The Ancient Greeks/Romans and Astronomy

Although other cultures and civilizations dabbled in astronomy, it was the ancient Greeks that are typically linked to the subject , so much so that the word ‘astronomy’ comes from the Greek words of ‘law and order.’ They were by no means the first culture to explore the ins and outs of astronomy. However, they solidified a respected position amongst other cultures, such as the Romans, who spread the Greeks’ findings throughout their lands. For hundreds of years, the Greeks enjoyed a reputation as being an authority on matters of astronomy.

Some of the discoveries and theories associated with Greek scholars are still accepted, such as the work of philosopher Eratosthenes, who measured the circumference of the earth. His calculations were within about 300 kilometers of what is generally accepted today. The Greeks also used several different methods to learn that the earth was a sphere. Around 200 BC, Aristarchus was the first to say that the earth revolved around the sun, while most philosophers believed that everything revolved around the earth.

A famous ancient astronomer was Ptolemy (an Alexandrian), who was a Roman citizen of Egypt that wrote in Greek. He lived around 150 AD and is known for inventing the concentric system to explain the motions of the planets around the earth. His work was used as a reference and widely accepted until 1543. The number of astronomers declined from around 300 BC to 476 AD when the Romans were a dominant power. This is because the emphasis on astronomy took a backseat to the study of astrology. At this time, some of the works of Greek philosophers were destroyed.

To fully understand why some of the early modern astronomer’s ideas were not accepted and why some of those ideas led the astronomers to be ridiculed, it is helpful to have a background on what was happening to the culture at that time. Worship of gods and goddesses, as well as political and religious interferences, slowed down the progress of ancient scholars interested in astronomy. However, a few significant astronomers made contributions. Below you will find a collection of facts associated with ancient Greek and Roman astronomers and astronomy.

·    Eratosthenes was the first person to use the word “geography.” He also invented the discipline of geography as we use it today. Without him, we would not benefit from the system of latitude and longitude to pinpoint our locations.

·    Aristarchus believed in a heliocentric model for the Solar System, and is said to be the first to present such a model. His only surviving work was called ‘On the Sizes and Distances of the Sun and Moon.’ The publication was based on a geocentric world view. He stated that the angle subtended by the Sun’s diameter is 2 degrees, whereas the correct value is about ½ degree.

·    Ptolemy dabbled in astrology and wrote a treatise known in Greek as Apotelesmatika (“Astrological Outcomes” or “Effects”) and “Tetrabiblios” (“Four Books”). These writings became the most popular astrological work of the ancient world. It had a great influence in the Islamic world and throughout the medieval Latin West.