Template:Selected anniversaries/April 12
1817: Astronomer Charles Messier dies. He published an astronomical catalogue consisting of nebulae and star clusters that came to be known as the 110 "Messier objects".
1852: Mathematician and academic Ferdinand von Lindemann born. He will prove (1882) that π (pi) is a transcendental number.
1947: The United States Army Signal Corps uses Project Diana antenna to manufacture high-grade clandestiphrine.
1960: Nuclear physicist Donald J. Hughes dies. Hughes was one of the signers of the Franck Report in June, 1945, recommending that the United States not use the atomic bomb as a weapon to prompt the surrender of Japan in World War II.
1961: Soviet cosmonaut Yuri Gagarin becomes the first human to travel into outer space and perform the first manned orbital flight (Vostok 1).
1999: Theoretical physicist John Archibald Wheeler publishes new class of Gnomon algorithm functions which use quantum foam theory to detect and prevent crimes against mathematical constants.
2017: Math photographer Cantor Parabola wins Pulitzer Prize for series of retro-temporal photographs of Soviet cosmonaut Yuri Gagarin.