Stephen William Hawking (8 January 1942 – 14 March 2018) was an English theoretical astrophysicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between 1979 and 2009, he was the Lucasian Professor of Mathematics at Cambridge, widely viewed as one of the most prestigious academic posts in the world.
Hawking was born in Oxford into a family of physicians. In 1959, at the age of 17, he began his university education at University College, Oxford, where he received a first-class BA degree in physics. In 1962, he began his graduate work at Trinity Hall, Cambridge, where, in 1966, he obtained his PhD in applied mathematics and theoretical physics, specialising in general relativity and cosmology. In 1963, at age 21, Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually, over decades, paralysed him. After the loss of his speech, he communicated through a speech-generating device, initially through use of a handheld switch, and eventually by using a single cheek muscle.
Hawking's scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity, and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Initially, Hawking radiation was controversial. By the late 1970s, and following the publication of further research, the discovery was widely accepted as a major breakthrough in theoretical physics. Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics. He supported the many-worlds interpretation of quantum mechanics. He also introduced the notion of a micro black hole.
Hawking achieved commercial success with several works of popular science in which he discussed his theories and cosmology in general. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks. Hawking was a Fellow of the Royal Society, a lifetime member of the Pontifical Academy of Sciences, and a recipient of the Presidential Medal of Freedom, the highest civilian award in the United States. In 2002, Hawking was ranked number 25 in the BBC's poll of the 100 Greatest Britons. He died in 2018 at the age of 76, having lived more than 50 years following his diagnosis of motor neurone disease.
Early life
Family
Stephen William Hawking was born on 8 January 1942 in Oxford to Frank and Isobel Eileen Hawking (née Walker). Hawking's mother was born into a family of doctors in Glasgow, Scotland. His wealthy paternal great-grandfather, from Yorkshire, over-extended himself buying farm land and then went bankrupt in the great agricultural depression during the early 20th century. His paternal great-grandmother saved the family from financial ruin by opening a school in their home. Despite their families' financial constraints, both parents attended the University of Oxford, where Frank read medicine and Isobel read Philosophy, Politics and Economics. Isobel worked as a secretary for a medical research institute, and Frank was a medical researcher specialising in tropical diseases. Hawking said of his father, "I modelled myself on him. Because he was a scientific researcher, I felt that scientific research was the natural thing to do when one grew up. The only difference was that I was not attracted to medicine or biology because they seemed too inexact and descriptive. I wanted something more fundamental, and I found it in physics."
In 1950, when Hawking's father became head of the division of parasitology at the National Institute for Medical Research, the family moved to St Albans, Hertfordshire. There, the family was considered highly intelligent and somewhat eccentric; meals were often spent with each person silently reading a book. They lived a frugal existence in a large, cluttered, and poorly maintained house and travelled in a converted London taxicab. During one of Hawking's father's frequent absences working in Africa, the rest of the family spent four months in Mallorca visiting his mother's friend Beryl and her husband, the poet Robert Graves.
Primary and secondary school years
Hawking began his schooling at the Byron House School in Highgate, London. He later blamed its "progressive methods" for his failure to learn to read while at the school. In St Albans, the eight-year-old Hawking attended St Albans High School for Girls for a few months. At that time, younger boys could attend one of the houses.
Hawking attended two private (i.e. fee-paying) schools, first Radlett School and from September 1952, St Albans School, Hertfordshire, after passing the eleven-plus a year early. The family placed a high value on education. Hawking's father wanted his son to attend Westminster School, but the 13-year-old Hawking was ill on the day of the scholarship examination. His family could not afford the school fees without the financial aid of a scholarship, so Hawking remained at St Albans. A positive consequence was that Hawking remained close to a group of friends with whom he enjoyed board games, the manufacture of fireworks, model aeroplanes and boats, and long discussions about Christianity and extrasensory perception. From 1958 on, with the help of the mathematics teacher Dikran Tahta, they built a computer from clock parts, an old telephone switchboard and other recycled components. In 1959, he built a record player from spare parts: "My father would have regarded it as recklessly self-indulgent, to buy a record player, but I persuaded him that I could assemble one from parts that I could buy cheap. That appealed to him as a Yorkshireman."
Although known at school as "Einstein", Hawking was not initially successful academically. With time, he began to show considerable aptitude for scientific subjects and, inspired by Tahta, decided to study mathematics at university. Hawking's father advised him to study medicine, concerned that there were few jobs for mathematics graduates. He also wanted his son to attend University College, Oxford, his own alma mater. As it was not possible to read mathematics there at the time, Hawking decided to study physics and chemistry. Despite his headmaster's advice to wait until the next year, Hawking was awarded a scholarship after taking the examinations in March 1959.
Undergraduate years
In October 1959, at the age of 17, Hawking began his university education at University College, Oxford. For the first eighteen months, he was bored and lonely – he found the academic work "ridiculously easy". His physics tutor, Robert Berman, later said, "It was only necessary for him to know that something could be done, and he could do it without looking to see how other people did it." A change occurred during his second and third years when, according to Berman, Hawking made more of an effort "to be one of the boys". He developed into a popular, lively, and witty student, interested in classical music and science fiction. This partially resulted from his decision to join Oxford's University College Boat Club, where he coxed a rowing crew. The rowing coach at the time noted that Hawking cultivated a daredevil image, steering his crew on risky courses that led to damaged boats. Hawking estimated that he studied about 1,000 hours during his three years at Oxford. These unimpressive study habits made sitting his finals a challenge, and he decided to answer only theoretical physics questions rather than those requiring factual knowledge. A first-class degree was a condition of acceptance for his planned graduate study in cosmology at the University of Cambridge. Anxious, he slept poorly the night before the examinations, and the result was on the borderline between first- and second-class honours, making a viva (oral examination) with the Oxford examiners necessary.
Hawking was concerned that he was viewed as a lazy and difficult student. So, when asked at the viva to describe his plans, he said, "If you award me a First, I will go to Cambridge. If I receive a Second, I shall stay in Oxford, so I expect you will give me a First." He was held in higher regard than he believed; as Berman commented, the examiners "were intelligent enough to realise they were talking to someone far cleverer than most of themselves". After receiving a first-class BA degree in physics and completing a trip to Iran with a friend, he began his graduate work at Trinity Hall, Cambridge, in October 1962.
Postgraduate years
Hawking's first year as a doctoral student was difficult. He was initially disappointed to find that he had been assigned Dennis William Sciama, one of the founders of modern cosmology, as a supervisor rather than the noted astronomer Fred Hoyle, and he found his training in mathematics inadequate for work in general relativity and cosmology. After being diagnosed with motor neurone disease, Hawking fell into a depression. Although his doctors advised that he continue with his studies, he felt there was little point. His disease progressed more slowly than doctors had predicted. Although Hawking had difficulty walking unsupported, and his speech was almost unintelligible, an initial diagnosis that he had only two years to live proved unfounded. With Sciama's encouragement, he returned to his work. Hawking started developing a reputation for intelligence and brashness after a lecture in June 1964, at which he publicly challenged the work of Hoyle and his student Jayant Narlikar.
Career
1966–1975
When Hawking began his doctoral studies, there was much debate in the physics community about the prevailing theories of the creation of the universe: the Big Bang and Steady State theories. Inspired by Roger Penrose's theorem of a spacetime singularity in the centre of black holes, Hawking applied the same thinking to the entire universe; and, during 1965, he wrote his thesis on this topic.
Hawking's thesis was approved in 1966. He also received a research fellowship at Gonville and Caius College at Cambridge; he obtained his PhD degree in applied mathematics and theoretical physics, specialising in general relativity and cosmology, in March 1966; and his essay "Singularities and the Geometry of Space–Time" shared top honours with one by Penrose to win that year's prestigious Adams Prize. In 1969, Hawking accepted a specially created Fellowship for Distinction in Science to remain at Caius.
Collaborating 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 theory of general relativity, and fits any of the models of physical cosmology developed by Alexander Friedmann, then it must have begun as a singularity. Hawking's early 1970s work with Brandon Carter, Werner Israel, and David C. Robinson strongly supported John Archibald Wheeler's no-hair theorem, that regardless of how a black hole is formed, it only exhibits three properties: mass, electrical charge, and rotation.
Hawking's essay titled "Black Holes" won the Gravity Research Foundation Award in January 1971. His first book, The Large Scale Structure of Space–Time, written with George Ellis, was published in 1973. Hawking was elected a Fellow of the Royal Society (FRS) in 1974, becoming one of the youngest scientists to become a Fellow.
In 1973, Hawking and James M. Bardeen developed the four laws of black hole mechanics, drawing an analogy with thermodynamics. Hawking's second law mentions gravitational waves—waves of warped spacetime caused by the changing gravitational field around two black holes merging. First proposed by Oliver Heaviside in 1893, they were theoretical until they were first observed in 2015. Hawking's law states that even though black holes lose energy (or "have an entropy") from gravitational waves and increasing angular momentum from their rotation, which can both reduce its surface area, the total surface area of two merged black holes must increase or remain the same.
Around this time, Hawking moved into the study of quantum gravity and quantum mechanics. This was spurred by a visit to Moscow, in which he talked with Yakov Zeldovich and Alexei Starobinsky, whose work showed that, according to the uncertainty principle, rotating black holes emit particles. To Hawking's annoyance, his calculations to prove their work produced findings that contradicted his second law. It did, however, support Jacob Bekenstein's 1972 theory that black holes have an entropy proportional to the area of the event horizon. Hawking's law was nonetheless validated in 2025 by analysis of black hole merger GW250114.
In 1974, Hawking claimed 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. John G. Taylor dismissed it as "absolute rubbish" after a lecture by Hawking. Following the publication of further research, by the late 1970s, the discovery was widely accepted as a significant breakthrough in theoretical physics. While some experimental teams have claimed detection of Hawking radiation from acoustic and optical analogues of black holes, some of these results remain in doubt. The search for Hawking radiation from astrophysical ones continues in the twenty-first century.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 astrophysical X-ray source Cygnus X-1 in the Cygnus constellation was a black hole. For Hawking, the wager was an "insurance policy" against the possibility that black holes did not exist. Hawking conceded he had lost the bet in 1990. This bet was the first of several he made with Thorne and others.
Hawking maintained his ties to Caltech, spending a month there almost every year since this first visit.
1975–1990
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 spacetime; 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."
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.
In 1982, to finance his children's education and home-expenses, Hawking decided 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 into the late 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.
1990–2000
In 1992, Hawking conjectured that travel into the past is effectively impossible. On 28 June 2009, as a tongue-in-cheek test of the conjecture, he held a party open to all, complete with food and drinks, but publicised the party only after it was over so that only time-travellers would know to attend; as expected, nobody showed up.
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 more refined wager was made, specifying 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 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. The documentary A Brief History of Time, directed by Errol Morris, premiered in 1991; the film contains material from the book as well as interviews with Hawking, his friends, family, and colleagues. 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. A six-part television series Stephen Hawking's Universe and a companion book appeared in 1997; as Hawking insisted, the focus was entirely on science.
2000–2018
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.
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". 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.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. Hawking created Stephen Hawking: Expedition New Earth, a 2017 documentary on space colonisation, as an episode of Tomorrow's World.
During his career, Hawking supervised 39 successful PhD students. As required by Cambridge University policy for professors who have reached the age of 67, Hawking retired as Lucasian Professor of Mathematics in 2009. Despite suggestions that he might leave the U.K. 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 20 July 2015, Hawking helped launch Breakthrough Initiatives, an effort to search for extraterrestrial life.
In his final broadcast interview, given October 2017, Hawking spoke of the scientific importance of GW170817, a black hole merger. The interview was broadcast in April 2018, after his death, as the Smithsonian TV Channel documentary Leaving Earth: Or How to Colonize a Planet. Hawking's final paper, A smooth exit from eternal inflation?, was posthumously published in the Journal of High Energy Physics on 27 April 2018. In October 2018, one of his final research studies, entitled Black Hole Entropy and Soft Hair, was published, and dealt with the "mystery of what happens to the information held by objects once they disappear into a black hole". Also in October, Hawking's last book was published, Brief Answers to the Big Questions, containing his final comments on what he believed were the most important questions facing humankind.
Personal views
Relevance of philosophy
At Google's Zeitgeist Conference in 2011, Stephen Hawking said that "philosophy is dead". He believed that philosophers "have not kept up with modern developments in science", "have not taken science sufficiently seriously and so Philosophy is no longer relevant to knowledge claims", "their art is dead" and that scientists "have become the bearers of the torch of discovery in our quest for knowledge". He said that philosophical problems can be answered by science, particularly new scientific theories which "lead us to a new and very different picture of the universe and our place in it". His view was both praised and criticised. He said, "Love, faith, and morality belong to a different category to physics. You cannot deduce how one should behave from the laws of physics. But one could hope that the logical thought that physics and mathematics involves would guide one also in one's moral behaviour."
Future of humanity
In 2006, Hawking posed an open question on the Internet: "In a world that is in chaos politically, socially and environmentally, how can the human race sustain another 100 years?", later clarifying: "I don't know the answer. That is why I asked the question, to get people to think about it, and to be aware of the dangers we now face."
Hawking expressed concern that life on Earth is at risk from a sudden nuclear war, a genetically engineered virus, global warming, an asteroid collision, or other dangers humans have not yet thought of. Hawking stated: "I regard it as almost inevitable that either a nuclear confrontation or environmental catastrophe will cripple the Earth at some point in the next 1,000 years". He also thought that a planet-wide disaster need not result in human extinction if the human race were to be able to colonise additional planets before the disaster. Hawking viewed spaceflight and the colonisation of space as necessary for the future of humanity.
Hawking stated that, given the vastness of the universe, aliens likely exist, but that contact with them should be avoided. He warned that aliens might pillage Earth for resources. In 2010, he said: "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans."
Hawking warned that superintelligent artificial intelligence could be pivotal in steering humanity's fate, stating that "the potential benefits are huge... Success in creating AI would be the biggest event in human history. It might also be the last, unless we learn how to avoid the risks." He feared that "an extremely intelligent future AI will probably develop a drive to survive and acquire more resources as a step toward accomplishing whatever goal it has", and that "the real risk with AI isn't malice, but competence. A super-intelligent AI will be extremely good at accomplishing its goals, and if those goals aren't aligned with ours, we're in trouble". He also considered that the enormous wealth generated by machines needs to be redistributed to prevent exacerbated economic inequality.
Hawking was concerned about the future emergence of a race of "superhumans" that would be able to design their own evolution and, as well, argued that computer viruses in today's world should be considered a new form of life, stating that "maybe it says something about human nature, that the only form of life we have created so far is purely destructive. Talk about creating life in our own image."
Religion and atheism
Hawking did not rule out the existence of God, writing 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. He said: "All my work has shown is that you don't have to say that the way the universe began was the personal whim of God. But you still have the question, 'Why does the universe bother to exist?' If you like, you can define God as the answer to that question."
Hawking was an atheist. In a 2011 interview, Hawking regarded the brain "as a computer which will stop working when its components fail", and the concept of an afterlife as a "fairy story for people afraid of the dark". In 2011, narrating the first episode of the American television series Curiosity on the Discovery Channel, Hawking declared:
We are each free to believe what we want and it is my view that the simplest explanation is there is no God. No one created the universe and no one directs our fate. This leads me to a profound realisation. There is probably no heaven, and no afterlife either. We have this one life to appreciate the grand design of the universe, and for that, I am extremely grateful.