Nicolaus Copernicus was a Polish astronomer born in 1473 who made groundbreaking discoveries about the structure of the solar system. He was educated at multiple universities, studying mathematics, astronomy, law, and medicine. Copernicus is most famous for his book "On the Revolutions of the Celestial Spheres", published just before his death in 1543, which put forth his heliocentric theory that the Sun, not the Earth, is at the center of the known universe. This was highly controversial at the time but helped inspire later scientists like Galileo, Kepler, and Newton. Copernicus made these discoveries through careful observation rather than advanced instruments, revolutionizing human understanding of astronomy.