May 24, 1543 — Copernicus publishes ‘De revolutionibus orbium coelestium’

Technically, this is actually the date of Copernicus’ death, however, since no authoritative dating other than ‘shortly before his death’ exists for the publication of ‘De revolutionibus orbium coelestium’, I have chosen to use this date.

‘De revolutionibus orbium coelestium’, or in English, ‘On the Revolutions of the Heavenly Spheres” is the single most famous work regarding the heliocentric theory of the solar system, i.e. the theory that the planets revolve around the Sun. It inspired considerable controversy in its day, which is one reason why Copernicus published it when he did – the historical evidence suggests that it was written between 1510 and 1530 – and effectively disproved the Platonic theory that the sun and planets revolved around the Earth.