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.

We can summarize electricity, magnetism and gravity into equations one inch long, and that's the power of field theory. And so I said to myself: I will create a field theory of strings. And when I did it one day, it was incredible, realizing that on a sheet of paper I can write down an equation which summarized almost all physical knowledge.

Computer chips will cost about a penny. That's the cost of scrap paper. The Internet will be basically for free and it will be inside our contact lens. When we blink, we will go online. When we see somebody that we don't recognize, our contact lens will identify who they are, print out their biography in your contact lens and translate, if they're speaking Chinese, into English with subtitles as they speak.

When you come up with a theory, you fall in love with the beauty the simplicity and elegance of it. But then you have to get a sheet of paper and pencil and crack out all the details. Hundreds and hundreds of pages. Because you have to prove it.

God throws dice, what can I say?

No one knows when a robot will approach human intelligence, but I suspect it will be late in the 21st century. Will they be dangerous? Possibly. So I suggest we put a chip in their brain to shut them off if they have murderous thoughts.

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.