Time travel science

The way that i see it, each second of every minute is lost forever once it passes, a good example would Stephen Kings 'The Langoliers' where the plane travels backwards in time to a hollow second which has already passed and is decaying into nothing. So i don't think travelling back in time to a point that has already passed is possible, because that implies that time is a tangible thing, which it isn't.

Time is as tangible as the lenght of an object.

Consider that as you wish.