Nicholas+Copernicus

= NICHOLAS COPERNICUS =

(http://staff.harrisonburg.k12.va.us/~cwalton/World%20Two/copernicus.jpg)

__Biographical information__
====Nicolaus Copernicus was an important renaissance astronomer. The German-Polish scientist was born in 1473 in what was then the Kingdom of Poland and passed away at the age of 70, in 1543. Copernicus is known mostly for his work in astronomy (especially for his theory of heliocentrism) but was also a mathematician, a physician and a scholar that held various positions in his country’s government, religious and educational institutions. He is known for having treated the illnesses of many Prussian dignitaries, for having led Royal Polish defense forces of the cities of Olsztyn and Warmia during the Polish-Teutonic War, for having brought monetary reform to Poland and Prussia, but more importantly for being the father of modern astronomy and proposing the heliocentric model of the Universe. Indeed, even though Copernicus considered astronomy a hobby rather than a vocation, we are lucky today that he decided to dedicate himself to the study of celestial bodies, otherwise the science of astronomy would not have progressed as much as it did [1].====

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__Heliocentrism__
====Heliocentrism consists of the theory affirming that the Sun is at the center of the Universe and that everything revolves around it. Copernicus was the one of the first scientists to propose this model while the majority of his predecessors, as well as the Church, supported geocentrism. Nonetheless, Copernicus based some aspects of his theory on the work of his predecessors [2].====



__Previous work__
====Copernicus was inspired by earlier astronomers. Many of them wrote about the motion of celestial bodies and their path as seen from our sky. Therefore, like many of the Muslim and Greek astronomers, Copernicus suggested that Earth was in movement.====

====Copernicus also drew inspiration from the Ptolemaic model, which was the main model in Europe at the time Copernicus was studying astronomy and researching. Ptolemy, believer of geocentrism, stated that the Earth was a stationary point around which the rest of the bodies of the Universe orbited. According to him, the Universe “was an enclosed space, a sphere of limited size [with Earth] occupying its center” [3]. This theory did explain successfully certain orbital movements of stars and planets but it failed to correctly portray others, such as the retrograde motion of planets. The original ptolemaic model looked like the diagram below:====



** The following page provides meaningful information about Ptolemy's geocentric model and the Church's approval: []**
The retrograde motion is the motion of a planetary body in a direction opposite to that of other bodies from the same system. Sometimes, planets appeared to rotate in the opposite direction than Ptolemy’s expectations, and also “appeared sometimes nearer and sometimes farther from the earth" [4]. ====  To explain those unexpected motions, Ptolemy had to suggest an additional pattern. The latter was a combination of epicycles, deferents and equants. The equant was a point placed at equal distance from the deferent as from Earth. The deferent is a point placed right between Earth and the equant. Finally, the epicycle had a center that revolved around Earth at the same speed the equant did, thus making the planet orbiting on the epicycle appear as it is rotating in the opposite direction and justifying the geocentric theory.   ====

__Copernicus’ observations__
====When Copernicus settled in Frauenburg, in 1513, he established himself in one of the towers of the city’s cathedral. The tower would serve him as observatory and as home. From there, he observed the motions of the planets and the stars and aimed to compare his findings to preexisting theories established by the Greeks and the Muslims as well as to create his own model. In order to achieve that, Copernicus measured sizes and motions of the celestial bodies anew.====

====Copernicus’ instruments did not include a telescope (not invented yet), but consisted of older mechanisms such as a quadrant, an astrolabe and a triquetrum. These instruments did not provide much accuracy and had not really evolved since the time of the Greeks and Muslims. Furthermore, not much data was known about celestial bodies, which made the task quite difficult for Copernicus.====

=== Copernicus measured the sizes of various celestial bodies with the technique of angular size and converted his measurements to numbers representing physical sizes. A table showing some of his measurements can be accessed here: []===

====Copernicus especially concentrated on the Moon in his measurements since it helped him build an accurate theory of planetary motions and star positions. His observations included things such as the eclipses of the Moon, the elevations of the Moon above the horizon, the passages of the Moon in front of bright stars, the constant distance between the Moon and the Earth and the positions of the planets in relation to the background stars. He also observed the order in which the planets succeed one another with increasing distance from the center of the universe. In his book, Copernicus writes that the heliocentric model explains why certain planets appear closer to us at certain moments and further at other moments. His calculations about specific planetary phases reassured him that they revolved around the Sun and not the Earth. Those planetary phases would indeed be observed later by Galileo and his telescope.====

__**Copernicus’ work**__
====After studying the movements of the stars and planets for years, Copernicus adopted the view that the Universe was heliocentric. He retained “the traditional conception of a finite space bounded by the sphere of stars; but he placed the sun instead of the earth at its center” [5]. He believed that the Earth (and other planets) was not stationary but revolved around a fixed point, the Sun, in a period of 365 days and also rotated around its own axis, in 24 hours. His published work first proceeded to undermine the notion of geocentrism but proving the movement of Earth and then described the heliocentric positions of the celestial bodies of the Universe [6].====




 * 1) ==== “ Heavenly motions are uniform, eternal, and circular or compounded of several circles (epicycles);====
 * 2) ====The center of the universe is near the Sun;====
 * 3) ====Around the Sun, in order, are Mercury, Venus, Earth and Moon, Mars, Jupiter, Saturn, and the fixed stars;====
 * 4) ====The Earth has three motions: daily rotation, annual revolution, and annual tilting of its axis;====
 * 5) ====Retrograde motion of the planets is explained by the Earth's motion;====
 * 6) The distance from the Earth to the sun is small compared to the distance to the star” [7].

Contrary to the Ptolemaic system that used the specific points system to attempt to portray orbits accurately, the Copernican model only used perfect circular motions to illustrate the planets’ movement around the Sun. According to Copernicus, “the equant is a problem because planets have to be moved by uniformly rotating spheres; the motion created by the equant [could not] be created only by a sphere rotating” [8].

====Nevertheless, there was still a problem with the explanation of retrograde motion. Copernicus’ system ended up having even more epicycles than Ptolemy’s model. While Ptolemy based his model on equant circles, Copernicus replaced them with only epicycles and thus was forced to add more of them to ensure that his model would accurate predict the movement of planets. Image A represents Copernicus' orginal drawing of the epicycles, while Image B is a modern adaptation of it.====

__Problems with the Copernican model__
==== A major problem appeared at the time Copernicus published his model. The fact that he had to add more epicycles made gaps between the spherical shells of each of the planets and according to the astronomical and religious beliefs of that time, that was impossible. Copernicus did not publish any solution to the doubts his model created and there was a considerable lack of details in his model. For that reason, it took many years for scientists to accept the Copernican model. ====

The document presented the heliocentric model in details and was divided into six parts:

 * 1) ====“General vision of the heliocentric theory, and a summarized exposition of his idea of the World;====
 * 2) ====Mainly theoretical, presents the principles of spherical astronomy and a list of stars (as a basis for the arguments developed in the subsequent books);====
 * 3) ====Mainly dedicated to the apparent motions of the Sun and to related phenomena;====
 * 4) ====Description of the Moon and its orbital motions;====
 * 5) ====Concrete exposition of the new system including planetary longitude;====
 * 6) ====Further concrete exposition of the new system Including planetary latitude” [9].====

====After Copernicus’ death, the theory took a long time to be widely accepted by the general public as well as the scientific community. Because of tradition, many astronomers were not ready to grant the fact that Earth was in motion and was not stationary in the middle of the Universe. Many Church officials also opposed the theory since it did not correspond to the facts that Scriptures claimed as true. They even went to the point of condemning Copernicus’ work.====

De Revolutionibus Orbium Coelestium can be accessed here: []
====Until telescopes were available and technology allowed precise observation of celestial body motion, Copernicus’ heliocentric model was not accepted. Once the observations proved the claims of Copernicus, other astronomers approved his model and built upon it in order to render it even more accurate.====

A gravity simulator based on Newton's law of Universal Gravitation demonstrates a heliocentric system versus a geocentric system. ([] )
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__Modern Astronomy__
====Today, Copernicus’ legacy has survived and our astronomical knowledge is based on the Sun as the center of our Solar System, but not the center of the Universe. Many additional discoveries allowed us to adjust Copernicus’ model to reality. Thanks to him, we were provided with an accurate basis on which we added information to accurately understand the world we share.====

====Copernicus is still very alive within the scientific fields and various suggestions have been proposed in order to honor his legacy. For that reason, the image of Copernicus today figures on many Polish bills and coins and the element 112 might be renamed “Copernicium”, after him.====


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 * ====Armitage, Angus. “Copernicus: the Founder of Modern Astronomy”. Thomas Yoseloff Inc. 1957. 236 pp.====
 * ====Armitage, Angus. “The World of Copernicus”. The New American Library August 1951. 165 pp.====
 * ====Barker, Peter. “Copernicus, the Orbs, and the Equant”. Synthese, Vol. 83, No. 2 Springer May 1990. pp.317-323.====
 * ====Biographies. “The Scientists: Nicolas Copernicus”. Peter Landry. Web. 14 July 2010. ====
 * Catholic Encyclopedia. “Nicolaus Copernicus”. Kevin Knight. Web. 14 July 2010. 
 * ====Conservapedia. “Nicolaus Copernicus”. Web. 14 July 2010. ====
 * ====Gingerich, Owen. “From Copernicus to Kepler: Heliocentrism as Model and as Reality”. American Philosophical Society Vol. 117, No. 6, December 1973. pp.513-522.====
 * ====Harvard University. “De Revolutionibus Orbium Coelestium”. Web. 14 July 2010. ====
 * ====NASA. “Nicolaus Copernicus”. World Book @ NASA for Students. Web. 14 July 2010. ====
 * ====New World Encyclopedia. “Nicolaus Copernicus”. Web. 14 July 2010. ====
 * ====“Nicolas Copernicus”. Crystalinks. Web. 14 July 2010. ====
 * ====Rose, Edward. “Copernicus and his Sucessors”. The Hambledon Press 1995. 244 pp.====
 * ====Stanford Encyclopedia of Philosophy. “Nicolaus Copernicus”. Sheila Rabin. Web. 14 July 2010. ====