Stephen Hawking dies aged 76: his best quotes

On humanity

"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."

Der Spiegel, 1988

On the pursuit of knowledge

"Ever since the dawn of civilisation, people have not been content to see events as unconnected and inexplicable. They have craved an understanding of the underlying order in the world. Today we still yearn to know why we are here and where we came from. 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."

A Brief History of Time, 1988

On curiosity

"Be curious, and try to make sense of what you see. We live in a universe governed by rational laws that we can discover and understand. Despite recent triumphs, there are many new and deep mysteries that remain for you to solve."

Radio Times, 2016

On the end of the universe

"All the evidence seems to indicate, that the universe has not existed forever, but that it had a beginning, about 15 billion years ago. This is probably the most remarkable discovery of modern cosmology. Yet it is now taken for granted. We are not yet certain whether the universe will have an end. When I gave a lecture in Japan, I was asked not to mention the possible re-collapse of the universe, because it might affect the stock market. However, I can re-assure anyone who is nervous about their investments that it is a bit early to sell: even if the universe does come to an end, it won't be for at least twenty billion years."

The Beginning of Time lecture, 1996

"It will take about a thousand million million million million years for the earth to run into the sun, so there’s no immediate cause for worry!"

A Brief History of Time, 1988

On God

"We shouldn't be surprised that conditions in the universe are suitable for life, but this is not evidence that the universe was designed to allow for life. We could call order by the name of God, but it would be an impersonal God. There's not much personal about the laws of physics."

Reason Magazine, 2002

"What I have done is to show that it is possible for the way the universe began to be determined by the laws of science. In that case, it would not be necessary to appeal to God to decide how the universe began. This doesn’t prove that there is no God, only that God is not necessary."

Der Spiegel, 1988

On artificial intelligence

"The development of full artificial intelligence could spell the end of the human race. We cannot quite know what will happen if a machine exceeds our own intelligence, so we can't know if we'll be infinitely helped by it, or ignored by it and sidelined, or conceivably destroyed by it."

BBC, 2014

On aliens

"Are we alone, or is there other life in the universe? We believe that life arose spontaneously on the Earth, so it must be possible for life to appear on other suitable planets, of which there seem to be a large number in the galaxy. We don't seem to have been visited by aliens. I am discounting the reports of UFOs. Why would they appear only to cranks and weirdos? If there is a government conspiracy to suppress the reports and keep for itself the scientific knowledge the aliens bring, it seems to have been a singularly ineffective policy so far.Furthermore, despite an extensive search by the SETI project, we haven't heard any alien television quiz shows. This probably indicates that there are no alien civilisations at our stage of development within a radius of a few hundred light years. Issuing an insurance policy against abduction by aliens seems a pretty safe bet."

TED Talk, 2008

On outer space – and the future of humanity

"I don’t think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars."

The Daily Telegraph, 2001

"We are entering an increasingly dangerous period of our history. 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. But our genetic code still carries the selfish and aggressive instincts that were of survival advantage in the past. It will be difficult enough to avoid disaster in the next hundred years, let alone the next thousand or million. Our only chance of long-term survival is not to remain inward-looking on planet Earth, but to spread out into space. The answers to these big questions show that we have made remarkable progress in the last hundred years. But if we want to continue beyond the next hundred years, our future is in space."

TED Talk, 2008

On climate change

"The danger is that global warming may become self-sustaining, if it has not done so already. The melting of the Arctic and Antarctic ice caps reduces the fraction of solar energy reflected back into space, and so increases the temperature further. Climate change may kill off the Amazon and other rain forests, and so eliminate once one of the main ways in which carbon dioxide is removed from the atmosphere. The rise in sea temperature may trigger the release of large quantities of carbon dioxide trapped as hydrides on the ocean floor. Both these phenomena would increase the greenhouse effect, and so global warming further. We have to reverse global warming urgently, if we still can."

ABC News, 2006

On nuclear power and self-destruction

"As scientists, we understand the dangers of nuclear weapons and their devastating effects, and we are learning how human activities and technologies are affecting climate systems in ways that may forever change life on Earth. As citizens of the world, we have a duty to alert the public to the unnecessary risks that we live with every day, and to the perils we foresee if governments and societies do not take action now to render nuclear weapons obsolete and to prevent further climate change... There’s a realisation that we are changing our climate for the worse. That would have catastrophic effects. Although the threat is not as dire as that of nuclear weapons right now, in the long term we are looking at a serious threat."

Bulletin of the Atomic Scientists, 2007

On black holes

"Black holes ain't as black as they are painted. They are not the eternal prisons they were once thought. Things can get out of a black hole, both to the outside, and possibly, to another universe. So, if you feel you are in a black hole, don't give up. There's a way out."

Into a Black Hole lecture, 2016

On disability

"When I turned 21, my expectations were reduced to zero. You probably know this already because there’s been a movie about it. It was important that I came to appreciate what I did have. Although I was unfortunate to get motor neurone disease, I’ve been very fortunate in almost everything else. I’ve been lucky to work in theoretical physics at a fascinating time, and its one of the few areas in which my disability is not a serious handicap. It’s also important not to become angry, no matter how difficult life is, because you can lose all hope if you can’t laugh at yourself and at life in general."

Radio Times, 2016

On perspective

"The human race is just a chemical scum on a moderate-sized planet, orbiting around a very average star in the outer suburb of one among a hundred billion galaxies. We are so insignificant that I can't believe the whole universe exists for our benefit."

Reality on the Rocks, 1995

On death

"I have lived with the prospect of an early death for the last 49 years. I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first... 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."

The Guardian, 2011

On IQ

"I have no idea. People who boast about their IQ are losers."

Response to being asked his IQ, The New York Times, 2004