Science is definitely part of America's infrastructure, the engine of prosperity. And yet science is given almost no visibility in the media.

You can mass-produce hardware; you cannot mass-produce software - you cannot mass-produce the human mind.

I vowed to myself that when I grew up and became a theoretical physicist, in addition to doing research, I would write books that I would have liked to have read as a child. So whenever I write, I imagine myself, as a youth, reading my books, being thrilled by the incredible advances being made in physics and science.

Think of all the nonsense you had to learn in psychology courses. None of which was testable. None of which was measurable. We had behaviorism, Freudian psychology, all of these theories that you learn in psychology. Totally untestable. Now, we can test it, because physics allows us to calculate energy flows in the brain.

Eternal life does not violate the laws of physics. After all, we only die because of one word: "error." The longer we live, the more errors there are that are made by our bodies when they read our genes. That means cells get sluggish. The body doesn't function as well as it could, which is why the skin ages. Then organs eventually fail, so that's why we die.

There's the caveman in us. The caveman in you says, "I want direct contact. I don't want a picture." The caveman in our body says once in a while, we have to go outside. We have to meet real people, talk to real people, and do real things.

One in 200 stars has habitable Earth-like planets surrounding it - in the galaxy, half a billion stars have Earth-like planets going around them - that's huge, half a billion. So when we look at the night sky, it makes sense that someone is looking back at us.