21 October in history.

1858

The can-can music is heard for the first time. Jacques Offenbach's operetta Orpheus in the Underworld, home of the tune most linked with the can-can, opened at the Théâtre des Bouffes-Parisiens in Paris.

Wikipedia: Jacques Offenbach

Photo: Nadar / Adam Cuerden / Wikimedia Commons (Public domain)

More from 21 October

1. 

   1879

   Edison files his light bulb patent

   Thomas Edison applied for a patent for his design of an incandescent light bulb.

   Wikipedia: Thomas EdisonWikipedia: Incandescent light bulb

   Photo: Louis Bachrach, Bachrach Studios , restored by Michel Vuijlsteke / Wikimedia Commons (Public domain)

2. 

   1959

   The Guggenheim Museum opens in New York

   The Solomon R. Guggenheim Museum, designed by architect Frank Lloyd Wright, opened its doors in New York City.

   Wikipedia: Solomon R. Guggenheim MuseumWikipedia: Frank Lloyd Wright

   Photo: Ajay Suresh from New York, NY, USA / Wikimedia Commons (CC BY 2.0)

3. 

   1983

   The metre is measured by light

   Scientists fixed the length of a metre using light itself: it became the distance light covers in a vacuum in 1/299,792,458 of a second.

   Wikipedia: Metre

   Photo: Yerpo / Wikimedia Commons (CC BY-SA 4.0)

4. 

   2003

   The first pictures of Eris are taken

   Astronomers took the images of the dwarf planet Eris that were later used to confirm its discovery.

   Wikipedia: Eris (dwarf planet)

   Photo: NASA/ESA/CSA JWST NIRCam; Ana Carolina de Souza Feliciano et al. & Melina Thévenot / Wikimedia Commons (CC BY-SA 4.0)

Moments chosen for discovery, creativity and courage. Each one links to a source where you can read more; photos are credited to their owners.