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.
Stephen Hawking

We are in danger of destroying ourselves by our greed and stupidity. We cannot remain looking inwards at ourselves on a small and increasingly polluted and overcrowded planet.
Stephen Hawking

We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet.
Stephen Hawking

Time travel used to be thought of as just science fiction, but Einstein's general theory of relativity allows for the possibility that we could warp space-time so much that you could go off in a rocket and return before you set out.
Stephen Hawking