Even to the casual observer, using just the ability of the human eye, there is a noticeable order in the manner of the movement of the celestial objects as they travel across the sky. The Sun, Moon, and the stars, all have a discernable pattern to their rising and setting. Upon closer observance, one might notice slight seasonal changes in the relative location on the horizon where the Sun rises and sets. Alternatively, one can notice more drastic variations in the Moon’s relative position, the timing of it’s appearances, and the variation of the portion of the Moon that is illuminated on any given night.
In addition, the stars, if tracked even for a short period, clearly have a pattern to their rising and setting on any given night. Again on careful observance over a period of time one can see that there is a seasonal variation to the location of some stars, with some not being visible at certain time of the year, and others appearing instead. Finally, still with the naked eye, if one were to place close attention, one would notice that some of these “stars” do not follow the same pattern, and seem to follow different rules.
So, what do the observable facts all add up to? Are there rules of order that the celestial objects follow? If one were to study the celestial objects long enough, could one discover the rules and be able to accurately predict the movements of celestial objects with accuracy? Surely, peoples of ancient civilizations pondered the same type of questions. Historians and archeologists have found physical evidence that ancient civilizations had an active interest it the apparent motion of the celestial objects.
Stonehenge in England, The Bighorn Medicine Wheel in the United States, and the Carncol temple in Mexico, are all thought to be examples of structures built by ancient peoples to mark the changing seasons and the corresponding movement of the celestial bodies. It is thought that ancient peoples kept track of the movement of celestial bodies for the purpose of establishing yearly calendars for planting and harvesting, and in the aid of navigating on the open seas (Chaisson 30-31). The exact intentions of the ancient peoples can not ascertained due to the lack of written records.
Many Historians assume it that the ancient’s quest for knowledge of the motion of celestial bodies was of a practical nature, not one of strict scientific inquiry. The ancient Greeks, who kept written records, applied the use of logic and careful observation in attempts to understand the physical and celestial world, as they knew it. The Greeks did not tend to study the practical and applied aspects of science, but were more so interested in the theoretical aspects of their inquiries (Adler 123).
One person who studied the apparent motion of the celestial bodies was the Greek philosopher Aristotle who lived between 384-322 B. C. Aristotle using careful observation and logic mistakenly concluded that the Earth was at the center of the Universe and that all of the celestial bodies such as the Sun, Moon and the Stars moved in perfect circular orbits around the earth (Window 1). Aristotle’s view of the Earth as the center of the Universe was widely accepted and was the basis for the theories of other ancient astronomers.
In an effort to further explain the Aristotelian concept of a geocentric universe, where every celestial object revolved around the earth, astronomers of that time came up with a model. In this model, each planet was assumed to move around a small circle, an epicycle. The center of this epicycle would then orbit in a larger circle around the Earth; this larger circle was termed as the deferent (see Fig. 1). With this type of model, the astronomers could explain the sometimes retrograde movement, the apparent reverse movement of some of the planets.
By fine tuning the size of the of the epicycle and deferent circles, the astronomers of that time could explain and predict the motions of the Moon and planets with some degree of accuracy (Chaisson 32-33). Figure 1: Epicycle (Ptolemy’s Devices 1) Astronomers sought to further fine tune the model of a geocentric universe as more observations and movements of the planets did not quite fit the existing models. One such astronomer was Ptolemy, who was of Greek nationality, but lived in Egypt in the second century A. D.
Ptolemy’s system consisted of 80 epicycles, set into a complex pattern, to explain and justify the movements of the five known planets at that time, the Sun, and the Moon. Ptolemy published his model and explanation in a thirteen book set called Mathematical Syntaxis. This geocentric model of the universe, termed the Ptolemaic model, was the accepted standard for the motion of celestial bodies for over a thousand years. It has been suggested that Ptolemy devised this model as a method for calculating positions, but may not have believed in it’s absolute depiction of reality (Nineplanets 1-2).
The Ptolemaic model, based upon the flawed premise that the earth was the center of the Universe, required a complex set of mathematical rules to explain the movements of the celestial bodies. Not all ancient astronomers agreed with the geocentric view, one notable exception was the Greek astronomer Aristarchus of Samos (310-230 B. C. ). Aristarchus views stated that the Sun was the center, with the Earth and all the other planets revolving around the Sun. The strength of Aristarchus’ argument could not overcome Aristotle’s persuasive logical and philosophical reasoning that man and therefore the Earth, was the center of the Universe.
Therefore, Aristotle’s philosophical argument supported by Ptolemy’s complex model remained the basis for the western world’s understanding of the Universe for over a thousand years (Chaisson 33-34). One must remember that during this time all observations and subsequent conclusions were based upon what the naked eye could see; these ancient astronomers and philosophers did not have telescopes. The geocentric concept based upon visual data, paired with Ptolemy’s model was accurate enough to fulfill the needs of the times.
One might wonder how this basic mistake could be passed along for centuries. The answer lies in the fact that after the fall of the Roman and Greek civilizations, the Western world reverted to small feudal states, where technology and the quest for scientific knowledge were not of importance. In this period of Western civilization, the Church was the main reservoir of knowledge (Adler 207-220). Since the geocentric view concurred with the language in the Bible, there was no reason to doubt the validity of Ptolemy’s model.
In the sixteenth-century, a Polish cleric, astronomer, and mathematician, Nicholas Copernicus, seeking to further understand the Universe, came upon Aristarchus’s heliocentric views, which the planets all revolved around the Sun, and reasserted them to explain the motions of the celestial bodies. Copernicus disagreed with the physics of Ptolemy’s model, believing that the underlying principles were incorrect, not the math or observations. The bold change that Copernicus suggested was that the Sun was the center of the Universe, with the planets revolving around the Sun in perfect circular orbits.
He felt that this heliocentric model would better express harmony in the Universe. Copernicus’s model although based upon the correct view of the Sun being the center of the known Universe, was still flawed with the idea that the planets had perfectly circular orbits. Because of this flaw, he had to retain the concept of epicycles and the accompanying complicated mathematical concepts to explain it all. Although his model was flawed, Copernicus was the first to combine physics and mathematics, to produce a working model that was giant step forward towards a correct astronomical model (Treasure-Trove 1-5).
It would take the careful observations of Tycho Brahe (1546-1601), under the thoughtful analysis of Johannes Kepler (1571-1630), with the supporting empirical observation of Galileo Galilei (1564-1642) with the use of a telescope of astronomical observations for the first time, to convince the western world that the heliocentric model was the correct view of the Universe. Even with this seemingly overwhelming evidence, not all accepted the heliocentric model, because the Church stuck to the geocentric model, which was agreed with the language and descriptions of the Universe in the Bible.
The Church was involved in a fundamental struggle of it’s own with the Protestant Reformation. The Church could not admit it had been wrong about the basic form of the Universe, without chancing that it’s detractors would then say it had been also wrong about other basic tenets (Stearns 230-232). Galileo’s observations and writings were instrumental in changing the Western world’s view, but it would take the equal brilliance of Sir Isaac Newton (1642-1727) to really expound upon the physics, empirical data and mathematics of the his predecessors and explain the workings of the known Universe of that time (Chaisson 34-50).
The current understanding of the Universe is that the planets revolve around the sun, but the Sun itself is by no means at the center of the known Universe. Modern astronomers, and scientists are face the same handicap that the ancients faced, one can only propose theories and come to conclusions based upon current knowledge and sometimes wild speculation, but one still has to wonder how that current accepted facts will hold up to future discoveries of science and astronomy.