Our galaxy, the Milky Way, was the subject of various theories among the ancient Greeks, ranging from mythological explanations to early scientific speculation. It’s a phenomenon that has fascinated philosophers and astronomers for millennia. Cosmology, theology and observations of celestial phenomena often influenced the different opinions of the ancient Greeks.
One of the most famous mythological accounts of the Milky Way’s origin comes from the Greek philosopher Eratosthenes. According to this tradition, the goddess Juno (Hera) pulled away her breast while nursing the infant Hercules, forming the Milky Way. As her divine milk spilled across the heavens, it left behind a glowing trail:
“Juno, detecting the affair, shook Hercules off, and thus the milk overflowing from its abundance, the milky circle was produced.” (Eratosthenes, via Johannes Grammaticus)
This explanation tied celestial phenomena to divine intervention and cosmic symbolism. Later Greek philosophers such as Empedocles and Damascius interpreted this story allegorically, seeing it as a metaphor for the movement of souls through the heavens.
Early Greek thinkers sought naturalistic explanations for the Milky Way. Anaxagoras argued that fiery celestial bodies formed the Milky Way, appearing as a continuous band because they were so far from Earth.
The Greek atomic philosopher Democritus expanded on this idea, suggesting that the Milky Way consisted of countless small stars clustered together. This view was remarkably prescient, aligning with modern astronomy’s understanding of the galaxy as a vast collection of stars:
“The galaxy is a multitude of small stars closely packed together.” (Democritus, Fragment 15)
The Greek philosopher Aristotle opposed Democritus and denied that distant stars formed the Milky Way. Instead, he argued that it was a phenomenon of the Earth’s atmosphere. He believed that exhalations from the upper air that ignited produced the phenomenon due to their interaction with celestial fire:
“The galaxy is a passive quality of the air [. . .] it consists of exhalations from the Earth that are gathered in the upper region and ignited by the motion of the heavens.”
He supported this claim by pointing out that the Milky Way did not change position relative to the stars. He also claimed that we always see it in the same part of the sky. This indicated to him that it was closer to Earth, rather than a feature of deep space.
The Pythagoreans, known for their mystical approach to the cosmos, had a different interpretation. They believed that the Milky Way was a celestial path along which souls traveled after death. Furthermore, Empedocles, a philosopher influenced by Pythagorean thought, described it as a purification route for the spirits of the dead:
“Empedocles then says that the milk is the path of souls proceeding through the Hades which is in the heavens.” (Damascius, Commentary on Meteors)
This idea has its roots in the Pythagorean belief in the transmigration of souls. The Pythagoreans had made a connection between celestial order and the afterlife.
The debate over the nature of the Milky Way continued in later antiquity. The Neoplatonist philosopher Olympiodorus (6th century CE) argued against Aristotle’s atmospheric theory. He insisted that the Milky Way was not an earthly phenomenon but rather a collection of stars:
“The galaxy is composed of small stars which are there crowded together.” (Olympiodorus, Commentary on Aristotle)
This perspective was later confirmed with the invention of the telescope. The astronomer Galileo Galilei’s observations in the 17th century revealed the true nature of the Milky Way as a vast assembly of stars. This confirmed the theory that Democritus had speculated centuries earlier.
Damascius, a Greek Neoplatonist philosopher, synthesized earlier theories and noted that the Milky Way’s brightness was due to the clustering of numerous small stars. The British Neoplatonist philosopher Thomas Taylor notes:
“According to Damascius, the milky splendour of the galaxy arises from the small stars which are there crowded together. By the assistance of the telescope this is now found to be true.”
This is remarkable as it anticipates Galileo’s later discovery with his telescope which revealed that countless individual stars made up the Milky Way.
The ancient Greeks laid the foundation for the study of the Milky Way, blending mythology, philosophy and early scientific thought. From Aristotle’s exhalation theory to Democritus’ star cluster hypothesis and the Pythagorean vision of a celestial soul path, their ideas illustrate the richness of ancient cosmology. While modern astronomy has provided definitive answers, these early theories remain a testament to humanity’s enduring quest to understand the universe.
