Today I learned on Nostr: TIL while viewing a solar eclipse on 18 August 1868, French astronomer Pierre Janssen ...

TIL while viewing a solar eclipse on 18 August 1868, French astronomer Pierre Janssen made an observation that led to the discovery of helium. It was the first time a chemical element was discovered on an extraterrestrial body before being found on the earth.

https://en.wikipedia.org/wiki/Pierre_Janssen
#til #todayilearned
https://www.reddit.com/r/todayilearned/comments/1euxfdz/til_while_viewing_a_solar_eclipse_on_18_august/