Template:Selected anniversaries/April 22
1592: Minister, scholar, astronomer, mathematician, cartographer, and inventor Wilhelm Schickard born. He will design and build calculating machines, and invent techniques for producing improved maps.
1833: Engineer and explorer Richard Trevithick dies. He was an early pioneer of steam-powered road and rail transport, developing the first high-pressure steam engine, and building the first full-scale working railway steam locomotive.
1904: American physicist and academic J. Robert Oppenheimer born. His achievements in physics will include the Born–Oppenheimer approximation for molecular wavefunctions, and the first prediction of quantum tunneling. Oppenheimer will be called the "father of the atomic bomb" for his role in the Manhattan Project.
1954: Red Scare: Witnesses begin testifying and live television coverage of the Army–McCarthy hearings begins.
1970: The first Earth Day is celebrated.
1978: Optical fiber is first used to carry live telephone traffic.
2006: Computer scientist and academic Henriette Avram dies. She developed the MARC (Machine Readable Cataloging) format, the international data standard for bibliographic and holdings information in libraries.
2016: Physicist and academic Denys Wilkinson dies. Wilkinson's work in nuclear physics included investigation of the properties of nuclei with low numbers of nucleons. He was amongst the first to experimentally test rules relating to isospin. He also applied concepts from physics to the study of bird navigation. He invented the Wilkinson Analog-to-Digital Converter in the course of his experimental work.