Aside from the myths, the ancient Greeks were interested in rational explanations for the celestial phenomena they observed. They were influenced by Egyptian & especially Babylonian astronomy: Babylonian astronomers could predict the planets' motions with extraordinary accuracy.
The 2nd century BCE astronomer Hipparchos wanted to achieve the same level of accuracy as the Babylonians.
Hipparchos based his improved model for the Sun on observations of the equinoxes, which explained both changes in the speed of the Sun and differences in the lengths of the seasons. He is credited with the discovery of a phenomenon called precession of the equinoxes. According to Roman astronomer Claudius Ptolemaeus, Hipparchos measured the longitude of several bright stars and compared his measurements with data from his predecessors.
@antiquidons Hipparchos concluded that the star Spica, part of the constellation #Virgo, had moved 2° relative to the #AutumnalEquinox.
When he compared the time it took the Sun to return to an #equinox with the time it took the Sun to return to a fixed star, he found a slight discrepancy. The equinoxes were moving ("precessing") through the zodiac, and that the rate of precession was at least 1° in a century. In other words: a full cycle through the zodiac is completed every 36,000 years.
@antiquidons#Astronomy and calendars are the domain of #Hermes. His grandfather Atlas turns the heavenly constellations and his mother Maia is one of the starry Pleiades.
Atlas instructed him in astronomy and the Greek mythographer Euhemeros says that #Aphrodite first established the constellations and taught Hermes. The planet #Mercury is attributed to Hermes because he first established the months and perceived the courses of the constellations.
#Hermes looks up at the sky as he ascends from the underworld. The constellation Virgo greets him with shining stars. It will be another 420 years before it's the lion marking summer's end. Hermes pulls his cloak tighter and leaps into the chilly air. Autumn is here.
Hipparchos was better in math than I'll ever be. But maybe the read was entertaining? If so, support this poor writer by joining her #Patreon: https://patreon.com/aimeemaroux
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