Thursday, March 15, 2012

The Galilean Parallax

by G. Jack Urso

Introduction to the Literature of the Copernican Revolution

Diagram of the Copernican model of the universe by Thomas Digges (c. 1545-c.1595) in his book A Perfit Description of the Coelestiall Orbes (1576), which translated part of Book I of Nicolaus Copernicus' De Revolutionibus into English.
The Ancient Universe

Staring up at the night skies and contemplating the nature of the universe must surely rank as one of the humanity's oldest philosophical pursuits. Often, how a particular culture defines the universe tells us more about the culture than the true nature of the universe. The ancient Egyptians, for example, imagined their universe as a sort of an elongated platter, closely resembling the dimensions of the Nile Valley. Like the Babylonians, the Egyptians imagined the heavens to be a sort of dome over the Earth (Kuhn 5, 27).

There is a story about the philosopher Ludwig Wittgenstein that is worth considering. Somebody commented to him once about how stupid Medieval Europeans before Copernicus must have been to look up at the sky and think that the Sun orbited the Earth. Anyone with a modicum of common sense, it was argued, could tell that it was the Earth that orbited the Sun. Wittgenstein reportedly responded, "I agree. But I wonder what it would look like if the Sun had been circling the Earth" (Burke 11).
Wittgenstein is suggesting that in both circumstances we would be seeing the same thing - the Sun moving across the sky. What we know is very often based on what we see, but, ironically, to see the truth our vision must often exceed our sight.
The ancient Greek astronomer and philosopher Anaximander of Miletus devised the two-sphere system in which to explain the nature of the Earth and Moon and the motion of the stars. Despite the common mistaken belief that all ancients thought the Earth was flat, the Greeks, in fact, did believe it was round. Anaximander taught the Sun and Moon were both circles and that the Sun was 28 times larger than the Earth, the Moon was 19 times larger, and the entire universe comprised of two spheres; an inner sphere for the Earth and an outer sphere of the heavens. A problem arose when early astronomers observed that the planets moved at different speeds. If the heavens were all located on a single sphere then they should all move at the same speed, and they did not. To make matters worse, sometimes the planets even appeared to move backwards (Kuhn 26-27).
Aristotle (384-322 B.C.E.) put forth the idea that the universe was comprised of 55 spheres and that the spheres were made up of aether, a material supposed to be crystalline.  Aether was said to be "transparent and weightless." By the time of Nicolaus Copernicus in the Sixteenth Century the aether was still thought to exist, albeit not quite like Aristotle imagined it (Kuhn 78-79).

Claudius Ptolemy, a Greek astronomer who lived in Alexandria, Egypt during the Second Century C.E., simplified things a bit and established a model of the universe with eight spheres. Each planet was assigned a sphere of its own and that seemed to solve the problem of retrograde motion, for now. A ninth sphere added by later astronomers was an effort to make the theory explain their observations. It is this nine-sphere model of the universe that Copernicus inherited, and ultimately refuted (Kuhn 66).
We still grope for answers to explain our observations of the night skies. Astronomers once said that aether, an invisible and undetectable substance, held our universe together. Today, astronomers suggest that something called "dark matter," an invisible and undetectable substance, must exist in order keep galaxies from flying apart (“Dark Matter”). Have our ideas changed, or just our terminology? One wonders if we are any closer to the truth in our time than Aristotle was in his.
Historical Context  

The Crusades opened up to Western Europe ancient Greek knowledge lost to the West. It was the contribution of the conquered Moorish culture in Southern Spain in the Twelfth Century that first let loose this flood of knowledge. So great became the deluge that the Archbishop of Toledo (liberated from the Moors in 1085 C.E.) established a group of translators to handle, and presumably control, the torrent of information pouring from the captured texts of Arabic translations and commentaries of ancient Greek texts. These texts contained information on such subjects as "medicine, astrology, astronomy, pharmacology, psychology, physiology, zoology, biology, botany, mineralogy, optics, chemistry, physics, mathematics, algebra, geometry, trigonometry, music, meteorology, geography, mechanics, hydrostatics, navigation and history” (Burke 41-42). For example, zero, as a mathematical concept, is introduced to European scholars while translating works with the assistance of Spanish and Arabic speaking Jewish scholars ("In the Light of the Above").
The Christian re-conquest of Southern Spain was not completed until the end of the Fifteenth Century. During Moslem rule some of the most important translations and commentaries of ancient Greco-Roman works are produced, such as those of Ibn Rushd of Cordoba (1126-1198 C.E.) whose translations of Aristotle with commentary (to explain to the Europeans what they were reading) greatly influenced scholars. Rushd, along with Ibn Tufayl of Granada (d. 1185/6 C.E.), and al-Bitruji and Jabir Ibn Aflah of Seville (both active circa 1200 C.E.), all attempted to "reformulate" Ptolemaic astronomy.  Copernicus was aware of the existence of the works of these Arabic scholars and we may infer from that that they had some influence on him. Unfortunately, these works have not been fully edited in both Arabic and Latin, nor completely published and made available for research (Saliba 63). This makes it difficult to attribute Copernicus' research to specific sources.
The end of the Fifteenth Century saw the beginning of an era of intellectual awakenings. Guttenberg's printing press debuts in 1455, allowing for the rapid and inexpensive reproduction of the written word. The kingdoms of Queen Isabella of Castile and King Ferdinand of Aragon were unified in 1479. This was a precursor to the end of the Moorish domination of Southern Spain when Grenada, the last Moslem city-state, fell in in January 1492 (Burne 429, 436).

The end of the war freed up enough money for Ferdinand and Isabella to fund Christopher Columbus' plan to reach the rich Asian trade markets by sailing west, which he did from September through October 1492 (Burne 433). While certainly this discovery led to the end of many indigenous American cultures, the opening up of new lands to an overcrowded Europe, combined with a flood of new wealth, sparked a cultural and economic revival responsible for much of the world as we know it today, for better and for worse.
Following Columbus' voyages (1492-1504), Copernicus writes his first treatise on planetary dynamics, the Commentariolus (Little Commentary), circa 1507-14 (Kuhn 184). In 1517, Martin Luther nails his 95 theses to the door of the Wittenberg church (Burne 465). That these events took place within a single generation suggests a profound change was occurring in Western Europe; for the further they reached outward, the deeper the change inward they experienced as a society.
The Parallax View

When Galileo Galilei turned his telescope up to the night sky he saw countless stars where before the naked eye saw only the blackness of the void. In 1755, Immanuel Kant speculated that the fuzzy patches of light he saw through his telescope were other galaxies, perhaps "just [island] universes" (Ross). Mainstream astronomy rejected the "theory" of other galaxies and the idea remained quite controversial until confirmation finally came in 1924, when our technology became advanced enough to detect them. Until then, most people thought the universe to be limited to just our own galaxy (Alfred).
We are eternally at that point where Galileo turned his telescope up to reveal what was always present, but never proven, until our imagination compelled us to ask what lies beyond the limits of our knowledge.

Works Cited

Alfred, Randy. “Dec. 30, 1924: We Are Not Alone.” Science:
       Discoveries, 30 Dec. 2008. Web. 11 Mar. 2012.

Burke, James. The Day the Universe Changed. Boston & Toronto:
       Little, Brown and Company, 1985. Print.

Burne, Jerome. ed., Chronicle of the World. Paris: Jacques LeGrand
       S.A. International Publishing, 1989. Print.

“Dark Matter-Introduction.” Dark Matter.,
       24 July 2007. Web. 11 Mar. 2012. <http://
       www. NASA’s
       Imagine the Universe>.

"In the Light of the Above," The Day the Universe Changed. Narr.
       James Burke. PBS, 1985. Web. 11 Mar. 2012.

Kuhn, Thomas S. The Copernican Revolution: Planetary Astronomy
       in the Development of Western Thought. Cambridge: Harvard
       University Press, 1957. Print.

Ross, Kelley L. Ph.D. “Immanuel Kant (1724-1804)” Immanuel Kant. 2008, Web. 11 Mar. 2012. <http://>.

Saliba, George. A History of Arabic Astronomy: Planetary Theories
       During the Golden Age of Islam. New York and London: New
       York University Press, 1994. Print.

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