If travelling backwards in time is possible, Novikov's Self Consistency Principle is a neat explanation of how the Grandfather Paradox may be avoided: http://en

If travelling backwards in time is possible, Novikov's Self Consistency Principle is a neat explanation of how the Grandfather Paradox may be avoided: http://en.wikipedia.org/wiki/Grandfather_paradox#Novikov_self-consistency_principle http://en.wikipedia.org/wiki/Grandfather_paradox#Novikov_sel.... Basically, the idea is that if you are alive and capable of travelling backwards in time to attempt (directly or indirectly) your own murder, then your attempt has to fail by virtue of the fact that you're alive in the present. There's a nice thought experiment with a billiard ball here: http://en.wikipedia.org/wiki/Novikov_self-consistency_principle#History_of_the_principle http://en.wikipedia.org/wiki/Novikov_self-consistency_princi...