1920 in science

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

Astronomy and space science

January 13 – The New York Times ridicules rocket scientist Robert H. Goddard, stating that spaceflight is impossible. In 1969, with Apollo 11 on its way to the Moon, the newspaper will publicly retract this position.
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.

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

July 15 – F. W. Aston shows that the molar mass of chlorine is a weighted average of the almost integral masses for the two isotopes ³⁵Cl and ³⁷Cl.

October 31 - Dr. Frederick Banting of Ontario first records his insight on how to isolate insulin for the treatment of diabetes; working with Charles Best, the first successful human trial of insulin will occur 15 months later.
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.
Black Cross Nurses founded in the United States.

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.

Megh Nad Saha states his ionization equation.
Albert Einstein delivers his Leiden Lecture.
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.

American psychologist Edward Thorndike names the halo effect and first provides empirical evidence that it is a specific cognitive bias.
American psychologist John B. Watson conducts the Little Albert experiment in classical conditioning.

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.

April 26 – Emil Racoviță establishes the world's first institute for the academic study of speleology at the Upper Dacia University in Cluj.
Publication in Prague of Karel Čapek's drama R.U.R: Rossum's Universal Robots, introducing the word Robot to the world.

January 20 – John Maynard Smith, British theoretical evolutionary biologist and geneticist.
February 7 – An Wang, Chinese-born computer engineer.
February 3 – Henry Heimlich, American thoracic surgeon.
March 11 – Nicolaas Bloembergen, Dutch physicist, Nobel Prize laureate.
March 15 – E. Donnall Thomas, American physician, Nobel Prize laureate.
March 22 – Katsuko Saruhashi Japanese geochemist.
March 23 – Barbara Low, English-born biochemist.
April 6 – Edmond H. Fischer, Swiss American biochemist, Nobel Prize laureate
April 9 – Alex Moulton, English mechanical engineer and inventor.
May 12 – Tang Dingyuan, Chinese physicist.
June 17 – François Jacob, French biologist, Nobel Prize laureate.
July 10 – Owen Chamberlain, American physicist, Nobel Prize laureate.
July 11 – David Challinor, American biologist, naturalist and scientific administrator at the Smithsonian Institution.
July 25 – Rosalind Franklin, English crystallographer.
July 30 – Marie Tharp, American geologist.
August 15 – Eleonore Trefftz, German molecular and nuclear physicist.
August 22 – Denton Cooley, American cardiac surgeon.
September 29 – Peter D. Mitchell, English chemist, Nobel Prize laureate.
October 29 – Baruj Benacerraf, Venezuelan immunologist, Nobel Prize laureate.
November 13 – Abraham Lilienfeld, American epidemiologist.
December 6 – George Porter, English chemist, Nobel Prize laureate.