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Arthur Eddington
Arthur Stanley Eddington
Born	December 28, 1882(1882-12-28) Kendal, England
Died	November 22, 1944 (aged 61) Cambridge, England
Residence	UK
Nationality	British
Field	Astrophysicist
Institutions	University of Cambridge
Alma mater	University of Cambridge
Academic advisor	Horace Lamb
Notable students	Leslie Comrie
Known for	Eddington limit Eddington number Eddington-Dirac number
Notable prizes	Royal SocietyRoyal Medal (1928)
Religious stance	Quaker
Eddington received an MA in 1905 and did not have a doctorate or doctoral advisor. However, Horace Lamb was a major academic influence and can be considered an equivalent mentor.

Sir Arthur Stanley Eddington, OM (December 28, 1882 – November 22, 1944) was an astrophysicist of the early 20th century. The Eddington limit, the natural limit to the luminosity that can be radiated by accretion onto a compact object, is named in his honour.

He is famous for his work regarding the Theory of Relativity. Eddington wrote an article in 1919, Report on the relativity theory of gravitation, which announced Einstein's theory of general relativity to the English-speaking world. Because of World War I, new developments in German science were not well known in England.

Eddington was born in Kendal, England, son of Quaker parents. His father, Arthur Henry Eddington, taught at a Quaker training college in Lancashire before moving to Kendal to become headmaster of Stramongate School. He died in the typhoid epidemic which swept England in 1884. His mother, Sarah Ann Shout, came from Darlington and was also from a Quaker family. When his father died, she was left to bring up Arthur and his older sister with relatively little income. The family moved to Weston-super-Mare where at first Arthur was educated at home before spending three years at a preparatory school.

In 1893 Arthur entered Brynmelyn School. He proved to be a brilliant scholar and excelled in mathematics and English literature. His records won him a 60 pounds scholarship in 1898, and he was able to attend Owens College in Manchester once he turned 16 later that year. He spent the first year in a general course, but turned to physics for the next three years. Eddington was greatly influenced by one of his mathematics teachers, Horace Lamb. His progress continued to be rapid, winning him several additional scholarships and allowing him to graduate with a B.Sc. with First Class Honours in 1902.

Based on his performance at Owens, he was awarded a 75 pound scholarship at Trinity College, Cambridge, which he entered in 1903. He graduated with a masters in 1905, and entered the Cavendish Laboratory researching thermionic emission. This did not go well, so he returned to mathematics, but appeared not to enjoy this very much.

After leaving university later in 1905, Eddington's first full-time position was as the chief assistant to the Astronomer Royal at the Royal Greenwich Observatory. He was put to work on a detailed analysis of the parallax of 433 Eros on photographic plates that had started in 1900. He developed a new statistical method based on the apparent drift of two background stars, winning him the Smith's Prize in 1907.

The prize won him a Trinity College Fellowship. In December 1912 George Darwin, son of Charles Darwin, died suddenly and Eddington was promoted to his chair as the Plumian Professor of Astronomy and Experimental Philosophy in early 1913. Later that year, Robert Ball, holder of the theoretical Lowndean chair also died, and Eddington was named the director of the entire Cambridge Observatory the next year. He was elected a Fellow of the Royal Society shortly thereafter.

During World War I, Eddington was called up for military service but because he was a member of the Religious Society of Friends (Quakers) and a pacifist, he refused to serve in the army. As a conscientious objector he requested alternative service instead. Scientific friends of his solved the problem by successfully arguing to relieve him from military duty because of his importance for science.

One of Eddington's photographs of the 1919 eclipse, presented in his 1920 paper announcing its success.

After the war, Eddington travelled to the island of Príncipe near Africa to watch the solar eclipse of May 29, 1919. During the eclipse, he took pictures of the stars in the region around the Sun. According to the theory of general relativity, stars near the Sun would appear to have been slightly shifted because their light had been curved by its gravitational field. This effect is noticeable only during an eclipse, since otherwise the Sun's brightness obscures the stars. Newtonian gravitation (or more precisely Einstein in 1910 before he developed general relativity) predicted half the shift of general relativity.

Eddington's observations published next year (Dyson, F.W., Eddington, A.S., & Davidson, C.R. 1920 A Determination of the Deflection of Light by the Sun's Gravitational Field, from Observations Made at the Total Eclipse of May 29, 1919 Mem. R. Astron. Soc., 220, 291-333) confirmed Einstein's theory, and were hailed at the time as a conclusive proof of general relativity over the Newtonian model, though Eddington had poor quality observations and had discounted simultaneous observations at Sobral, Brazil which appeared closer to the Newtonian model;^[1] the news was reported in newspapers all over the world as a major story. It is also the source of the urban legend that only three people understand relativity; when asked by a reporter who suggested this, Eddington jokingly replied "Oh, who's the third?"

Eddington also investigated the interior of stars through theory, and developed the first true understanding of stellar processes. He modeled stars as gas in radiative equilibrium; the star was stabilized by gravity pulling in, and gas pressure (temperature) and radiation pressure pushing out. Noting that the temperatures meant that the atoms in stars would be almost entirely ionized, he theorized that they would behave as almost-ideal gases, thereby making the mathematics much more tractable.

With these assumptions, he demonstrated that the interior temperature of stars must be millions of degrees. He discovered the mass-luminosity relationship for stars, he calculated the abundance of hydrogen and he produced a theory to explain the pulsation of Cepheid variable stars.

The first suggestion that stars obtained their energy from nuclear fusion of hydrogen to helium is commonly attributed to Eddington, but was in fact made earlier by the French Nobel Prize winner Jean Baptiste Perrin. Eddington was one of the most vocal champions of this theory, and he had a long-running argument with James Jeans over it. Later, in 1938 and 1939, Hans Bethe introduced the theory for the fusion, which made the process seem rather "natural" and the debate generally ended.

Throughout this period Eddington lectured on relativity, and was particularly well known for his ability to explain the concepts in lay terms as well as scientific. He collected many of these into the Mathematical Theory of Relativity in 1923, which Albert Einstein suggested was "the finest presentation of the subject in any language."

He strongly opposed the budding scientist Subrahmanyan Chandrasekhar about his theory on the maximum mass of white dwarf stars, the mass above which the star collapses and becomes a neutron star, quark star or black hole. Chandrasekhar was subsequently proven to be right, and went on to win the Nobel Prize in Physics in 1983. The distinguished astronomer Sir Arthur Eddington publicly ridiculed his suggestion that stars could collapse into such objects( black holes). Disappointed, and reluctant to engage in public debate, Chandrasekhar moved to America and in 1937 joined the faculty as an Assistant Professor of Astrophysics at the University of Chicago and remained there till his death. At Chicago, he immersed himself in a personalized style of research and teaching, tackling first one field of astrophysics and then another in great depth. He wrote more than half a dozen definitive books describing the results of his investigations.

During the 1920s until his death, he increasingly concentrated on what he called "fundamental theory" which was intended to be a unification of quantum theory, relativity and gravitation. At first he progressed along "traditional" lines, but turned increasingly to an almost numerological analysis of the dimensionless ratios of fundamental constants.

His basic approach was to combine several fundamental constants in order to produce a dimensionless number. In many cases these would result in numbers close to 10⁴⁰, its square, or its square root. He was convinced that the mass of the proton and the charge of the electron, were a natural and complete specification for constructing a Universe and that their values were not accidental. One of the discoverers of quantum mechanics, Paul Dirac, also pursued this line of investigation, which has become known as the Dirac large numbers hypothesis, and some scientists even today believe it has something to it.

A particularly damaging statement in his defence of these concepts involved the fine structure constant α. At the time it was measured to be very close to 1/136, and he argued that the value should in fact be exactly 1/136 for various reasons. Later measurements placed the value much closer to 1/137, at which point he switched his line of reasoning and claimed that the value should in fact be exactly 1/137, the Eddington number. Wags at the time started calling him "Arthur Adding-one". At this point most other researchers stopped taking his concepts very seriously. The current measured value is estimated at 1/137.035999679(94).

Eddington believed he had discovered an algebraic basis for fundamental physics, which he termed "E-frames" (representing a particular group). While his theory has long been abandoned by the general physics community, similar algebraic notions underlie many modern attempts at a grand unified theory.

He did not complete this line of research before his death in 1944, and his book entitled Fundamental Theory was published posthumously in 1946. Eddington died in Cambridge, England.

Awards

• Bruce Medal (1924)
• Henry Draper Medal (1924)
• Gold Medal of the Royal Astronomical Society (1924)
• Royal Medal of the Royal Society (1928)
• Knighted (1930)
• Order of Merit (1938)

Named after him

• Eddington Crater on the Moon
• asteroid 2761 Eddington
• Royal Astronomical Society's Eddington Medal
• Eddington mission, now cancelled

Eddington was a superb populariser of science, writing many books aimed at the layman. He promoted the infinite monkey theorem in his 1928 book The Nature of the Physical World, with the phrase "If an army of monkeys were strumming on typewriters, they might write all the books in the British Museum".

• 1914. Stellar Movements and the Structure of the Universe. London: Macmillan.
• 1920. Space, Time and Gravitation: An Outline of the General Relativity Theory. Cambridge University Press. ISBN 0-521-33709-7
• 1923, 1952. The Mathematical Theory of Relativity. Cambridge University Press.
• 1926. Stars and Atoms. Oxford: British Association.
• 1926. The Internal Constitution of Stars. Cambridge University Press. ISBN 0-521-33708-9
• 1928. The Nature of the Physical World. MacMillan. 1935 replica edition: ISBN 0-8414-3885-4, University of Michigan 1981 edition: ISBN 0-472-06015-5 (1926–27 Gifford lectures)
• 1929. Science and the Unseen World. Macmillan. ISBN 0-8495-1426-6, 2004 reprint: ISBN 1-4179-1728-8
• 19nn. The Expanding Universe: Astronomy's 'Great Debate', 1900-1931. Cambridge University Press. ISBN 0-521-34976-1
• 1930. Why I Believe in God: Science and Religion, as a Scientist Sees It
• 1935. New Pathways in Science. Cambridge University Press.
• 1936. Relativity Theory of Protons and Electrons. Cambridge Univ. Press.
• 1939. Philosophy of Physical Science. Cambridge University Press. ISBN 0-7581-2054-0 (1938 Tarner lectures at Cambridge))
• 1925. The Domain of Physical Science. 2005 reprint: ISBN 1-4253-5842-X
• 1946. Fundamental Theory. Cambridge University Press.

Eddington will be played by actor David Tennant in the upcoming television film Einstein and Eddington, a co-production of the BBC and HBO^[2].

• Astronomy: Eddington limit, Chandrasekhar limit, Gravitational lens, Stellar nucleosynthesis, Timeline of stellar astronomy, Astronomers, Astrophysicists
• Science: Pathological science, Fundamental physical constant, Timeline of gravitational physics and relativity, General relativity, Special relativity, Luminiferous aether, Experiments, Fundamental theory, Eddington number, Eddington-Dirac number, Time's arrow.
• Organizations: Trinity College, Cambridge, Religious Society of Friends, Royal Astronomical Society
• Other: Georges Lemaître, Infinite monkey theorem, One hundred thirty-seven, Numerology, Eddington (locations), List of English people, List of astronomical topics

Wikimedia Commons has media related to:

Arthur Stanley Eddington

Wikiquote has a collection of quotations related to:

Arthur Stanley Eddington

• O'Connor, J. J., and E. F. Robertson, "Arthur Stanley Eddington". School of Mathematics and Statistics, University of St Andrews, Scotland.
• Eddington Quotations
• Bennett, Clark, "Sir Arthur Eddington (1882-1944)". Founding Fathers of Relativity.
• Tenn, Joseph S.,"Arthur Stanley Eddington". The Bruce Medalists.
• Clausen, Ben, "Men of Science and of Faith in God, Sir Arthur Stanley Eddington (1882–1944)".
• Russell, Henry Norris, "Review of The Internal Constitution of the Stars by A.S. Eddington". Ap.J. 67, 83 (1928).
• Durham, Ian T., "Eddington & Uncertainty". Physics in Perspective (Sept. – Dec.). Arxiv, History of Physics.
• Kilmister, C. W. (1994). Eddington's search for a fundamental theory. Cambridge Univ. Press. 
• Awarding of Bruce Medal: PASP 36 (1924) 2
• Awarding of RAS gold medal: MNRAS 84 (1924) 548
• Waller, John, "Einstein's Luck: The Truth Behind Some of the Greatest Scientific Discoveries". Oxford University Press, 2003. ISBN 0-19-860719-9
• Experiments of Sobral and Príncipe repeated in the space project in proceeding in fórum astronomical.
• O'Connor, John J; Edmund F. Robertson "Arthur Stanley Eddington". MacTutor History of Mathematics archive.  

• ApJ 101 (1943-46) 133
• JRASC 39 (1943-46) 1
• MNRAS 105 (1943-46) 68
• Obs 66 (1943-46) 1