Although I cannot move and I have to speak through a computer, in my mind I am free. - Stephen Hawking

the future is unknown and open, so it might well have the curvature required. This would mean that any time travel would be confined to the future. There would be no chance of Captain Kirk and the Starship Enterprise turning up at the present time.

Disorder increases with time because we measure time in the direction in which disorder increases.

I have noticed even people who claim everything is predestined, and that we can do nothing to change it, look before they cross the road.