The theory on the structure of the universe underwent a series of evolutions starting with the Greek astronomer Ptolemy who suggested that the universe was made up of concentric spheres made up of crystalline that spun around the Earth center. (Rabb and Marshall, 1993, p. 258). The other heavenly bodies were stuck in the crystalline at different levels, so their speeds were different. This was the explanation of why things appeared to be moving across the sky at night. Copernicus was not really a scientist, but he was a great observer, and he found Ptolemy’s explanations troubling, as he noticed that this theory would have some planets moving backwards. In order to explain these phenomenon, semi-demiepiclcles and sub-spheres were created to make the model fit the current understanding of the universe.
Copernicus found this system to complicated and confusing, so he set out to improve the model.Copernicus first made the sun the center of the system. Because he was a mathematician, Copernicus was able to come up with more accurate formulas and statistics that fit the observations made of the universe by watching the night sky. (Rabb and Marshall, 1993, pp. 260-261). Because he was respected for his skills in math, his calculations had to be taken seriously, and these changes created a more accurate calendar that was eventually adopted as the official calendar as sanctioned by Pope Gregory XIII. (p. 261).While Copernicus’ models seemed right, there was no way to prove them, until Brahe, the best astronomer of the day, created a model that could be considered both heliocentric and geocentric. This solved the religious tension over making the sun the center of the system. He made observations of the night sky for 20 years, carefully documenting stellar movement. (Rabb and Marshall, 1993, p. 261). However, he was unable to use these observations in his lifetime, so his notes were passed down to his student Kepler.
Kepler used mathematics to support his theories and ideas on the movement of heavenly bodies, and the structure that kept the universe together. Using the amazing observations gathered by his mentor Brahe, he was able to come up with three laws of planetary motion:
(1) planetary orbits were elliptical, not circular, with the Sun as one focus of the ellipse;
(2) the speed of the orbit increased as the planet came closer to the Sun in such a way that if a line were drawn from the planet to the Sun, it would sweep equal area in equal time;
(3) there was a relationship that united all the planets, that linked their distance from the Sun and the time of their complete orbits. (Rabb and Marshall, 1993, p. 262).
The next advancements in the universe theory would be made by Galileo who had a new instrument, the telescope. Through the extended clarity of details of heavenly bodies, Galileo learned a great deal more about the universe than did his predecessors. He learned that the Moon had mountains like the Earth, and that Jupiter had three satellites, which he named the Medicean Stars. Galileo’s observations confirmed that the Sun was the center of the system and that the Earth and other planets orbited around it. This went against Biblical scripture and placed Galileo under the suspicion of the Inquisition.
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Rabb, Theodore. (1975). The Struggle for Stability in Early Modern Europe. New York: Oxford University Press.
Rabb, Theodore K. & Marshall, Sherrin. (1993). Origins of the Modern West: Essays and Sources in Renaissance & Early Modern European History. New York: McGraw-Hill, Inc.