Background

Paul Adrien Maurice Dirac was born on August 8, 1902, in the city of Bristol, United Kingdom.

His father was Charles Dirac, a school teacher and private tutor who had emigrated from Switzerland to the United Kingdom. His mother was Florence Holten, a former librarian. She was named after Florence Nightingale, whom her father had met and admired.

Although Paul was born in the United Kingdom and his mother was British, his father made sure his children were Swiss rather than British citizens. Paul only became a British citizen at age 17, on October 22, 1919, when his father also took citizenship.

Paul had an unhappy childhood. His parents disliked one another and there was often tension in their home. Very early in life, Paul noticed that his father spoke only French, while his mother spoke only English. Nobody ever visited their home and for a while, Paul believed men and women spoke different languages. Paul's father dined with Paul. His mother dined with Paul's older brother Felix and younger sister Betty.

Paul was his father's unwilling companion: his father forced Paul to speak French, and Paul was not allowed to leave the table if he made any mistakes in that language, which invariably he did. Paul had a lifelong stomach acid problem, which was only correctly diagnosed when he was elderly. As a result of this problem he often vomited at the table because his father would not allow him to leave it. He learned to minimize his French language mistakes by minimizing the number of words he spoke.

Paul ended up despising his tyrannical father and in later life refused to speak French anywhere. In fact, Paul grew to hardly speak at all. He withdrew into his own mind. He would never start conversations, and he became both famous and infamous for the brevity of his responses to anyone who tried to start a conversation with him.

Education

Paul's first school was the Bishop Road Primary School. Later he was educated at the Merchant Venturer's Secondary School.

Dirac entered the University of Bristol in 1918 at the age of 16 and graduated with a degree in electrical engineering in 1921. He then earned an additional degree in mathematics two years later.

After his time at the University of Bristol, Dirac attended St. John's College and in 1926 graduated with his doctoral degree in physics.

Career

Dirac visited the Soviet Union in 1928. It was the first of many visits for he went again in 1929, 1930, 1932, 1933, 1935, 1936, 1937, 1957, 1965, and 1973. Also in 1928, he found a connection between relativity and quantum mechanics, his famous spin-1/2 Dirac equation. In 1929 he made his first visit to the United States, lecturing at the Universities of Wisconsin and Michigan. After the visit, along with Heisenberg, he crossed the Pacific and lectured in Japan. He returned via the trans-Siberian railway.

In 1930 Dirac published The principles of Quantum Mechanics and for this work, he was awarded the Nobel Prize for Physics in 1933. Also in 1930, Dirac was elected a Fellow of the Royal Society. This honor came on the first occasion that his name was put forward, in itself quite an unusual event which says much about the extremely high opinion that Dirac's fellow scientists had of him.

Dirac was appointed Lucasian professor of mathematics at the University of Cambridge in 1932, a post he held for 37 years. In 1933 he published a pioneering paper on Lagrangian quantum mechanics which became the foundation on which Feynman later built his ideas of the path integral. In the same year, Dirac received the Nobel prize for physics which he shared with Schrödinger. It is an interesting comment on Dirac's nature that his first thought was to turn down the prize on the grounds that he hated publicity. However, when it was pointed out to him that he would receive far more publicity if he turned down the prize, he accepted it. Another comment about this event is that Dirac was told that he could invite his parents to the award ceremony in Stockholm, but he chose to invite only his mother and not his father.

In 1937, Dirac published his first paper on large numbers and cosmological matters. We comment further on his ideas on cosmology below. He published his famous paper on classical electron theory, which included mass renormalization and radiative reaction in 1938. Dirac worked during World War II on uranium separation and nuclear weapons. In particular, he acted as a consultant to a group in Birmingham working on atomic energy. This association led to Dirac being prevented by the British government from visiting the Soviet Union after the end of the war; he was not able to visit again until 1957.

Dirac was awarded the Royal Society's Royal Medal in 1939 and the Society awarded him their Copley Medal in 1952 "in recognition of his remarkable contributions to relativistic dynamics of a particle in quantum mechanics."

In 1969 Dirac retired from the Lucasian chair of mathematics at Cambridge and went with his family to Florida in the United States. He held visiting appointments at the University of Miami and at Florida State University. Then, in 1971, Dirac was appointed professor of physics at Florida State University where he continued his research.

In 1973 and 1975 Dirac lectured in the Physical Engineering Institute in Leningrad. In these lectures, he spoke about the problems of cosmology or, to be more precise, to the problems of non-dimensional combinations of world constants.

Although Dirac made vastly important contributions to physics, it is important to realize that he was always motivated by principles of mathematical beauty. Dirac unified the theories of quantum mechanics and relativity theory, but he also is remembered for his outstanding work on the magnetic monopole, fundamental length, antimatter, the d-function, bra-kets, etc.

Achievements

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  Paul Dirac was a famous physicist and brilliant mathematician who made revolutionary and significant contributions to the field of physics. Dirac made significant contributions to the field of quantum mechanics by helping develop a quantum atomic field theory and by developing a better model for electrons in the atomic model, all before he received his doctorate in physics in 1926. Additionally, in 1927, Paul Dirac created the field of quantum electrodynamics or the theory that describes how light interacts with matter, which today is one of the most important branches of physics. In 1928 Dirac, unsatisfied with how the current quantum model didn't work when electrons were moving near the speed of light, created the famous Dirac Equation which described the relativistic motion of the wave function of the electron and inadvertently predicted the existence of antimatter.
  
  Paul Dirac was awarded the Nobel Prize in Physics with Erwin Schrodinger in 1933 for their study of atomic theory. Dirac was also awarded the Royal Medal in 1939 and both the Copley Medal and the Max Planck medal in 1952. He was elected a Fellow of the Royal Society in 1930, and of the American Physical Society in 1948.
  
  Immediately after his death, two organizations of professional physicists established annual awards in Dirac's memory. The Institute of Physics, the United Kingdom's professional body for physicists, awards the Paul Dirac Medal and Prize for "outstanding contributions to theoretical (including mathematical and computational) physics." The first three recipients were Stephen Hawking (1987), John Bell (1988), and Roger Penrose (1989). The Abdus Salam International Centre for Theoretical Physics (ICTP) awards the Dirac Medal of the ICTP each year on Dirac's birthday (August 8).
  
  The street on which the National High Magnetic Field Laboratory in Tallahassee, Florida, is located was named Paul Dirac Drive. There is also a road named after him in his home town of Bristol, United Kingdom. The BBC named its video codec Dirac in his honor. And in the popular British television show Doctor Who, the character Adric was named after him (Adric is an anagram of Dirac).

Works

More photos

• book

  • General Theory of Relativity

    (Einstein's general theory of relativity requires a curved...)

    1975
  • The Principles of Quantum Mechanics 1930
  • Lectures on Quantum Mechanics 1931

Religion

Dirac was something of a militant atheist, prompting quantum physicist Wolfgang Pauli to remark, to Dirac's amusement: "Well, our friend Dirac has got a religion and its guiding principle is: There is no God and Paul Dirac is His prophet."

Politics

In Britain, many academics, Dirac included, were desperately concerned about mass unemployment and the rise of fascism. In Cambridge - where students had mobilized to break the 1926 general strike - the late 1920s and early 1930s saw the growth of socialist ideas.

Many scientists looked towards the Soviet Union as a model of a better society - a planned economy seemed a positive alternative to the depression gripping the west and among Dirac's few friends at Cambridge was Peter Kapitza, a Russian physicist. Dirac himself used his Nobel speech in 1933 to call for redistribution to provide goods for all, despite the fact that speeches are expected to be non-controversial. He visited the USSR several times in the 1930s with Kapitza, made friends with other leading Russian physicists, and was elected to the Soviet Academy of Sciences. But when, in 1937, Stalin cracked down on Kapitza, refusing to allow him to return to Cambridge and putting him under virtual house arrest, Dirac organized a petition of leading physicists and lobbied the Russians, leading to an odd compromise where Kapitza's whole laboratory was shipped from Cambridge to a new institute in Moscow purpose-built for him.

As the crisis of the 1930s slipped into war, physicists scattered. Einstein fled to the USA. Schrödinger left Austria and finally settled in neutral Dublin. Heisenberg remained in Germany and continued working but not openly supporting Hitler, unlike some leading German scientists who became avid Nazis. Back in Cambridge, Dirac organized support for Jewish scientists fleeing from Germany. Horrified even before the war by the treatment of Jews in Germany, he resolved never to speak German again, except to refugees. He took part in the programme to build a nuclear bomb, devising a method of isotope separation and carrying out calculations on chain reactions.

Views

When Paul Dirac started his doctorate studies in physics at the University of Cambridge, Niels Bohr's atomic model was seen as the most complete and accurate version at that time. Bohr had created an atomic model that placed electrons in circular orbits around the nucleus. These orbits had different energy levels and the electrons could jump to higher energy levels or fall to lower energy levels depending on if the atom was receiving energy from incoming light particles, or photons. However, many other leading physicists at that time were unhappy with Bohr's atomic model, Dirac included. At that time, the field of quantum mechanics, or the study of the physics of particles at the atomic and subatomic level, had recently been created and was already in full swing. Therefore Dirac set out to create a better version. Together with Werner Heisenberg and Erwin Schrodinger, Dirac was able to theorize a new atomic model that represented electrons not as just one number, but as a matrix of numbers. Additionally, during this work, Paul Dirac created new mathematical terminology to represent quantum states, called bra-ket notation, which is still used today.

Paul Dirac is also famous for the creation of the field of quantum electrodynamics. Quantum electrodynamics (usually abbreviated QED) is the study of how light interacts with matter. Dirac launched QED with his 1927 paper The Quantum Theory of the Emission and Absorption of Radiation. His new theory unified the previously separate phenomena of the light-wave and the light-quantum.

It was the first theory that dealt successfully with the fact that when an atom absorbs a photon, the light disappears from the universe; and when an atom releases light, a photon appears in the universe. No theory before had accounted for the creation and annihilation of quantum objects such as photons. Dirac pictured a universe in which atoms contain an infinite supply of zero-energy photons available for release as real photons if energy is supplied to them.

Dirac's, Heisenberg's, and Schrodinger's work on quantum mechanics provided a much better model for the electron then Bohr's atomic model. However, there was still a problem: their electron model only worked for electrons that were moving relatively slowly; it didn't work for fast-moving electrons, or for electrons moving close to the speed of light. Paul Dirac was not satisfied with this. Therefore he set out to create a new equation, one that would create an electron model within quantum mechanics but also encompass Albert Einstein's theory of general relativity for the electrons moving close to the speed of light. It would also factor in an electron's spin, which the famous physicist Wolfgang Pauli had discovered shortly beforehand. Encompassing all of these elements, Paul Dirac created what is called the Dirac equation, an equation of motion for the wave function of the electron, for all speeds. Once the Dirac equation was published in 1928, the physics community was astounded. It still is regarded as one of the greatest physics papers ever written.

However, Dirac's equation did produce a confusing result. While mathematically perfect, the Dirac equation had produced twice the amount of electrons then the amount that was previously thought. Dirac, although perplexed, trusted the mathematics in his theory and predicted the existence of antimatter, and in this case the existence of a positron, a particle that had exactly the same mass and characteristics of an electron but with a positive charge. The existence of antimatter, or antiprotons, antineutrons, and positrons, was proven experimentally only a few years later in 1932 by the physicist Carl Anderson.

In 1955, Dirac proposed that particles such as electrons are in fact one-dimensional strings. This enabled him to dispense with concepts he found objectionable in QED - namely: the "bare" electron that existed separately from its own field; the infinities caused by the "bare" electron that required renormalization. Dirac's gauge-invariant theory achieved the goals he set it, but never became popular.

String theory, in which particles are represented as one-dimensional strings, was reborn in the 1960s and 1970s, although in a different form to Dirac's original conception.

Quotations: "In science one tries to tell people, in such a way as to be understood by everyone, something that no one ever knew before. But in poetry, it's the exact opposite."

"Pick a flower on Earth and you move the farthest star."

"The measure of greatness in a scientific idea is the extent to which it stimulates thought and opens up new lines of research."

"Mathematics is only a tool and one should learn to hold the physical ideas in one's mind without reference to the mathematical form."

"God is a mathematician of a very high order and He used advanced mathematics in constructing the universe."

Membership

Dirac refused to accept honorary degrees but he did accept honorary membership of academies and learned societies. The list of these is long but among them are the USSR Academy of Sciences (1931), Indian Academy of Sciences (1939), Chinese Physical Society (1943), Royal Irish Academy (1944), Royal Society of Edinburgh (1946), Institut de France (1946), National Institute of Sciences of India (1947), American Physical Society (1948), National Academy of Sciences (1949), National Academy of Arts and Sciences (1950), Accademia delle Scienze di Torino (1951), Academia das Ciencias de Lisboa (1953), Pontifical Academy of Sciences, Vatican City (1958), Accademia Nazionale dei Lincei, Rome (1960), Royal Danish Academy of Sciences (1962), and Académie des Sciences, Paris (1963).

• USSR Academy of Sciences

  1931

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  Indian Academy of Sciences

  1939

• Chinese Physical Society

  1943

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  Royal Irish Academy

  1944

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  Royal Society of Edinburgh

  1946

• Institut de France

  1946

• 

  National Institute of Sciences of India

  1947

• 

  American Physical Society

  1948

• 

  National Academy of Sciences

  1949

• 

  National Academy of Arts and Sciences

  1950

• 

  Accademia delle Scienze di Torino

  1951

• 

  Academia das Ciencias de Lisboa

  1953

• 

  Pontifical Academy of Sciences

  1958

• 

  Accademia Nazionale dei Lincei

  1960

• 

  Royal Danish Academy of Sciences

  1962

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  Académie des Sciences

  1963

Personality

In the early part of his life, Dirac was very nearly a workaholic. He worked extremely hard for almost all of his waking hours six days a week. On Sundays, he went for long walks.

Dirac hated publicity. He reluctantly accepted the Nobel Prize after being told by Ernest Rutherford that refusing it would create more publicity than accepting it. Nevertheless, he turned down most honors including the knighthood offered to him in 1953.

Quotes from others about the person

• Stephen Hawking: "...Heisenberg and Schrödinger can claim to have caught the first glimpses of the theory. But it was Dirac who put them together and revealed the whole picture."

Interests

• Walking, climbing, reading

• Writers

  Agatha Christie, Arthur Conan Doyle

Connections

In 1934, Dirac visited the Institute for Advanced Study at Princeton and became friendly with Eugene Wigner. There he was introduced to Wigner's sister Margit who lived in Budapest and was visiting her brother. This chance meeting led, in January 1937, to Dirac marrying Margit in London. Margit had been married before and had two children, Judith and Gabriel from her first marriage. Both children adopted the name Dirac and step-son Gabriel Andrew Dirac went on the became a mathematician who mainly worked in graph theory. Paul and Margit Dirac also had two children together, both daughters, Mary Elizabeth and Florence Monica.

Father:

Charles Dirac

Mother:

Florence Holten

Spouse:

Margit Wigner

Step-son:

Gabriel Dirac

step-daughter:

Judith Dirac

Daughter:

Mary Elizabeth Dirac

Daughter:

Florence Monica Dirac

Friend:

Pyotr Kapitza

colleague:

Erwin Schrodinger

References

• The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom
  2009