 the year 1920 in science and technology involved some significant events, listed below. ==astronomy== * december 13 â 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 â the hiv pandemic almost certainly originates in lÃ©opoldville, modern-day kinshasa, the capital of the belgian congo.based on its genetic history.  ==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 creutzfeldtâjakob disease. * hydrocodone, a narcotic analgesic closely related to codeine, is first synthesized in germany by carl mannich and helene lÃ¶wenheim. ==meteorology== * milutin milankoviÄ 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").thÃ©orie mathÃ©matique des phÃ©nomÃ¨nes thermiques produits par la radiation solaire (paris). ==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.{{cite journal|last=dyson|first=f.w.|author2=eddington, a.s.|author3= davidson, c.r.|year=1920|title=a determination of the deflection of light by the sun's gravitational field, from observations made at the solar eclipse of may 29, 1919|journal=philosophical transactions of the royal society a: physical, mathematical and engineering sciences|volume=220|is
1920_in_science