[color=#000000
ost_uid0]Can't avoid paradox if the traveller remains rooted in the timestream. I always favor the systems where the traveller is somehow disconnected from the new timestream - so if you kill you own grandfather, you yourself survive, even though in the new stream, you're never born.
Another neat system is that you can go back, except you can't make any changes to what you already know.
Meaning you can go back in time to when your grandfather was born, find his bassinet, and kill him... ON THE CONDITION that you then kidnap a similar looking baby, and put it in his place, because actually he was your grandfather all along...
A better example would be, you and your friend are walking along a corridor. Your friend, walking ahead, turns the corridor, then suddenly you hear a zap, see a flash of light, and then all is still.
Well, no problem. You go back in time, and teleport your friend to safety just as he turns the corner. The zap gun misses him entirely. Who are you to say that's not what happened the first time around?
Ah, what if you already turned the corner and saw his charred body? Well, even so, there's no reason to discard the possibility that this is only the charred remains of a [i
ost_uid0]clone[/i
ost_uid0], which your time-travelling self thoughtfully remembered to beam in as he got your friend out. So the only way for your friend to be absolutely, irrevocably dead, is if you scan him with your ReallyReallyDead-O-Tron, and see that it's really him, and he was really killed right now.
Unless, of course, you were to go back in time, pick up your scanner, and cause a minor malfunction...
I love time travel.[/color
ost_uid0]