Physicist Karl Jansky was born #OTD in 1905. While searching for the source of radio hiss that interfered with transatlantic phone calls for Bell Labs, he discovered that astrophysical objects emit radio waves. It was the birth of radio astronomy.
Credit: NRAO/AUI/NSF

Jansky built a directional antenna to pinpoint the source of radio static that was interfering with phone calls. He referred to the antenna as his "merry-go-round" – it rotated on a set of wheels from a Model-T Ford.
Image: Bell Telephone Laboratories

Here's a thread from a few months ago, describing Jansky's discovery of radio waves "apparently of extraterrestrial origin." https://twitter.com/mcnees/status/1300431198850887682

The Very Large Array, part of @TheNRAO, turned 40 a few weeks ago. In 2012 it was renamed the "Karl G. Jansky Very Large Array."

Friends he called that hiss "star noise."