In 1961 it took NASA 8 years from the start of the Apollo program to get to the moon. Then they went back in 1971 for two weeks. Then they never went back. We haven't gone past low earth orbit since. The human race has developed an insane amount of technology since then, and we have to keep going. If we don't, if something happens to earth and we all die, all this progress was for nothing. Calculus was invented over 300 years ago. Look at the internet, wi-fi, touchscreen, 3d without glasses... We're on the brink of "the future" in my opinion and its time we started acting like it. We have the technology to live on other worlds, sure it will be hard and risky, but so was putting the first man into space. As Hawking says, we can't keep all our eggs in one basket, you drop the basket you have no more eggs.