I had two passions when I was a child. First was to learn about Einstein's theory and help to complete his dream of a unified theory of everything. That's my day job. I work in something called string theory. I'm one of the founders of the subject. We hope to complete Einstein's dream of a theory of everything.

It's pointless to have a nice clean desk, because it means you're not doing anything.

Scientists who have dedicated their lives to building machines that think, feel that it's only a matter of time before some form of consciousness is captured in the laboratory.

The reactors in Japan are stable in the same way that a ticking time bomb is also stable. It wouldn't take much to light the fuse - a 6.6 earthquake, like what happened today in Japan, a pipe break, an over-pressurized containment vessel - anything could set it off, in which case we would have another Chernobyl, three times the magnitude of a Chernobyl accident.

I realized very early in life what my abilities and limitations were, and foreign languages was definitely one of my limitations. With strenuous effort, I just barely passed my French class at Harvard so I could graduate.

You know; when I look at the night sky and I see this enormous splendor of stars and galaxies, I sometimes ask the question, well how many worlds are we talking about? Well do the math, there are about 100 billion galaxies that are in the visible universe and each galaxy in turn contains about 100 billion stars, you multiply and you get about ten billion trillion stars. Well I think it is the height of arrogance to believe that we are alone in the universe, my attitude is that the universe is teaming, teaming with different kinds of life forms

Physicists often quote from T. H. White's epic novel The Once and Future King, where a society of ants declares, "Everything not forbidden is compulsory." In other words, if there isn't a basic principle of physics forbidding time travel, then time travel is necessarily a physical possibility. (The reason for this is the uncertainty principle. Unless something is forbidden, quantum effects and fluctuations will eventually make it possible if we wait long enough. Thus, unless there is a law forbidding it, it will eventually occur.)