When Stephen Hawking was diagnosed with motor neurone disease at age 21, doctors thought he'd only survive a few more years. But the theoretical physicist defied the odds: Hawking, who passed away yesterday, lived to be 76. Here are 12 quotes from the director of research and founder of the Centre for Theoretical Cosmology at Cambridge and author of A Brief History of Time.

1. ON HIS SCHOOLING

"At school, I was never more than about halfway up the class. It was a very bright class. My classwork was very untidy, and my handwriting was the despair of my teachers. But my classmates gave me the nickname Einstein, so presumably they saw signs of something better. When I was twelve, one of my friends bet another friend a bag of sweets that I would never come to anything. I don't know if this bet was ever settled, and if so, which way it was decided."

— From the lecture "My Brief History," 2010

2. ON ALIEN LIFE

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

— From Into the Universe with Stephen Hawking, 2010

3. ON THE EUREKA MOMENT SCIENTIFIC DISCOVERY

“I wouldn’t compare it to sex, but it lasts longer.”

— From a lecture at Arizona State University, April 2011

4. ON DISABILITIES

"If you are disabled, it is probably not your fault, but it is no good blaming the world or expecting it to take pity on you. One has to have a positive attitude and must make the best of the situation that one finds oneself in; if one is physically disabled, one cannot afford to be psychologically disabled as well. In my opinion, one should concentrate on activities in which one's physical disability will not present a serious handicap. I am afraid that Olympic Games for the disabled do not appeal to me, but it is easy for me to say that because I never liked athletics anyway. On the other hand, science is a very good area for disabled people because it goes on mainly in the mind. Of course, most kinds of experimental work are probably ruled out for most such people, but theoretical work is almost ideal. My disabilities have not been a significant handicap in my field, which is theoretical physics. Indeed, they have helped me in a way by shielding me from lecturing and administrative work that I would otherwise have been involved in. I have managed, however, only because of the large amount of help I have received from my wife, children, colleagues and students. I find that people in general are very ready to help, but you should encourage them to feel that their efforts to aid you are worthwhile by doing as well as you possibly can."

— From "Handicapped People and Science," Science Digest 92, No. 9, September 1984

5. ON TIME TRAVEL

"I would go back to 1967, and the birth of my first child, Robert. My three children have brought me great joy."

— To The New York Times, May 2011

6. ON FATE VERSUS FREE WILL

"I have noticed that even people who claim everything is predetermined and that we can do nothing to change it, look before they cross the road."

— From Black Holes and Baby Universes and Other Essays

7. ON SCIENCE VERSUS RELIGION

"There is a fundamental difference between religion, which is based on authority, [and] science, which is based on observation and reason. Science will win, because it works."

— To Diane Sawyer/ABC News, June 2010

8. ON IMPERFECTION

"Next time someone complains that you have made a mistake, tell him that may be a good thing. Because without imperfection, neither you nor I would exist."

— From Into the Universe with Stephen Hawking, 2010

9. On HIS I.Q.

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

— To The New York Times, December 2004

10. ON WOMEN

“They are a complete mystery.”

— To New Scientist, January 2012

11. ON THE ADVICE HE GAVE HIS CHILDREN

"One, remember to look up at the stars and not down at your feet. Two, never give up work. Work gives you meaning and purpose and life is empty without it. Three, if you are lucky enough to find love, remember it is there and don't throw it away."

— To Diane Sawyer/ABC News, June 2010

12. On optimism

"Most of the threats we face come from the progress we’ve made in science and technology. We are not going to stop making progress, or reverse it, so we must recognize the dangers and control them. I’m an optimist, and I believe we can."

— To the Radio Times, January 2016