“If believing in a geocentric universe is wrong,

then I don’t want to be right!”:

A Study of the Development of the Heliocentric World View (600 BC- 200 AD)

In considering the “Development of the Heliocentric World View” between 600 BC and 200 AD, there immediately arises certain superficial difficulties even before one gets beyond this title - namely that for most of this period no such view existed. Only Aristarchus of Samos held the opinion that the earth, moon, and planets all revolve and rotate around a motionless sun, making him the first to propose the heliocentric hypothesis. However, he was also accused of “impiety”, possessed only one follower in this doctrine, the little known Seleucus, and faced the general public disagreement and later amnesia as a heliocentrist. Luckily for Aristarchus, his contemporaries respected him enough as a mathematician to “forgive” him for proposing this model, which eighteen centuries later would surface again with Copernicus, when heliocentrism came to be accepted.

However, in studying the development of Greek astronomical views that led up to and replaced Aristarchus’s hypothesis, one realizes the difficulties these early astronomers faced in shaping these views. With only the most primitive equipment, these men attempted to understand and order both the world around them and the heavens above them. The Greeks knew that this was no small task and often reflected it in their work. Sophocles, the fifth century BC playwright,

describes in praise how man as citizen, “...conquers all, taming with his techniques.” That this drive to conquer should reach to the heavens is not surprising and in fact manifests itself throughout the “Development of a Heliocentric World View”, as the astronomy of this period consisted in applying mathematical models to subdue and predict unknown celestial phenomena. for the Greeks, this was done in such a way as to appeal to both their sense of aesthetics and conception of themselves at the center of the universe. To see this, one only has to watch the development of astronomical thought during this period and consider why exactly the heliocentric world view was rejected on grounds of being “impious and contrary to sound physical principles...”.

The first astronomer to deal with the motions of the heavens in this time period is Thales of Miletus (ca. 624-547 BC), who drawing much upon the Egyptian and Babylonian conception of “a domed heaven”, conceived of the earth as a “circular or cylindrical disk floating on water” and of the sun, moon, and stars as moving “laterally around the earth”. Additionally, Thales is credited as having predicted a solar eclipse that occurred in 585 BC and as being the founder of the “art of geometry”, demonstrating with each instance the Greeks’ attempt to both predict and order the phenomena that surrounded them. The other Milesian philosophers, Anaximander (ca. 611-547 BC) and Anaximenes (ca. 545 BC), rejected water as holding up the earth and conceived of a flat earth surrounded by (and in the latter’s view supported by) air. Later Anaximenes, who believed in the flatness of the earth, would be grouped with Anaxagoras and Democritus by Aristotle. In his description, Aristotle demonstrates the combination of the astronomical with the aesthetic that was prevalent in statements like, “Just as our soul, being air, holds us together, so does breath and air encompass the whole world...”.

Meanwhile, in other parts of the Greek empire there existed a different school in the south of Italy that would also offer ideas as to how both the earth and heavens were shaped. Its leader and founder, Pythagoras (ca. 580-500 BC), was first to conclude that the earth is a sphere, perhaps by observing the shadow of the earth in lunar eclipses or for aesthetic reasons as mathematics considered the sphere the most “beautiful” of shapes. He also described the universe as a celestial sphere in which the stars rested and through which the planets were carried while traveling in “a motion of their own” around the earth’s sphere which was fixed at the center. This model seemed in many ways “a great step” towards “the true, Copernican view of the universe”, mainly because in introducing the shape of a sphere to the earth allows that rotation of certain heavenly bodies completely (not just laterally) around others.

At the end of the fifth century one of Pythagoras’s followers, Philolaus, would take another great step towards the heliocentric world model by displacing the earth from the center and theorizing that sun, moon, planets, and earth alike all revolve around a central fire. This was not by any means a heliocentric model - in fact Philolaus maintained that the sun was “transparent like glass” and reflected the central fire - but it did allow him to account for the “risings and settings of the heavenly bodies”, as well as the seasons that were attributed to “the inclination of the earth’s equator to the ecliptic.

However, even as his system offered a certain order to the universe, it was without adherents, the only exceptions being other Pythagoreans. Additionally, neither Pythagoras’s nor Philolaus’s account took into account retrogradal motion which led to the philosophy and astronomy of Plato (ca. 427-347 BC). In his study of the universe, Plato devised a geometrical system of hemispheres fitting one into another along whose rims or “whorls” traveled the stars, planets, sun and moon with the stationary earth at center. Having established order, he also links the heavenly bodies with man and all living creatures, attributing to them a “life” or “soul” which leads them to be (much like the men who study them) “self-acting source of motion”. While this concept provides a homocentric way of explaining retrogradal motion, Plato still sought a geometrical explanation as to this phenomena, leading him to ask the following which is often referred to as Plato’s Problem: “What are the uniform and ordered movements by the assumption of which the apparent movements of the planets can be accounted for?”.

Plato’s student, Eudoxus (ca. 400-350 BC), was the first to attempt to solve this problem and invented a system of sets of concentric spheres, in which each set fits inside one another and each set simulates “the various motions of a particular planet, the sun, or the moon” independently from the others. The earth was still at the center, thus this was not a heliocentric model but Eudoxus’s theory establishes the growing conception of heavenly bodies that both revolve and rotate independently. In this way, Eudoxus described the motions of the sun, moon, Saturn and Jupiter successfully, but failed in describing Mars, whose “arcs of retrogression are more considerable than those of the more distant planets”, as well as the inequality of the seasons.

Both Callippus (ca. 370-300 BC) and Aristotle (384-322 BC) accepted and tried to improve Eudoxus’s system by adding more spheres, the latter postulating upon a “divine sphere” that was the only “self-moving” sphere and that embraced all other fifty-five spheres. However, Aristotle realized that this system was not absolute and allowed criticism of his cosmology, admitting himself that both the change in brightness and position of Mercury and Venus in the sky were problematic if he were to maintain an earth-centered universe. Such admonitions were crucial for the development of heliocentrism, but also suggests why this view would later be so unacceptable as it would mean that Greek mathematics failed to tame the cosmos, that the universe was not perfect, and that they themselves were not at the center.

In response to the inconsistencies that arose with Aristotle, Heraclides (ca. 388-338 BC) suggested both that the earth rotates about its axis and that Mercury and Venus revolved around the sun while the sun revolved in a larger circle about the earth. As this latter theory would later be extended to Mars, Jupiter, and Saturn it becomes clear that the development of the heliocentric hypothesis of Aristarchus was about to reach fruition. However, the common belief of the day still reflected otherwise, showing once again the motives for Greek aversion to Heraclides’s theories:

Even as Heraclides’s ideas seemed “unthinkable”, there was one philosopher who only accepted these ideas but expanded upon them, namely Aristarchus of Samos in the early third century BC. While the work he did was lost, both Archimedes and Plutarch provide accounts that declare with “no doubt” that “Aristarchus, indeed, was the first to declare a sun-centered universe.” That his contemporaries (specifically Cleanthes) accused this hypothesis of being “impious” has already been mentioned. In addition, the Greeks argued that this model would

produce a stellar parallax which for them did not exist. Aristarchus’s views were soon laid aside, only to be taken up a century later by a mathematician named Seleucus, who in forming a theory on the tides allowed that the earth moved as well as rotated around.

A much more famous contemporary of Seleucus was Hipparchus, whose innovations among the invention of trigonometry and discovery of equinox precession, also consisted of a more successful geocentric theory with the notion of eccentric circles and epicycles. Using this theory, Hipparchus was able to account for the retrogradal motion of the planets, as it maintained that, “a planet moves uniformly on a small circle, the epicycle, whose center moves on the circumference

of a larger circle whose center is earth. During the course of the next two hundred years more data on the orbits of the planets became available, leading to the addition of more epicycles.

Hipparchus’s theory leads straight to the Greco-Egyptian astronomer Ptolemy, who around 150 AD produced his book Almagest or “The Greatest” which recorded both the astronomy of antiquity and his own cosmological framework. This system keeps with the theory of Hipparchus, also makes a few adjustments:

By the end of the second century AD, this cosmology was officially accepted by the public and Ptolemy’s Almagest would dominate and mold astronomy for the next millennium and a half.

That the refutation to Aristarchus’s heliocentric model should come in such an elegant and elaborate mathematical system clearly demonstrates the Greek drive to conquer and systematize the cosmos. Western history shows this drive throughout, as Greek astronomy not only shaped the way man saw his place in the universe for eighteen centuries but also convinced him that there was no other way to see it, that the earth was the center and that was all. Whether this was done out of aesthetics or egoism does not matter, the eventual Copernican Revolution would see to that when it overthrew the geocentric model. However what the history of the “Development of the Heliocentric World View (600 BC- 200 AD) does clearly offer is insight as to how it becomes easy to forget or deny the true model of natural phenomena when it represents something as vast and incomprehensible as the heavens above us.