On the Revolutions of the Celestial Spheres is a seminal work by Nicolaus Copernicus, published in 1543, that presented the heliocentric model of the universe. This model proposed that the Earth and other planets revolve around the Sun, challenging the long-standing geocentric view held by Ptolemy and the Church. The book laid the groundwork for the scientific revolution, fundamentally altering humanity's understanding of its place in the cosmos.