Stephen Hawking, the British physicist and black-hole theorist who brought science to a mass audience with the best-selling book A Brief History of Time, has died. He was 76.

Hawking died peacefully at his home in Cambridge in England in the early hours of Wednesday morning, a spokesman for his family said in an emailed statement.

"We are deeply saddened that our beloved father passed away today," his children Lucy, Robert and Tim said in the statement. "He was a great scientist and an extraordinary man whose work and legacy will live on for many years. His courage and persistence with his brilliance and humor inspired people across the world. He once said, 'It would not be much of a universe if it wasn't home to the people you love.' We will miss him forever."

Hawking suffered from amyotrophic lateral sclerosis, also known as Lou Gehrig's disease, and was confined to an electric wheelchair for much of his adult life. Diagnosed at age 21, he was one of the world's longest survivors of ALS.

A Cambridge University professor, Hawking redefined cosmology by proposing that black holes emit radiation and later evaporate. He also showed that the universe had a beginning by describing how Albert Einstein's theory of general relativity eventually breaks down when time and space are traced back to the Big Bang about 13.7 billion years ago.

"Stephen's remarkable combination of boldness, vision, insight and courage have enabled him to produce ideas that have transformed our understanding of space and time, black holes and the origin of the universe," James Hartle, professor of physics at the University of California, Santa Barbara, said in 2002.

Best-seller

A Brief History of Time, first published in 1988, earned its author worldwide acclaim, selling at least 10 million copies in 40 languages and staying on the best-seller list of the U.K.'s Sunday Times newspaper for a record 237 weeks.

Often referred to as "one of the most unread books of all time" for the hard-to-grasp concepts, it included only one equation: E mc2 or the equivalence of mass and energy, deduced by Einstein from his theory of special relativity. The book outlined the basics of cosmology for the general reader.

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Hawking's fame increased as his health worsened. After his degenerative muscle disorder was diagnosed, he defied medical opinion by living five decades longer than expected. He communicated his ideas through an American-accented speech synthesizer after a life-saving tracheotomy in 1985 took away his ability to speak. To the layman, the robot-like voice only seemed to give his words added authority.

"To my colleagues, I'm just another physicist, but to the wider public, I became possibly the best-known scientist in the world," Hawking wrote in his 2013 memoir My Brief History. "This is partly because scientists, apart from Einstein, are not widely known rock stars, and partly because I fit the stereotype of a disabled genius."

Black holes

Hawking applied quantum theory -- governing the subatomic world -- to black holes, which he claimed discharge radiation that causes them to disappear. This process helps explain the notion that black holes have existed at a micro level since the Big Bang, and the smaller they are, the faster they evaporate.

Black holes are formed when a massive star collapses under the weight of its own gravity. Detected by the movement of surrounding matter, they devour everything in their path and may play a role in the birth of galaxies. Physicists say these invisible cosmic vacuums might allow travel through time and space via "wormholes," a favorite of science-fiction writers.

With mathematician Roger Penrose, Hawking used Einstein's theory of relativity to trace the origins of time and space to a single point of zero size and infinite density. Their work gave mathematical expression to the Big Bang theory, proposed by Belgian priest Georges Lemaitre in 1927 and supported two years later by Edwin Hubble's discovery that the universe is expanding.

With Hartle, Hawking later tried to marry relativity with quantum theory by proposing the no-boundary principle, which held that space-time is finite and the laws of physics determined how the universe began in a self-contained system, without the need for a creator or prior cause.

'Profound impact'

The Nobel Prize in Physics proved elusive for Hawking, whose theories required observational data to win the praise of the awarding committee in Stockholm. The Nobel Foundation excludes posthumous nominees.

"By any reasonable standard, Stephen Hawking is a great scientist. Even if time shows some of his more radical proposals to be incorrect, Hawking will have had a profound impact on the history of science," Henry F. Schaefer III, a chemistry professor at the University of Georgia, said in a 2001 lecture.

Stephen William Hawking was born in Oxford, England, on Jan. 8, 1942, exactly 300 years after the death of Italian physicist Galileo Galilei. Hawking's father, Frank, was a doctor of tropical medicine. His mother, Isobel, was a tax inspector and a secretary. He had two younger sisters and a brother.

At age 8, Hawking moved with his family to St. Albans, where he went to school. He then graduated with first-class honors in natural science at Oxford's University College. While he was a doctoral candidate at Cambridge, Hawking was diagnosed with ALS, also known as motor neuron disease. He was told he had only a few years to live.

Universe's origin

As the illness progressed slower than expected and he found inspiration in his girlfriend, Jane Wilde, Hawking began to work at his studies for the first time. He completed his doctorate on the origins of the universe, became a research fellow at Caius College and married Wilde in 1965.

In 1970, Hawking realized the mathematical approaches he developed with Penrose could be applied to black holes, a term coined by physicist John Wheeler. Hawking worked for the next four years on black holes, discovering they weren't totally black, but leaked radiation, now known as "Hawking radiation."

For 30 years, Hawking was Cambridge's Lucasian professor of mathematics, a chair once held by Isaac Newton. U.S. President Barack Obama awarded the Presidential Medal of Freedom to Hawking in 2009, the year of his retirement.

His other popular books included The Universe in a Nutshell (2001), On the Shoulders of Giants (2002), A Briefer History of Time (2005) and The Grand Design (2010).

In 2015, Eddie Redmayne won an Oscar for his portrayal of Hawking in "The Theory of Everything," a film about the scientist's life.

Hawking separated from his wife in 1991 and married his nurse, Elaine Mason, four years later. They divorced in 2007.

By 2017 Hawking was spending more time pondering humanity's future and concluding that we should plan to colonize other planets. "We are running out of space, and the only place we can go to are other worlds," he told a gathering of scientists. "'It is time to explore other solar systems. Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth."

By David Henry, Bloomberg

Posted by Claire Cardona, Breaking News producer