Astronomy in Ancient Greece

I am an avid enthusiast of astronomy and cosmology. I therefore would like to present a basic missive on astronomy in ancient Greece. Enjoy!

Greek astronomy is the astronomy of those who wrote in the Greek language in classical antiquity (see Aristarchus of Samos, Greek astronomer/mathematician, and his heliocentric model of the solar system). Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not geographically limited to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander. While this phase of Greek astronomy is also known as Hellenistic astronomy, the pre-Hellenistic phase is known as Classical Greek astronomy. During the Hellenistic and Roman periods, much of the Greek and non-Greek astronomers working in the Greek tradition studied at the famous Musaeum and the Library of Alexandria in Ptolemaic Egypt. The development of astronomy by the Greek and Hellenistic astronomers is considered by historians to be a major phase in the history of astronomy in Western culture. It was influenced by Babylonian astronomy, and in turn, it influenced Islamic, Indian, and Western European astronomy.

Most ancient civilizations watched the heavens as patterns in the sky that mainly allowed them to know when the seasons changed; this dictated calendars and harvest times, among other important functions. They built great stone monuments called astronomical observatories, such as Stonehenge, as celestial clocks to mark these events as well as the passage of time.

These civilizations believed that the gods lived in the skies, and so named the constellations after them. This is the reason astrology and mythology follow the same patterns. In the end, the answers were in the sky since that is where the gods dwell. In metaphysics, this is called 'moving into a higher frequency' than what we experience in our third dimensional bodies. Our creators are from higher realms; this implies that they have powers that are lost to us in the physical body, even though many seek to activate those powers now.

Since early Egyptian farmers discovered the annual reappearance of Sirius a few days before the yearly rising of the Nile, ancient civilizations around the Mediterranean have sought to explain the movements of the heavens as a sort of calendar to help them conduct Earthly activities. Counting phases of the moon or observing the annual variations of day-length could, after many years of observations, serve as vital indicators for planting and harvesting times, safe or stormy season for sailing, or time to bring the flocks from winter to summer pastures.

In our time, and such observation behind us, we sometimes forget that seeing and recording anything less obvious than the rough position of the sun or nightly change of the moon's phases requires inventing both accurate observation tools (a stone circle, a gnomon (picture at left), etc.) and a system of recording the data in a way that could be understood by others. The ancient Greeks struggled with these problems too, using native technology, inquiry, and drawing upon the large body of observations and theories gradually gleaned from their older neighbors across the sea, Egypt and Babylonia.

Gradually moving from a system of gods and divine powers ordering the world, to a system of elements, mathematics, and physical laws, the Greeks slowly adapted old ideas to fit into a less supernatural, more hyper-rational universe. As ancient peoples began to realize that sun, moon and stars follow certain rhythms in step with the seasons, they made the leap of thought to postulate that some conscious set of rules must be dictating these movements and seasonal changes which, for agrarian or pastoral societies, were a matter of life or starvation. Who or what could be causing these all-important changes to come about? Certainly nothing on earth, no beast or human, had the power. Thus, gods were born.

There are hints of the Greek conception of the universe in Homer, who mentions many subjects on his two epics describing war and the perils of trying to come home after long absence. Homer mentions the movements of sun, moon, and many stars by name. The fact that Hades is on the underside of earth has an important impact on conceptions of heaven: it is unlit by the sun, therefore the sun--and by extension, other heavenly bodies - must sink only to the level of Ocean, which (at the time) is a river circling Earth's edge. From it the Sun must also rise -though how it gets back to the eastern bank of Ocean is never explained.
These popular conceptions of sky are more fully explained in Hesiod, whose works on gods and on agriculture and animal-herding are more closely connected to the practical application of astronomy. He clocks spring, summer, and harvest by solstices and the rising and setting of certain stars, and notices that the sun migrates southwards in winter. Night is a substance welling up from under the Earth, as if it were a dark flowing mist. One early and popular cult, that of Orpheus, developed its own of gods and universe-creation variant from those in Homer and Hesiod; there, a primeval egg is birthed by the early gods, and the upper half of its broken shell becomes heaven's vault.

Various cults, cities and tribes of Greece (who were unified only by language and common culture, and both of these had regional variants) probably had different versions of cosmogony and slightly different gods in charge of astronomical movement, but the general physical conception of the sky is alluded to by many authors of plays and other popular works, and was probably held by the majority of people.