Throughout the universe, things are in constant flux. Stars are formed and galaxies are consumed, and no one would ever notice if not for the many advances in astronomy. In the early days of travel, being able to decode the stars was a necessity to get where you wanted to go. One of the very first notable events in astronomy was the realization of the geocentric model. This was later realized to be a flawed model, but at the time it was useful for navigation purposes.
At some point between 127-41 AD, Claudius Ptolemy made observations of the stars patterns in Alexandria of Egypt. Being a mathematician, he was able to calculate the phases of the moon, the lengths of the seasons, and the length of the year. However, having primitive instruments, there were some errors in his calculations. He also based his calculations on the geocentric model with the Earth as the center of it. He is still considered one of the first great astronomers despite these facts due to his many discoveries despite having little equipment to work with.
The second great event following Ptolemy’s calculations was Nicolaus Copernicus’ discovery (1510-1514) that the Sun was the center of our solar system and was responsible for the path the planets followed and for the season and length of the year This became known as the heliocentric model. This satisfied Copernicus because it fit Aristotle’s requirement of circular planetary motion and laws of inertia. Finally the lunar cycles and changes in seasons made sense!
Galileo was the first to experiment with gravity and the acceleration of falling objects. He proved through experiments that mass had no effect on an object’s acceleration. He also designed and used his own telescopes, which most likely inspired Newton along with his insights into gravity’s relationship to mass.
These facts were further confirmed by Isaac Newton in his “Principia,” published in 1687, which described the three laws of motion and universal gravity. Newton deserves further credit for advancing astronomy by building the first practical reflecting telescope and developing a theory of colour based on how prisms deconstruct white light into separate colors. This would be something that would later inspire Einstein as he studied the qualities of photons and their interaction with gravity.
Newton can be considered the person to tie together all the facts that were before him and make sense of them. The last great astronomical event up until these modern times would be Einstein finally proving that mass does affect light by viewing stars during solar eclipses. There have been numerous achievements since these early times in astronomy, however none of them would have been achievable without these primitive but profound discoveries that laid the foundations.