The long-term survival of the human race is at risk as long as it is confined to a single planet. Sooner or later, disasters such as an asteroid collision or nuclear war could wipe us all out. But once we spread out into space and establish independent colonies, our future should be safe. There isn’t anywhere like the Earth in the solar system, so we would have to go to another star. If we used chemical fuel rockets like the Apollo mission to the moon, the journey to the nearest star would take 50,000 years. This is obviously far too long to be practical, so science fiction has developed the idea of warp drive, which takes you instantly to your destination. Unfortunately, this would violate the scientific law which says that nothing can travel faster than light. However, we can still within the law, by using matter/antimatter annihilation, at least reach just below the speed of light. With that, it would be possible to reach the next star in about six years, though it wouldn’t seem so long for those on board.
- - Stephen Hawking, accepting the Royal Society’s Copley Medal, December 1, 2006.