His courage and persistence with his brilliance and humour inspired people across the world. His genre-defining book, A Brief History of Time, has sold more than 10 million copies since its publication in 1988, and has been translated into more than 35 languages. He appeared on Star Trek: The Next Generation, The Simpsons and The Big Bang Theory. His early life was the subject of an Oscar-winning performance by Eddie Redmayne in the 2014 film The Theory of Everything. He was routinely consulted for on everything from time travel and to Middle Eastern politics and. He had an endearing sense of humour and a daredevil attitude — relatable human traits that, combined with his seemingly superhuman mind, made Hawking eminently marketable. But his cultural status — amplified by his disability and the media storm it invoked — often overshadowed his scientific legacy. Arriving at the University of Cambridge in 1962 to begin his PhD, he was told thathis chosen supervisor, already had a full complement of students. The most famous British astrophysicist at the time, Hoyle was a magnet for the more ambitious students. Instead, he was to work with Dennis Sciama, a physicist Hawking knew nothing about. In the same year, Hawking was diagnosed with amyotrophic lateral sclerosis, a degenerative motor neurone disease that quickly robs people of the ability to voluntarily move their muscles. hawking a brief history of time He was told he had two years to live. Two years into his PhD, he was having trouble walking and talking, but it was clear that the disease was progressing more slowly than the doctors had initially feared. Meanwhile, — with whom he later had three children, Robert, Lucy and Tim — renewed his drive to make real progress in physics. Those discussions stimulated the young Hawking to pursue his own scientific vision. Sciama, on the other hand, was happy for Hawking to investigate the beginning of time. If physicists wanted to understand the origin of the universe, Hawking had just shown them exactly where to look:. Black holes were a subject ripe for investigation in the early 1970s. Although Karl Schwarzschild had found such objects lurking in the equations of general relativity back in 1915, and were reluctant to believe they could actually exist. Albeit frightening, their action is reasonably straightforward: black holes have such strong gravitational fields that nothing, not even light, can escape their grip. Any matter that falls into one is forever lost to the outside world. This, however, is a dagger in the heart of thermodynamics. Thermodynamic threat The is one of the most well-established laws of nature. It states that the entropy, or level of disorder in a system, always increases. The second law gives form to the observation that ice cubes will melt into a puddle, but a puddle of water will never spontaneously turn into a block of ice. All matter contains entropy, so what happens when it is dropped into a black hole. Is entropy lost along with it. If so, the total entropy of the universe goes down and black holes would violate the second law of thermodynamics. Hawking thought that this was fine. He was happy to discard any concept that stood in the way to a deeper truth. And if that meant the second law, then so be it. Bekenstein and breakthrough But Hawking met his match at a 1972 physics summer school in the French ski resort of Les Houches, France. Princeton University graduate student thought that the second law of thermodynamics should apply to black holes too. Bekenstein had been studying the entropy problem and had reached a possible solution thanks to. A black hole hides its singularity with a boundary known as the event horizon. Nothing that crosses the event horizon can ever return to the outside. Bekenstein realised this was key to the entropy problem. Every time a black hole swallows matter, its entropy appears to be lost, and at the same time, its event horizon grows. So, Bekenstein suggested, what if — to preserve the second law — the area of the horizon is itself a measure of entropy. Hawking immediately disliked the idea and was angry that his own work had been used in support of hawking a brief history of time concept so flawed. During a break from the lectures, Hawking got together with colleagues Brandon Carter, who also studied under Sciama, hawking a brief history of time James Bardeen, of the University of Washington, and confronted Bekenstein. I was just out of my PhD. Back in Cambridge, Hawking set out to prove Bekenstein wrong. Rather than destroying the idea, he had confirmed it. Hawking radiation Hawking now embraced the idea that thermodynamics played a part in black holes. Anything that has entropy, he reasoned, also has a temperature — and anything that has a temperature can radiate. His original mistake, Hawking realised, was in only considering general relativity, which says that nothing — no particles, no heat — can escape the grip of a black hole. That changes when comes into play. According to quantum mechanics, fleeting pairs of particles and antiparticles are constantly appearing out of empty space, only to annihilate and disappear in the blink of an eye. When this happens in the vicinity of an event horizon, a particle-antiparticle pair can be separated — one falls behind the horizon while one escapes, leaving them forever unable to meet and annihilate. The randomness of quantum creation becomes the randomness of heat. For a large black hole — the kind astronomers can study with a telescope — the temperature of the radiation is too insignificant to measure. As Hawking himself often noted, it was for this reason that he was never awarded a Nobel Prize. Some have suggested that they should more appropriately be called Bekenstein-Hawking radiation, but Bekenstein himself rejects this. I wrote it down first, Hawking found the numerical value of the constant, so together we found the formula as it is today. I had no idea how a black hole could radiate. Hawking brought that out very clearly. So that should be called Hawking radiation. The presence of these diverse constants hinted at a theory of everything, in which all physics is unified. If black holes can radiate, they will eventually evaporate and disappear. So what happens to all the information that fell in. If so, it will violate a central tenet of quantum mechanics. With the discovery of black hole radiation, Hawking had pit the ultimate laws of physics against one another. Hawking staked his position in another entitled Breakdown of predictability in gravitational collapse, published in Physical Review D in 1976. He argued that when a black hole radiates away its mass, it does take all of its information with it — despite the fact that quantum mechanics expressly forbids information loss. Soon other physicists would pick sides, for or against this idea, in a debate that continues to this day. Indeed, many feel that information loss is the most pressing obstacle in understanding quantum gravity. Concession By the late 1990s, results emerging from had most theoretical physicists convinced that Hawking was wrong about information loss, but Hawking, known for his stubbornness, dug in his heels. And he did it with flair — dramatically showing up at a conference in Dublin and : black holes cannot lose information. It is clear that the question Hawking raised is at the core of the quest for quantum gravity. Hawking continued pushing the boundaries of theoretical physics at a seemingly impossible pace for the rest of his life. He made important inroads towards understanding how quantum mechanics applies to the universe as a whole, leading the way in the field known as quantum cosmology. His progressive disease pushed him to tackle problems in novel hawking a brief history of time, which contributed to his remarkable intuition for his subject. As he lost the ability to write out long, complicated equations, Hawking found new and inventive hawking a brief history of time to solve problems in his head, usually by reimagining them in geometric form. But, like Einstein before him, Hawking never produced anything quite as revolutionary as his early work. He never seemed to mind. In it, she investigated the way. That public image undoubtedly made his life easier than it might otherwise have been. This, in turn, let him continue doing the thing for which he should ultimately be remembered: his science. He is an inspirational figure, and history will certainly remember him that way. When pairs of particles and antiparticles spawn near a black hole's event horizon, each pair shares a connection called entanglement. But what happens to this link and the information it holds when one of the pair falls in, leaving its twin to become a particle of Hawking radiation see main story. One school of thought holds that the information is preserved as the hole evaporates, and that it is placed into subtle correlations among these particles of Hawking radiation. According to Bob, who remains outside the black hole, that particle has been separated from its antiparticle partner by the horizon. In order to preserve information, it must become entangled with another particle of Hawking radiation. But what's happening from the point of view of Alice, who falls into the black hole. General relativity says that for a free-falling observer, gravity disappears, so she doesn't see the event horizon. According to Alice, the particle in question remains entangled with its antiparticle partner, because there is no horizon to separate them. If it's Bob, then Alice will not encounter empty space at the horizon as general relativity claims. Instead she will be burned to a crisp by a wall of Hawking radiation — a firewall. If it's Alice who's right, then information will be lost, breaking a fundamental rule of quantum mechanics. The answer awaits us in the theory of everything.
