On Wednesday, Stephen Hawking, likely the most famous physicist in the world, died at his home in Cambridge, England at the age of 76.

Hawking became famous with the publication of his book “A Brief History of Time” in 1988; it sold 10 million copies. But Hawking was well known in the scientific community before that, having joined physicist Roger Penrose to merge Einstein's theory of relativity with quantum theory to suggest that space and time would begin with the Big Bang and end in black holes. In 1974, he also proposed his famous theory that black holes leak energy and fade to nothing.

Hawking attended University College, Oxford starting in October 1959, where he coxed a rowing crew while studying physics. He later did his graduate work at Trinity Hall, Cambridge, starting in 1962. But at the age of 22, he was diagnosed with motor neurone disease and was given two years to live. He started having trouble walking and speaking; he fell into a depression. But his teacher, Dennis William Scarma, one of the founders of modern cosmology, encouraged him to return to his work, which he did.

In 1970, he and Roger Penrose published a proof arguing that the universe must have begun as a singularity. Hawking proposed the second law of black hole dynamics: that the event horizon of a black hole can never diminish. But Hawking’s work was superseded by Jacob Bekenstein, who went further and applied thermodynamic concepts literally, a fact that irritated Hawking.

In 1973, Hawking found evidence that contradicted his second law, supporting Bekenstein’s assumptions about their entropy. But that prompted Hawking’s theory that black holes emit radiation, known today as Hawking radiation, later accepted as a scientific breakthrough.

Hawking liked making bets with other physicists; he lost a bet with physicist Kip Thorne over whether the dark star Cygnus X-1 was a black hole. In 2004, he acknowledged losing a bet with Thorne and John Preskill; Hawking had argued that Penrose's proposal that there could be no "naked singularities" unclothed within a horizon was correct. In 2012, Hawking conceded he had lost his bet that the Higgs boson would never be found.

In 1981, Hawking proposed that information in a black hole is lost when a black hole evaporates, which led to years of debate. That same year, speaking at the Vatican, he suggested that there might be no boundary, or beginning or ending, to the universe. In 1983, he and Jim Hartle proposed that prior to the Planck epoch, the universe had no boundary in space-time; thus, before the Big Bang, time did not exist. This theory thus predicted a closed universe.

Hawking gradually lost the use of his hands, and in 2005 he started to use a communication device with movements of his cheek muscles.

Hawking posited that aliens exist but humans should avoid them, saying in 2010, "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.”

Hawking made various statements about God; he stated, "The laws may have been decreed by God, but God does not intervene to break the laws." In 2011, he asserted, "We are each free to believe what we want and it is my view that the simplest explanation is there is no God. No one created the universe and no one directs our fate." In 2014, he added, "Before we understand science, it is natural to believe that God created the universe. But now science offers a more convincing explanation."