Ancient cultures studied the sky and developed early calendars and astronomy by observing cyclic patterns of celestial objects like the sun, moon, and stars. They used structures like Stonehenge and sites in Egypt to track solstices and help form early understandings of days, months and years. Over millennia, models evolved from geocentric views to the eventual heliocentric model established by Copernicus, Kepler, Galileo and Newton, through precise observations, mathematical laws, and the discovery of gravity.