Stephen Hawking has died at the age of 76.
The British theoretical physicist was known for his groundbreaking work with black holes and relativity, and was the author of several popular science books including A Brief History of Time.
What he said：
“Life would be tragic if it weren't funny.”
“My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
“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.”
“Eternity is a very long time, especially towards the end.”
His children said：
His children, Lucy, Robert and Tim, said: "We are deeply saddened that our beloved father passed away today.
"He was a great scientist and an extraordinary man whose work and legacy will live on for many years."
They praised his "courage and persistence" and said his "brilliance and humour" inspired people across the world.
Factfile: Stephen Hawking
Born 8 January 1942 in Oxford, England
Earned place at Oxford University to read natural science in 1959, before studying for his PhD at Cambridge
By 1963, was diagnosed with motor neurone disease and given two years to live
Outlined his theory that black holes emit "Hawking radiation" in 1974
Published his book A Brief History of Time in 1988, which has sold more than 10 million copies
His life story was the subject of the 2014 film The Theory of Everything, starring Eddie Redmayne
The scientist gained popularity outside the academic world and appeared in several TV shows including The Simpsons, Red Dwarf and The Big Bang Theory.