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Sunday, February 1, 2015

Stephen Hawking


From Wikipedia, the free encyclopedia

Stephen Hawking
CH CBE FRS FRSA
black and white photo of Hawking in a chair, in an office.
Hawking at NASA, 1980s
Born Stephen William Hawking
(1942-01-08) 8 January 1942 (age 73)
Oxford, England
Residence United Kingdom
Fields
Institutions
Alma mater
Thesis Properties of Expanding Universes (1965[2])
Doctoral advisor Dennis Sciama[3]
Other academic advisors Robert Berman[citation needed]
Doctoral students
Known for
Notable awards
Spouse
  • Jane Wilde
    (m. 1965–1995, divorced)
  • Elaine Mason
    (m. 1995–2006, divorced)
Children
  • Robert (b. 1967)
  • Lucy (b. 1970)
  • Timothy (b. 1979)
Website
hawking.org.uk

Stephen William Hawking CH CBE FRS FRSA (Listeni/ˈstvən ˈhɔːkɪŋ/; born 8 January 1942) is an English theoretical physicist, cosmologist, author and Director of Research at the Centre for Theoretical Cosmology within the University of Cambridge.[15][16] His scientific works include 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. Hawking was the first to set forth a cosmology explained by a union of the general theory of relativity and quantum mechanics. He is a vigorous supporter of the many-worlds interpretation of quantum mechanics.[17][18][19]

Hawking is an Honorary Fellow of the Royal Society of Arts, 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. Hawking was the Lucasian Professor of Mathematics at the University of Cambridge between 1979 and 2009.

Hawking has achieved success with works of popular science in which he discusses his own theories and cosmology in general; his A Brief History of Time stayed on the British Sunday Times best-sellers list for a record-breaking 237 weeks.

Hawking suffers from a rare early-onset slow-progressing form of amyotrophic lateral sclerosis (ALS), or motor neurone disease, that has gradually paralysed him over the decades.[20] He communicates using a single cheek muscle attached to a speech-generating device. Hawking married twice and has three children.

Family

Parents

Hawking was born on 8 January 1942[1] in Oxford, England, to Frank and Isobel Hawking.[21][22] His mother was Scottish.[23] Despite their families' financial constraints, both parents attended the University of Oxford, where Frank studied medicine and Isobel, Philosophy, Politics and Economics.[22] The two met shortly after the beginning of the Second World War at a medical research institute where she was working as a secretary and he as a medical researcher.[22][24] They lived in Highgate, but as London was being bombed in those years, Isobel went to Oxford to give birth in greater safety.[25] Hawking has two younger sisters, Philippa and Mary, and an adopted brother, Edward.[26]

In 1950, when his father became head of the division of parasitology at the National Institute for Medical Research, Hawking and his family moved to St Albans, Hertfordshire.[27][28] In St Albans, the family were considered highly intelligent and somewhat eccentric;[27][29] meals were often spent with each person silently reading a book.[27] They lived a frugal existence in a large, cluttered, and poorly maintained house, and travelled in a converted London taxicab.[30][31] During one of Hawking's father's frequent absences working in Africa,[32] the rest of the family spent four months in Majorca visiting his mother's friend Beryl and her husband, the poet Robert Graves.[33]

Marriages

When Hawking was a graduate student at Cambridge, his relationship with a friend of his sister, Jane Wilde, whom he had met shortly before his diagnosis with motor neurone disease, continued to develop. The couple were engaged in October 1964[34][35]—Hawking later said that the engagement gave him "something to live for"[36]—and the two were married on 14 July 1965.[37]

During their first years of marriage, Jane lived in London during the week as she completed her degree, and they travelled to the United States several times for conferences and physics-related visits. The couple had difficulty finding housing that was within Hawking's walking distance to the Department of Applied Mathematics and Theoretical Physics (DAMTP). Jane began a PhD programme, and a son, Robert, was born in May 1967.[38][39] A daughter, Lucy, was born in 1970.[40] A third child, Timothy, was born in April 1979.[41]

Hawking rarely discussed his illness and physical challenges, even—in a precedent set during their courtship—with Jane.[42] His disabilities meant that the responsibilities of home and family rested firmly on his wife's increasingly overwhelmed shoulders, leaving him more time to think about physics.[43] When in 1974 he was appointed to a position in Pasadena, California, Jane proposed that a graduate or post-doctoral student live with them and help with his care. Hawking accepted, and Bernard Carr travelled with them as the first of many students who fulfilled this role.[44][45] The family spent a generally happy and stimulating year in Pasadena.[46]

In the late 1960s, Hawking's physical abilities declined once more: he began to use crutches and ceased lecturing regularly.[47] As he slowly lost the ability to write, he developed compensatory visual methods, including seeing equations in terms of geometry.[48][49] The physicist Werner Israel later compared the achievements to Mozart composing an entire symphony in his head.[50][51] Hawking was, however, fiercely independent and unwilling to accept help or make concessions for his disabilities. He preferred to be regarded as "a scientist first, popular science writer second, and, in all the ways that matter, a normal human being with the same desires, drives, dreams, and ambitions as the next person."[52] Jane Hawking later noted that "Some people would call it determination, some obstinacy. I've called it both at one time or another."[53] He required much persuasion to accept the use of a wheelchair at the end of the 1960s,[54] but ultimately became notorious for the wildness of his wheelchair driving.[53] Hawking was a popular and witty colleague, but his illness as well as his reputation for brashness and intelligence distanced him from some.[55]

Hawking returned to Cambridge in 1975 to a new home, a new job—as reader. Don Page, with whom Hawking had begun a close friendship at Caltech, arrived to work as the live-in graduate student assistant. With Page's help and that of a secretary, Jane's responsibilities were reduced so she could return to her thesis and her new interest in singing.[56]

By December 1977, Jane had met organist Jonathan Hellyer Jones when singing in a church choir. Hellyer Jones became close to the Hawking family, and by the mid-1980s, he and Jane had developed romantic feelings for each other.[57][58][59] According to Jane, her husband was accepting of the situation, stating "he would not object so long as I continued to love him."[57][60][61] Jane and Hellyer Jones determined not to break up the family and their relationship remained platonic for a long period.[62]

Hawking's speech deteriorated, and by the late 1970s he could only be understood by his family and closest friends. To communicate with others, someone who knew him well would translate his speech into intelligible speech.[63] Spurred by a dispute with the university over who would pay for the ramp needed for him to enter his workplace, Hawking and his wife campaigned for improved access and support for those with disabilities in Cambridge,[64][65] including adapted student housing at the university.[66] In general, however, Hawking had ambivalent feelings about his role as a disability rights champion: while wanting to help others, he sought to detach himself from his illness and its challenges.[67] His lack of engagement led to some criticism.[68]

During a visit to the European Organisation for Nuclear Research on the border of France and Switzerland in the mid-1985, Hawking contracted pneumonia which in his condition was life-threatening; he was so ill that Jane was asked if life support should be terminated. She refused but the consequence was a tracheotomy, which would require round-the-clock nursing care, and remove what remained of his speech.[69][70] The National Health Service would pay for a nursing home but Jane was determined that he would live at home. The cost of the care was funded by an American foundation.[71][72] Nurses were hired for the three shifts required to provide the round-the-clock support he required. One of those employed was Elaine Mason, who was to become Hawking's second wife.[73] For his communication, Hawking initially raised his eyebrows to choose letters on a spelling card.[74] But he then received a computer program called the "Equalizer" from Walt Woltosz. In a method he uses to this day, using a switch he selects phrases, words or letters from a bank of about 2500–3000 that are scanned.[75][76] The program was originally run on a desktop computer. However, Elaine Mason's husband, David, a computer engineer, adapted a small computer and attached it to his wheelchair.[77] Released from the need to use somebody to interpret his speech, Hawking commented that "I can communicate better now than before I lost my voice."[78] The voice he uses has an American accent and is no longer produced.[79][80] Despite the availability of other voices, Hawking has retained his original voice, saying that he prefers his current voice and identifies with it.[81] At this point, Hawking activated a switch using his hand and could produce up to 15 words a minute.[82] Lectures were prepared in advance and were sent to the speech synthesiser in short sections to be delivered.[79]

Hawking's marriage had been strained for many years. Jane felt overwhelmed by the intrusion into their family life of the required nurses and assistants. The impact of his celebrity was challenging for colleagues and family members, and in one interview Jane described her role as "simply to tell him that he's not God".[83][84] Hawking's views of religion also contrasted with her strong Christian faith, and resulted in tension.[85][84][86] In the late 1980s Hawking had grown close to one of his nurses, Elaine Mason, to the dismay of some colleagues, caregivers and family members who were disturbed by her strength of personality and protectiveness.[87] Hawking told Jane that he was leaving her for Mason,[88] and departed the family home in February 1990.[89] After his divorce from Jane in the spring of 1995, Hawking married Mason in September,[90][89] declaring "It's wonderful—I have married the woman I love."[91]

In 1999 Jane Hawking published a memoir, Music to Move the Stars, describing her marriage to Hawking and its breakdown. Its revelations caused a sensation in the media, but as was his usual practice regarding his personal life, Hawking made no public comment except to say that he did not read biographies about himself.[92] After his second marriage, Hawking's family felt excluded and marginalised from his life.[86][93] For a period of about five years in the early 2000s, his family and staff became increasingly worried that he was being physically abused.[93][94] Police investigations took place, but were closed as Hawking refused to make a complaint.[93][95][96]

In 2006 Hawking and Elaine quietly divorced,[97][98] following which Hawking resumed closer relationships with Jane, his children, and grandchildren.[98][84] Reflecting this happier period, a revised version of Jane's book called Travelling to Infinity, My Life with Stephen appeared in 2007.[93]

Education

Primary and secondary

Hawking began his schooling at the Byron House School; he later blamed its "progressive methods" for his failure to learn to read while at the school.[27] 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.[33][99]

He attended Radlett School for a year[99] and from September 1952, St Albans School.[100] The family placed a high value on education.[27] Hawking's father wanted his son to attend the well-regarded 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.[101][102] A positive consequence was that Hawking remained with a close group of friends with whom he enjoyed board games, the manufacture of fireworks, model aeroplanes and boats,[103] and long discussions about Christianity and extrasensory perception.[104] From 1958, and with the help of the mathematics teacher Dikran Tahta, they built a computer from clock parts, an old telephone switchboard and other recycled components.[105][106] Although at school he was known as "Einstein," Hawking was not initially successful academically.[107] With time, he began to show considerable aptitude for scientific subjects, and inspired by Tahta, decided to study mathematics at university.[108][109][110] Hawking's father advised him to study medicine, concerned that there were few jobs for mathematics graduates.[111] He wanted Hawking 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.[112][113]

Undergraduate

Hawking began his university education at the University of Oxford in October 1959 at the age of 17.[114] For the first 18 months, he was bored and lonely: he was younger than many other students, and found the academic work "ridiculously easy".[115][116] 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."[117] A change occurred during his second and third year when, according to Berman, Hawking made more effort "to be one of the boys". He developed into a popular, lively and witty college member, interested in classical music and science fiction.[114]
Part of the transformation resulted from his decision to join the college Boat Club, where he coxed a rowing team.[118][119] The rowing trainer at the time noted that Hawking cultivated a daredevil image, steering his crew on risky courses that led to damaged boats.[120][118] Hawking has estimated that he studied about a thousand 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 honours degree was a condition of acceptance for his planned graduate study in cosmology at the University of Cambridge.[121][122] Anxious, he slept poorly the night before the examinations, and the final result was on the borderline between first- and second-class honours, making a viva (oral examination) necessary.[122][123] Hawking was concerned that he was viewed as a lazy and difficult student, so when asked at the oral to describe his future 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."[122][124] 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".[122] After receiving a first-class BA (Hons.) degree, and following a trip to Iran with a friend, he began his graduate work at Trinity Hall, Cambridge, in October 1962.[125][126]

Graduate

Hawking's first year as a doctoral student[2] 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 noted astronomer Fred Hoyle,[127][128] and he found his training in mathematics inadequate for work in general relativity and cosmology.[129] He also struggled with his health.
Hawking had experienced increasing clumsiness during his final year at Oxford, including a fall on some stairs and difficulties when rowing.[130][131] The problems worsened, and his speech became slightly slurred; his family noticed the changes when he returned home for Christmas and medical investigations were begun.[132][133] The diagnosis of motor neurone disease came when Hawking was 21, in 1963. At the time, doctors gave him a life expectancy of two years.[134][135] After his diagnosis, Hawking fell into a depression; though his doctors advised that he continue with his studies, he felt there was little point.[136] Despite the disease's progression—Hawking had difficulty walking without support, and his speech was almost unintelligible—he now returned to his work with enthusiasm.[137] Hawking started developing a reputation for brilliance and brashness when he publicly challenged the work of Fred Hoyle and his student Jayant Narlikar at a lecture in June 1964.[138][139]

When Hawking began his graduate studies, there was much debate in the physics community about the prevailing theories of the creation of the Universe: the Big Bang and the Steady State theories.[140] 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 wrote his thesis on this topic.[141] There were other positive developments: Hawking received a research fellowship at Gonville and Caius College.[37] He obtained his doctorate of philosophy degree in March 1966,[142] and his essay entitled "Singularities and the Geometry of Space-Time" shared top honours with one by Penrose to win that year's prestigious Adams Prize.[143][142]

Career

1966–1975

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.[144][145] 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.[146][147][148] In 1969, Hawking accepted a specially created Fellowship for Distinction in Science to remain at Caius.[149]

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.[150] With James M. Bardeen and Brandon Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics.[151] To Hawking's irritation, Jacob Bekenstein, a graduate student of John Wheeler, went further—and ultimately correctly—to apply thermodynamic concepts literally.[152][153] In the early 1970s, Hawking's work with Carter, Werner Israel and David C. Robinson strongly supported Wheeler's no-hair theorem that no matter what the original material from which a black hole is created it can be completely described by the properties of mass, electrical charge and rotation.[154][155] His essay titled "Black Holes" won the Gravity Research Foundation Award in January 1971.[156] Hawking's first book, The Large Scale Structure of Space-Time. written with George Ellis, was published in 1973.[157]

Beginning in 1973, Hawking moved into the study of quantum gravity and quantum mechanics.[158][157] 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.[159] To Hawking's annoyance, his much-checked calculations produced findings that contradicted his second law, which claimed black holes could never get smaller,[160] and supported Bekenstein's reasoning about their entropy.[161][159] 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.[162][163][164] Initially, Hawking radiation was controversial. However by the late 1970s and following the publication of further research, the discovery was widely accepted as a significant breakthrough in theoretical physics.[165][166][167] In March 1974, a few weeks after the announcement of Hawking radiation, Hawking was invested as a Fellow of the Royal Society, one of the youngest scientists to be so honoured.[168][169]

Hawking was appointed to the Sherman Fairchild Distinguished visiting professorship at the California Institute of Technology (Caltech) in 1970. He worked with a friend on the faculty, Kip Thorne,[170] and engaged him in a scientific wager about whether the dark star Cygnus X-1 was a black hole. The wager was a surprising "insurance policy" against the proposition that black holes did not exist.[171] Hawking acknowledged that he had lost the bet in 1990, which was the first of several that he was to make with Thorne and others.[172] Hawking has maintained ties to Caltech, spending a month there almost every year since this first visit.[173]

1975–1990

Hawking returned to Cambridge in 1975 to a more advanced academic senior position —as reader. The mid to late 1970s were a period of growing public interest in black holes and of the physicist who was studying them. Hawking was regularly interviewed for print and television.[174][175] He also received increasing academic recognition of his work.[41] In 1975 he was awarded both the Eddington Medal and the Pius XI Gold Medal, and in 1976 the Dannie Heineman Prize, the Maxwell Prize and the Hughes Medal.[176][177] Hawking was appointed a professor with a chair in gravitational physics in 1977.[57] The following year he received the Albert Einstein Medal and an honorary doctorate from the University of Oxford.[35][41]

In the late 1970s Hawking was elected Lucasian Professor of Mathematics at the University of Cambridge.[41][178] His inaugural lecture as Lucasian Professor of Mathematics was titled: "Is the end in sight for Theoretical Physics" and proposed N=8 Supergravity as the leading theory to solve many of the outstanding problems physicists were studying.[179] Hawking's promotion coincided with a health crisis which led to Hawking accepting, albeit reluctantly, some nursing services at home.[180] 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.[181] 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.[182][183]

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.[184] Following a conference in Moscow in October 1981, Hawking and Gary Gibbons organized a three-week Nuffield Workshop in the summer of 1982 on the Very Early Universe at Cambridge University, which focused mainly on inflation theory.[185][186][187] 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.[188][189] He 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.[190] 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.[191][192] 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."[193]

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?"[194] In his early work, Hawking spoke of God in a metaphorical sense. In A Brief History of Time he wrote: "If we discover a complete theory, it would be the ultimate triumph of human reason—for then we should know the mind of God."[195] In the same book he suggested the existence of God was unnecessary to explain the origin of the Universe. Later discussions with Neil Turok led to the realisation that it is also compatible with an open universe.[196]

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.[197] A paper by Don Page and independent calculations by Raymond Laflamme led Hawking to withdraw this concept.[198] Honours continued to be awarded: in 1981 he was awarded the American Franklin Medal,[199] and in 1982 made a Commander of the Order of the British Empire (CBE).[89][200] Awards do not pay the bills, however, and motivated by the need to finance the children's education and home expenses, in 1982 Hawking determined to write a popular book about the Universe that would be accessible to the general public.[201][202] 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.[203][204] A first draft of the book, called A Brief History of Time, was completed in 1984.[205]

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.[82] Peter Guzzardi, his editor at Bantam, pushed him to explain his ideas clearly in non-technical language, a process that required multiple revisions from an increasingly irritated Hawking.[206] The book was published in April 1988 in the US and in June in the UK, and proved to be an extraordinary success, rising quickly to the top of bestseller lists in both countries and remaining there for months.[207][208][209] The book was translated into multiple languages,[210] and ultimately sold an estimated 9 million copies.[209] Media attention was intense,[210] and 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.[211] Hawking travelled extensively to promote his work, and enjoyed partying and dancing into the small hours.[210] He had difficulty refusing the invitations and visitors which left limited time for work and his students.[212] Some colleagues were resentful of the attention Hawking received, feeling it was due to his disability.[213][214] He received further academic recognition, including five further honorary degrees,[215] the Gold Medal of the Royal Astronomical Society (1985),[216] the Paul Dirac Medal (1987)[215] and, jointly with Penrose, the prestigious Wolf Prize (1988).[217] In 1989, he was appointed Member of the Order of the Companions of Honour (CH).[212] He reportedly declined a knighthood.[218]

1990–2000

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.[219] In 1994 at Cambridge's Newton Institute, Hawking and Penrose delivered a series of six lectures, which were published in 1996 as "The Nature of Space and Time".[220] 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.[221] After discovering his concession might have been premature, a new, more refined, wager was made. This specified that such singularities would occur without extra conditions.[222] The same year, Thorne, Hawking and Preskill made another bet, this time concerning the black hole information paradox.[223][224] 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.[225]

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 was persuaded otherwise. The film, while a critical success, was however not widely released.[226] A popular-level collection of essays, interviews and talk titled Black Holes and Baby Universes and Other Essays was published in 1993[227] and six-part television series Stephen Hawking's Universe and companion book appeared in 1997. As Hawking insisted, this time the focus was entirely on science.[228][229]

2000–present

Hawking outside, in his wheelchair, talking to David Gross and Edward Witten
Hawking with string theorists David Gross and Edward Witten at the 2001 Strings Conference, TIFR, India
Hawking sitting in his wheelchair inside
Hawking on 5 May 2006, during the press conference at the Bibliothèque nationale de France to inaugurate the Laboratory of Astronomy and Particles in Paris and the French release of his work God Created the Integers

Hawking continued his writings for a popular audience, publishing The Universe in a Nutshell in 2001,[230] and A Briefer History of Time which he wrote in 2005 with Leonard Mlodinow to update his earlier works to make them accessible to a wider audience, and God Created the Integers, which appeared in 2006.[231] Along with Thomas Hertog at the European Organisation for Nuclear Research (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.[232] 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.[233][234]

Hawking continued to travel widely, including trips to Chile, Easter Island, South Africa, Spain (to receive the Fonseca Prize in 2008),[235][236] Canada,[237] and multiple trips to the United States.[238] 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.[239]

By 2003, consensus among physicists was growing that Hawking was wrong about the loss of information in a black hole.[240] 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.[241][225] 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.[224][242] In January 2014 he called the alleged loss of information in black holes his "biggest blunder".[243]

As part of another longstanding scientific dispute, Hawking had emphatically argued, and bet, that the Higgs Boson would never be found.[244] 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."[245] 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[246][247] and said that Higgs should win the Nobel Prize for Physics,[248] 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.[249] The book was followed by sequels in 2009 and 2011.[250]

Hawking's disease-related deterioration continued, and in 2005 he began to control his communication device with movements of his cheek muscles,[251][252][253] with a rate of about one word per minute.[252] With this decline there is a risk of him developing locked-in syndrome, so Hawking is collaborating with researchers on systems that could translate Hawking's brain patterns or facial expressions into switch activations.[234][253][254] By 2009 he could no longer drive his wheelchair independently.[255] He has increased breathing difficulties, requiring a ventilator at times, and has been hospitalised several times.[234] In 2002, following a UK-wide vote, the BBC included him in their list of the 100 Greatest Britons. Hawking was awarded the Copley Medal from the Royal Society (2006),[256] the Presidential Medal of Freedom which is America's highest civilian honour(2009),[257][258] and the Russian Special Fundamental Physics Prize (2013).[259]
Barack Obama talking to Stephen Hawking in the White House
U.S. President Barack Obama talks with Stephen Hawking in the Blue Room of the White House before a ceremony presenting him and 15 others with the Presidential Medal of Freedom on 12 August 2009

Several buildings have been named after him, including the Stephen W. Hawking Science Museum in San Salvador, El Salvador,[260] the Stephen Hawking Building in Cambridge,[261] and the Stephen Hawking Centre at Perimeter Institute in Canada.[262] 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.[263][264]

During his career Hawking has supervised 39 successful PhD students.[265]

As required by Cambridge University regulations, 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,[266] Hawking has continued to work as director of research at the Cambridge University Department of Applied Mathematics and Theoretical Physics, and indicated in 2012 that he had no plans to retire.[267]

Views

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?" A month later he confessed: "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."[268]

Hawking has expressed concern that life on earth is at risk due to "a sudden nuclear war, a genetically engineered virus or other dangers we have not yet thought of".[269] He views spaceflight and the colonisation of space as necessary for the future of humanity.[269][270] Hawking has stated that, given the vastness of the Universe, aliens likely exist, but that contact with them should be avoided.[271][272] Hawking has argued 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."[273][274]

Hawking has argued that computer viruses should be considered a new form of life, and has stated 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."[275]

Science vs. philosophy

At Google's Zeitgeist Conference in 2011, Hawking said that "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 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".[276]

Religion

Hawking has stated that he is "not religious in the normal sense" and he believes that "the universe is governed by the laws of science. The laws may have been decreed by God, but God does not intervene to break the laws".[277] In an interview published in The Guardian, Hawking regarded the concept of Heaven as a myth, believing that there is "no heaven or afterlife" and that such a notion was a "fairy story for people afraid of the dark".[195] In 2011, when 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 realization. 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."[278][279]
In September 2014, Hawking declared himself an atheist.[280]

Politics

In March 1968, Hawking was one of the leaders (alongside Tariq Ali and Vanessa Redgrave) of a large demonstration in London to protest against the Vietnam War.[281] He is a longstanding Labour Party supporter.[282][283] He recorded a tribute for the 2000 Democratic presidential candidate Al Gore,[284] called the 2003 invasion of Iraq a "war crime",[283][285] boycotted a conference in Israel due to concerns about Israel's policies towards Palestinians,[286][287][288] campaigned for nuclear disarmament,[282][289][283] and has supported stem cell research,[283][290] universal health care,[291] and action to prevent climate change.[289] In August 2014, Hawking was one of 200 signatories to a letter opposing Scottish independence in the run-up to September's referendum on that issue.[292]

Disability outreach

Since the 1990s, Hawking has accepted the mantle of role model for disabled people, lecturing and participating in fundraising activities.[293] At the turn of the century, he and eleven other luminaries signed the Charter for the Third Millennium on Disability which called on governments to prevent disability and protect disabled rights.[294][295] In 1999 Hawking was awarded the Julius Edgar Lilienfeld Prize of the American Physical Society.[296] Motivated by the desire to increase public interest in spaceflight and to show the potential of people with disabilities, in 2007 he participated in zero-gravity flight in a "Vomit Comet", courtesy of Zero Gravity Corporation, during which he experienced weightlessness eight times.[269][297][298][299]
Hawking, without his wheelchair, floating weightless in the air inside a plane
Hawking taking a zero-gravity flight in a "Vomit Comet"

In August 2012 Hawking narrated the "Enlightenment" segment of the 2012 Summer Paralympics opening ceremony.[300] In 2013, the biographical documentary film Hawking, in which Hawking himself is featured, was released.[301] In September 2013, he expressed support for the legalisation of assisted suicide for the terminally ill.[302] In August 2014, Hawking accepted the Ice Bucket Challenge to promote ALS/MND awareness and raise contributions for research. As he had had pneumonia in 2013, he was advised not to have ice poured over him, but his children volunteered to accept the challenge on his behalf.[303]
"We are all different – but we share the same human spirit. Perhaps it's human nature that we adapt – and survive."  – Stephen Hawking, Hawking[304]

Appearances in popular media

At the release party for the home video version of the A Brief History of Time, Leonard Nimoy, who had played Spock on Star Trek, learned that Hawking was interested in appearing on the show.
Nimoy made the necessary contact, and Hawking played a holographic simulation of himself in an episode of Star Trek: The Next Generation in 1993.[305][306][307] The same year, his synthesiser voice was recorded for the Pink Floyd song "Keep Talking",[308][227] and in 1999 for an appearance on The Simpsons.[309] Hawking appeared in documentaries entitled The Real Stephen Hawking (2001),[310] Stephen Hawking: Profile (2002) [311] and Hawking (2013), and the documentary series Stephen Hawking, Master of the Universe (2008).[312] Hawking has also guest-starred in Futurama[234] and The Big Bang Theory.[313]

Hawking has used his fame to advertise products, including a wheelchair,[295] National Savings,[314] British Telecom, Specsavers, Egg Banking[315] and Go Compare.[316]

Awards and honours

Hawking has received numerous awards and honours. Already early in the list, in 1974 he was elected a Fellow of the Royal Society (FRS). At that time, his nomination read:
"Hawking has made major contributions to the field of general relativity. These derive from a deep understanding of what is relevant to physics and astronomy, and especially from a mastery of wholly new mathematical techniques. Following the pioneering work of Penrose he established, partly alone and partly in collaboration with Penrose, a series of successively stronger theorems establishing the fundamental result that all realistic cosmological models must possess singularities. Using similar techniques, Hawking has proved the basic theorems on the laws governing black holes: that stationary solutions of Einstein's equations with smooth event horizons must necessarily be axisymmetric; and that in the evolution and interaction of black holes, the total surface area of the event horizons must increase. In collaboration with G. Ellis, Hawking is the author of an impressive and original treatise on "Space-time in the Large". The citation continues:
"Other important work by Hawking relates to the interpretation of cosmological observations and to the design of gravitational wave detectors."[14]

Bibliography

Selected academic works

Popular publications

Children's fiction

Hawking and his daughter Lucy on stage at a presentation
Stephen Hawking being presented by his daughter Lucy Hawking at the lecture he gave for NASA's 50th anniversary
Co-written with his daughter Lucy.

Films and series


Thorium-based nuclear power


From Wikipedia, the free encyclopedia
A sample of thorium.

Thorium-based nuclear power is nuclear reactor-based electrical power generation fueled primarily by the fission of the isotope uranium-233 produced from the fertile element thorium. According to proponents, a thorium fuel cycle offers several potential advantages over a uranium fuel cycle—including much greater abundance on Earth, superior physical and nuclear fuel properties, and reduced nuclear waste production. However, development of thorium power has significant start-up costs. Proponents also cite the lack of weaponization potential as an advantage of thorium, while critics say that development of breeder reactors in general (including thorium reactors that are breeders by nature) increase proliferation concerns. Since about 2008, nuclear energy experts have become more interested in thorium to supply nuclear fuel in place of uranium to generate nuclear power. This renewed interest has been highlighted in a number of scientific conferences, the latest of which, ThEC13 [1] was held at CERN by iThEC and attracted over 200 scientists from 32 countries.
A nuclear reactor consumes certain specific fissile isotopes to produce energy. The three most practical types of nuclear reactor fuel are:
  • Uranium-235, purified (i.e. "enriched") by reducing the amount of uranium-238 in natural mined uranium. Most nuclear power has been generated using low-enriched uranium (LEU), whereas high-enriched uranium (HEU) is necessary for weapons.
  • Plutonium-239, transmuted from uranium-238 obtained from natural mined uranium. Plutonium is also used for weapons.
  • Uranium-233, transmuted from thorium-232, derived from natural mined thorium. That is this article's subject.
Some believe thorium is key to developing a new generation of cleaner, safer nuclear power.[2] According to an opinion piece (not peer-reviewed) by a group of scientists at the Georgia Institute of Technology, considering its overall potential, thorium-based power "can mean a 1000+ year solution or a quality low-carbon bridge to truly sustainable energy sources solving a huge portion of mankind’s negative environmental impact."[3]

After studying the feasibility of using thorium, nuclear scientists Ralph W. Moir and Edward Teller suggested that thorium nuclear research should be restarted after a three-decade shutdown and that a small prototype plant should be built.[4][5][6] Research and development of thorium-based nuclear reactors, primarily the liquid fluoride thorium reactor, (LFTR), MSR design, has been or is now being done in India, China, Norway, U.S., Israel and Russia.

Background and brief history

After World War II, uranium-based nuclear reactors were built to produce electricity. These were similar to the reactor designs that produced material for nuclear weapons. During that period, the U.S. government also built an experimental molten salt reactor using U-233 fuel, the fissile material created by bombarding thorium with neutrons. The reactor, built at Oak Ridge National Laboratory, operated critical for roughly 15000 hours from 1965 to 1969. In 1968, Nobel laureate and discoverer of Plutonium, Glenn Seaborg, publicly announced to the Atomic Energy Commission, of which he was chairman, that the thorium-based reactor had been successfully developed and tested:
So far the molten-salt reactor experiment has operated successfully and has earned a reputation for reliability. I think that some day the world will have commercial power reactors of both the uranium-plutonium and the thorium-uranium fuel cycle type.[7]
In 1973, however, the U.S. government shut down all thorium-related nuclear research—which had by then been ongoing for approximately twenty years at Oak Ridge National Laboratory. The reasons were that uranium breeder reactors were more efficient, the research was proven, and byproducts could be used to make nuclear weapons. In Moir and Teller’s opinion, the decision to stop development of thorium reactors, at least as a backup option, “was an excusable mistake.”[4]

Science writer Richard Martin states that nuclear physicist Alvin Weinberg, who was director at Oak Ridge and primarily responsible for the new reactor, lost his job as director because he championed development of the safer thorium reactors.[8][9] Weinberg himself recalls this period:
[Congressman] Chet Holifield was clearly exasperated with me, and he finally blurted out, "Alvin, if you are concerned about the safety of reactors, then I think it may be time for you to leave nuclear energy." I was speechless. But it was apparent to me that my style, my attitude, and my perception of the future were no longer in tune with the powers within the AEC.[10]
Martin explains that Weinberg's unwillingness to sacrifice potentially safe nuclear power for the benefit of military uses forced him to retire:
Weinberg realized that you could use thorium in an entirely new kind of reactor, one that would have zero risk of meltdown. . . . his team built a working reactor . . . . and he spent the rest of his 18-year tenure trying to make thorium the heart of the nation’s atomic power effort. He failed. Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs. Increasingly shunted aside, Weinberg was finally forced out in 1973.[11]
Despite the documented history of thorium nuclear power, many of today’s nuclear experts were nonetheless unaware of it. According to Chemical & Engineering News, "most people—including scientists—have hardly heard of the heavy-metal element and know little about it...," noting a comment by a conference attendee that "it's possible to have a Ph.D. in nuclear reactor technology and not know about thorium energy."[12] Nuclear physicist Victor J. Stenger, for one, first learned of it in 2012:
It came as a surprise to me to learn recently that such an alternative has been available to us since World War II, but not pursued because it lacked weapons applications.[13]
Others, including former NASA scientist and thorium expert Kirk Sorensen, agree that "thorium was the alternative path that was not taken … "[14][15]:2 According to Sorensen, during a documentary interview, he states that if the U.S. had not discontinued its research in 1974 it could have "probably achieved energy independence by around 2000."[7]

Possible benefits


Early thorium-based (MSR) nuclear reactor at Oak Ridge National Laboratory in the 1960s

The World Nuclear Association explains some of the possible benefits[16]
The thorium fuel cycle offers enormous energy security benefits in the long-term – due to its potential for being a self-sustaining fuel without the need for fast neutron reactors. It is therefore an important and potentially viable technology that seems able to contribute to building credible, long-term nuclear energy scenarios.[17]
Moir and Teller agree, noting that the possible advantages of thorium include "utilization of an abundant fuel, inaccessibility of that fuel to terrorists or for diversion to weapons use, together with good economics and safety features … "[4] Thorium is considered the "most abundant, most readily available, cleanest, and safest energy source on Earth," adds science writer Richard Martin.[15]:7
  • Thorium is three times as abundant as uranium and nearly as abundant as lead and gallium in the Earth's crust.[18] The Thorium Energy Alliance (TEA) estimates "there is enough thorium in the United States alone to power the country at its current energy level for over 1,000 years."[17][18] "America has buried tons as a by-product of rare earth metals mining," notes Evans-Pritchard.[19] Almost all thorium is fertile Th-232, compared to uranium that is composed of 99.3% fertile U-238 and 0.7% more valuable fissile U-235.
  • It is difficult to make a practical nuclear bomb from a thorium reactor's byproducts. According to Alvin Radkowsky, designer of the world's first full-scale atomic electric power plant, "a thorium reactor's plutonium production rate would be less than 2 percent of that of a standard reactor, and the plutonium's isotopic content would make it unsuitable for a nuclear detonation."[15]:11[20] Several uranium-233 bombs have been tested, but the presence of uranium-232 tended to "poison" the uranium-233 in two ways: intense radiation from the uranium-232 made the material difficult to handle, and the uranium-233 led to possible pre-detonation. Separating the uranium-232 from the uranium-233 proved very difficult, although newer laser techniques could facilitate that process.[21][22]
  • There is much less nuclear waste—up to two orders of magnitude less, states Moir and Teller,[4] eliminating the need for large-scale or long-term storage;[15]:13 "Chinese scientists claim that hazardous waste will be a thousand times less than with uranium."[19] The radioactivity of the resulting waste also drops down to safe levels after just a few hundred years, compared to tens of thousands of years needed for current nuclear waste to cool off.[23]
  • According to Moir and Teller, "once started up [it] needs no other fuel except thorium because it makes most or all of its own fuel."[4] This only applies to breeding reactors, that produce at least as much fissile material as they consume. Other reactor require additional fissile material, such as uranium-235 or plutonium.[17]
  • Since all natural thorium can be used as fuel no expensive fuel enrichment is needed.[23] However the same is true for U-238 as fertile fuel in the uranium-plutonium cycle.
  • Comparing the amount of thorium needed with coal, Nobel laureate Carlo Rubbia of CERN, (European Organization for Nuclear Research), estimates that one ton of thorium can produce as much energy as 200 tons of uranium, or 3,500,000 tons of coal.[24] Coal, makes up 42% of U.S. electrical power generation and 65% in China.[25]
  • Liquid fluoride thorium reactors are designed to be meltdown proof. A plug at the bottom of the reactor melts in the event of a power failure or if temperatures exceed a set limit, draining the fuel into an underground tank for safe storage.[26]
  • Mining thorium is safer and more efficient than mining uranium. Thorium's ore monazite generally contains higher concentrations of thorium than the percentage of uranium found in its respective ore. This makes thorium a more cost efficient and less environmentally damaging fuel source. Thorium mining is also easier and less dangerous than uranium mining, as the mine is an open pit which doesn't require ventilation, unlike underground uranium mines, where radon levels can be potentially harmful.[27]
Summarizing some of the potential benefits, Martin offers his general opinion: "Thorium could provide a clean and effectively limitless source of power while allaying all public concern—weapons proliferation, radioactive pollution, toxic waste, and fuel that is both costly and complicated to process.[15]:13 From an economics viewpoint, U.K. business editor Ambrose Evans-Pritchard has suggested that "Obama could kill fossil fuels overnight with a nuclear dash for thorium," suggesting a "new Manhattan Project," and adding, "If it works, Manhattan II could restore American optimism and strategic leadership at a stroke …"[24] Moir and Teller estimated in 2004 that the cost for their recommended prototype would be "well under $1 billion with operation costs likely on the order of $100 million per year," and as a result a "large-scale nuclear power plan" usable by many countries could be set up within a decade.[4]

Possible disadvantages

Some experts note possible specific disadvantages of thorium nuclear power:[28]
  • Breeding in a thermal neutron spectrum is slow and requires extensive reprocessing. The feasibility of reprocessing is still open.[29]
  • Significant and expensive testing, analysis and licensing work is first required, requiring business and government support.[17] According to a 2012 report by the Bulletin of the Atomic Scientists, about using thorium fuel with existing water-cooled reactors, it would "require too great an investment and provide no clear payoff," noting that "from the utilities’ point of view, the only legitimate driver capable of motivating pursuit of thorium is economics."[28]
  • There is a higher cost of fuel fabrication and reprocessing than those that use traditional solid fuel rods.[17]
  • Thorium, when being irradiated for use in reactors, will make uranium-232, which is very dangerous due to the gamma rays it emits. This irradiation process may be able to be altered slightly by removing protactinium-233. The irradiation would then make uranium-233 in lieu of uranium-232, which can be used in nuclear weapons to make thorium into a dual purpose fuel.[30]

Current projects

Research and development of thorium-based nuclear reactors, primarily the Liquid fluoride thorium reactor, (LFTR), MSR design, has been or is now being done in the U.S., U.K., Germany, Brazil, India, China, France, the Czech Republic, Japan, Russia, Canada, Israel and the Netherlands.[13][15]
Conferences with experts from as many as 32 countries are held, including one by the European Organization for Nuclear Research (CERN) in 2013, which focuses on thorium as an alternative nuclear technology without requiring production of nuclear waste.[31] Recognized experts, such as Hans Blix, former head of the International Atomic Energy Agency, calls for expanded support of new nuclear power technology, and states, "the thorium option offers the world not only a new sustainable supply of fuel for nuclear power but also one that makes better use of the fuel's energy content."[32]

Canada

CANDU reactors of Atomic Energy Canada Limited are capable of using thorium,[33][34] and TPC (Thorium Power Canada) has, in 2013, planned and proposed developing thorium power projects for Chile and Indonesia.[35]

China

At the 2011 annual conference of the Chinese Academy of Sciences it was announced that "China has initiated a research and development project in thorium molten-salt reactor technology."[36] In addition, Dr. Jiang Mianheng, son of China's former leader Jiang Zemin, led a thorium delegation in non-disclosure talks at Oak Ridge National Laboratory, Tennessee, and by late 2013 China had officially partnered with Oak Ridge to aid China in its own development.[37][38] The World Nuclear Association notes that the China Academy of Sciences in January 2011 announced its R&D program, "claiming to have the world's largest national effort on it, hoping to obtain full intellectual property rights on the technology."[17] According to Martin, "China has made clear its intention to go it alone," adding that China already has a monopoly over most of the world's rare earth minerals.[15]:157[19]

In March 2014, with their reliance on coal-fired power having become a major cause of their current "smog crisis," they reduced their original goal of creating a working reactor from 25 years down to 10. "In the past, the government was interested in nuclear power because of the energy shortage. Now they are more interested because of smog," said Professor Li Zhong, a scientist working on the project. "This is definitely a race," he added.[39]

In early 2012, it was reported that China, using components produced by the West and Russia, planned to build two prototype thorium molten salt reactors by 2015, and had budgeted the project at $400 million and requiring 400 workers."[15]:157 China also finalized an agreement with a Canadian nuclear technology company to develop improved CANDU reactors using thorium and uranium as a fuel.[40]

Germany

The German THTR-300 was a prototype commercial power station using thorium as fertile and highly enriched U-235 as fissile fuel. Though named thorium high temperature reactor, mostly U-235 was fissioned. The THTR-300 was a helium-cooled high-temperature reactor with a pebble-bed reactor core consisting of approximately 670,000 spherical fuel compacts each 6 centimetres (2.4 in) in diameter with particles of uranium-235 and thorium-232 fuel embedded in a graphite matrix. It fed power to Germany's grid for 432 days in the late 1980s, before it was shut down for cost, mechanical and other reasons.

India

India has one of the largest supplies of thorium in the world, with comparatively poor quantities of uranium. India has projected meeting as much as 30% of its electrical demands through thorium by 2050.[41]

In February 2014, Bhabha Atomic Research Centre (BARC), in Mumbai, India, presented their latest design for a "next-generation nuclear reactor" that will burn thorium as its fuel ore. Once built, with a target date of 2016, they estimate that the reactor could function without an operator for 120 days.[42]

According to Dr R K Sinha, chairman of their Atomic Energy Commission, "This will reduce our dependence on fossil fuels, mostly imported, and will be a major contribution to global efforts to combat climate change." Because of its inherent safety, they expect that similar designs could be set up "within" populated cities, like - Mumbai or Delhi.[42]

India's government is also developing up to 62, mostly thorium reactors, which it expects to be operational by 2025. It is the "only country in the world with a detailed, funded, government-approved plan" to focus on thorium-based nuclear power. The country currently gets under 3% of its electricity from nuclear power, relying for the rest on coal and oil imports. It expects to produce around 25% of its electricity from nuclear power.[15]:144 In 2009 the chairman of the Indian Atomic Energy Commission said that India has a "long-term objective goal of becoming energy-independent based on its vast thorium resources."[43][44]

In late June 2012, India announced that their "first commercial fast reactor" was near completion making India the most advanced country in thorium research." We have huge reserves of thorium. The challenge is to develop technology for converting this to fissile material," stated their former Chairman of India's Atomic Energy Commission.[45] That vision of using thorium in place of uranium was set out in the 1950s by physicist Homi Bhabha.[46][47] India's first commercial fast breeder reactor — the 500 MWe Prototype Fast Breeder Reactor (PFBR) — is approaching completion at the Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu.

As of July 2013 the major equipment of the PFBR had been erected and the loading of "dummy" fuels in peripheral locations was in progress. The reactor was expected to go critical by September 2014.[48]

The Centre had sanctioned Rs. 5,677 crore for building the PFBR and “we will definitely build the reactor within that amount,” Mr. Kumar asserted. The original cost of the project was Rs. 3,492 crore, revised to Rs. 5,677 crore. Electricity generated from the PFBR would be sold to the State Electricity Boards at Rs. 4.44 a unit. BHAVINI builds breeder reactors in India. India's 300 MWe AHWR (pressurized heavy water reactor) reactor began construction in 2011. The design envisages a start up with reactor grade plutonium that will breed U-233 from Th-232. Thereafter thorium is to be the only fuel.[49]

Israel

In May 2010, researchers from Ben-Gurion University in Israel and Brookhaven National Laboratory in New York began to collaborate on the development of thorium reactors,[50] aimed at being self-sustaining, "meaning one that will produce and consume about the same amounts of fuel," which is not possible with uranium in a light water reactor.[50]

Japan

In June, 2012, Japan utility Chubu Electric Power, wrote that they regard thorium as “one of future possible energy resources.”[51]

Norway

In late 2012, Norway's privately owned Thor Energy, in collaboration with the government and Westinghouse, announced a four-year trial using thorium in an existing nuclear reactor."[52] In 2013, Aker Solutions purchased patents from Nobel Prize winning physicist Carlo Rubbia for the design of a proton accelerator-based thorium nuclear power plant.[53]

U.K.

In Britain, a few organizations are either promoting or examining research on thorium-based nuclear plants. House of Lords member Bryony Worthington is promoting thorium, calling it “the forgotten fuel” that could alter Britain’s energy plans.[54] However, in 2010, the UK’s National Nuclear Laboratory (NNL) concluded that for the short to medium term, "...the thorium fuel cycle does not currently have a role to play," in that it is "technically immature, and would require a significant financial investment and risk without clear benefits," and concluded that the benefits have been "overstated."[17] Friends of the Earth UK considers research into it as "useful" as a fallback option.[55]

U.S.

In its January 2012 report to the Secretary of Energy, the Blue Ribbon Commission on America's Future notes that a "molten-salt reactor using thorium [has] also been proposed."[56] That same month it was reported that the U.S. Department of Energy is "quietly collaborating with China" on thorium-based nuclear power designs using a molten salt reactor.[57]

Some experts and politicians want thorium to be "the pillar of the U.S. nuclear future."[58] Senators Harry Reid and Orrin Hatch have supported using $250 million in federal research funds to revive ORNL research.[3] In 2009, Congressman Joe Sestak unsuccessfully attempted to secure funding for research and development of a destroyer-sized reactor [reactor of a size to power a destroyer] using thorium-based liquid fuel.[59][60]

Alvin Radkowsky, chief designer of the world’s second full-scale atomic electric power plant in Shippingport, Pennsylvania, founded a joint U.S. and Russian project in 1997 to create a thorium-based reactor, considered a "creative breakthrough."[61] In 1992, while a resident professor in Tel Aviv, Israel, he founded the U.S. company, Thorium Power Ltd., near Washington, D.C., to build thorium reactors.[61]

The primary fuel of the proposed HT3R research project near Odessa, Texas, USA, will be ceramic-coated thorium beads. The earliest date the reactor will become operational is in 2015.[62]

World sources of thorium

World thorium sources (2007)[63]
Country Tons  %
Australia 489,000 18.7%
USA 400,000 15.3%
Turkey 344,000 13.2%
India 319,000 12.2%
Brazil 302,000 11.6%
Venezuela 300,000 11.5%
Norway 132,000 5.1%
Egypt 100,000 3.8%
Russia 75,000 2.9%
Greenland (Denmark) 54,000 2.1%
Canada 44,000 1.7%
South Africa 18,000 0.7%
Other countries 33,000 1.2%
World Total 2,610,000 100.0%

Thorium is mostly found with the rare earth phosphate mineral, monazite, which contains up to about 12% thorium phosphate, but 6-7% on average. World monazite resources are estimated to be about 12 million tons, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India. There are substantial deposits in several other countries (see table "World thorium sources").[17]

Another estimate of reasonably assured reserves (RAR) and estimated additional reserves (EAR) of thorium comes from OECD/NEA, Nuclear Energy, "Trends in Nuclear Fuel Cycle", Paris, France (2001).[64] (see table "IAEA Estimates in tonnes")

IAEA Estimates in tons (2005)
Country RAR Th EAR Th
India 519,000 21%
Australia 489,000 19%
USA 400,000 13%
Turkey 344,000 11%
Venezuela 302,000 10%
Brazil 302,000 10%
Norway 132,000 4%
Egypt 100,000 3%
Russia 75,000 2%
Greenland 54,000 2%
Canada 44,000 2%
South Africa 18,000 1%
Other countries 33,000 2%
World Total 2,810,000 100%

The preceding reserve figures refer to the amount of thorium in high-concentration deposits inventoried so far and estimated to be extractable at current market prices; millions of times more total exist in Earth's 3×1019 tonne crust, around 120 trillion tons of thorium, and lesser but vast quantities of thorium exist at intermediate concentrations.[65][66][67] Proved reserves are "a poor indicator of the total future supply of a mineral resource."[67]

Types of thorium-based reactors

According to the World Nuclear Association there are seven types of reactors that can be designed to use thorium as a nuclear fuel. The first five of these have all entered into operational service at some point. The last two are still conceptual, although currently in development by many countries:[17]
Additionally, in the 1958 Atoms for Peace publication entitled Fluid Fueled Reactors, Aqueous Homogeneous Reactors (AHRs) were proposed as a fluid fueled design that could accept naturally occurring uranium and thorium suspended in a heavy water solution.[68] AHRs have been built and according to the IAEA reactor database, 7 are currently in operation as research reactors.

Distance education

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Distance_...