Not to leave planet Earth would be like castaways on a desert island not trying to escape...Sending humans to other planets ... will shape the future of the human race in ways we don't yet understand, and may determine whether we have any future at all.

Theology is unnecessary.

I'm here to chew gum and kick some ass, and I'm all out of gum.

When I get to heaven I'm gonna find the guy in charge of the weather and kick his rear.

If it were only a few degrees, that would be serious, but we could adapt to it. But the danger is the warming process might be unstable and run away. We could end up like Venus, covered in clouds and with the surface temperature of 400 degrees. It could be too late if we wait until the bad effects of warming become obvious. We need action now to reduce emission of carbon dioxide.

I think the next [21st] century will be the century of complexity. We have already discovered the basic laws that govern matter and understand all the normal situations. We don't know how the laws fit together, and what happens under extreme conditions. But I expect we will find a complete unified theory sometime this century. The is no limit to the complexity that we can build using those basic laws.

Only time - whatever that may be - will tell.