In his work, and in collaboration with Penrose, Hawking extended the singularity theorem concepts first explored in his doctoral thesis. This included not only the existence of singularities but also the theory that the Universe might have started as a singularity. Their joint essay was the runner-up in the 1968 Gravity Research Foundation competition.[151][152] In 1970 they published a proof that if the Universe obeys the general theory of relativity and fits any of the models of physical cosmology developed by Alexander Friedmann, then it must have begun as a singularity.[153][154][155] In 1969, Hawking accepted a specially created Fellowship for Distinction in Science to remain at Caius.[156] In 1970 Hawking postulated what became known as the second law of black hole dynamics, that the event horizon of a black hole can never get smaller.[157] With James M. Bardeen and Brandon Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics.[158] To Hawking's irritation, Jacob Bekenstein, a graduate student of John Wheeler, went further—and ultimately correctly—to apply thermodynamic concepts literally.[159][160] In the early 1970s, Hawking's work with Carter, Werner Israel and David C. Robinson strongly supported Wheeler's no-hair theorem that no matter what the original material from which a black hole is created it can be completely described by the properties of mass, electrical charge and rotation.[161][162] His essay titled "Black Holes" won the Gravity Research Foundation Award in January 1971.[163] Hawking's first book, The Large Scale Structure of Space-Time. written with George Ellis, was published in 1973.[164] Beginning in 1973, Hawking moved into the study of quantum gravity and quantum mechanics.[165][164] His work in this area was spurred by a visit to Moscow and discussions with Yakov Borisovich Zel'dovich and Alexei Starobinsky, whose work showed that according to the uncertainty principle rotating black holes emit particles.[166] To Hawking's annoyance, his much-checked calculations produced findings that contradicted his second law, which claimed black holes could never get smaller,[167] and supported Bekenstein's reasoning about their entropy.[168][166] His results, which Hawking presented from 1974, showed that black holes emit radiation, known today as Hawking radiation, which may continue until they exhaust their energy and evaporate.[169][170][171] Initially, Hawking radiation was controversial. However by the late 1970s and following the publication of further research, the discovery was widely accepted as a significant breakthrough in theoretical physics.[172][173][174] In March 1974, a few weeks after the announcement of Hawking radiation, Hawking was invested as a Fellow of the Royal Society, one of the youngest scientists to be so honoured.[175][176] Hawking was appointed to the Sherman Fairchild Distinguished visiting professorship at the California Institute of Technology (Caltech) in 1970. He worked with a friend on the faculty, Kip Thorne,[177] and engaged him in a scientific wager about whether the dark star Cygnus X-1 was a black hole. The wager was a surprising "insurance policy" against the proposition that black holes did not exist.[178] Hawking acknowledged that he had lost the bet in 1990, which was the first of several that he was to make with Thorne and others.[179] Hawking has maintained ties to Caltech, spending a month there almost every year since this first visit. In the late 1970s Hawking was elected Lucasian Professor of Mathematics at the University of Cambridge.[82][185] His inaugural lecture as Lucasian Professor of Mathematics was titled: "Is the end in sight for Theoretical Physics" and proposed N=8 Supergravity as the leading theory to solve many of the outstanding problems physicists were studying.[186] Hawking's promotion coincided with a health crisis which led to Hawking accepting, albeit reluctantly, some nursing services at home.[187] At the same time he was also making a transition in his approach to physics, becoming more intuitive and speculative rather than insisting on mathematical proofs. "I would rather be right than rigorous" he told Kip Thorne.[188] In 1981 he proposed that information in a black hole is irretrievably lost when a black hole evaporates. This information paradox violates the fundamental tenet of quantum mechanics, and led to years of debate, including "the Black Hole War" with Leonard Susskind and Gerard 't Hooft. Cosmological inflation—a theory proposing that following the Big Bang the Universe initially expanded incredibly rapidly before settling down to a slower expansion—was proposed by Alan Guth and also developed by Andrei Linde. http://en.wikipedia.org/wiki/Stephen_Hawking

• published: 12 May 2015
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