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.
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).
1984: United States Navy Admiral Edwin Thomas Layton dies. Layton served as a Naval intelligence officer before and during World War II.
2020: Math photographer Cantor Parabola wins Pulitzer Prize for series of exo-temporal photographs of Minicon 55 in 2021.