The scientific community is mourning the loss of one of its brightest stars.
During his life, Stephen Hawking wrote extensively on time, space, and black holes and is one of the best known theoretical physicists of our time.
His book, 'A Brief History of Time' was an international bestseller.
Hawking died peacefully at his home in Cambridge at the age of 76.
Although his body was paralysed by ALS when Hawking was 21, doctors were stunned as he defied the odds by living with the normally fatal illness for more than 50 years.
The disease did not slow down his brilliant mind as he continued to search for the great goal of physics, a unified theory.
His life inspired the movie 'The Theory of Everything' with Eddie Redmayne winning the Academy Award for best actor for his portrayal of the scientist's early life.
Here in Canada, he was named Distinguished Visiting Research Chair at the Perimeter Institute for Theoretical Physics in Waterloo.
Lucy Hawking has said her father had an exasperating "inability to accept that there is anything he cannot do."
"I accept that there are some things I can't do," he told The Associated Press in 1997. "But they are mostly things I don't particularly want to do anyway."
Then, grinning widely, he added, "I seem to manage to do anything that I really want."
His passing has left an intellectual vacuum in his wake. But it's not empty. Think of it as a kind of vacuum energy permeating the fabric of spacetime that defies measure. Stephen Hawking, RIP 1942-2018. pic.twitter.com/nAanMySqkt
— Neil deGrasse Tyson (@neiltyson) March 14, 2018
Remembering Stephen Hawking, a renowned physicist and ambassador of science. His theories unlocked a universe of possibilities that we & the world are exploring. May you keep flying like superman in microgravity, as you said to astronauts on @Space_Station in 2014 pic.twitter.com/FeR4fd2zZ5
— NASA (@NASA) March 14, 2018