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Arthur Eddington Biography
Sir Arthur Stanley Eddington (December 28, 1882 November 22, 1944) was arguably the most important astrophysicist from 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, 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.

In 1924 he won the Bruce Medal, the Henry Draper Medal and the Gold Medal of the Royal Astronomical Society. He won the Royal Medal of the Royal Society in 1928.

A crater on the Moon is named after him, as is the asteroid 2761 Eddington.

Biography
Early years
Eddington was born in Kendal, England.

In 1906, Arthur Eddington began his statistical study of stellar motions.

During World War I, Eddington was called up for military service. Being a Quaker and a pacifist, he refused to serve in the army, and wanted to be allowed to do alternative service instead, but such a thing was not possible at the time. Scientific friends of his solved the problem by successfully arguing to relieve him from military duty because of his importance for science.

After the war, Eddington travelled to the island of Principe near Africa to watch the solar eclipse of May 29, 1919. During the eclipse, he took pictures of the region around the Sun. According to the general theory of 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. This shift was indeed found.

Eddington also investigated the interior of stars, and calculated their temperature based on what would be necessary to withstand the pressure of the higher-laying layers. 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.

Later years
In 1920, Eddington, on the basis of the precise measurements of atoms by F. W. Aston, was the first to suggest that stars obtained their energy from nuclear fusion of hydrogen to helium. This was the first suggestion that stars obtained their energy from nuclear fusion, a theory which was later shown to be correct, but over which he had a long running argument with James Jeans.

During 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, based on almost numerological analysis of the dimensionless ratios of fundamental constants.

Eddington at one time thought the fine structure constant α, which had been measured at approximately 1/137, should be exactly 1/137, based on aesthetic and numerological arguments. Measurements have currently shown this not to be the case for the value of α and the current value is estimated at 1/137.035 999 76(50) (Eddington, though in error to the exact value, was not far off in his theories). Around 1938, when another measurement showed α to have a value nearer 1/136, Eddington constructed an argument relating the number 136 to the Eddington number. This was his best estimate of the number of electrons in the Universe.

Eddington died in Cambridge, England.

Writer
Eddington was a superb populariser of science, writing many books aimed at the layman. He is also attributed with introducing the Infinite Monkey Theorem with the 1929 phrase "If an army of monkeys were strumming on typewriters, they might write all the books in the British Museum".

Publications
Eddington, Arthur S., "Stars and Atoms (http://www.bibliomania.com/NonFiction/Eddington/Stars/index.html)". British Association, Oxford. August 1926.
Eddington, Arthur S., "The internal Constitution of Stars". Cambridge University Press, Cambridge. 1926. ISBN 0521337089
Eddington, Arthur S., "Fundamental Theory" Cambridge University Press, London. 1928.
Eddington, Arthur S., "Science and the Unseen World". New York: Macmillan, 1929. ISBN 0849514266
Eddington, Arthur S., "Expanding Universe: Astronomy's 'Great Debate', 1900-1931". Cambridge University Press. ISBN 0521349761
Eddington, Arthur S., "The Nature of the Physical World". Folcroft Library Editions. June 1935. ASIN 0841438854
Eddington, Arthur S., "New Pathways in Science". Cambridge University Press, Cambridge. 1935.
Eddington, Arthur S., "Space, Time and Gravitation: An Outline of the General Relativity Theory". Cambridge University Press. ISBN 0521337097
Eddington, Arthur S., "Philosophy of Physical Science". Textbook Publishers. ISBN 0758120540
Eddington, Arthur S., "The Domain of Physical Science".

Quotes
" [...] it is [sound judgment] to hope that in the not too distant future we shall be competent to understand so simple a thing as a star". Arthur Stanley Eddington, "The Internal Constitution of Stars".
 
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Arthur Eddington.