When you look at the calculation, it's amazing that every time you try to prove or disprove time travel, you've pushed Einstein's theory to the very limits where quantum effects must dominate. That's telling us that you really need a theory of everything to resolve this question. And the only candidate is string theory.

I think that by creating a world of plenty, by creating institutions and organizations that promote knowledge and promote understanding, I think I could be part of being in a better world.

The Internet frees people to realize they don't have to live like slaves.

No one knows who wrote the laws of physics or where they come from. Science is based on testable, reproducible evidence, and so far we cannot test the universe before the Big Bang.

The river of time may fork into rivers, in which case you have a parallel reality and so then you can become a time traveler and not have to worry about causing a time paradox.

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.

Some people are a little bit afraid about the future because they see all these gadgets and gizmos coming down the pike and they think they're too old to learn all this new stuff. But eventually they begin to realize, 'Hey, some of this stuff is useful.'

In the 1950s, we had all these B-grade science-fiction movies. The point was to scare the public and get them to buy popcorn. No attempt was made to create movies that were somewhat inherent to the truth.

Democracies are slow to anger and hesitant to go to war: Voters don't want to sacrifice their children for the glory of a selfish king.

The quest for a quantum gravity is one of the greatest unsolved problems in all of science.

A lot of the things you see in science fiction revolve around black holes because black holes are strong enough to rip the fabric of space and time.

I think the 'Terminator' idea is a reasonable one - that is that one day the Internet becomes self-aware and simply says that humans are in the way. After all, if you meet an ant hill and you're making a 10-lane super highway, you just pave over the ants. It's not that you don't like the ants, it's not that you hate ants; they are just in the way.

Science fiction without the science just becomes, you know, sword and sorcery, basically stories about heroism and not much more.

Growing new organs of the body as they wear out, extending the human lifespan? What's not to like?

In the future, I can imagine that we will genetically modify ourselves using the genes that have doubled our life span since we were chimpanzees.

You see, I'm also a futurist. I dream about the world 50, 100, maybe even 1,000 years in the future. But I also realize I'm probably not going to see it. However, I wouldn't mind having at least a copy of myself see the future, maybe 50, 100, 1,000 years into the future. It would be a fantastic ride.

Aging is basically the build-up of error: error at the genetic level, error at the cellular level. Cells normally repair themselves; that's why you heal when you get a cut. But even the mechanism of repair eventually falls apart.

Consciousness-one level is understanding where we are in space. Consciousness two is where we understand our position in society: who's top dog, who's underdog and who's in the middle. And type-three consciousness is simulating the future. And type-three consciousness, only humans have this ability to see far into the future.

To me, it is clear that we exist in a plan which is governed by rules that were created, shaped by a universal intelligence and not by chance.

Anything that promotes a kernel of science, even though it's exaggerated and hyped by Hollywood, I think is a step forward. We in the ivory tower ultimately have to realize that in some sense we have to sing for our supper.

You have to have a cultural ethic that allows for making mistakes. It cannot be that just because you make mistakes, you're out. You have to make mistakes in order to innovate.

I'm a physicist, and we have something called Moore's Law, which says computer power doubles every 18 months. So every Christmas, we more or less assume that our toys and appliances are more or less twice as powerful as the previous Christmas.

I think Newton would be the greatest scientist who ever lived.

Now, we used to think the brain was like a computer. But now, we realize that's not true. There's no programming of the brain. There's no Windows. And we think the brain is more like a large corporation. Because think of the unconscious mind. In a corporation, you have subdivisions which operate independently of the main office.