Astronomy is the study of the stars and planets and other celestial objects such as the Sun, Moon, comets, asteroids, star clusters, nebulas and galaxies. It is, indeed, the study of the entire universe on scales both large and small.
Not blinded by light pollution, the first humans undoubtedly looked up at night in wonder, even as we do today from dark-sky locations, and saw a sky full of stars. They saw that the Sun moved across the sky during the day, and that the Moon and stars followed a similar path at night. Other bright "stars", that we now know to be planets, also wandered among the stars, changing position against the starry background.
When civilization first developed thousands of years ago, the timings of the rise of certain stars and constellations were used to predict the coming of the seasons, and the planting and harvesting of crops for food. Getting this right was important in sustaining these different civilizations, and led to the development of astronomy. With astronomy, people could keep track of time. The Sun marked days, and the phases of the Moon marked months. The first rising of Sirius, the brightest star, before the Sun, marked the span of a year. Keeping track of time was also important in the observance of religous holidays.
Early civilizations in the near and far east in India, China, Egypt and Persia, as well as the Maya in South America and the American Indians in North America, began to develop astronomical observatories to follow the events in the heavens, keep track of time, and to facilitate their predictive abilities for the timing of the seasons.
The Geocentric World View
Some early astronomical world views, and the most famous philosophers of the time, such as Aristotle and Ptolemy, believed that the Earth was the center of the universe and that everything revolved around it. This was called the geocentric model.
But even as early as Aristarchus in Greece around 200 B.C., some believed that the Earth and planets revolved around the Sun - the heliocentric model. In general though, this philosophy was rejected for the next 1800 years, in particular by the Catholic Church.
Copernicus' Heliocentric World View
In 1543, Nicolaus Copernicus published De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), and showed that the motion of the planets could be predicted by assuming that the Sun was the center of the solar system instead of the Earth.
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