Stephen Hawking

Stephen William Hawking CH, CBE, FRS, FRSA( i/ˈstiːvən ˈhɔːkɪŋ/; born 8 January 1942) is an En-glish theoretical physicist, cosmologist, author and Di-rector of Research at the Centre for Theoretical Cos-mology within the University of Cambridge.[16][17] Hisscientific works include a collaboration with Roger Pen-rose on gravitational singularity theorems in the frame-work of general relativity, and the theoretical predictionthat black holes emit radiation, often called Hawking ra-diation. Hawking was the first to set forth a theory ofcosmology explained by a union of the general theoryof relativity and quantum mechanics. He is a vigoroussupporter of the many-worlds interpretation of quantummechanics.[18][19]

He is an Honorary Fellow of the Royal Society of Arts, alifetime member of the Pontifical Academy of Sciences,and a recipient of the Presidential Medal of Freedom,the highest civilian award in the United States. Hawkingwas the Lucasian Professor of Mathematics at the Uni-versity of Cambridge between 1979 and 2009 and hasachieved commercial success with works of popular sci-ence in which he discusses his own theories and cosmol-ogy in general; his bookA Brief History of Time appearedon the British Sunday Times best-seller list for a record-breaking 237 weeks.Hawking suffers from a rare early-onset, slow-progressingform of amyotrophic lateral sclerosis (ALS), also knownas motor neurone disease or Lou Gehrig's disease, thathas gradually paralysed him over the decades.[20] He nowcommunicates using a single cheek muscle attached to aspeech-generating device. Hawking married twice andhas three children.

1 Personal life

1.1 Parents

Hawking was born on 8 January 1942[1] in Oxford, Eng-land, to Frank (1905–1986) and Isobel Hawking (néeWalker; 1915–2013).[21][22] His mother was Scottish.[23]Despite their families’ financial constraints, both parentsattended the University of Oxford, where Frank stud-ied medicine and Isobel, Philosophy, Politics and Eco-nomics.[22] The two met shortly after the beginning ofthe Second World War at a medical research institutewhere she was working as a secretary and he as a medicalresearcher.[22][24] They lived in Highgate, but as Lon-don was being bombed in those years, Isobel went to

Oxford to give birth in greater safety.[25] Hawking hastwo younger sisters, Philippa and Mary, and an adoptedbrother, Edward.[26]

In 1950, when his father became head of the divisionof parasitology at the National Institute for Medical Re-search, Hawking and his family moved to St Albans,Hertfordshire.[27][28] In St Albans, the family were con-sidered highly intelligent and somewhat eccentric;[27][29]meals were often spent with each person silently read-ing a book.[27] They lived a frugal existence in a large,cluttered, and poorly maintained house, and travelled ina converted London taxicab.[30][31] During one of Hawk-ing’s father’s frequent absences working in Africa,[32] therest of the family spent four months in Majorca visit-ing his mother’s friend Beryl and her husband, the poetRobert Graves.[33]

1.2 Disability

Hawking suffers from a rare early-onset slow-progressingform of amyotrophic lateral sclerosis (ALS), also knownas motor neurone disease or Lou Gehrig’s disease, thathas gradually paralysed him over the decades.[20]

Hawking had experienced increasing clumsiness duringhis final year at Oxford, including a fall on some stairs anddifficulties when rowing.[34][35] The problems worsened,and his speech became slightly slurred; his family noticedthe changes when he returned home for Christmas andmedical investigations were begun.[36][37] The diagnosisof motor neurone disease came when Hawking was 21,in 1963. At the time, doctors gave him a life expectancyof two years.[38][39]

In the late 1960s, Hawking’s physical abilities de-clined: he began to use crutches and ceased lecturingregularly.[40] As he slowly lost the ability to write, hedeveloped compensatory visual methods, including see-ing equations in terms of geometry.[41][42] The physi-cist Werner Israel later compared the achievements toMozart composing an entire symphony in his head.[43][44]Hawking was, however, fiercely independent and unwill-ing to accept help or make concessions for his disabilities.He preferred to be regarded as “a scientist first, popu-lar science writer second, and, in all the ways that mat-ter, a normal human being with the same desires, drives,dreams, and ambitions as the next person.”[45] His wifeJane Hawking later noted that “Some people would call itdetermination, some obstinacy. I've called it both at onetime or another.”[46] He required much persuasion to ac-

1

2 1 PERSONAL LIFE

cept the use of a wheelchair at the end of the 1960s,[47]but ultimately became notorious for the wildness of hiswheelchair driving.[48] Hawking was a popular and wittycolleague, but his illness, as well as his reputation forbrashness, distanced him from some.[46]

Hawking’s speech deteriorated, and by the late 1970she could only be understood by his family and closestfriends. To communicate with others, someone whoknew him well would translate his speech into intelligi-ble speech.[49] Spurred by a dispute with the universityover who would pay for the ramp needed for him to en-ter his workplace, Hawking and his wife campaigned forimproved access and support for those with disabilities inCambridge,[50][51] including adapted student housing atthe university.[52] In general, however, Hawking had am-bivalent feelings about his role as a disability rights cham-pion: while wanting to help others, he sought to detachhimself from his illness and its challenges.[53] His lack ofengagement led to some criticism.[54]

During a visit to the European Organisation for NuclearResearch on the border of France and Switzerland inmid-1985, Hawking contracted pneumonia, which in his con-dition was life-threatening; he was so ill that Jane wasasked if life support should be terminated. She refusedbut the consequence was a tracheotomy, which would re-quire round-the-clock nursing care, and remove what re-mained of his speech.[55][56] The National Health Servicewould pay for a nursing home, but Jane was determinedthat he would live at home. The cost of the care wasfunded by an American foundation.[57][58] Nurses werehired for the three shifts required to provide the round-the-clock support he required. One of those employedwas Elaine Mason, who was to become Hawking’s sec-ond wife.[59]

For his communication, Hawking initially raised his eye-brows to choose letters on a spelling card.[60] But in 1986he received a computer program called the “Equalizer”from Walter Woltosz, CEO of Words Plus, who had de-veloped an earlier version of the software to help hismother-in-law, who also suffered from ALS and had losther ability to speak and write.[61] In a method he usesto this day, Hawking could now simply press a switchto select phrases, words or letters from a bank of about2,500–3,000 that are scanned.[62][63] The program wasoriginally run on a desktop computer. However, ElaineMason’s husband, David, a computer engineer, adapteda small computer and attached it to his wheelchair.[64]Released from the need to use somebody to interprethis speech, Hawking commented that “I can commu-nicate better now than before I lost my voice.”[65] Thevoice he uses has an American accent and is no longerproduced.[66][67] Despite the availability of other voices,Hawking has retained this original voice, saying that heprefers it and identifies with it.[68] At this point, Hawkingactivated a switch using his hand and could produce up to15 words a minute.[69] Lectures were prepared in advanceand were sent to the speech synthesiser in short sections

to be delivered.[66]

Hawking gradually lost the use of his hand, and in 2005he began to control his communication device with move-ments of his cheek muscles,[70][71][72] with a rate of aboutone word per minute.[71] With this decline there is arisk of him developing locked-in syndrome, so Hawk-ing is collaborating with researchers on systems thatcould translate his brain patterns or facial expressions intoswitch activations.[72][73][74] By 2009 he could no longerdrive his wheelchair independently.[75] He has increasedbreathing difficulties, requiring a ventilator at times andhas been hospitalised several times.[73]

1.3 Marriages

When Hawking was a graduate student at Cambridge, hisrelationship with a friend of his sister, Jane Wilde, whomhe had met shortly before his diagnosis with motor neu-rone disease, continued to develop. The couple becameengaged in October 1964[76][77] — Hawking later saidthat the engagement gave him “something to live for”[78]— and the two were married on 14 July 1965.[79]

During their first years of marriage, Jane lived in Lon-don during the week as she completed her degree, andthey travelled to the United States several times for con-ferences and physics-related visits. The couple had diffi-culty finding housing that was within Hawking’s walkingdistance to the Department of Applied Mathematics andTheoretical Physics (DAMTP). Jane began a PhD pro-gramme, and a son, Robert, was born inMay 1967.[80][81]A daughter, Lucy, was born in 1970.[82] A third child,Timothy, was born in April 1979.[83]

Hawking rarely discussed his illness and physical chal-lenges, even—in a precedent set during their courtship—with Jane.[84] His disabilities meant that the responsibili-ties of home and family rested firmly on his wife’s increas-ingly overwhelmed shoulders, leaving him more time tothink about physics.[85] Upon his appointment in 1974 toa year-long position at the California Institute of Technol-ogy in Pasadena, California, Jane proposed that a gradu-ate or post-doctoral student live with them and help withhis care. Hawking accepted, and Bernard Carr travelledwith them as the first of many students who fulfilled thisrole.[86][87] The family spent a generally happy and stim-ulating year in Pasadena.[88]

Hawking returned to Cambridge in 1975 to a new home, anew job—as reader. Don Page, with whom Hawking hadbegun a close friendship at Caltech, arrived to work as thelive-in graduate student assistant. With Page’s help andthat of a secretary, Jane’s responsibilities were reducedso she could return to her thesis and her new interest insinging.[89]

By December 1977, Jane had met organist JonathanHellyer Jones when singing in a church choir. HellyerJones became close to the Hawking family, and by the

2.2 Undergraduate 3

mid-1980s, he and Jane had developed romantic feelingsfor each other.[90][91][92] According to Jane, her husbandwas accepting of the situation, stating “he would not ob-ject so long as I continued to love him.”[90][93][94] Jane andHellyer Jones determined not to break up the family andtheir relationship remained platonic for a long period.[95]

By the 1980s, Hawking’s marriage had been strained formany years. Jane felt overwhelmed by the intrusion intotheir family life of the required nurses and assistants. Theimpact of his celebrity was challenging for colleagues andfamily members, and in one interview Jane describedher role as “simply to tell him that he’s not God”.[96][97]Hawking’s views of religion also contrasted with herstrong Christian faith and resulted in tension.[98][97][99] Inthe late 1980s, Hawking had grown close to one of hisnurses, Elaine Mason, to the dismay of some colleagues,caregivers and family members who were disturbed byher strength of personality and protectiveness.[100] Hawk-ing told Jane that he was leaving her for Mason[101] anddeparted the family home in February 1990.[102] Afterhis divorce from Jane in 1995, Hawking married Masonin September,[103][102] declaring “It’s wonderful — I havemarried the woman I love.”[104]

In 1999 Jane Hawking published a memoir, Music toMove the Stars, describing her marriage to Hawking andits breakdown. Its revelations caused a sensation in themedia, but as was his usual practice regarding his per-sonal life, Hawking made no public comment except tosay that he did not read biographies about himself.[105]After his second marriage, Hawking’s family felt ex-cluded and marginalised from his life.[99][106] For a pe-riod of about five years in the early 2000s, his familyand staff became increasingly worried that he was be-ing physically abused.[106][107] Police investigations tookplace, but were closed as Hawking refused to make acomplaint.[106][108][109]

In 2006 Hawking and Mason quietly divorced,[110][111]and Hawking resumed closer relationships with Jane,his children, and grandchildren.[111][97] Reflecting thishappier period, a revised version of Jane’s book calledTravelling to Infinity: My Life with Stephen appeared in2007,[106] and was made into a film The Theory of Every-thing in 2014. ⋅

2 Education

2.1 Primary and secondary

Hawking began his schooling at the Byron House School;he later blamed its “progressive methods” for his failureto learn to read while at the school.[27] In St Albans, theeight-year-old Hawking attended St Albans High Schoolfor Girls for a few months; at that time, younger boyscould attend one of the houses.[33][112]

He attended Radlett School for a year[112] and from

September 1952, St Albans School.[1][113] The familyplaced a high value on education.[27] Hawking’s fatherwanted his son to attend the well-regarded WestminsterSchool, but the 13-year-old Hawking was ill on the dayof the scholarship examination. His family could not af-ford the school fees without the financial aid of a schol-arship, so Hawking remained at St Albans.[114][115] Apositive consequence was that Hawking remained witha close group of friends with whom he enjoyed boardgames, the manufacture of fireworks, model aeroplanesand boats,[116] and long discussions about Christianity andextrasensory perception.[117] From 1958, and with thehelp of the mathematics teacher Dikran Tahta, they builta computer from clock parts, an old telephone switch-board and other recycled components.[118][119] Althoughat school he was known as “Einstein”, Hawking was notinitially successful academically.[120] With time, he be-gan to show considerable aptitude for scientific subjects,and inspired by Tahta, decided to study mathematics atuniversity.[121][122][123] Hawking’s father advised him tostudy medicine, concerned that there were few jobs formathematics graduates.[124] He wanted Hawking to at-tend University College, Oxford, his own alma mater. Asit was not possible to read mathematics there at the time,Hawking decided to study physics and chemistry. De-spite his headmaster’s advice to wait until the next year,Hawking was awarded a scholarship after taking the ex-aminations in March 1959.[125][126]

2.2 Undergraduate

Hawking began his university education at UniversityCollege, Oxford[1] in October 1959 at the age of 17.[127]For the first 18 months, he was bored and lonely: he wasyounger than many other students, and found the aca-demic work “ridiculously easy”.[128][129] His physics tu-tor, Robert Berman, later said, “It was only necessaryfor him to know that something could be done, and hecould do it without looking to see how other people didit.”[130] A change occurred during his second and thirdyear when, according to Berman, Hawking made moreeffort “to be one of the boys”. He developed into a pop-ular, lively and witty college member, interested in clas-sical music and science fiction.[127] Part of the transfor-mation resulted from his decision to join the college BoatClub, where he coxed a rowing team.[131][132] The rowingtrainer at the time noted that Hawking cultivated a dare-devil image, steering his crew on risky courses that led todamaged boats.[133][131]

Hawking has estimated that he studied about a thousandhours during his three years at Oxford. These unimpres-sive study habits made sitting his finals a challenge, andhe decided to answer only theoretical physics questionsrather than those requiring factual knowledge. A first-class honours degree was a condition of acceptance forhis planned graduate study in cosmology at the Universityof Cambridge.[134][135] Anxious, he slept poorly the night

4 3 CAREER

before the examinations, and the final result was on theborderline between first- and second-class honours, mak-ing a viva (oral examination) necessary.[135][136] Hawk-ing was concerned that he was viewed as a lazy and dif-ficult student, so when asked at the oral to describe hisfuture plans, he said, “If you award me a First, I will goto Cambridge. If I receive a Second, I shall stay in Ox-ford, so I expect you will give me a First.”[135][137] He washeld in higher regard than he believed: as Berman com-mented, the examiners “were intelligent enough to realisethey were talking to someone far cleverer than most ofthemselves”.[135] After receiving a first-class BA (Hons.)degree, and following a trip to Iran with a friend, he beganhis graduate work at Trinity Hall, Cambridge, in October1962.[1][138][139]

2.3 Graduate

Hawking’s first year as a doctoral student[2] was difficult.He was initially disappointed to find that he had beenassigned Dennis William Sciama, one of the foundersof modern cosmology, as a supervisor rather than notedastronomer Fred Hoyle,[140][141] and he found his train-ing in mathematics inadequate for work in general rel-ativity and cosmology.[142] After being diagnosed withmotor neurone disease, Hawking fell into a depression;though his doctors advised that he continue with his stud-ies, he felt there was little point.[143] However, his diseaseprogressed more slowly than doctors had predicted. Al-though Hawking had difficulty walking unsupported andhis speech was almost unintelligible, an initial diagno-sis that he had only two years to live proved unfounded.With the encouragement of Sciama, he returned to hiswork.[144][145] Hawking started developing a reputationfor brilliance and brashness when he publicly challengedthe work of Fred Hoyle and his student Jayant Narlikar ata lecture in June 1964.[146][147]

When Hawking began his graduate studies, there wasmuch debate in the physics community about the pre-vailing theories of the creation of the universe: the BigBang and the Steady State theories.[148] Inspired by RogerPenrose's theorem of a spacetime singularity in the cen-tre of black holes, Hawking applied the same thinking tothe entire universe, and during 1965 wrote his thesis onthis topic.[149] There were other positive developments:Hawking received a research fellowship at Gonville andCaius College.[79] He obtained his PhD degree in cosmol-ogy in March 1966,[150] and his essay entitled “Singular-ities and the Geometry of Space-Time” shared top hon-ours with one by Penrose to win that year’s prestigiousAdams Prize.[151][150]

3 Career

3.1 1966–1975

In his work, and in collaboration with Penrose, Hawkingextended the singularity theorem concepts first exploredin his doctoral thesis. This included not only the exis-tence of singularities but also the theory that the universemight have started as a singularity. Their joint essay wasthe runner-up in the 1968 Gravity Research Foundationcompetition.[152][153] In 1970 they published a proof thatif the universe obeys the general theory of relativity andfits any of the models of physical cosmology developed byAlexander Friedmann, then it must have begun as a singu-larity.[154][155][156] In 1969, Hawking accepted a speciallycreated Fellowship for Distinction in Science to remainat Caius.[157]

In 1970, Hawking postulated what became known asthe second law of black hole dynamics, that the eventhorizon of a black hole can never get smaller.[158] WithJames M. Bardeen and Brandon Carter, he proposedthe four laws of black hole mechanics, drawing an anal-ogy with thermodynamics.[159] To Hawking’s irritation,Jacob Bekenstein, a graduate student of John Wheeler,went further—and ultimately correctly—to apply ther-modynamic concepts literally.[160][161] In the early 1970s,Hawking’s work with Carter, Werner Israel and David C.Robinson strongly supported Wheeler’s no-hair theoremthat no matter what the original material from which ablack hole is created it can be completely described by theproperties of mass, electrical charge and rotation.[162][163]His essay titled “Black Holes” won the Gravity ResearchFoundation Award in January 1971.[164] Hawking’s firstbook, The Large Scale Structure of Space-Time, writtenwith George Ellis, was published in 1973.[165]

Beginning in 1973, Hawking moved into the study ofquantum gravity and quantum mechanics.[166][165] Hiswork in this area was spurred by a visit to Moscowand discussions with Yakov Borisovich Zel'dovich andAlexei Starobinsky, whose work showed that accord-ing to the uncertainty principle rotating black holesemit particles.[167] To Hawking’s annoyance, his much-checked calculations produced findings that contradictedhis second law, which claimed black holes could never getsmaller,[168] and supported Bekenstein’s reasoning abouttheir entropy.[169][167] His results, which Hawking pre-sented from 1974, showed that black holes emit radiation,known today as Hawking radiation, which may continueuntil they exhaust their energy and evaporate.[170][171][172]Initially, Hawking radiation was controversial. However,by the late 1970s and following the publication of fur-ther research, the discovery was widely accepted as a sig-nificant breakthrough in theoretical physics.[173][174][175]Hawking was elected a Fellow of the Royal Society (FRS)in 1974, a few weeks after the announcement of Hawk-ing radiation. At the time, he was one of the youngestscientists to become a Fellow.[176][177]

Hawking was appointed to the Sherman Fairchild Dis-tinguished visiting professorship at the California Insti-

3.2 1975–1990 5

tute of Technology (Caltech) in 1970. He worked with afriend on the faculty, Kip Thorne,[178] and engaged him ina scientific wager about whether the dark star Cygnus X-1 was a black hole. The wager was an “insurance policy”against the proposition that black holes did not exist.[179]Hawking acknowledged that he had lost the bet in 1990,which was the first of several that he was to make withThorne and others.[180] Hawking has maintained ties toCaltech, spending a month there almost every year sincethis first visit.[181]

3.2 1975–1990

Hawking returned to Cambridge in 1975 to a more ad-vanced academic senior position —as reader. The mid-to late 1970s were a period of growing public interestin black holes and of the physicists who were studyingthem. Hawking was regularly interviewed for print andtelevision.[182][183] He also received increasing academicrecognition of his work.[83] In 1975, he was awardedboth the Eddington Medal and the Pius XI Gold Medal,and in 1976 the Dannie Heineman Prize, the MaxwellPrize and the Hughes Medal.[184][185] Hawking was ap-pointed a professor with a chair in gravitational physics in1977.[90] The following year he received the Albert Ein-stein Medal and an honorary doctorate from the Univer-sity of Oxford.[77][83]

In the late 1970s, Hawking was elected LucasianProfessor of Mathematics at the University ofCambridge.[83][186] His inaugural lecture as LucasianProfessor of Mathematics was titled: “Is the end in sightfor Theoretical Physics” and proposed N=8 Supergravityas the leading theory to solve many of the outstandingproblems physicists were studying.[187] Hawking’spromotion coincided with a health crisis which led toHawking accepting, albeit reluctantly, some nursingservices at home.[188] At the same time, he was alsomaking a transition in his approach to physics, becomingmore intuitive and speculative rather than insisting onmathematical proofs. “I would rather be right than rigor-ous”, he told Kip Thorne.[189] In 1981, he proposed thatinformation in a black hole is irretrievably lost when ablack hole evaporates. This information paradox violatesthe fundamental tenet of quantum mechanics, and ledto years of debate, including "the Black Hole War" withLeonard Susskind and Gerard 't Hooft.[190][191]

Cosmological inflation—a theory proposing that follow-ing the Big Bang the universe initially expanded incredi-bly rapidly before settling down to a slower expansion—was proposed by Alan Guth and also developed by AndreiLinde.[192] Following a conference in Moscow in Oc-tober 1981, Hawking and Gary Gibbons organized athree-week Nuffield Workshop in the summer of 1982on the Very Early Universe at Cambridge University,which focused mainly on inflation theory.[193][194][195]Hawking also began a new line of quantum theory re-search into the origin of the universe. In 1981 at a Vati-

can conference, he presented work suggesting that theremight be no boundary—or beginning or ending—to theuniverse.[196][197] He subsequently developed the researchin collaboration with Jim Hartle, and in 1983 they pub-lished a model, known as the Hartle–Hawking state. Itproposed that prior to the Planck epoch, the universe hadno boundary in space-time; before the Big Bang, time didnot exist and the concept of the beginning of the universeis meaningless.[198] The initial singularity of the classicalBig Bang models was replaced with a region akin to theNorth Pole. One cannot travel north of the North Pole,but there is no boundary there—it is simply the pointwhere all north-running lines meet and end.[199][200] Ini-tially the no-boundary proposal predicted a closed uni-verse which had implications about the existence of God.As Hawking explained “If the universe has no boundariesbut is self-contained... then God would not have had anyfreedom to choose how the universe began.”[201]

Hawking did not rule out the existence of a Creator, ask-ing in A Brief History of Time “Is the unified theory socompelling that it brings about its own existence?"[202] Inhis early work, Hawking spoke of God in a metaphoricalsense. In A Brief History of Time he wrote: “If we dis-cover a complete theory, it would be the ultimate triumphof human reason—for then we should know the mind ofGod.”[203] In the same book he suggested the existenceof God was unnecessary to explain the origin of the uni-verse. Later discussions with Neil Turok led to the reali-sation that it is also compatible with an open universe.[204]

Further work by Hawking in the area of arrows of timeled to the 1985 publication of a paper theorising thatif the no-boundary proposition were correct, then whenthe universe stopped expanding and eventually collapsed,time would run backwards.[205] A paper by Don Pageand independent calculations by Raymond Laflamme ledHawking to withdraw this concept.[206] Honours contin-ued to be awarded: in 1981 he was awarded the AmericanFranklin Medal,[207] and in 1982 made a Commander ofthe Order of the British Empire (CBE).[102][208] Awardsdo not pay the bills, however, and motivated by the needto finance the children’s education and home expenses,in 1982 Hawking determined to write a popular bookabout the universe that would be accessible to the generalpublic.[209][210] Instead of publishing with an academicpress, he signed a contract with Bantam Books, a massmarket publisher, and received a large advance for hisbook.[211][212] Afirst draft of the book, calledABrief His-tory of Time, was completed in 1984.[213]

One of the first messages Hawking produced with hisspeech-generating device was a request for his assistantto help him finish writing A Brief History of Time.[69]Peter Guzzardi, his editor at Bantam, pushed him to ex-plain his ideas clearly in non-technical language, a pro-cess that required multiple revisions from an increasinglyirritated Hawking.[214] The book was published in April1988 in the US and in June in the UK, and proved tobe an extraordinary success, rising quickly to the top of

6 3 CAREER

bestseller lists in both countries and remaining there formonths.[215][216][217] The book was translated into mul-tiple languages,[218] and ultimately sold an estimated 9million copies.[217] Media attention was intense,[218] andNewsweek magazine cover and a television special bothdescribed him as “Master of the Universe”.[219] Successled to significant financial rewards, but also the chal-lenges of celebrity status.[220] Hawking travelled exten-sively to promote his work, and enjoyed partying anddancing into the small hours.[218] He had difficulty re-fusing the invitations and visitors which left limited timefor work and his students.[221] Some colleagues wereresentful of the attention Hawking received, feeling itwas due to his disability.[222][223] He received furtheracademic recognition, including five further honorarydegrees,[219] the Gold Medal of the Royal Astronomi-cal Society (1985),[224] the Paul Dirac Medal (1987)[219]and, jointly with Penrose, the prestigious Wolf Prize(1988).[225] In 1989, he was appointed Member of theOrder of the Companions of Honour (CH).[221] He re-portedly declined a knighthood.[226]

3.3 1990–2000

Hawking with string theorists David Gross and Edward Witten atthe 2001 Strings Conference, TIFR, India

Hawking pursued his work in physics: in 1993 he co-edited a book on Euclidean quantum gravity with GaryGibbons and published a collected edition of his ownarticles on black holes and the Big Bang.[227] In 1994at Cambridge’s Newton Institute, Hawking and Penrosedelivered a series of six lectures, which were publishedin 1996 as “The Nature of Space and Time”.[228] In1997 he conceded a 1991 public scientific wager madewith Kip Thorne and John Preskill of Caltech. Hawk-ing had bet that Penrose’s proposal of a “cosmic cen-sorship conjecture”—that there could be no “naked sin-gularities” unclothed within a horizon—was correct.[229]After discovering his concession might have been pre-mature, a new, more refined, wager was made. Thisspecified that such singularities would occur without ex-tra conditions.[230] The same year, Thorne, Hawking and

Preskill made another bet, this time concerning the blackhole information paradox.[231][232] Thorne and Hawkingargued that since general relativity made it impossible forblack holes to radiate and lose information, the mass-energy and information carried by Hawking radiationmust be “new”, and not from inside the black hole eventhorizon. Since this contradicted the quantum mechan-ics of microcausality, quantum mechanics theory wouldneed to be rewritten. Preskill argued the opposite, thatsince quantum mechanics suggests that the informationemitted by a black hole relates to information that fell inat an earlier time, the concept of black holes given bygeneral relativity must be modified in some way.[233]

Hawking also maintained his public profile, includingbringing science to a wider audience. A film version of ABrief History of Time, directed by Errol Morris and pro-duced by Steven Spielberg, premiered in 1992. Hawkinghad wanted the film to be scientific rather than biograph-ical, but he was persuaded otherwise. The film, whilea critical success, was however not widely released.[234]A popular-level collection of essays, interviews and talktitled Black Holes and Baby Universes and Other Es-says was published in 1993[235] and six-part television se-ries Stephen Hawking’s Universe and companion book ap-peared in 1997. As Hawking insisted, this time the focuswas entirely on science.[236][237]

3.4 2000–present

Hawking continued his writings for a popular audience,publishing The Universe in a Nutshell in 2001,[238] andA Briefer History of Time which he wrote in 2005 withLeonard Mlodinow to update his earlier works to makethem accessible to a wider audience, and God Createdthe Integers, which appeared in 2006.[239] Along withThomas Hertog at the European Organisation for NuclearResearch (CERN) and Jim Hartle, from 2006 on Hawk-ing developed a theory of “top-down cosmology”, whichsays that the universe had not one unique initial state butmany different ones, and therefore that it is inappropriateto formulate a theory that predicts the universe’s currentconfiguration from one particular initial state.[240] Top-down cosmology posits that the present “selects” the pastfrom a superposition of many possible histories. In doingso, the theory suggests a possible resolution of the fine-tuning question.[73][241]

Hawking continued to travel widely, including trips toChile, Easter Island, South Africa, Spain (to receive theFonseca Prize in 2008),[242][243] Canada,[244] and multi-ple trips to the United States.[245] For practical reasons re-lated to his disability, Hawking increasingly travelled byprivate jet, and by 2011 that had become his only modeof international travel.[246]

By 2003, consensus among physicists was growing thatHawking was wrong about the loss of information ina black hole.[247] In a 2004 lecture in Dublin, he con-

7

Hawking on 5 May 2006, during the press conference at theBibliothèque nationale de France to inaugurate the Laboratoryof Astronomy and Particles in Paris and the French release ofhis work God Created the Integers

ceded his 1997 bet with Preskill, but described his own,somewhat controversial solution, to the information para-dox problem, involving the possibility that black holeshave more than one topology.[248][233] In the 2005 pa-per he published on the subject, he argued that the in-formation paradox was explained by examining all thealternative histories of universes, with the informationloss in those with black holes being cancelled out bythose without.[232][249] In January 2014 he called thealleged loss of information in black holes his “biggestblunder”.[250]

As part of another longstanding scientific dispute, Hawk-ing had emphatically argued, and bet, that the Higgs bo-son would never be found.[251] The particle was proposedto exist as part of the Higgs field theory by Peter Higgs in1964. Hawking and Higgs engaged in a heated and publicdebate over the matter in 2002 and again in 2008, withHiggs criticising Hawking’s work and complaining thatHawking’s “celebrity status gives him instant credibilitythat others do not have.”[252] The particle was discoveredin July 2012 at CERN following construction of the LargeHadron Collider. Hawking quickly conceded that he hadlost his bet[253][254] and said that Higgs should win theNobel Prize for Physics,[255] which he did in 2013.

In 2007 Hawking and his daughter Lucy publishedGeorge’s Secret Key to the Universe, a children’s book de-signed to explain theoretical physics in an accessible fash-ion and featuring characters similar to those in the Hawk-ing family.[256] The book was followed by sequels in 2009and 2011.[257]

In 2002, following a UK-wide vote, the BBC includedhim in their list of the 100 Greatest Britons. Hawkingwas awarded the Copley Medal from the Royal Society(2006),[258] the Presidential Medal of Freedom which isAmerica’s highest civilian honour (2009),[259][260] and theRussian Special Fundamental Physics Prize (2013).[261]

Several buildings have been named after him, includingthe Stephen W. Hawking Science Museum in San Sal-vador, El Salvador,[262] the Stephen Hawking Buildingin Cambridge,[263] and the Stephen Hawking Centre atPerimeter Institute in Canada.[264] Appropriately, givenHawking’s association with time, he unveiled the me-chanical “Chronophage” (or time-eating) Corpus Clockat Corpus Christi College Cambridge in September2008.[265][266]

During his career Hawking has supervised 39 successfulPhD students.[267]

As required by Cambridge University regulations, Hawk-ing retired as Lucasian Professor ofMathematics in 2009.Despite suggestions that he might leave the United King-dom as a protest against public funding cuts to basic sci-entific research,[268] Hawking has continued to work asdirector of research at the Cambridge University Depart-ment of Applied Mathematics and Theoretical Physics,and indicated in 2012 that he had no plans to retire.[269]

On 20 July 2015, Stephen Hawking helped launchBreakthrough Initiatives, an effort to search forextraterrestrial life and attempt to answer the question:Are we alone?[270]

4 Views

4.1 Future of humanity

In 2006 Hawking posed an open question on the Internet:“In a world that is in chaos politically, socially and envi-ronmentally, how can the human race sustain another 100years?", later clarifying: “I don’t know the answer. Thatis why I asked the question, to get people to think aboutit, and to be aware of the dangers we now face.”[271]

Hawking has expressed concern that life on Earth isat risk from “a sudden nuclear war, a genetically engi-neered virus or other dangers we have not yet thoughtof”.[272] He views spaceflight and the colonisation ofspace as necessary for the future of humanity.[272][273]Hawking has stated that, given the vastness of the uni-verse, aliens likely exist, but that contact with them shouldbe avoided.[274][275] Hawking has argued superintelligent

8 6 DISABILITY OUTREACH

U.S. President Barack Obama talks with Stephen Hawking in theBlue Room of the White House before a ceremony presenting himand 15 others with the Presidential Medal of Freedom on 12 Au-gust 2009

artificial intelligence could be pivotal in steering human-ity’s fate, stating that “the potential benefits are huge...Success in creating AI would be the biggest event in hu-man history. It might also be the last, unless we learn howto avoid the risks.”[276][277]

Hawking has argued that computer viruses should be con-sidered a new form of life, and has stated that “maybe itsays something about human nature, that the only formof life we have created so far is purely destructive. Talkabout creating life in our own image.”[278]

4.2 Science vs. philosophy

At Google’s Zeitgeist Conference in 2011, Hawking saidthat “philosophy is dead”. He believes that philosophers“have not kept up with modern developments in science”and that scientists “have become the bearers of the torchof discovery in our quest for knowledge”. He said thatphilosophical problems can be answered by science, par-ticularly new scientific theories which “lead us to a newand very different picture of the universe and our placein it”.[279]

4.3 Religion

Hawking has stated that he is “not religious in the normalsense” and he believes that “the universe is governed bythe laws of science. The laws may have been decreed byGod, but God does not intervene to break the laws”.[280]In an interview published in The Guardian, Hawking re-garded the concept of Heaven as a myth, believing thatthere is “no heaven or afterlife” and that such a notion wasa “fairy story for people afraid of the dark”.[203] In 2011,when narrating the first episode of the American televi-sion series Curiosity on the Discovery Channel, Hawkingdeclared:

“We are each free to believe what we want

and it is my view that the simplest explanationis there is no God. No one created the uni-verse and no one directs our fate. This leadsme to a profound realization. There is prob-ably no heaven, and no afterlife either. Wehave this one life to appreciate the grand designof the universe, and for that, I am extremelygrateful.”[281][282]

In September 2014 he joined Starmus Festival as keynotespeaker and declared himself an atheist.[283]

5 Politics

In March 1968, Hawking marched alongside TariqAli and Vanessa Redgrave to protest against theVietnam War.[284] He is a longstanding Labour Partysupporter.[285][286] He recorded a tribute for the 2000Democratic presidential candidate Al Gore,[287] calledthe 2003 invasion of Iraq a "war crime",[286][288]boycotted a conference in Israel because of concernsabout Israel’s policies towards Palestinians,[289][290][291]campaigned for nuclear disarmament,[285][292][286] andhas supported stem cell research,[286][293] universal healthcare,[294] and action to prevent climate change.[292] In Au-gust 2014, Hawking was one of 200 signatories to a letteropposing Scottish independence in the run-up to Septem-ber’s referendum on that issue.[295]

6 Disability outreach

Hawking taking a zero-gravity flight in a "Vomit Comet"

Since the 1990s, Hawking has accepted the mantle ofrole model for disabled people, lecturing and participat-ing in fundraising activities.[296] At the turn of the cen-tury, he and eleven other luminaries signed the Charterfor the Third Millennium on Disability which called ongovernments to prevent disability and protect disabilityrights.[297][298] In 1999 Hawking was awarded the JuliusEdgar Lilienfeld Prize of the American Physical Soci-ety.[299] Motivated by the desire to increase public inter-

9

est in spaceflight and to show the potential of people withdisabilities, in 2007 he participated in zero-gravity flightin a "Vomit Comet", courtesy of Zero Gravity Corpora-tion, during which he experienced weightlessness eighttimes.[272][300][301][302]

In August 2012 Hawking narrated the “Enlightenment”segment of the 2012 Summer Paralympics opening cer-emony.[303] In 2013, the biographical documentary filmHawking, in which Hawking himself is featured, wasreleased.[304] In September 2013, he expressed supportfor the legalisation of assisted suicide for the terminallyill.[305] In August 2014, Hawking accepted the Ice BucketChallenge to promote ALS/MND awareness and raisecontributions for research. As he had pneumonia in 2013,he was advised not to have ice poured over him, buthis children volunteered to accept the challenge on hisbehalf.[306]

7 Appearances in popular media

Further information: Stephen Hawking in popular culture

At the release party for the home video version of the ABrief History of Time, Leonard Nimoy, who had playedSpock on Star Trek, learned that Hawking was interestedin appearing on the show. Nimoy made the necessarycontact, and Hawking played a holographic simulationof himself in an episode of Star Trek: The Next Gen-eration in 1993.[307][308][309] The same year, his synthe-siser voice was recorded for the Pink Floyd song "KeepTalking",[310][235] and in 1999 for an appearance on TheSimpsons.[311] Hawking appeared in documentaries en-titled The Real Stephen Hawking (2001),[298] StephenHawking: Profile (2002) [312] and Hawking (2013), andthe documentary series Stephen Hawking, Master of theUniverse (2008).[313] Hawking has also guest-starred inFuturama[73] and The Big Bang Theory.[314] Hawking al-lowed the use of his copyrighted voice[315][316] in the bi-ographical 2014 film The Theory of Everything.[317]

Hawking has used his fame to advertise products, includ-ing a wheelchair,[298] National Savings,[318] British Tele-com, Specsavers, Egg Banking[319] and Go Compare.[320]He has applied to trademark his name.[321]

8 Awards and honours

Hawking has received numerous awards and honours. Al-ready early in the list, in 1974 he was elected a Fellow ofthe Royal Society (FRS). At that time, his nominationread:

“Hawking has made major contributions to thefield of general relativity. These derive froma deep understanding of what is relevant to

Stephen Hawking being presented by his daughter Lucy Hawkingat the lecture he gave for NASA’s 50th anniversary

physics and astronomy, and especially froma mastery of wholly new mathematical tech-niques. Following the pioneering work of Pen-rose he established, partly alone and partly incollaboration with Penrose, a series of succes-sively stronger theorems establishing the fun-damental result that all realistic cosmologicalmodels must possess singularities. Using simi-lar techniques, Hawking has proved the basictheorems on the laws governing black holes:that stationary solutions of Einstein’s equationswith smooth event horizonsmust necessarily beaxisymmetric; and that in the evolution and in-teraction of black holes, the total surface areaof the event horizons must increase. In collab-oration with G. Ellis, Hawking is the author ofan impressive and original treatise on “Space-time in the Large”.

The citation continues:

“Other important work by Hawking relatesto the interpretation of cosmological observa-tions and to the design of gravitational wavedetectors.”[15]

9 Bibliography

9.1 Selected academic works

• Hawking, S. W.; Penrose, R. (1970). “The Singu-larities of Gravitational Collapse and Cosmology”.Proceedings of the Royal Society A: Mathematical,Physical and Engineering Sciences 314 (1519):529–548. Bibcode:1970RSPSA.314..529H.doi:10.1098/rspa.1970.0021.

• Hawking, S. (1971). “Gravitational Ra-diation from Colliding Black Holes”.

10 11 REFERENCES

Physical Review Letters 26 (21): 1344–1346. Bibcode:1971PhRvL..26.1344H.doi:10.1103/PhysRevLett.26.1344.

• Hawking, S.W. (1972). “Black holes in general rel-ativity”. Communications in Mathematical Physics25 (2): 152–166. Bibcode:1972CMaPh..25..152H.doi:10.1007/BF01877517.

• Hawking, S. W. (1974). “Black holeexplosions?". Nature 248 (5443): 30–31. Bibcode:1974Natur.248...30H.doi:10.1038/248030a0.

• Hawking, S.W. (1982). “The developmentof irregularities in a single bubble inflation-ary universe”. Physics Letters B 115 (4):295–297. Bibcode:1982PhLB..115..295H.doi:10.1016/0370-2693(82)90373-2.

• Hartle, J.; Hawking, S. (1983). “Wave functionof the Universe”. Physical Review D 28 (12):2960–2975. Bibcode:1983PhRvD..28.2960H.doi:10.1103/PhysRevD.28.2960.

• Hawking, S. (2005). “Informationloss in black holes”. Physical Re-view D 72 (8): 084013. arXiv:hep-th/0507171. Bibcode:2005PhRvD..72h4013H.doi:10.1103/PhysRevD.72.084013.

9.2 Popular publications

• A Brief History of Time (1988)[257]

• Black Holes and Baby Universes and Other Essays(1993)[322]

• The Universe in a Nutshell (2001)[257]

• On The Shoulders of Giants (2002)[257]

• A Briefer History of Time (2005)[257]

• God Created the Integers: The Mathematical Break-throughs That Changed History (2005)[257]

• The Grand Design (2010)[257]

• My Brief History (2013)[257]

9.3 Children’s fiction

Co-written with his daughter Lucy.

• George’s Secret Key to the Universe (2007)[257]

• George’s Cosmic Treasure Hunt (2009)[257]

• George and the Big Bang (2011)[257]

9.4 Films and series

• A Brief History of Time (1992)[323]

• Stephen Hawking’s Universe (1997)[324][93]

• Hawking – BBC television film (2004) starringBenedict Cumberbatch

• Horizon: The Hawking Paradox (2005)[325]

• Masters of Science Fiction (2007)[326]

• Stephen Hawking and the Theory of Everything(2007)

• Stephen Hawking: Master of the Universe (2008)[327]

• Into the Universe with Stephen Hawking (2010)[328]

• Brave New World with Stephen Hawking (2011)[329]

• Stephen Hawking’s Grand Design (2012)[330]

• The Big Bang Theory (2012)

• Stephen Hawking: A Brief History of Mine(2013)[331]

• The Theory of Everything – Feature film (2014) star-ring Eddie Redmayne[332]

10 See also

• Gibbons–Hawking ansatz

• Gibbons–Hawking effect

• Gibbons–Hawking space

• Gibbons–Hawking–York boundary term

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[155] White & Gribbin 2002, pp. 115–16.

[156] Hawking, Stephen; Penrose, Roger (1970). “TheSingularities of Gravitational Collapse and Cosmol-ogy”. Proceedings of the Royal Society A 314(1519): 529–548. Bibcode:1970RSPSA.314..529H.doi:10.1098/rspa.1970.0021.

[157] Ferguson 2011, p. 49.

[158] Ferguson 2011, pp. 65–67.

[159] Larsen 2005, p. 38.

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[163] R. D. Blandford (30 March 1989). “Astrophysical BlackHoles”. In S. W. Hawking and W. Israel. Three HundredYears of Gravitation. CambridgeUniversity Press. p. 278.ISBN 978-0-521-37976-2.

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[170] Hawking, Stephen W. (1974). “Black holeexplosions?". Nature 248 (5443): 30–31.Bibcode:1974Natur.248...30H. doi:10.1038/248030a0.

[171] Hawking, Stephen W. (1975). “Particle creation byblack holes”. Communications in Mathematical Physics43 (3): 199–220. Bibcode:1975CMaPh..43..199H.doi:10.1007/BF02345020.

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[233] Preskill, John. “John Preskill’s comments about StephenHawking’s concession”. Retrieved 29 February 2012.

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[236] Ferguson 2011, p. 189.

[237] Larsen 2005, p. 97.

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[246] Ferguson 2011, p. 197,269.

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[284] “Photographs by Lewis Morley”. The Guardian. 7September 2013. Retrieved 21 January 2015.

[285] White & Gribbin 2002, p. 195.

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17

[291] Harriet Sherwood and Matthew Kalman in Jerusalem (8May 2013). “Stephen Hawking joins academic boycott ofIsrael”. The Guardian. Retrieved 8 May 2013.

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[308] Larsen 2005, pp. 93–94.

[309] Okuda & Okuda 1999, p. 380.

[310] Larsen 2005, pp. xiii, 94.

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[312] Ferguson 2011, p. 221.

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18 12 EXTERNAL LINKS

11.1 Sources

• Hawking, Stephen (2013). 0-345-53913-3My BriefHistory Check |url= scheme (help). Bantam. ISBN978-0-345-53528-3. Retrieved 9 September 2013.

• Baird, Eric (2007). Relativity in Curved Space-time: LifeWithout Special Relativity. Chocolate TreeBooks. ISBN 978-0-9557068-0-6.

• Boslough, John (1989). Stephen Hawking’s universe:an introduction to themost remarkable scientist of ourtime. Avon Books. ISBN 978-0-380-70763-8. Re-trieved 4 March 2012.

• Ferguson, Kitty (2011). Stephen Hawking: His Lifeand Work. Transworld. ISBN 978-1-4481-1047-6.

• Gibbons, Gary W.; Hawking, Stephen W.; Siklos,S.T.C., eds. (1983). The Very early universe: pro-ceedings of the Nuffield workshop, Cambridge, 21June to 9 July, 1982. Cambridge University Press.ISBN 0-521-31677-4.

• Hawking, Jane (2007). Travelling to Infinity: MyLife With Stephen. Alma. ISBN 978-1-84688-115-2.

• Hawking, StephenW. (1994). Black holes and babyuniverses and other essays. Bantam Books. ISBN978-0-553-37411-7.

• Hawking, Stephen W.; Ellis, George F.R. (1973).The Large Scale Structure of Space-Time. Cam-bridge University Press. ISBN 978-0-521-09906-6.

• Hawking, Stephen W. (1992). Stephen Hawking’s Abrief history of time: a reader’s companion. BantamBooks. ISBN 978-0-553-07772-8.

• Hawking, StephenW.; Israel, Werner (1989). ThreeHundred Years of Gravitation. Cambridge Univer-sity Press. ISBN 978-0-521-37976-2.

• Larsen, Kristine (2005). Stephen Hawking: a biog-raphy. ISBN 978-0-313-32392-8.

• Mialet, Hélène (2003). “Is the end in sight for theLucasian chair? Stephen Hawking as MillenniumProfessor”. In Knox, Kevin C. & Noakes, Richard.From Newton to Hawking: A History of CambridgeUniversity’s Lucasian Professors of Mathematics.Cambridge University Press. pp. 425–460. ISBN978-0-521-66310-6.

• Mialet, Hélène (2012). Hawking Incorporated:Stephen Hawking and the Anthropology of the Know-ing Subject. University of Chicago Press. ISBN 978-0-226-52226-5.

• Okuda, Michael; Okuda, Denise (1999). The Startrek encyclopedia: a reference guide to the future.Pocket Books. ISBN 978-0-671-53609-1.

• Pickover, Clifford A. (2008). Archimedes to Hawk-ing: laws of science and the great minds behind them.Oxford University Press. ISBN 978-0-19-533611-5. Retrieved 4 March 2012.

• White, Michael; Gribbin, John (2002). StephenHawking: A Life in Science (2nd ed.). NationalAcademies Press. ISBN 978-0-309-08410-9.

• Yulsman, Tom (2003). Origins: the quest for ourcosmic roots. CRC Press. ISBN 978-0-7503-0765-9.

12 External links• Official website

• Stephen Hawking at the Internet Movie Database

• Stephen Hawking (character) at the Internet MovieDatabase

• Stephen Hawking on Facebook

• Portraits of Stephen William Hawking at theNational Portrait Gallery, London

• Archival material relating to Stephen Hawking listedat the UK National Archives

• Stephen Hawking collected news and commentaryat The New York Times

• Stephen Hawking’s publications indexed by theScopus bibliographic database, a service providedby Elsevier.

• Stephen Hawking at Encyclopædia Britannica

• Appearances on C-SPAN

• Works by or about Stephen Hawking in libraries(WorldCat catalog)

• Stephen Hawking collected news and commentaryat The Guardian

• Stephen Hawking at TED

• “Stephen Hawking at 70: Exclusive interview”. NewScientist. 4 January 2012.

• Stephen Hawking sings => “Galaxy Song” (02:43)on YouTube - a classic song.

19

13 Text and image sources, contributors, and licenses

13.1 Text• Stephen Hawking Source: https://en.wikipedia.org/wiki/Stephen_Hawking?oldid=683730159 Contributors: AxelBoldt, Chenyu, Kpjas,

General Wesc, Mav, 0, The Anome, Tarquin, Malcolm Farmer, Css, RK, Andre Engels, Danny, Hajhouse, XJaM, Novalis, William Avery,Roadrunner, Ben-Zin~enwiki, Mswake, Hbw, Heron, Rsabbatini, Robot5005, Mintguy, Montrealais, Olivier, Stevertigo, Rbrwr, Nevil-ley, Frecklefoot, Edward, Bdesham, Patrick, Kchishol1970, JohnOwens, Michael Hardy, Gabbe, Ixfd64, Tango, Phoe6, TakuyaMurata,GTBacchus, Skysmith, Paul A, Minesweeper, Alfio, Dgrant, Looxix~enwiki, Mdebets, Mortene, Ahoerstemeier, KAMiKAZOW, AndersFeder, Theresa knott, Den fjättrade ankan~enwiki, Jdforrester, Julesd, Salsa Shark, Sir Paul, Rossami, TraxPlayer, Kwekubo, Andres, Ev-ercat, Samw, John K, Oliver Crow, Thegline, Ilyanep, Conti, Adam Bishop, Timwi, Janko, Przepla, RickK, N-true, Hydnjo, Geary, DanielQuinlan, Rednblu, Doradus, Piolinfax, Jogloran, Wik, Zoicon5, Steinsky, DJ Clayworth, Markhurd, Peregrine981, Tpbradbury, Mrand,Furrykef, Saltine, Miterdale, Ed g2s, Floydian, Thomasedavis, Bevo, Prisonblues, Raul654, Ortonmc, Pakaran, Proteus, Johnleemk, Flock-meal, BenRG, Carbuncle, Mprf, Jeffq, Owen, Phil Boswell, Chuunen Baka, 2toise, Sjorford, Bearcat, Robbot, Dale Arnett, Sander123, Pig-sonthewing, Fredrik, Chris 73, Jredmond, Kristof vt, Biggins, RedWolf, Donreed, Campdavid, Moncrief, Stephan Schulz, Nurg, Lowellian,Gandalf61, Sverdrup, Othersider, Academic Challenger, PxT, Premeditated Chaos, Meelar, Timrollpickering, DHN, Hadal, JackofOz,Wereon, Robinh, Ungvichian, Ianml, Naelphin, Mushroom, Aggelophoros, Lupo, Diberri, Xanzzibar, Dmn, Oobopshark, Mattflaschen,Dina, Jooler, David Gerard, Ncox, Marekpetrik, Aomarks, Giftlite, Jacoplane, Barbara Shack, ShaneKing, Mblaze, Geeoharee, Ævar Arn-fjörð Bjarmason, Tom harrison, Lupin, Ferkelparade, Dersen, Ausir, Xerxes314, Wwoods, Everyking, Curps, Henry Flower, Gamaliel,BalthCat, Snap Davies, Wikibob, Home Row Keysplurge, Cantus, Duncharris, Beardo, Andris, Yekrats, Tom-, Bluejay Young, Shane Lin,AlistairMcMillan, Eequor, Solipsist, Phongn, Adam McMaster, Jackol, SWAdair, Golbez, KirbyMeister, Wmahan, Ato, Auximines, Paul-moloney, Utcursch, Andycjp, Bact, Geni, Mendel, CryptoDerk, Workman161, Jpkoester1, Abu badali, Slowking Man, Quadell, Juntung,Indyfitz, Blankfaze, Antandrus, BozMo, Beland, Ravikiran r, Kaldari, Jossi, Ehsan~enwiki, Mikko Paananen, Zerbey, RetiredUser2, Jasco,Bumm13, Thincat, Kevin B12, Tomruen, Bodnotbod, Halo, Ludootje, Necrothesp, Icairns, Jareha, Two Bananas, Lumidek, Sergey~enwiki,Fintor, Mschlindwein, Ukexpat, AmRadioHed, Djyang~enwiki, Jh51681, Sonett72, Kadambarid, M1ss1ontomars2k4, Trevor MacInnis,Canterbury Tail, Flex, The stuart, Gazpacho, Chris Howard, D6, KeyStorm, Simonides, Freakofnurture, Fede2, Bonalaw, Archer3, CALR,DanielCD, JTN, WOW, A-giau, Discospinster, William Pietri, Rich Farmbrough, Vague Rant, H0riz0n, Supercoop, Igorivanov~enwiki,Kenj0418, Randomuser0101, Pjacobi, Rsanchezsaez, Inkypaws, Andrewferrier, Florian Blaschke, Tsumetai, Bufordsmegma, Smyth,1pezguy, TigerZukeX, Bender235, ESkog, MattTM, Kjoonlee, Kaisershatner, Violetriga, Evice, BjarteSorensen, Billlion, Brian0918,RJHall, JustPhil, Mattisgoo, Zenohockey, Bluap, Kwamikagami, Mwanner, Surachit, Tverbeek, Aude, Shanes, Sietse Snel, RoyBoy,Bookofjude, Orlady, Gershwinrb, Orestes~enwiki, Pablo X, CDN99, Thuresson, Bobo192, Deathawk, 23skidoo, Smalljim, Mpk, Viriditas,Cmdrjameson, NightDragon, Dungodung, Maurreen, Guiltyspark, Mark Musante, Franl, VBGFscJUn3, Townmouse, Anonymous Cow,Rje, Twobells, DCEdwards1966, Helix84, Krellis, Pearle, Benbread, Merope, Jcrocker, Knucmo2, Danski14, Alansohn, Gary, Jhertel, Gar-gaj, Vslashg, Mo0, Jamyskis, Mr Adequate, Keenan Pepper, Andrewpmk, Dachannien, Craigy144, Riana, Ashley Pomeroy, Axl, MarkGal-lagher, SlimVirgin, Scarecroe, Water Bottle, Julianortega, Lightdarkness, InShaneee, Cdc, Plange, Malo, Titanium Dragon, PeteVerdon,Rwendland, Bart133, Snowolf, Historian, Laundry, Wtmitchell, Velella, TheRealFennShysa, Gbeeker, Bbsrock, TaintedMustard, Cburnett,Stephan Leeds, HenkvD, Evil Monkey, Harej, Tony Sidaway, RainbowOfLight, Drat, Dirac1933, Sciurinæ, Poseidon^3, H2g2bob, Death-phoenix, BlastOButter42, Cmprince, Ianblair23, Pauli133, Dr. Schnellkopf, Mattbrundage, Elpoca, Cxxl, Panchurret, Fryede, RyanGer-bil10, Dismas, Oleg Alexandrov, Jblogs, Pcpcpc, FrancisTyers, Richard Arthur Norton (1958- ), Kelly Martin, Jeffrey O. 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20 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

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Carver, Figmillenium, Dendodge, Lostfr, Martin451, Leafyplant, SpockisRock,Brian Eisley, Johaven, Lordlee, LeaveSleaves, Ichigo9559, RanMan08, Legolas536, Bcody80, Officerkc, Mannafredo, Snowbot, Blod-dyfriday, Duncan.Hull, K!netic, Natural Philosopher, Maxim, Blueeyedmaiden, Nigelpwsmith, Llamahunter, TJollans, Jkerrigan, Arktu-ruz, Kacser, Nikosgreencookie, Pyroven, Jaqen, Lerdthenerd, Bashereyre, Dirkbig, Finngall, Tarantula Woman, Wolfrock, Jamesbondahh,Wilbur2012, DisassemblyOfReason, 9allenride9, Enviroboy, Benaravo, Thisismyrofl, Henceaxis, Gspinoza, Jeffutz, Rcb1, Zarek, DickShane, Nagy, Zerohero52, Matrixoleadership, Stanley Balboa, Planet-man828, Andysmith12, Burgercat, Snip3rNife, Neparis, Glitchrf,GirasoleDE, LilahTovah, JulesN, SieBot, Brenont, Nubiatech, Tresiden, Graham Beards, WereSpielChequers, Mbcellphone, Cooky-cy,Nevzatcizmeci, Mundo tarantino, Archangelseal, Ninington, Krawi, Gerakibot, Theopapada, Plinkit, Mungo Kitsch, Rob.bastholm, Cal-tas, Matthew Yeager, PolocDoc, Xymmax, June w, Albanman, MATT DEMAYPOO, Crash Underride, Stratman07, Industrialg33k, Jrun,Simmonds001, Lethaldeath, Utternutter, TheTruth300, Abhishikt, Tomaskas, Aillema, Tiptoety, Exert, Humanityisthedisease, Arbor toSJ, Dfelix555, Mjeromee, DirkHoffmann, Mimihitam, Arthur Smart, Macdp, Faradayplank, Outhwest, Lightmouse, Maddenplayer92,Tombomp, Zeleritas, TheRoonster, DivineBurner, OKBot, Pediainsight, FghIJklm, Barryz1, Aumnamahashiva, MadmanBot, StaticGull,Dodger67, Sean.hoyland, Mygerardromance, Hamiltondaniel, Realm of Shadows, OboeCrack, WikiLaurent, Ledzeppelin21~enwiki, Flo-rentino floro, Jza84, Pinkadelica, Wjemather, Gantuya eng, Unusual Cheese, Finetooth, Thorncrag, Tripod86, Crazy-dancing, Vanishe-dUser sdu9aya9fs787sads, Troy 07, TheCatalyst31, Faithlessthewonderboy, Atif.t2, Ricklaman, Dp67, Martarius, ClueBot, Mariordo,Binksternet, Artichoker, Snigbrook, The Thing That Should Not Be, NancyHeise, All Hallow’s Wraith, Newzild, QueenAdelaide, Mike-Vitale, Pi zero, Gaia Octavia Agrippa, Arakunem, Der Golem, HiltonLange, Cube lurker, Night Goblin, SuperHamster, Boing! saidZebedee, Hyerk, Hotdogwheel, CounterVandalismBot, Spetnik, Ben Bender, Blanchardb, LizardJr8, TypoBoy, Otolemur crassicauda-

13.2 Images 21

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22 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

• File:Physicist_Stephen_Hawking_in_Zero_Gravity_NASA.jpg Source: https://upload.wikimedia.org/wikipedia/commons/0/08/Physicist_Stephen_Hawking_in_Zero_Gravity_NASA.jpg License: Public domain Contributors: http://www.flickr.com/photos/39735679@N00/475109138/ / http://mediaarchive.ksc.nasa.gov/detail.cfm?mediaid=31873 Original artist: Jim Campbell/Aero-NewsNetwork

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