developing theories about the design of the universe (early science of astronomy)

The study of our universe is not new and it's actually our oldest science. People have been looking up, trying to explain what they saw for as long as there have been people. The earliest astronomers were priests, priestesses, and other "elites" who  studeied the movement of celestial bodies to determine celebrations and planting cycles. With their ability to observe and even forecast celestial events, these people held great power among their societies.

However, their observations were not always as scientific as they are today, and people often imagined that the stars could "foretell" their own futures, which led to the now-discounted practice of astrology. 

The ancient Greeks were the first to start developing theories about the design of the universe (early science of astronomy), and there's much evidence that early Asian societies also relied on the heavens as a sort of calendar.

Certainly navigators and travelers used the positions of the Sun, Moon, and stars to find their way around the planet. 

Previous observations of the Moon had already taught observers that Earth was round. When coupled with Plato’s assertion that the sphere was the perfect geometrical shape, the original geocentric, or Earth-centered view of the universe seemed like a natural fit. 

While many earlier observers in history believed the heavens were a giant bowl covering the Earth, this new philosophy, expounded by astronomer Eudoxus and philosopher Aristotle in the 4th century BC, said the Sun, Moon, and planets hung on concentric spheres, all surrounding Earth.

Although helpful to ancient people trying to make sense of an unknown universe, this model did not help in properly tracking the motions planets, the moon, or stars as seen from Earth's surface.

Still, with few refinements, it remained the predominant scientific view of the universe for another 600 years.

In the 2nd century BC, Claudius Ptolemaeus (Ptolemy), a Roman astronomer working in Egypt, added a curious invention of his own, called epicycles, to the geocentric model. He said that the planets moved in perfect circles, attached to perfect spheres, that all rotated around the Earth.

While it was wrong, this theory could, at least, predict the paths of the planets fairly well. Ptolemy's view remained the "preferred explanation for another 14 centuries!

That all changed in the the 16th century, when Nicolaus Copernicus, a Polish astronomer, tiring of the cumbersome and imprecise nature of the Ptolemaic Model, began working on a theory of his own. He thought there had to be a better way to explain the perceived motions of planets and the Moon in the sky. He theorized that the Sun was at the center of the universe, and that Earth and other planets revolved around it. The fact that this idea conflicted with the Holy Roman church's idea (which was largely based on the "perfection" of Ptolemy's theory), caused him some trouble. That's because in the Church's view, humanity and its planet were always and only to be considered the center of all things. But, Copernicus persisted.

The Copernican Model of the universe, while still incorrect, did three main things. It explained the prograde and retrograde motions of the planets. It took Earth out of its spot as the center of the universe. And, it expanded the size of the universe. (In a geocentric model, the size of the universe is limited so that it can revolve once every 24 hours, or else the stars would get slung off due to centrifugal force.)

While it was a major step in the right direction, Copernicus’ theories were still quite cumbersome and imprecise. His book, On the Revolutions of the Heavenly Bodies, which was published as he lay on his deathbed, was still a key element in the beginning of the Renaissance and the Age of Enlightenment.