Time Travel a la Stephen Hawking

[Darwinian]

Or perhaps time travel is possible but in order to travel back in time you must also travel at least as far in distance that light can travel in that time.

So, in order to travel a year back in time you must travel at least one light year in distance. This would therefore prevent you from being able to create paradoxes, meet yourself, influence past events for which the outcome is known by you etc.

Also, if time travel from the future to the past was possible, wouldn't that mean that the future was pre-determined? I mean, from our perspective the past has already happened and is fixed in history, but what if I was to travel back to the 1950's and told someone there that I knew the precise details of the next 60 years because to me it has already happened? What makes 'our' present any different to someone from the 2070's who has just arrived here and now?

Which also means that past can be influenced by the future by the very fact that someone from the future arrived to the past and influenced it. The fact that he travelled back in time to arrive in the past was always going to happen and is still the original version of history.