Stephen Hawking

At 76 years old, Stephen Hawking has this physical status:

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. 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. In 1969, Hawking accepted a specially created Fellowship for Distinction in Science to remain at Caius.

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. With James M. Bardeen and Brandon Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics. To Hawking's irritation, Jacob Bekenstein, a graduate student of John Wheeler, went further—and ultimately correctly—to apply thermodynamic concepts literally.

In the early 1970s, Hawking's work with Carter, Werner Israel, and David C. Robinson strongly supported Wheeler's no-hair theorem, one that states 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. His essay titled "Black Holes" won the Gravity Research Foundation Award in January 1971. Hawking's first book, The Large Scale Structure of Space-Time, written with George Ellis, was published in 1973.

Beginning in 1973, Hawking moved into the study of quantum gravity and quantum mechanics. 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. To Hawking's annoyance, his much-checked calculations produced findings that contradicted his second law, which claimed black holes could never get smaller, and supported Bekenstein's reasoning about their entropy.

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. Initially, Hawking radiation was controversial. By the late 1970s and following the publication of further research, the discovery was widely accepted as a significant breakthrough in theoretical physics. Hawking was elected a Fellow of the Royal Society (FRS) in 1974, a few weeks after the announcement of Hawking radiation. At the time, he was one of the youngest scientists to become a Fellow.

Hawking was appointed to the Sherman Fairchild Distinguished Visiting Professorship at the California Institute of Technology (Caltech) in 1974. He worked with a friend on the faculty, Kip Thorne, and engaged him in a scientific wager about whether the X-ray source Cygnus X-1 was a black hole. The wager was an "insurance policy" against the proposition that black holes did not exist. Hawking acknowledged that he had lost the bet in 1990, a bet that was the first of several he was to make with Thorne and others. Hawking had maintained ties to Caltech, spending a month there almost every year since this first visit.

Hawking returned to Cambridge in 1975 to a more academically senior post, as reader in gravitational physics. The mid-to-late 1970s were a period of growing public interest in black holes and the physicists who were studying them. Hawking was regularly interviewed for print and television. He also received increasing academic recognition of his work. In 1975, he was awarded both the Eddington Medal and the Pius XI Gold Medal, and in 1976 the Dannie Heineman Prize, the Maxwell Medal and Prize and the Hughes Medal. He was appointed a professor with a chair in gravitational physics in 1977. The following year he received the Albert Einstein Medal and an honorary doctorate from the University of Oxford.

In 1979, Hawking was elected Lucasian Professor of Mathematics at the University of Cambridge. His inaugural lecture in this role 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. His promotion coincided with a health-crisis which led to his accepting, albeit reluctantly, some nursing services at home. 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. 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. Following a conference in Moscow in October 1981, Hawking and Gary Gibbons organised a three-week Nuffield Workshop in the summer of 1982 on "The Very Early Universe" at Cambridge University, a workshop that focused mainly on inflation theory. Hawking also began a new line of quantum-theory research into the origin of the universe. In 1981 at a Vatican conference, he presented work suggesting that there might be no boundary – or beginning or ending – to the universe.

Hawking subsequently developed the research in collaboration with Jim Hartle, and in 1983 they published a model, known as the Hartle–Hawking state. It proposed that prior to the Planck epoch, the universe had no boundary in space-time; before the Big Bang, time did not exist and the concept of the beginning of the universe is meaningless. The initial singularity of the classical Big Bang models was replaced with a region akin to the North Pole. One cannot travel north of the North Pole, but there is no boundary there – it is simply the point where all north-running lines meet and end. Initially, the no-boundary proposal predicted a closed universe, which had implications about the existence of God. As Hawking explained, "If the universe has no boundaries but is self-contained... then God would not have had any freedom to choose how the universe began."

Hawking did not rule out the existence of a Creator, asking in A Brief History of Time "Is the unified theory so compelling that it brings about its own existence?", also stating "If we discover a complete theory, it would be the ultimate triumph of human reason – for then we should know the mind of God"; in his early work, Hawking spoke of God in a metaphorical sense. In the same book he suggested that the existence of God was not necessary to explain the origin of the universe. Later discussions with Neil Turok led to the realisation that the existence of God was also compatible with an open universe.

Further work by Hawking in the area of arrows of time led to the 1985 publication of a paper theorising that if the no-boundary proposition were correct, then when the universe stopped expanding and eventually collapsed, time would run backwards. A paper by Don Page and independent calculations by Raymond Laflamme led Hawking to withdraw this concept. Honours continued to be awarded: in 1981 he was awarded the American Franklin Medal, and in the 1982 New Year Honours appointed a Commander of the Order of the British Empire (CBE). These awards did not significantly change Hawking's financial status, and motivated by the need to finance his children's education and home-expenses, he decided in 1982 to write a popular book about the universe that would be accessible to the general public. Instead of publishing with an academic press, he signed a contract with Bantam Books, a mass-market publisher, and received a large advance for his book. A first draft of the book, called A Brief History of Time, was completed in 1984.

One of the first messages Hawking produced with his speech-generating device was a request for his assistant to help him finish writing A Brief History of Time. Peter Guzzardi, his editor at Bantam, pushed him to explain his ideas clearly in non-technical language, a process that required many revisions from an increasingly irritated Hawking. The book was published in April 1988 in the US and in June in the UK, and it proved to be an extraordinary success, rising quickly to the top of best-seller lists in both countries and remaining there for months. The book was translated into many languages, and as of 2009, has sold an estimated 9 million copies.

Media attention was intense, and a Newsweek magazine-cover and a television special both described him as "Master of the Universe". Success led to significant financial rewards, but also the challenges of celebrity status. Hawking travelled extensively to promote his work, and enjoyed partying and dancing into the small hours. A difficulty refusing the invitations and visitors left him limited time for work and his students. Some colleagues were resentful of the attention Hawking received, feeling it was due to his disability.

He received further academic recognition, including five more honorary degrees, the Gold Medal of the Royal Astronomical Society (1985), the Paul Dirac Medal (1987) and, jointly with Penrose, the prestigious Wolf Prize (1988). In the 1989 Birthday Honours, he was appointed a Companion of Honour (CH). He reportedly declined a knighthood in the late 1990s in objection to the UK's science funding policy.

Hawking pursued his work in physics: in 1993 he co-edited a book on Euclidean quantum gravity with Gary Gibbons and published a collected edition of his own articles on black holes and the Big Bang. In 1994, at Cambridge's Newton Institute, Hawking and Penrose delivered a series of six lectures that were published in 1996 as "The Nature of Space and Time". In 1997, he conceded a 1991 public scientific wager made with Kip Thorne and John Preskill of Caltech. Hawking had bet that Penrose's proposal of a "cosmic censorship conjecture" – that there could be no "naked singularities" unclothed within a horizon – was correct.

After discovering his concession might have been premature, a new and more refined wager was made. This one specified that such singularities would occur without extra conditions. The same year, Thorne, Hawking and Preskill made another bet, this time concerning the black hole information paradox. Thorne and Hawking argued that since general relativity made it impossible for black holes to radiate and lose information, the mass-energy and information carried by Hawking radiation must be "new", and not from inside the black hole event horizon. Since this contradicted the quantum mechanics of microcausality, quantum mechanics theory would need to be rewritten. Preskill argued the opposite, that since quantum mechanics suggests that the information emitted by a black hole relates to information that fell in at an earlier time, the concept of black holes given by general relativity must be modified in some way.

Hawking also maintained his public profile, including bringing science to a wider audience. A film version of A Brief History of Time, directed by Errol Morris and produced by Steven Spielberg, premiered in 1992. Hawking had wanted the film to be scientific rather than biographical, but he was persuaded otherwise. The film, while a critical success, was not widely released. A popular-level collection of essays, interviews, and talks titled Black Holes and Baby Universes and Other Essays was published in 1993, and a six-part television series Stephen Hawking's Universe and a companion book appeared in 1997. As Hawking insisted, this time the focus was entirely on science.

Hawking continued his writings for a popular audience, publishing The Universe in a Nutshell in 2001, and A Briefer History of Time, which he wrote in 2005 with Leonard Mlodinow to update his earlier works with the aim of making them accessible to a wider audience, and God Created the Integers, which appeared in 2006. Along with Thomas Hertog at CERN and Jim Hartle, from 2006 on Hawking developed a theory of top-down cosmology, which says that the universe had not one unique initial state but many different ones, and therefore that it is inappropriate to formulate a theory that predicts the universe's current configuration from one particular initial state. Top-down cosmology posits that the present "selects" the past from a superposition of many possible histories. In doing so, the theory suggests a possible resolution of the fine-tuning question.

Hawking continued to travel widely, including trips to Chile, Easter Island, South Africa, Spain (to receive the Fonseca Prize in 2008), Canada, and numerous trips to the United States. For practical reasons related to his disability, Hawking increasingly travelled by private jet, and by 2011 that had become his only mode of international travel.

By 2003, consensus among physicists was growing that Hawking was wrong about the loss of information in a black hole. In a 2004 lecture in Dublin, he conceded his 1997 bet with Preskill, but described his own, somewhat controversial solution to the information paradox problem, involving the possibility that black holes have more than one topology. In the 2005 paper he published on the subject, he argued that the information paradox was explained by examining all the alternative histories of universes, with the information loss in those with black holes being cancelled out by those without such loss. In January 2014, he called the alleged loss of information in black holes his "biggest blunder".

As part of another longstanding scientific dispute, Hawking had emphatically argued, and bet, that the Higgs boson would never be found. The particle was proposed to exist as part of the Higgs field theory by Peter Higgs in 1964. Hawking and Higgs engaged in a heated and public debate over the matter in 2002 and again in 2008, with Higgs criticising Hawking's work and complaining that Hawking's "celebrity status gives him instant credibility that others do not have." The particle was discovered in July 2012 at CERN following construction of the Large Hadron Collider. Hawking quickly conceded that he had lost his bet and said that Higgs should win the Nobel Prize for Physics, which he did in 2013.

In 2007, Hawking and his daughter Lucy published George's Secret Key to the Universe, a children's book designed to explain theoretical physics in an accessible fashion and featuring characters similar to those in the Hawking family. The book was followed by sequels in 2009, 2011, 2014 and 2016.

In 2002, following a UK-wide vote, the BBC included Hawking in their list of the 100 Greatest Britons. He was awarded the Copley Medal from the Royal Society (2006), the Presidential Medal of Freedom, which is America's highest civilian honour (2009), and the Russian Special Fundamental Physics Prize (2013).

Several buildings have been named after him, including the Stephen W. Hawking Science Museum in San Salvador, El Salvador, the Stephen Hawking Building in Cambridge, and the Stephen Hawking Centre at the Perimeter Institute in Canada. Appropriately, given Hawking's association with time, he unveiled the mechanical "Chronophage" (or time-eating) Corpus Clock at Corpus Christi College, Cambridge in September 2008.

During his career, Hawking supervised 39 successful PhD students. One doctoral student did not successfully complete the PhD. As required by Cambridge University policy, Hawking retired as Lucasian Professor of Mathematics in 2009. Despite suggestions that he might leave the United Kingdom as a protest against public funding cuts to basic scientific research, Hawking worked as director of research at the Cambridge University Department of Applied Mathematics and Theoretical Physics.

On 28 June 2009, as a tongue-in-cheek test of his 1992 conjecture that travel into the past is effectively impossible, Hawking held a party open to all, complete with hors d'oeuvres and iced champagne, but publicised the party only after it was over so that only time-travellers would know to attend; as expected, nobody showed up to the party.

On 20 July 2015, Hawking helped launch Breakthrough Initiatives, an effort to search for extraterrestrial life. Hawking created Stephen Hawking: Expedition New Earth, a documentary on space colonisation, as a 2017 episode of Tomorrow's World.

In August 2015, Hawking said that not all information is lost when something enters a black hole and there might be a possibility to retrieve information from a black hole according to his theory. In July 2017, Hawking was awarded an Honorary Doctorate from Imperial College London.

Hawking's final paper – A smooth exit from eternal inflation? – was posthumously published in the Journal of High Energy Physics on 27 April 2018.

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