Stephen Hawking
Stephen William Hawking, the Cambridge University physicist and best-selling author who roamed the cosmos from a wheelchair + , pondering the nature of gravity and the origin of the universe and becoming an emblem of human determination and curiosity, died early Wednesday at his home in Cambridge, England. He was 76.

"Not since Albert Einstein has a scientist so captured the public imagination and endeared himself to tens of millions of people around the world," Michio Kaku, a professor of theoretical physics at the City University of New York, said in an interview. Coincidentally, Einstein was born on March 14 (in 1879), the date on which Hawking died. Equally remarkably, Hawking was born on January 8, 1942 - exactly 300 years after the death of another great scientist, Galileo Galilei.

Hawking's book "A Brief History of Time: From the Big Bang to Black Holes," published in 1988, sold more than 10 million copies and inspired a documentary film by Errol Morris. The 2014 film about his life, "The Theory of Everything," was nominated for several Academy Awards and Eddie Redmayne, who played Hawking, won the Oscar for best actor.

Scientifically, Hawking will be best remembered + for a discovery so strange that it might be expressed in the form of a Zen koan: When is a black hole not black? When it explodes.

What is equally amazing is that he had a career at all. As a graduate student in 1963, he learned he had amyotrophic lateral sclerosis, a neuromuscular wasting disease also known as Lou Gehrig's disease. He was given only a few years to live.

The disease reduced his bodily control to the flexing of a finger and voluntary eye movements but left his mental faculties untouched.

He went on to become his generation's leader in exploring gravity and the properties of black holes, the bottomless gravitational pits so deep and dense that not even light can escape them.

That work led to a turning point in modern physics, playing itself out in the closing months of 1973 on the walls of his brain when Hawking set out to apply quantum theory, the weird laws that govern subatomic reality, to black holes. In a long and daunting calculation, Hawking discovered to his befuddlement that black holes - those mythological avatars of cosmic doom - were not really black at all. In fact, he found, they would eventually fizzle, leaking radiation and particles, and finally explode and disappear over the eons.

Nobody, including Hawking, believed it at first - that particles could be coming out of a black hole. "I wasn't looking for them at all," he recalled in an interview in 1978. "I merely tripped over them. I was rather annoyed."

That calculation, in a thesis published in 1974 in the journal Nature under the title "Black Hole Explosions?," is hailed by scientists as the first great landmark in the struggle to find a single theory of nature - to connect gravity and quantum mechanics, those warring descriptions of the large and the small, to explain a universe that seems stranger than anybody had thought.

The discovery of Hawking radiation, as it is known, turned black holes upside down. It transformed them from destroyers to creators - or at least to recyclers - and wrenched the dream of a final theory in a strange, new direction.

Dennis W Sciama, a cosmologist and Hawking's thesis adviser at Cambridge, called Hawking's thesis in Nature "the most beautiful paper in the history of physics." In 2002, Hawking said he wanted the formula for Hawking radiation to be engraved on his tombstone.

He was a man who pushed the limits - in his intellectual life, to be sure, but also in his professional and personal lives. He traveled the globe to scientific meetings, visiting every continent, including Antarctica; wrote best-selling books about his work; married twice; fathered three children; and was not above appearing on "The Simpsons," "Star Trek: The Next Generation" or "The Big Bang Theory."

He celebrated his 60th birthday by going up in a hot-air balloon. The same week, he also crashed his electric-powered wheelchair while speeding around a corner in Cambridge, breaking his leg.

In April 2007, a few months after his 65th birthday, he took part in a zero-gravity flight aboard a specially equipped Boeing 727, a padded aircraft that flies a roller-coaster trajectory to produce fleeting periods of weightlessness. It was a prelude to a hoped-for trip to space with Richard Branson's Virgin Galactic company aboard SpaceShipTwo.

Asked why he took such risks, Hawking said, "I want to show that people need not be limited by physical handicaps as long as they are not disabled in spirit." His own spirit left many in awe.

The oldest of four children, Stephen was a mediocre student at St Albans School in London, though his innate brilliance was recognised by some classmates and teachers.

Later, at University College, Oxford, he found his studies in mathematics and physics so easy that he rarely consulted a book or took notes. "Nothing seemed worth making an effort for," he said. The only subject he found exciting was cosmology because, he said, it dealt with "the big question: Where did the universe come from?"

Upon graduation, he moved to Cambridge. Before he could begin his research, however, he was stricken by what his research adviser, Sciama, came to call "that terrible thing."

The young Hawking had been experiencing occasional weakness and falling spells for several years. Shortly after his 21st birthday, in 1963, doctors told him that he had ALS. They gave him less than three years to live.

His first response was severe depression. He dreamed he was going to be executed, he said. Then, against all odds, the disease appeared to stabilise. Though he was slowly losing control of his muscles, he was still able to walk short distances and perform simple tasks, though laboriously, like dressing and undressing. He felt a new sense of purpose.

"When you are faced with the possibility of an early death," he recalled, "it makes you realize that life is worth living and that there are a lot of things you want to do."

In 1965, he married Jane Wilde, a student of linguistics. Now, by his own account, he not only had "something to live for"; he also had to find a job, which gave him an incentive to work seriously toward his doctorate.

His illness, however, had robbed him of the ability to write down the long chains of equations that are the tools of the cosmologist's trade. Characteristically, he turned this handicap into a strength, gathering his energies for daring leaps of thought, which, in his later years, he often left for others to codify in proper mathematical language.

Until 1974, Hawking was still able to feed himself and to get in and out of bed. At Jane's insistence, he would drag himself, hand over hand, up the stairs to the bedroom in his Cambridge home every night, in an effort to preserve his remaining muscle tone. After 1980, care was supplemented by nurses.

Hawking retained some control over his speech up to 1985. But on a trip to Switzerland, he came down with pneumonia. The doctors asked Jane if she wanted his life support turned off, but she said no. To save his life, doctors inserted a breathing tube. He survived, but his voice was permanently silenced.

It appeared for a time that he would be able to communicate only by pointing at individual letters on an alphabet board. But when a computer expert, Walter Woltosz, heard about Hawking's condition, he offered him a program he had written called Equalizer. By clicking a switch with his still-functioning fingers, Hawking was able to browse through menus that contained all the letters and more than 2,500 words.

Word by word - and when necessary, letter by letter - he could build up sentences on the computer screen and send them to a speech synthesizer that vocalized for him. The entire apparatus was fitted to his motorized wheelchair.

Even when too weak to move a finger, he communicated through the computer by way of an infrared beam, which he activated by twitching his right cheek or blinking his eye. The system was expanded to allow him to open and close the doors in his office and to use the telephone and internet without aid.

Although he averaged fewer than 15 words per minute, Hawking found he could speak through the computer better than he had before losing his voice. His only complaint, he confided, was that the speech synthesizer, manufactured in California, had given him an American accent.

His decision to write "A Brief History of Time" was prompted, he said, by a desire to share his excitement about "the discoveries that have been made about the universe" with "the public that paid for the research." He wanted to make the ideas so accessible that the book would be sold in airports.

He also hoped to earn enough money to pay for his children's education. He did. The book's extraordinary success made him wealthy, a hero to disabled people everywhere and even more famous.

Asked by New Scientist magazine what he thought about most, Dr. Hawking answered: "Women. They are a complete mystery."

In 1990, Hawking and his wife separated after 25 years of marriage; Jane Hawking wrote about their years together in two books, "Music to Move the Stars: A Life With Stephen Hawking" and "Traveling to Infinity: My Life With Stephen." The latter became the basis of the 2014 movie "The Theory of Everything."

In 1995, he married Elaine Mason, a nurse who had cared for him since his bout of pneumonia. She had been married to David Mason, the engineer who had attached Hawking's speech synthesizer to his wheelchair.

In 2004, British newspapers reported that the Cambridge police were investigating allegations that Elaine had abused Hawking, but no charges were filed, and Hawking denied the accusations. They agreed to divorce in 2006.

Among his many honors, Hawking was named a commander of the British Empire in 1982. In the summer of 2012, he had a star role in the opening of the Paralympics Games in London. The only thing lacking was the Nobel Prize, and his explanation for this was characteristically pithy: "The Nobel is given only for theoretical work that has been confirmed by observation. It is very, very difficult to observe the things I have worked on."

In "A Brief History of Time," he had referred to the "mind of God," but in "The Grand Design," a 2011 book he wrote with Leonard Mlodinow, he was more bleak about religion. "It is not necessary to invoke God to light the blue touch paper," he wrote, referring to the British term for a firecracker fuse, "and set the universe going."

He went further in an interview that year in The Guardian, saying: "I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken-down computers; that is a fairy story for people afraid of the dark."

Having spent the best part of his life grappling with black holes and cosmic doom, Dr. Hawking had no fear of the dark.

"They're named black holes because they are related to human fears of being destroyed or gobbled up," he once told an interviewer. "I don't have fears of being thrown into them. I understand them. I feel in a sense that I am their master."

(Matthew Haag, Matt Stevens and Gerald Jonas contributed reporting)