Belgian physicist, mathematician, astronomer Georges Lemaître died #OTD in 1966.
He was the 1st to theorize that the recession of nearby galaxies can be explained by an expanding universe, which was observationally confirmed soon afterwards by Hubble. He 1st derived the Hubble–Lemaître law. He also proposed the "Big Bang theory" of the origin of the universe, calling it the "hypothesis of the primeval atom", and later calling it "the beginning of the world".
https://en.wikipedia.org/wiki/Georges_Lema%C3%AEtre
