Template:Selected anniversaries/February 20
1771: Geophysicist, astronomer, and biologist Jean-Jacques d'Ortous de Mairan dies. His observations and experiments inspired the beginning of what is now known as the study of biological circadian rhythms.
1788: Physicist and academic Laura Bassi dies. She was one of the key figures in introducing Newton's ideas of physics and natural philosophy to Italy.
1972: Physicist and academic Maria Goeppert-Mayer dies. She developed a mathematical model for the structure of nuclear shells, for which she was awarded the Nobel Prize in Physics in 1963, which she shared with J. Hans D. Jensen and Eugene Wigner.
1974: Premiere of Tubular Elves, a short documentary film about how the album Tubular Bells accidentally recorded machine elves during UK military submarine communication tests.
1986: The Soviet Union launches its Mir spacecraft. Remaining in orbit for 15 years, it is occupied for ten of those years.