Editing Paul Dirac (section)

==Personal life==

===Early years===
Paul Adrien Maurice Dirac was born at his parents' home in [[Bristol]], England, on 8 August 1902,<ref>{{harvnb|Farmelo|2009|p=[https://books.google.com/books?id=-TT_z4llWoIC&pg=PA10 10]}}</ref> and grew up in the [[Bishopston, Bristol|Bishopston]] area of the city.<ref>{{harvnb|Farmelo|2009|pp=[https://books.google.com/books?id=-TT_z4llWoIC&pg=PA18 18–19]}}</ref> His father, Charles Adrien Ladislas Dirac, was an immigrant from [[Saint-Maurice, Switzerland]], of [[French people|French]] descent,<ref name="frs">{{Cite journal | last1 = Dalitz | first1 = R. H. | author-link1 = Richard Dalitz| last2 = Peierls | first2 = R. | author-link2 = Rudolf Peierls| doi = 10.1098/rsbm.1986.0006 | title = Paul Adrien Maurice Dirac. 8 August 1902 – 20 October 1984 | journal = [[Biographical Memoirs of Fellows of the Royal Society]] | volume = 32 | pages = 137–185 | year = 1986 | jstor = 770111| doi-access = free }}</ref> who worked in Bristol as a French teacher. His mother, Florence Hannah Dirac, née Holten, was born to a [[Cornish people|Cornish]] [[Methodism|Methodist]] family in [[Liskeard]], [[Cornwall]].<ref name="Cern Courier-2002">{{cite web|title=Paul Dirac: a genius in the history of physics|url=http://cerncourier.com/cws/article/cern/28693|work=Cern Courier|access-date=4 February 2022|date=15 August 2002}}</ref><ref>{{harvnb|Farmelo|2009|pp=8, 441}}</ref> She was named after [[Florence Nightingale]] by her father, a ship's captain, who had met Nightingale while he was a soldier during the Crimean War.<ref>{{harvnb|Farmelo|2009|pp=8}}</ref> His mother moved to Bristol as a young woman, where she worked as a librarian at the [[Bristol Central Library]]; despite this she still considered her identity to be Cornish rather than English.<ref>{{harvnb|Farmelo|2009|pp=441}}</ref> Paul had a younger sister, Béatrice Isabelle Marguerite, known as Betty, and an older brother, Reginald Charles Félix, known as Felix,<ref>{{harvnb|Kragh|1990|p=1}}</ref><ref>{{harvnb|Farmelo|2009|pp=10–11}}</ref> who died by suicide in March 1925.<ref>{{harvnb|Farmelo|2009|pp=[https://books.google.com/books?id=-TT_z4llWoIC&pg=PA77 77–78]}}</ref> Dirac later recalled: "My parents were terribly distressed. I didn't know they cared so much ... I never knew that parents were supposed to care for their children, but from then on I knew."<ref>{{harvnb|Farmelo|2009|p=[https://books.google.com/books?id=-TT_z4llWoIC&pg=PA79 79]}}</ref>

Charles and the children were officially Swiss nationals until they became [[naturalised]] on 22 October 1919.<ref>{{harvnb|Farmelo|2009|p=34}}</ref> Dirac's father was strict and authoritarian, although he disapproved of corporal punishment.<ref>{{harvnb|Farmelo|2009|p=22}}</ref> Dirac had a strained relationship with his father, so much so that after his father's death, Dirac wrote, "I feel much freer now, and I am my own man." Charles forced his children to speak to him only in French so that they might learn the language. When Dirac found that he could not express what he wanted to say in French, he chose to remain silent.<ref>{{harvnb|Mehra|1972|p=17}}</ref><ref>{{harvnb|Kragh|1990|p=2}}</ref>

===Education===
Dirac was educated first at [[Bishop Road Primary School]]<ref>{{harvnb|Farmelo|2009|pp=13–17}}</ref> and then at the all-boys [[Society of Merchant Venturers|Merchant Venturers']] Technical College (later [[Cotham School]]), where his father was a French teacher.<ref>{{harvnb|Farmelo|2009|pp=20–21}}</ref> The school was an institution attached to the [[University of Bristol]], which shared grounds and staff.<ref name="Mehra18"/> It emphasised technical subjects like bricklaying, shoemaking and metalwork, and modern languages.<ref>{{harvnb|Farmelo|2009|p=23}}</ref> This was unusual at a time when secondary education in Britain was still dedicated largely to the classics, and something for which Dirac would later express his gratitude.<ref name="Mehra18">{{harvnb|Mehra|1972|p=18}}</ref> One of his peers at Bishop Road School was Archibald Leach, later famous as [[Cary Grant]].{{sfnp| Farmelo| 2009| p=14}}

Dirac studied [[electrical engineering]] on a City of Bristol University Scholarship at the University of Bristol's engineering faculty, which was co-located with the Merchant Venturers' Technical College.<ref>{{harvnb|Farmelo|2009|p=28}}</ref> Shortly before he completed his degree in 1921, he sat for the entrance examination for [[St John's College, Cambridge]]. He passed and was awarded a £70 scholarship, but this fell short of the amount of money required to live and study at Cambridge. Despite having graduated with a [[first class honours]] Bachelor of Science degree in electrical engineering, the economic climate of the [[Post–World War I recession|post-war depression]] was such that he was unable to find work as an engineer. Instead, he took up an offer to study for a [[Bachelor of Arts]] degree in mathematics at the University of Bristol free of charge. He was permitted to skip the first year of the course owing to his engineering degree.<ref>{{harvnb|Farmelo|2009|pp=46–47}}</ref> Under the influence of Peter Fraser, whom Dirac called the best mathematics teacher, he had the most interest in projective geometry, and began applying it to the geometrical version of relativity [[Hermann Minkowski|Minkowski]] developed.<ref>{{Cite journal |last=Galison |first=Peter |date=2000 |title=The Suppressed Drawing: Paul Dirac's Hidden Geometry |url=https://www.jstor.org/stable/2902912 |journal=Representations |issue=72 |pages=145–166 |doi=10.2307/2902912 |jstor=2902912 |issn=0734-6018}}</ref>

In 1923, Dirac graduated, once again with first class honours, and received a £140 scholarship from the [[Department of Scientific and Industrial Research (United Kingdom)|Department of Scientific and Industrial Research]].<ref>{{harvnb|Farmelo|2009|p=53}}</ref> Along with his £70 scholarship from St John's College, this was enough to live at Cambridge. There, Dirac pursued his interests in the theory of [[general relativity]], an interest he had gained earlier as a student in Bristol, and in the nascent field of [[quantum physics]], under the supervision of [[Ralph Fowler]].<ref>{{harvnb|Farmelo|2009|pp=52–53}}</ref> From 1925 to 1928 he held an [[1851 Research Fellowship]] from the [[Royal Commission for the Exhibition of 1851]].<ref name="1851 Royal Commission Archives">1851 Royal Commission Archives</ref> He completed his PhD in June 1926 with the first thesis on quantum mechanics to be submitted anywhere.<ref>{{harvnb|Farmelo|2009|p=101}}</ref> He then continued his research in [[Copenhagen]] and [[Göttingen]].<ref name="1851 Royal Commission Archives"/> In the spring of 1929, he was a visiting professor at the [[University of Wisconsin–Madison]].<ref>{{cite book |editor1-last=Kursunoglu |editor1-first=Behram N. |editor2-last=Wigner |editor2-first=Eugene Paul |title=Paul Adrien Maurice Dirac: Reminiscences about a Great Physicist |date=1990 |publisher=Cambridge University Press |isbn=0521386888 |page=132 |url=https://books.google.com/books?id=1Pg7t9a_AX4C&q=paul+dirac+university+of+wisconsin+1929&pg=PA132 |access-date=30 September 2020}}</ref><ref>{{cite web |title=Paul Adrien Maurice Dirac |url=https://pages.hep.wisc.edu/~ldurand/715html/courseinfo/biographies/dirac.html |publisher=University of Wisconsin-Madison |access-date=30 September 2020}}</ref>

===Family===
[[File:Dirac,Paul 1963 Kopenhagen.jpg|thumb|Paul and Manci Dirac in [[Copenhagen]], July 1963]]
In 1937, Dirac married<ref>{{harvnb|Farmelo|2009|p=284}}</ref> Margit Wigner, a sister of physicist [[Eugene Wigner]]<ref>{{harvnb|Farmelo|2009|p=253}}</ref> and a divorcee.<ref>{{harvnb|Farmelo|2009|p=256}}</ref> Dirac raised Margit's two children, Judith and [[Gabriel Andrew Dirac|Gabriel]], as if they were his own.<ref>{{harvnb|Farmelo|2009|p=288}}</ref> Paul and Margit Dirac also had two daughters together, Mary Elizabeth and Florence Monica.<ref>{{harvnb|Farmelo|2009|pp=305, 323}}</ref>

Margit, known as Manci, had visited her brother in 1934 in [[Princeton, New Jersey]], from their native Hungary and, while at dinner at the Annex Restaurant, met the "lonely-looking man at the next table". This account from a Korean physicist, [[Young Suh Kim|Y. S. Kim]], who met and was influenced by Dirac, also says: "It is quite fortunate for the physics community that Manci took good care of our respected Paul A. M. Dirac. Dirac published eleven papers during the period 1939–46. Dirac was able to maintain his normal research productivity only because Manci was in charge of everything else".<ref>{{cite web |url=http://ysfine.com/dirac/wigsis.html |title=Wigner's Sisters |last=Kim |first=Young Suh |year=1995 |archive-url= https://web.archive.org/web/20080303112257/https://ysfine.com/dirac/wigsis.html |archive-date= 3 March 2008}}</ref>

===Personality===
[[File:Clara Ewald - Paul Dirac.jpg|thumb|upright|Portrait of Paul Dirac by [[Clara Ewald]], 1939]]
Dirac was regarded by his friends and colleagues as unusual in character. In a 1926 letter to [[Paul Ehrenfest]], [[Albert Einstein]] wrote of a Dirac paper, "I am toiling over Dirac. This balancing on the dizzying path between genius and madness is awful." In another letter concerning the [[Compton scattering|Compton effect]] he wrote, "I don't understand the details of Dirac at all."<ref>{{harvnb|Kragh|1990|p=82]}}  "Dirac verstehe ich im Einzelnen überhaupt nicht (Compton-Effekt)"</ref>
Dirac was known among his colleagues for his precise and taciturn nature. His colleagues in Cambridge jokingly defined a unit called a "dirac", which was one word per hour.<ref>{{harvnb|Farmelo|2009|p=89}}</ref> When [[Niels Bohr]] complained that he did not know how to finish a sentence in a scientific article he was writing, Dirac replied, "I was taught at school never to start a sentence without knowing the end of it."<ref name="standy">{{cite web |url=http://www-history.mcs.st-and.ac.uk/Printonly/Dirac.html |title=Paul Adrien Maurice Dirac |publisher=University of St. Andrews |access-date=4 April 2013}}</ref> He criticised the physicist [[J. Robert Oppenheimer]]'s interest in poetry: "The aim of science is to make difficult things understandable in a simpler way; the aim of poetry is to state simple things in an incomprehensible way. The two are incompatible."<ref>{{harvnb|Mehra|1972|pp=[https://books.google.com/books?id=CpJiqUFkHGoC&pg=PA17 17–59]}}</ref> Bohr called Dirac "a complete logical genius" and also the "strangest man" who had ever visited his Institute.{{sfnp| Farmelo| 2009| p=120}}

Dirac himself wrote in his diary during his postgraduate years that he concentrated solely on his research, and stopped only on Sunday when he took long strolls alone.<ref>{{harvnb|Kragh|1990|p=17}}</ref>

An anecdote recounted in a review of the 2009 biography tells of [[Werner Heisenberg]] and Dirac sailing on an ocean liner to a conference in Japan in August 1929. "Both still in their twenties, and unmarried, they made an odd couple. Heisenberg was a ladies' man who constantly flirted and danced, while Dirac—'an Edwardian geek', as biographer [[Graham Farmelo]] puts it—suffered agonies if forced into any kind of socializing or small talk. 'Why do you dance?' Dirac asked his companion. 'When there are nice girls, it is a pleasure,' Heisenberg replied. Dirac pondered this notion, then blurted out: 'But, Heisenberg, how do you know beforehand that the girls are nice?{{' "}}<ref name="mckie">{{cite web |url=https://www.theguardian.com/books/2009/feb/01/strangest-man-paul-dirac-review |title=Anti-matter and madness |last1=McKie |first1=Rob |date=1 February 2009 |work=The Guardian |access-date=4 April 2013}}</ref>

Margit Dirac told both [[George Gamow]] and Anton Capri in the 1960s that her husband had said to a house visitor, "Allow me to present Wigner's sister, who is now my wife."<ref>{{harvnb|Gamow|1966|p=121}}</ref><ref>{{harvnb|Capri|2007|p=148}}</ref>

[[File:Paul Dirac and Richard Feynman at Jabłonna 1962.png|thumb|Paul Dirac and Richard Feynman at Jabłonna, Poland. July 1962.]]
Another story told of Dirac is that when he first met the young [[Richard Feynman]] at a conference, he said after a long silence, "I have an equation. Do you have one too?"<ref>{{harvnb|Zee|2010|p=105}}</ref>

After he presented a lecture at a conference, one colleague raised his hand and said: "I don't understand the equation on the top-right-hand corner of the blackboard". After a long silence, the moderator asked Dirac if he wanted to answer the question, to which Dirac replied: "That was not a question, it was a comment."<ref>{{cite news | url=https://www.theglobeandmail.com/arts/books-and-media/review-the-strangest-man-by-graham-farmelo/article4289494/ | title=A quantum leap into oddness | first=Chet | last=Raymo | newspaper=[[The Globe and Mail]] | date=17 October 2009}} (Review of Farmelo's ''The Strangest Man''.)</ref><ref>{{harvnb|Farmelo|2009|pp=161–162}}, who attributes the story to [[Niels Bohr]].</ref>

Dirac was also noted for his personal modesty. He called the equation for the [[time evolution]] of a quantum-mechanical operator, which he was the first to write down, the "Heisenberg equation of motion". Most physicists speak of [[Fermi–Dirac statistics]] for half-integer-spin particles ([[fermions]]) and [[Bose–Einstein statistics]] for integer-spin particles ([[bosons]]). While lecturing later in life, Dirac always insisted on calling the former "Fermi statistics". He referred to the latter as "Bose statistics" for reasons, he explained, of "symmetry".<ref>{{cite book|last1=Mehra|first1=Jagdish|last2=Rechenberg|first2=Helmut|author-link1=Jagdish Mehra |author-link2=Helmut Rechenberg |title=The Historical Development of Quantum Theory|year=2001|publisher=Springer Science & Business Media|isbn=9780387951805|page=746|url=https://books.google.com/books?id=-pL56OcVubgC&q=Paul+Dirac+Einstein+statistics+Symmetry&pg=PA746}}</ref>

===Philosophy of physics ===
When asked to summarize his philosophy of physics, Dirac wrote "Physical laws should have mathematical beauty."{{sfnp| Farmelo| 2009| p=359}}

Dirac was famously not bothered by [[Interpretations of quantum mechanics|issues of interpretation in quantum theory]]. In fact, in a paper published in a book in his honour, he wrote: "The interpretation of quantum mechanics has been dealt with by many authors, and I do not want to discuss it here.  I want to deal with more fundamental things."<ref>Dirac, "The inadequacies of quantum field theory", in B. N. Kursunoglu & E. P. Wigner, eds., [https://books.google.com/books?id=1Pg7t9a_AX4C ''Paul Adrien Maurice Dirac''] (Cambridge: Cambridge University Press, 1987), p. 194.</ref>

===Views on religion===
Heisenberg recollected a conversation among young participants at the 1927 [[Solvay Conference]] about Einstein and [[Max Planck|Planck]]'s views on religion between [[Wolfgang Pauli]], Heisenberg and Dirac. Dirac's contribution was a criticism of the political purpose of religion, which Bohr regarded as quite lucid when hearing it from Heisenberg later.<ref>[[Abraham Pais|Pais, A.]], ''Niels Bohr's Times: In Physics, Philosophy, and Polity'' (Oxford: [[Oxford University Press#Clarendon Press|Clarendon Press]], 1991), [https://archive.org/details/nielsbohrstimesi0000pais/page/320 p. 320].</ref> Among other things, Heisenberg imagined that Dirac might say:
<blockquote>I don't know why we are discussing religion. If we are honest—and scientists have to be—we must admit that religion is a jumble of false assertions, with no basis in reality. The very idea of God is a product of the human imagination. It is quite understandable why primitive people, who were so much more exposed to the overpowering forces of nature than we are today, should have personified these forces in fear and trembling. But nowadays, when we understand so many natural processes, we have no need for such solutions. I can't for the life of me see how the postulate of an Almighty God helps us in any way. What I do see is that this assumption leads to such unproductive questions as to why God allows so much misery and injustice, the exploitation of the poor by the rich, and all the other horrors He might have prevented. If religion is still being taught, it is by no means because its ideas still convince us, but simply because some of us want to keep the lower classes quiet. Quiet people are much easier to govern than clamorous and dissatisfied ones. They are also much easier to exploit. Religion is a kind of opium that allows a nation to lull itself into wishful dreams and so forget the injustices that are being perpetrated against the people. Hence the close alliance between those two great political forces, the State and the Church. Both need the illusion that a kindly God rewards—in heaven if not on earth—all those who have not risen up against injustice, who have done their duty quietly and uncomplainingly. That is precisely why the honest assertion that God is a mere product of the human imagination is branded as the worst of all mortal sins.<ref name="religion">{{harvnb|Heisenberg|1971|pp=85–86}}</ref></blockquote>

Heisenberg's view was tolerant. Pauli, raised as a Catholic, had kept silent after some initial remarks, but when finally he was asked for his opinion, said: "Well, our friend Dirac has got a religion and its guiding principle is 'There is no God, and Paul Dirac is His prophet.{{' "}} Everybody, including Dirac, burst into laughter.<ref>{{harvnb|Heisenberg|1971|p=87}}</ref><ref>{{harvnb|Farmelo|2009|p=[https://books.google.com/books?id=-TT_z4llWoIC&pg=PA138 138]}}, who says this was an old joke, pointing out a [[Punch (magazine)|''Punch'']] footnote in the 1850s that "There is no God, and [[Harriet Martineau]] is her prophet."</ref>

Later in life, in an article mentioning God that appeared in the May 1963 edition of ''[[Scientific American]]'', Dirac wrote:
<blockquote>It seems to be one of the fundamental features of nature that fundamental [[physical law]]s are described in terms of a [[mathematical theory of great beauty]] and power, needing quite a high standard of mathematics for one to understand it. You may wonder: Why is nature constructed along these lines? One can only answer that our present knowledge seems to show that nature is so constructed. We simply have to accept it. One could perhaps describe the situation by saying that God is a mathematician of a very high order, and He used very advanced mathematics in constructing the universe. Our feeble attempts at mathematics enable us to understand a bit of the universe, and as we proceed to develop higher and higher mathematics we can hope to understand the universe better.<ref>{{cite web |url=http://blogs.scientificamerican.com/guest-blog/2010/06/25/the-evolution-of-the-physicists-picture-of-nature/ |title=The Evolution of the Physicist's Picture of Nature |last1=Dirac |first1=Paul |date=May 1963 |work=[[Scientific American]] |access-date=4 April 2013}}</ref></blockquote>

In 1971, at a conference meeting, Dirac expressed his views on the existence of God.<ref>{{harvnb|Kragh|1990|pp=256–257}}</ref> Dirac explained that the existence of God could be justified only if an improbable event were to have taken place in the past:

<blockquote>It could be that it is extremely difficult to [[Abiogenesis|start life]]. It might be that it is so difficult to start a life that it has happened only once among all the planets... Let us consider, just as a conjecture, that the chance of life starting when we have got suitable physical conditions is 10<sup>−100</sup>. I don't have any logical reason for proposing this figure, I just want you to consider it as a possibility. Under those conditions ... it is almost certain that life would not have started. And I feel that under those conditions it will be necessary to assume the existence of a god to start off life. I would like, therefore, to set up this connection between the existence of a god and the physical laws: if physical laws are such that to start off life involves an excessively small chance so that it will not be reasonable to suppose that life would have started just by blind chance, then there must be a god, and such a god would probably be showing his influence in the quantum jumps which are taking place later on. On the other hand, if life can start very easily and does not need any divine influence, then I will say that there is no god.<ref name="Kragh 1990">{{harvnb|Kragh|1990}}</ref></blockquote>

Dirac did not commit himself to any definite view, but he described the possibilities for scientifically answering the question of God.<ref name="Kragh 1990"/>