Many Twitter users are quoting Prof Hawking when he gave a symposium at Cambridge University last year - with Cambridge News reporting at the time that his speech left some in the audience in tears.
- World renowned physicist Stephen Hawking has died at the age of 76
- He died peacefully at his home in Cambridge early on Wednesday
- The Briton was known for his work with black holes and relativity
- He suffered from a rare form of motor neurone disease
- The illness left him in a wheelchair and he learned to communicate through a voice synthesiser
- His life story was dramatised in the award-winning film The Theory of Everything
- Eddie Redmayne, who won an Oscar for his portrayal, said: "We have lost a truly beautiful mind."
- Copyright: NASA/Science Photo Library
Hawking's genius is to have brought together several different but equally fundamental fields of physical theory: gravitation, cosmology, quantum theory, thermodynamics and information theory, BBC Earth's Philip Ball wrote back in 2016.
The legendary physicist has helped explain the behaviour of black holes and even examined the origin of the universe.
Prof Hawking brought science into the domain of everyday life - his thoughts delivered via his distinctive voice synthesizer, which became familiar to millions.
- On the reason why the universe exists: "If we find the answer to that, it would be the ultimate triumph of human reason - for then we would know the mind of God" - A Brief History Of Time, published 1988
- On an imperfect world: "Without imperfection, you or I would not exist" - On Into The Universe With Stephen Hawking, The Discovery Channel, 2010
- 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." - Interview in The Guardian, May 2011
Prof Hawking's death has garnered an outpouring of reaction on Twitter and other social media
Prof Hawking was diagnosed with a rare form of motor neurone disease at 22. But he defied doctors' predictions that he would not have long to live.
See his life in pictures.Copyright: AFP
Prof Hawking died on the birthday of fellow physicist Albert Einstein.
The scientific community has been at the forefront of those paying tribute to Stephen Hawking. US TV scientist Neil DeGrasse Tyson said Hawking's death left a huge vacuum.
US space agency Nasa also paid its respects.
Tributes from around the world are pouring in for Professor Stephen Hawking, the renowned physicist, who has died at his home in Cambridge.
Prof Hawking was famed for his work on black holes and relativity, but also for popular books including A Brief History of Time.
He also inspired millions with his battle against motor neurone disease after being given just a few years to live at the age of 22.