The Presocratics and Astronomy
Living in a time when people attributed the stars, sun, and moon to gods, the Presocratic philosophers defied convention and tried to discover what these celestial objects really were. In the ancient city of Miletus human thought took a dramatic turn. St. Augustine writes that the Milesian Thales “was an investigator into the nature of things” and that “Thales makes no mention of the divine” (Wheelwright 51). Thales and the other Milesians gained knowledge through observation rather than attributing the natural processes of the world to the gods. As Wheelwright writes, the Milesians were “teaching themselves to ask ‘What?’ instead of ‘Who?’ and to ask ‘How?’ instead of ‘With what intent and purpose?’ ” (43). This method of questioning was common to the Presocratics and had a considerable impact on their thoughts. Astronomy was one of the many areas that the Presocratics were interested in. The Presocratics’ desire to discover the nature of the world around them through observation and reason resulted in unique individual philosophies that served as the foundations of independent astronomical views.
A key belief for many of the Presocratics was that “nothing either comes-to-be or is destroyed” (46). In wrestling with this issue many philosophers held that there must be some kind of first-principle which the entire universe consists of. As a result of his observations of the world around him, Thales concluded that the basic nature, or first-principle of the world, was water. This view was the foundation of many of Thales’s theories about the world, including astronomy. Thales, like other Presocratics, wondered how the earth was held in place. Thales’s answer to that question was based upon his view that water was the first-principle. Aristotle writes that, “Thales […] declared the first-principle to be water, and for that reason he also held that the earth rests upon water” (46). Thales’s inquiring mind also led him to ask the question “Why do the stars move?” In Refutatio Hippolytus writes that Thales’s view of water being the first-principle led him to associate the solidifying and melting of water with the movements of the stars (50). Thales also proposed that the fire of the sun and stars was created by evaporations of water (51). As we can see Thales’s idea that water was the first principle was an essential basis of his philosophy and had a huge impact on his astronomical views.
Many astronomical achievements were attributed to Anaximander. It is recorded that he constructed a chart of the stars, invented the gnomon, and declared the earth to be spherical and at the center of the universe. Unlike Thales and many of his contemporaries, Anaximander did not declare an element to be the first-principle. He felt that all things were constantly changing. He felt that there had to be something that didn’t change because if everything was constantly changing then one couldn’t know anything. He imagined a boundless unlimited which he called the Apeiron. Anaximander explained the coming to be and perishing of opposites such as night and day through this Apeiron that was a storehouse of qualities. He held that by logical necessity different qualities were stored in the Apeiron while their opposite qualities remained in the world. This worldview contributed to his astronomical theories. He believed the earth was at the center of the universe. To explain this he drew upon his view of the Apeiron by saying that it is impossible for what is situated “at the very center equally distant from every extreme point […] to move in opposite directions at the same time”; therefore the earth must remain still (55). Anaximander thought it was by logical necessity that the earth was at the center of the universe. Perhaps Anaximander believed that the earth could not perish because that would allow every other opposite to come into being.
Anaximander’s theory of the Apeiron influenced his theory of eclipses. He conceived of the sun, moon, and stars as being surrounded by air. Hippolytus writes that Anaximander believed that “The air has little breathing holes somewhat like the holes in a flute, and through them the orbs are seen” (57). Anaximander explained that these wholes clog and unclog (as a result of logical necessity) resulting in the moon’s phases and eclipses. In the same way that Anaximander explained how night and day give way to each other through logical necessity by the Apeiron, he explained how the moon had eclipses and phases as a result of holes in the air clogging and unclogging.
Anaximenes held that the first principle was air. Just as Thales’s astronomy was significantly influenced by his view that the first-principle was water, so too Anaximenes’s astronomy reflected his view that the first principle was air. In the one fragment from Anaximenes that we have he writes “As our souls, being air, hold us together, so breath and air embrace the entire universe” (60). It seems as though Anaximenes is saying that air holds the universe and everything in it together. In answering the question of how the earth is held in place, Anaximenes’s belief that air is the first principle leads him to theorize that the world is flat, and it rests on air (61). It was thought that Anaximenes held the belief “that the stars revolve because they are pushed by condensed air” (63). Thales and Anaximenes answered the same questions in very different ways. Anaximenes’s philosophy was based on the view that air was the first-principle. This view was the foundation of his astronomical theories.
Parmenides declared that “Being is complete on every side, like the mass of a well-rounded sphere, equally balanced in every direction from the center” (98). Diogenes Laeritus wrote that “Parmenides was the first to declare that the earth is spherical and is situated at the center” (103). Parmenides’s belief that the earth was spherical and situated at the center of the universe was directly influenced by his monistic philosophy of the “Is”.
Heraclitus explains the creation of the stars, sun, and moon through evaporations from the sea collecting in “bowls” in the sky (83). He explains the phases of the moon and the eclipses of the sun by the bowls being turned certain ways (83). Diogenes Laertius writes that Heraclitus believed that “The moon is nearer to the earth, but it has to travel in a region that is impure. The sun, on the other hand, moves in a region that is transparent and unmixed, which is why it gives us more heat and light (83). The common factor in all of these astronomical theories is change. Heraclitus held that everything was in constant flux. Heraclitus’s astronomy is based on this principle of flux.
The ways in which foundational philosophies influenced views of astronomy is especially apparent in the views of the Pythagoreans. An important truth of the Pythagorean school was that “All is number” (203). Number was essentially the first-principle to Pythagoras. Aristotle writes that the Pythagoreans “concluded that the elements of numbers must be the elements of everything, and that the visible heavens in their entirety consist of harmony and number” (213). Pythagoras found music to be “identical with number”; and because “all his number” Pythagoras came to the conclusion that there existed a “universal harmony in the movements of the universe” (207). This Pythagoras called the “Music of the Spheres”. To the Pythagoreans, this affirmed “the presence of a geometrical order among the motions of sun, moon, planets, and fixed stars” (207). The Pythagoreans attributed the circle to the geometrical order. They were able to observe that the known planets, Mercury, Venus, Mars, Jupiter, and Saturn, were traveling in circular motions. They then assumed that the sun, moon, and fixed stars must also be rotating in circular motions. Now the Pythagoreans had recognized eight rotating bodies. But as Wheelwright writes, “Eight, however, was not a good Pythagorean number; the next good number above it was ten, the Decad” (208). The Pythagoreans had to find two new rotating bodies to reach the Decad and preserve perfect geometrical order in the universe. They included the earth as one of their rotating bodies as well as a counter-earth located “behind the earth (on the side opposite to that on which the Greeks and all known peoples resided)” (208). The Pythagoreans had no observational evidence for this counter-earth. They simply stipulated that in a harmonious geometric universe there must be ten orbits because ten was a sacred number.
The Presocratics ability to think rationally about the world enabled them to develop unique ideas to explain the nature of the cosmos. Each individual philosopher had his own foundational beliefs that led to unique conclusions. The Presocratics developed a number of astronomical views based on the foundations of their individual philosophies. The Presocratics played an important role in the development of astronomical ideas.
Wheelwright, Philip. The Presocratics. Upper Saddle River, NJ. Prentice-Hall Inc.,