Eddington's eclipse expeditions confirm general relativity

Date

29 May 1919 (announced 6 November 1919)

Category

Science, technology & invention

Region

Global (Atlantic: Principe & Brazil)

Era

Modern

Significance

During the total solar eclipse of 29 May 1919, British expeditions led by Arthur Eddington (on Principe, off West Africa) and a Greenwich party at Sobral, Brazil, photographed stars near the obscured Sun and measured the deflection of their light by the Sun's gravity.

The observed deflection of roughly 1.75 arcseconds matched the prediction of Albert Einstein's 1915 general theory of relativity rather than the smaller Newtonian value. On 6 November 1919 the results were announced to a joint meeting of the Royal Society and Royal Astronomical Society, providing the first major experimental confirmation of general relativity. The announcement made headlines worldwide and transformed Einstein into an international celebrity, while marking a shift in the understanding of gravity as the curvature of spacetime. The measurements had wide error bars and were later criticised for possible systematic error and selection of data, though subsequent analyses and far more precise modern tests have upheld the conclusion.

Empires active in 29 May 1919 (announced 6 November 1919)

• Empire of Japan
  1868 CE to 1947 CE
• French Colonial Empire (Second)
  1830 CE to 1962 CE
• British Empire
  1583 CE to 1997 CE
• Spanish Empire
  1492 CE to 1976 CE
• Portuguese Empire
  1415 CE to 1999 CE
• Solomonic dynasty
  1270 CE to 1974 CE

Related science, technology & invention events

• Formulation of quantum mechanics
  1925 to 1927
• Haber-Bosch Process Industrialises Synthetic Nitrogen Fertiliser
  September 1913
• Penicillin and the dawn of the antibiotic era
  1928 (developed for clinical use 1940 to 1945)
• The Wright Brothers' Powered Flight
  17 December 1903
• Discovery of nuclear fission
  December 1938 (explained January to February 1939)
• Discovery of X-rays and radioactivity
  1895 to 1898

Essential reading

• Haber-Bosch Process Industrialises Synthetic Nitrogen Fertiliser
  September 1913
• 1931 Central China Floods
  June to August 1931
• The Dust Bowl
  1930 to 1940 (peak 1934 to 1936)
• Cárdenas Nationalises Mexico's Oil
  1938

Further reading

A Little History of Science

The wider story

A Little History of Science

William Bynum

Warm, jargon-free tour of discovery from Babylonian stargazers to the genome.

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