1. Astronomy is one of the oldest sciences, with early observations made by cultures like Babylonians, Greeks, Egyptians, and Chinese. 2. Ancient structures like Stonehenge may have been used to track the sun's motion, especially solstices. Chinese astronomy also recorded supernovas. 3. Copernicus revolutionized astronomy by correctly proposing the heliocentric model where the Earth and planets orbit the Sun, rather than the geocentric Ptolemaic system, providing a simpler explanation for phenomena like retrograde motion.