The Copernicus's heliocentric (Sun-centered) theory stated that the Sun is at rest near the center of the Universe, and that the Earth, spinning on its axis once daily, revolves annually around the Sun. He proved this theory by discovering that Venus went through phases just like the moon by recording his observations through the telescope.He also disproved the theory that the sun and other planets revolve around the earth through his recorded observations seen via the telescope.