1920 in science

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The year 1920 in science and technology involved some significant events, listed below.

Astronomy

• December 13 – The red giant star Betelgeuse is the first to have its diameter determined by an optical astronomical interferometer, the Michelson stellar interferometer on Mount Wilson Observatory's reflector telescope.

Biology

• Andrew Douglass proposes dendrochronology dating.
• Approximate date – The HIV pandemic almost certainly originates in Léopoldville, modern-day Kinshasa, the capital of the Belgian Congo.

History of science and technology

• Newcomen Society founded in the United Kingdom for the study of the history of engineering and technology.

Medicine

• Frederick Banting and Charles Best co-discover insulin.
• Hans Gerhard Creutzfeldt first describes some of the symptoms of what will become known as Creutzfeldt–Jakob disease.
• Hydrocodone, a narcotic analgesic closely related to codeine, is first synthesized in Germany by Carl Mannich and Helene Löwenheim.

Meteorology

• Milutin Milanković proposes that long term climatic cycles may be due to changes in the eccentricity of the Earth's orbit and changes in the Earth's obliquity ("Milankovitch cycles").

Physics

• Megh Nad Saha states his ionization equation.
• Albert Einstein delivers his Leiden Lecture.
• Publication of Arthur Eddington's observation of the "bending of light" during the total solar eclipse of May 29, 1919, confirming Einstein's theory of general relativity.
• Ernest Rutherford predicts the existence of the neutron.
• James Jeans discovers that the dynamical constants of motion determine the distribution function for a system of particles.
• Publication of Alan A. Griffith's analysis of the process of brittle fracture.

Psychology

• John B. Watson conducts the Little Albert experiment in classical conditioning.

Technology

• July 25 – The first transatlantic two-way radio broadcast is made.
• September 29 – First domestic radio sets come to stores in the United States – a Westinghouse radio costs $10.
• October – Young Russian physicist Lev Sergeyevich Termen first develops the electronic musical instrument which will become the Theremin.

Events

• Publication in Prague of Karel Čapek's drama R.U.R: Rossum's Universal Robots, introducing the word Robot to the world.

Births

• January 20 – John Maynard Smith (died 2004), British theoretical evolutionary biologist and geneticist.
• February 7 – An Wang, Chinese-born computer engineer (died 1990).
• March 11 – Nicolaas Bloembergen, Dutch physicist, Nobel Prize laureate.
• March 15 – E. Donnall Thomas, American physician, Nobel Prize laureate.
• April 6 – Edmond H. Fischer, Swiss American biochemist, Nobel Prize laureate.
• April 9 – Alex Moulton, English mechanical engineer and inventor (died 2012)
• June 17 – François Jacob, French biologist, Nobel Prize laureate.
• July 10 – Owen Chamberlain, American physicist, Nobel Prize laureate (died 2006).
• July 11 – David Challinor (died 2008), American biologist, naturalist, and scientific administrator at the Smithsonian Institution.
• July 25 – Rosalind Franklin, English crystallographer (died 1958).
• September 29 – Peter D. Mitchell, English chemist, Nobel Prize laureate (died 1992).
• October 29 – Baruj Benacerraf, Venezuelan immunologist, Nobel Prize laureate. (died 2011)
• November 13 – Abraham Lilienfeld, American epidemiologist (died 1984)
• December 6 – George Porter, English chemist, Nobel Prize laureate (died 2002).

Deaths

• January 3 – Zygmunt Janiszewski, Polish mathematician (born 1888).
• January 6 – Hieronymus Georg Zeuthen, Danish mathematician (born 1839).
• March 13 – Charles Lapworth, English geologist (born 1842).
• March 26 – William Chester Minor, American surgeon (born 1834).
• March 31 – Paul Bachmann, German mathematician (born 1837).
• April 3 – Mary Katharine Brandegee, American botanist (born 1844).
• April 8 – John Brashear, American astronomer (born 1840 in science).
• April 9 – Moritz Cantor, German historian of mathematics (born 1829).
• April 26 – Srinivasa Ramanujan, Indian mathematician (born 1887).
• June 20
  • Marie Adolphe Carnot, French chemist and mining engineer (born 1839).
  • John Grigg, New Zealand astronomer (born 1838).
• August 10 – Ádám Politzer (born 1835), Hungarian otologist.
• August 12 – Hermann Struve, Russian-born astronomer (born 1854).
• August 16 – Norman Lockyer, English astronomer (born 1836).
• August 31 – Wilhelm Wundt, German physiologist and psychologist (born 1832).
• October 17 – Reginald Farrer, English botanist (born 1880).
• November 4 – Ludwig Struve, Russian astronomer (born 1858).
• December 3 – William de Wiveleslie Abney, English astronomer and photographer (born 1843).