August 20

1858 – Charles Darwin first publishes his theory of evolution through natural selection in The Journal of the Proceedings of the Linnean Society of London.
1922 – Surgeon Akutsu Tetsuzo is born. He built the first artificial heart that was implanted and kept an animal alive.
1975 – NASA launches the probe Viking 1 towards Mars, with the mission of observation through photography, as well as passive scans for life.
1977 – NASA launches the Voyager 2 probe towards the outer Sol System planets of Jupiter, Saturn, Uranus, and Neptune. While on its mission, the probe also discovered and photographed many previously unknown moons, rings and other features of the distant planets. In addition, a 12-inch copper phonograph record carried on board contained greetings in dozens of languages, samples of music and sounds of nature.

2407 – Torgh is assigned as commanding officer of the USS Gettysburg, BC-1863.