“The past, like the future, is indefinite and exists only as a spectrum of possibilities.”

“‘The Simpsons’ appearances were great fun. But I don’t take them too seriously. I think ‘The Simpsons’ have treated my disability responsibly.”

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

“All my adult life people have been helping me.”

“Although almost every theoretical physicist agrees with my prediction that a black hole should glow like a hot body, it would be very difficult to verify experimentally because the temperature of a macroscopic black hole is so low.”

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

“As scientists, we step on the shoulders of science, building on the work that has come before us – aiming to inspire a new generation of young scientists to continue once we are gone.”

“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 we understand science, it is natural to believe that God created the universe.”

“Computers double their performance every month.”

“Earth might one day soon resemble the planet Venus.”

“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?”

“Exploration by real people inspires us.”

“God is the name people give to the reason we are here. But I think that reason is the laws of physics rather than someone with whom one can have a personal relationship. An impersonal God.”

“God not only plays dice, He also sometimes throws the dice where they cannot be seen.”

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

“I am just a child who has never grown up. I still keep asking these ‘how’ and ‘why’ questions. Occasionally, I find an answer.”

“I believe everyone should have a broad picture of how the universe operates and our place in it. It is a basic human desire. And it also puts our worries in perspective.”

“I believe the universe is governed by the laws of science. The laws may have been decreed by God, but God does not intervene to break the laws.”

“I believe things cannot make themselves impossible.”

“I can’t say that my disability has helped my work, but it has allowed me to concentrate on research without having to lecture or sit on boring committees.”

“I don’t have much positive to say about motor neuron disease, but it taught me not to pity myself because others were worse off, and to get on with what I still could do. I’m happier now than before I developed the condition.”

“I don’t think the human race will survive the next thousand years, unless we spread into space.”

“I enjoy all forms of music – pop, classical and opera.”

“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.”

“I had a bet with Gordon Kane of Michigan University that the Higgs particle wouldn’t be found.”

“I had not expected ‘A Brief History of Time’ to be a best seller. It was my first popular book and aroused a great deal of interest. Initially, many people found it difficult to understand. I therefore decided to try to write a new version that would be easier to follow.”

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

“I have so much that I want to do. I hate wasting time.”

“I have wanted to fly into space for many years, but never imagined it would really be feasible.”

“I hope I have helped to raise the profile of science and to show that physics is not a mystery but can be understood by ordinary people.”

“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 think the brain is essentially a computer and consciousness is like a computer program. It will cease to run when the computer is turned off. Theoretically, it could be re-created on a neural network, but that would be very difficult, as it would require all one’s memories.”

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

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

“I want my books sold on airport bookstalls.”

“I was born on January 8, 1942, exactly three hundred years after the death of Galileo. I estimate, however, that about two hundred thousand other babies were also born that day. I don’t know whether any of them was later interested in astronomy.”

“I was not a good student. I did not spend much time at college; I was too busy enjoying myself.”

“I wouldn’t be here today if it were not for the NHS. I have received a large amount of high-quality treatment without which I would not have survived.”

“I’m never any good in the morning. It is only after four in the afternoon that I get going.”

“If I had a time machine, I’d visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens.”

“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans.”

“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.”

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

“Imaginary time is a new dimension, at right angles to ordinary, real time.”

“In less than a hundred years, we have found a new way to think of ourselves. From sitting at the center of the universe, we now find ourselves orbiting an average-sized sun, which is just one of millions of stars in our own Milky Way galaxy.”

“In my school, the brightest boys did math and physics, the less bright did physics and chemistry, and the least bright did biology. I wanted to do math and physics, but my father made me do chemistry because he thought there would be no jobs for mathematicians.”

“Intelligence is the ability to adapt to change.”

“It is generally recognised that women are better than men at languages, personal relations and multi-tasking, but less good at map-reading and spatial awareness. It is therefore not unreasonable to suppose that women might be less good at mathematics and physics.”

“It is not clear that intelligence has any long-term survival value.”

“It was Einstein’s dream to discover the grand design of the universe, a single theory that explains everything. However, physicists in Einstein’s day hadn’t made enough progress in understanding the forces of nature for that to be a realistic goal.”

“It’s time to commit to finding the answer, to search for life beyond Earth. Mankind has a deep need to explore, to learn, to know. We also happen to be sociable creatures. It is important for us to know if we are alone in the dark.”

“Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global nuclear war, a genetically engineered virus or other dangers we have not yet thought of.”

“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.”

“Many badly needed goals, like fusion and cancer cure, would be achieved much sooner if we invested more.”

“Maybe I don’t have the most common kind of motor neuron disease, which usually kills in two or three years.”

“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.”

“My discovery that black holes emit radiation raised serious problems of consistency with the rest of physics. I have now resolved these problems, but the answer turned out to be not what I expected.”

“My first popular book, ‘A Brief History of Time,’ aroused a great deal of interest, but many found it difficult to understand.”

“My ideal role would be a baddie in a James Bond film. I think the wheelchair and the computer voice would fit the part.”

“My wife and I love each other very much.”

“No one can resist the idea of a crippled genius.”

“Not only does God play dice, but… he sometimes throws them where they cannot be seen.”

“Observations indicate that the universe is expanding at an ever increasing rate. It will expand forever, getting emptier and darker.”

“One can’t predict the weather more than a few days in advance.”

“Only black holes of very low mass would emit a significant amount of radiation.”

“Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill.”

“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 not only a disciple of reason but, also, one of romance and passion.”

“Scientists have become the bearers of the torch of discovery in our quest for knowledge.”

“Some forms of motor neuron disease are genetically linked, but I have no indication that my kind is. No other member of my family has had it. But I would be in favour of abortion if there was a high risk.”

“Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.”

“Sometimes I wonder if I’m as famous for my wheelchair and disabilities as I am for my discoveries.”

“Success in creating AI would be the biggest event in human history. Unfortunately, it might also be the last, unless we learn how to avoid the risks.”

“The Planck satellite may detect the imprint of the gravitational waves predicted by inflation. This would be quantum gravity written across the sky.”

“The doctor who diagnosed me with ALS, or motor neuron disease, told me that it would kill me in two or three years.”

“The human race may be the only intelligent beings in the galaxy.”

“The missing link in cosmology is the nature of dark matter and dark energy.”

“The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to minus 271.3*C – not much good for defrosting the pizza, let alone cooking it.”

“The universe is not indifferent to our existence – it depends on it.”

“The voice I use is a very old hardware speech synthesizer made in 1986. I keep it because I have not heard a voice I like better and because I have identified with it.”

“Theology is unnecessary.”

“There are grounds for cautious optimism that we may now be near the end ofthe search for the ultimate laws of nature.”

“There are plenty of dead scientists I admire, but I can’t think of any living ones. This is probably because it is only in retrospect that one can see who made the important contributions.”

“There could be shadow galaxies, shadow stars, and even shadow people.”

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

“There is no unique picture of reality.”

“There’s no way to remove the observer – us – from our perceptions of the world.”

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

“Time travel was once considered scientific heresy, and I used to avoid talking about it for fear of being labelled a ‘crank.’”

“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.”

“Using e-mail, I can communicate with scientists all over the world.”

“We are all different. There is no such thing as a standard or run-of-the-mill human being, but we share the same human spirit.”

“We are in danger of destroying ourselves by our greed and stupidity. We cannot remain looking inwards at ourselves on a small and increasingly polluted and overcrowded planet.”

“We are the product of quantum fluctuations in the very early universe.”

“We lived in a tall, narrow Victorian house, which my parents had bought very cheaply during the war, when everyone thought London was going to be bombed flat. In fact, a V-2 rocket landed a few houses away from ours. I was away with my mother and sister at the time, but my father was in the house.”

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

“We think that life develops spontaneously on Earth, so it must be possible for life to develop on suitable planets elsewhere in the universe. But we don’t know the probability that a planet develops life.”

“What I’d really like to control is not machines, but people.”

“When one’s expectations are reduced to zero, one really appreciates everything one does have.”

“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.”

“With genetic engineering, we will be able to increase the complexity of our DNA, and improve the human race. But it will be a slow process, because one will have to wait about 18 years to see the effect of changes to the genetic code.”

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