In physics, one of the most exciting areas is in nanotech. With computers exhausting the power of silicon, Silicon Valley could become a Rust Belt, unless we can find replacements, such as quantum computers and molecular computers. To be a leader in any field, one has to have a great imagination. Sure, we have to know the basics and fundamentals. But beyond that, we have to let our imagination soar.

After that cancellation [of the Superconducting Super Collider in Texas, after $2 billion had been spent on it], we physicists learned that we have to sing for our supper. ... The Cold War is over. You can't simply say "Russia!" to Congress, and they whip out their checkbook and say, "How much?" We have to tell the people why this atom-smasher is going to benefit their lives.

Science is about principles. It's about concepts. It's not about memorizing the parts of a flower. It helps to know some of these things, but if that's all you do that's not science, science is about principles and concepts.

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.

There are dangers, but only dangers if people don't understand where technology is taking us.

Already from your own cells scientists can grow skin, cartilage, noses, blood vessels, bladders and windpipes. In the future, scientists will grow more complex organs, like livers and kidneys. The phrase 'organ failure' will disappear.

Chances are, the aliens will not want to land on our backyard, or even the White House lawn, with their flying saucers. They may have tiny, robotic self-replicating probes which can reach near light speed and can proliferate around the galaxy. So instead of the Enterprise and huge star ships, the aliens might actually send tiny probes to explore the universe. One might land on our lawn and we won't even know.