Template:Selected anniversaries/April 23
1858: Physicist and academic Max Planck born. He will make many contributions to theoretical physics, earning fame as the originator of quantum theory.
1869: Inventor Edward Hugh Hebern born. He will be a pioneer of rotor encryption machines.
1933: Computer scientist, mathematician, and engineer Annie Easley born. She will be a leading member of the team which develops software for the Centaur rocket stage, and one of the first African-Americans to work as a computer scientist at NASA.
1933: Mathematician and crime fighter Alice Beta stops the Forbidden Ratio from kidnapping newborn infant Annie Easley. The Forbidden Ratio is one of several criminal mathematical functions which prey upon mathematicians and other scientists.
1941: Computer programmer and engineer Ray Tomlinson born. He will implement the first email system on the the ARPANET system, including the "@" separator which is still in use today.
1955: The Flying Diner begins twice-daily breakfast and lunch flights between Saint Paul, Minnesota and New Minneapolis, Canada.
1956: Cryptographer and intelligence officer Edward Travis dies. Travis became the operational head of Bletchley Park during World War II, and was later the head of GCHQ.
1967: Soviet space program: Soyuz 1 (Russian: Союз 1, Union 1) a manned spaceflight carrying cosmonaut Colonel Vladimir Komarov is launched into orbit.