We live in a bewildering world.

I think we have a good chance of surviving long enough to colonize the solar system.

I think the human race doesn't have a future if it doesn't go into space.

Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?

Theology is unnecessary.

Does general relativity predict that our universe should have had a big bang, a beginning of time?

I first had the idea of writing a popular book about the universe in 1982. My intention was partly to earn money to pay my daughter's school fees.

Einstein never accepted that the universe was governed by chance; his feelings were summed up in his famous statement God does not play dice.

The thing about smart people is that they seem like crazy people to dumb people.

What did God do before he created the universe?

There is nothing bigger or older than the universe.

My goal is simple. It is complete understanding of the universe, why it as it is and why it exists as all.

If we do discover a complete theory, it should be in time understandable in broad principle by everyone. Then we shall all, philosophers, scientists, and just ordinary people be able to take part in the discussion of why we and the universe exist.

But in 1929, Edwin Hubble made the landmark observation that wherever you look, distant galaxies are moving rapidly away from us. In other words, the universe is expanding.

If the government is covering up knowledge of aliens, they are doing a better job of it than they do at anything else.

Feynman once wrote, I think I can safely say that nobody understands quantum mechanics.

It is no good getting furious if you get stuck. What I do is keep thinking about the problem but work on something else. Sometimes it is years before I see the way forward. In the case of information loss and black holes, it was 29 years.

My work and my family are very important to me.

Humanity's deepest desire for knowledge is justification enough for our continuing quest. And our goal is nothing less than a complete description of the universe we live in.

There is no picture- or theory-independent concept of reality.

Keeping an active mind has been vital to my survival, as has been maintaining a sense of humor.

A million million million million (1 with twenty-four zeros after it) miles, the size of the observable universe.

Some people make a great mystery of this idea, sometimes called the multiverse concept, but these are just different expressions of the Feynman sum over histories.

We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet.

Someone told me that each equation I included in the book would halve the sales.

Visible light has a wavelength of between only forty and eighty millionths of a centimeter. Even shorter wavelengths are known as ultraviolet, X rays, and gamma rays. Maxwell's theory predicted that radio or light waves should travel at a certain fixed speed.

Time travel used to be thought of as just science fiction, but Einstein's general theory of relativity allows for the possibility that we could warp space-time so much that you could go off in a rocket and return before you set out.

In other words, the theory of relativity put an end to the idea of absolute time!

If we find the answer to that (why the universe exists), it would be the ultimate triumph of human reason. For then we would know the mind of God.

Earth might one day soon resemble the planet Venus.

It now appears that the way the universe began can indeed be determined, using imaginary time.

The universe is not indifferent to our existence - it depends on it.

Today, we commit to this next great leap into the cosmos because we're human, and our nature is to fly.

Only light, or other waves that have no intrinsic mass, can move at the speed of light.

The usual approach of science of constructing a mathematical model cannot answer the questions of why there should be a universe for the model to describe. Why does the universe go to all the bother of existing?

A proton or neutron is made up of three quarks, one of each color. A proton contains two up quarks and one down quark; a neutron contains two down and one up.

I'm not afraid of death, but I'm in no hurry to die.

The discovery that the universe was expanding was one of the great intellectual revolutions of the twentieth century.

Nevertheless, it seems clear that there are relatively few ranges of values for the numbers that would allow the development of any form of intelligent life. Most sets of values would give rise to universes that, although they might be very beautiful, would contain no one able to wonder at that beauty.

Science predicts that many different kinds of universe will be spontaneously created out of nothing. It is a matter of chance which we are in.

I have wondered about time all my life.

Although September 11 was horrible, it didn't threaten the survival of the human race, like nuclear weapons do.

One of the basic rules of the universe is that nothing is perfect. Perfection simply doesn't exist.....Without imperfection, neither you nor I would exist.

Time can behave like another direction in space under extreme conditions.

There is no way that we can predict the weather six months ahead beyond giving the seasonal average.

The electromagnetic attraction between negatively charged electrons and positively charged protons in the nucleus causes the electrons to orbit the nucleus of the atom, just as gravitational attraction causes the earth to orbit the sun.

It also meant that whenever a body is not acted on by any force, it will keep on moving in a straight line at the same speed.

I think the discovery of supersymmetric partners for the known particles would revolutionize our understanding of the universe.

But a machine that was powerful enough to accelerate particles to the grand unification energy would have to be as big as the Solar System—and would be unlikely to be funded in the present economic climate.