Stephen Hawking

"A zero-gravity flight is a first step toward space travel."

"As Irving Good realised in 1965, machines with superhuman intelligence could repeatedly improve their design even further, triggering what Vernor Vinge called a 'singularity.'"

"Before 1915, space and time were thought of as a fixed arena in which events took place, but which was not affected by what happened in it. Space and time are now dynamic quantities... space and time not only affect but are also affected by everything that happens in the universe."

"Before I lost my voice, it was slurred, so only those close to me could understand, but with the computer voice, I found I could give popular lectures. I enjoy communicating science. It is important that the public understands basic science, if they are not to leave vital decisions to others."

"Before we understand science, it is natural to believe that God created the universe."

"Computers double their performance every month."

"Even if it turns out that time travel is impossible, it is important that we understand why it is impossible."

"God may exist, but science can explain the universe without the need for a creator."

"However difficult life may seem, there is always something you can do and succeed at."

"I believe there are no questions that science can't answer about a physical universe."

"I don't have much positive to say about motor neurone disease. But it taught me not to pity myself because others were worse off, and to get on with what I could still do."

"I don't think the human race will survive the next thousand years, unless we spread into space."

"I have found far greater enthusiasm for science in America than here in Britain. There is more enthusiasm for everything in America."

"I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark."

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."

"I used to think information was destroyed in black hole. This was my biggest blunder, or at least my biggest blunder in science."

"I would like nuclear fusion to become a practical power source. It would provide an inexhaustible supply of energy, without pollution or global warming."

"I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first."

"If you believe in science, like I do, you believe that there are certain laws that are always obeyed."

"In the past, there was active discrimination against women in science. That has now gone, and although there are residual effects, these are not enough to account for the small numbers of women, particularly in mathematics and physics."

"Look up at the stars and not down at your feet. Try to make sense of what you see, and wonder about what makes the universe exist. Be curious."

"People won't have time for you if you are always angry or complaining."

"Philosophers have not kept up with modern developments in science. Particularly physics."

"Science is beautiful when it makes simple explanations of phenomena or connections between different observations. Examples include the double helix in biology and the fundamental equations of physics."

"Science is increasingly answering questions that used to be the province of religion."

"Science is not only a disciple of reason but, also, one of romance and passion."

"The universe is governed by science. But science tells us that we can't solve the equations, directly in the abstract."

"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?"

"There is a real danger that computers will develop intelligence and take over. We urgently need to develop direct connections to the brain so that computers can add to human intelligence rather than be in opposition."

"There is no heaven or afterlife for broken-down computers; that is a fairy story for people afraid of the dark."

"Throughout history, people have studied pure science from a desire to understand the universe rather than practical applications for commercial gain. But their discoveries later turned out to have great practical benefits."

"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."

"To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like."

"We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special."

"While physics and mathematics may tell us how the universe began, they are not much use in predicting human behavior because there are far too many equations to solve. I'm no better than anyone else at understanding what makes people tick, particularly women."

"Women. They are a complete mystery."

"Work gives you meaning and purpose and life is empty without it."