Heliocentrism (THE COPERNICAN REVOLUTION)
In the medieval ages, it was believed that the earth was the centre of the earth. Nicolaus Copernicus, a Polish astronomer, was the first to challenge this theory with his revolutionary De revolutionibus orbium coelestium (1543).Copernicus used mathematics and astronomical observations to formulate a theory that the earth revolved around the sun. It was revolutionary for challenging the orthodoxy of Aristotleian philosophy and the view of the Catholic Church. 60 years later Galileo Galilee published a work supporting this Copernican view; it led to Galileo’s arrest for heresy and his book was banned, but ultimately, the heliocentric view became accepted, marking the start of a new Scientific era.
The recognition that the Earth orbits the Sun (and not vice versa) arguably marks the start of the modern era.
Later, astronomers came to see our solar system as one part of one galaxy among billions.