre and an observer outside sees the light hit the back of the train before it hits the front. However, observers on the train see it hit both walls at the same time. if FLT is possible, it may be possible to travel to the front of the train where the light hasn't hit and hence go back in time. Is it possible that instead as you approach the front of the train faster than light, you would gradually change to its true time reference where the light has hit the wall and hence you will have traveled there quicker than light could but causality wouldn't be broken. Not very good explanation but potentially you could travel across the universe nearly instantaneously with a wormhole for example, much faster than light, and a change in time reference would stop causality being broken. I hope I am making sense. Just a suggestion, tell me if it's ridiculous!