The Ph.D. system was designed for a job in academics. And it works really well if you really want to be an academic, and the system actually works quite well. So for people who have the gift and like to go spend their lives as scholars, it's fine. But the trouble is that it's become a kind of a meal ticket - you can't get a job if you don't have a Ph.D.

Everything in my life was luck. The key to having an interesting life is to always say "yes" to anything crazy.

When World War II came along, which was when I was a teenager, we all expected we would have anthrax bombs and this kind of stuff. We thought it would be a biological war. Fortunately it wasn't and, but it's because the danger is still there and by some miracle we escaped all that, so you never can tell what it going to happen, but biology certainly could be even worse than physics and chemistry.

For a physicist mathematics is not just a tool by means of which phenomena can be calculated, it is the main source of concepts and principles by means of which new theories can be created.

It's as great a part of the human adventure to invent things as to understand them. John Randall wasn't a great scientist, but he was a great inventor. There's been lots more like him, and it's a shame they don't get Nobel Prizes.

There are three reasons, . . . apart from scientific considerations, mankind needs to travel in space. The first . . . is garbage disposal; we need to transfer industrial processes into space so that the earth may remain a green and pleasant place for our grandchildren to live in. The second . . . to escape material impoverishment: the resources of this planet are finite, and we shall not forego forever the abundance of solar energy and minerals and living space that are spread out all around us. The third . . . our spiritual need for an open frontier.

Our thinking is permeated by our historical myths