Pythagorean astronomical system

An astronomical system positing that the Earth, Moon, Sun, and planets revolve around an unseen "Central Fire" was developed in the fifth century BC and has been attributed to the Pythagorean philosopher Philolaus. The system has been called "the first coherent system in which celestial bodies move in circles", anticipating Copernicus in moving "the earth from the center of the cosmos [and] making it a planet". Although its concepts of a Central Fire distinct from the Sun, and a nonexistent "Counter-Earth" were erroneous, the system contained the insight that "the apparent motion of the heavenly bodies" was (in large part) due to "the real motion of the observer". How much of the system was intended to explain observed phenomena and how much was based on myth, mysticism, and religion is disputed. While the departure from traditional reasoning is impressive, other than the inclusion of the five visible planets, very little of the Pythagorean system is based on genuine observation. In retrospect, Philolaus's views are "less like scientific astronomy than like symbolical speculation."

Before Philolaus Knowledge of contributions to Pythagorean astronomy before Philolaus is limited. Hippasus, another early Pythagorean philosopher, did not contribute to astronomy, and no evidence of Pythagoras's work on astronomy remains. None for the remaining astronomical contributions can be attributed to a single person and, therefore, Pythagoreans as whole take the credit. However, it should not be presumed that the Pythagoreans as a unanimous group agreed on a single system before the time of Philolaus. One surviving theory from the Pythagoreans before Philolaus, the harmony of the spheres, is first mentioned in Plato’s Republic. Plato presents the theory in a mythological sense by including it in the Myth of Er, which concludes the Republic. Aristotle mentions the theory in De Caelo, in which he presents the theory as a "physical doctrine" that coincides with the rest of the Pythagorean cosmology, rather than attributing it to myth.

Zhmud summarizes the theory thus:1) the circular motion of the celestial bodies produces a sound; 2) the loudness of the sound is proportional to their speed and magnitude (according to Achytas, the loudness and pitch of the sound depends on the force with which it is produced; 3) the velocities of the celestial bodies, being proportional to their distances from the earth, have the ratios of concords; 4) hence the planets and stars produce harmonious sounds; 5) we cannot hear this harmonious sound.

Philolaus Philolaus (c. 470 to c. 385 BC) was a follower of the pre-Socratic Greek philosopher Pythagoras of Samos. Pythagoras developed a school of philosophy that was both dominated by mathematics and "profoundly mystical". Philolaus has been called one of "the three most prominent figures in the Pythagorean tradition" and "the outstanding figure in the Pythagorean school", who may have been the first "to commit Pythagorean doctrine to writing". Most of what is known today about the Pythagorean astronomical system is derived from Philolaus's views. Because of questions about the reliability of ancient non-primary documents, scholars are not absolutely certain that Philolaus developed the astronomical system based on the Central Fire, but they do believe that either he, or someone else in the late fifth century BC, created it. Another issue with attributing the whole of Pythagorean astronomy to Philolaus is that he may have had teachers who were associated with other schools of thought.

The system In the Pythagorean view, the universe is an ordered unit. Beginning from the middle, the universe expands outward around a central point, implying a spherical nature. In Philolaus’s view, for the universe to be formed, the "limiters" and "unlimited" must harmonize and be fitted together. Unlimited units are defined as continuous elements, such as water, air, or fire. Limiters, such as shapes and forms, are defined as things that set limits in a continuum. Philolaus believed that universal harmony was achieved in the Central Fire, where the combination of an unlimited unit, fire, and the central limit formed the cosmos. It is presumed as such because fire is the "most precious" of elements, and the center is a place of honor. Therefore, there must be fire at the center of the cosmos. According to Philolaus, the central fire and cosmos are surrounded by an unlimited expanse. Three unlimited elements: time, breath, and void, were drawn in toward the central fire, where the interaction between fire and breath created the elements of earth and water. Additionally, Philolaus reasoned that separated pieces of the Central Fire may have created the heavenly bodies. In Philolaus's system, these heavenly bodies, namely the earth and planets, revolved around a central point. This could not be called a Heliocentric "solar system", because in his concept, the central point that the earth and planets revolved around was not the sun, but the so-called Central Fire. He postulated that this Central Fire was not visible from the surface of Earth—at least not from Greece.

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