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The Copernican Revolution The Sun-Centered Universe To me, whether the Earth revolves around the Sun, or the other way around, no question could have any less importance. - Albert Camus Astronomy 20 1 Copernicus What's in the Center? 1) 2) Two Questions Does the Earth rotate or the Celestial Sphere? Does the Earth go around the Sun or the Sun around the Earth? Astronomy 20 2 Astronomy 20 3 Copernicus Aristotle The Celestial Sphere rotates. The Sun moves around the Earth. The Earth is completely stationary. Aristotle Universe 1 Copernicus Aristarchos 1) 2) According to Archimedes, taught: The Earth rotates on its axis. The Earth moves around the Sun. Archimedes Astronomy 20 4 Copernicus The Stellar Parallax Astronomy 20 5 Copernicus Ptolemy The Great Astronomer - 150 AD the Almagest—astronomy textbook Found no stellar parallax. Argued against Aristarchos. Developed theory of motion of the planets. Astronomy 20 Universe 6 2 Copernicus Stellar Parallax Q. The failure to observe the stellar parallax proved that… 1) The Sun went around the Earth. 2) The Earth went around the Sun. 3) Somebody needed to get busy and invent the telescope. Astronomy 20 7 Copernicus The Problem of Planetary Motion 1) 2) Why do the inferior planets never reach opposition? Why do the superior planets go backward (retrograde) at opposition? Retrograde motion of Mars Astronomy 20 8 Copernicus The Ptolemaic Theory The Earth is the center. The Sun and all the planets orbit the Earth. The planets move in epicycles. Earth Astronomy 20 Universe 9 3 Copernicus Unanswered Questions Why do the superior planets go into retrograde only at opposition? Why do the inferior planets go into retrograde only at inferior conjunction? Astronomy 20 10 Copernicus The Dark Ages Astronomy 20 11 Copernicus Astronomy in 1500 Earth-centered model unquestioned. Alphonsine Tables (1252) used to calculate planet motions. Planets often far from predicted positions. Astronomy 20 Universe 12 4 Copernicus Nicolaus Copernicus Born Torun, Poland 1473. Educated Cracow and Italy Canon at Cathedral of Frauenburg, Ermland, Prussia Published On the Revolution of the Spheres in 1543 Died 1543. Astronomy 20 13 Copernicus The Sun-centered System Q. What is not going around the Sun? Sun Astronomy 20 14 Copernicus Europe in 1500 Aristotle was considered the authority in philosophy. Experimentation was unrespectable. Astronomy was the only respectable natural science. Earth-centered Universe was tied to Christian theology. Earth the place of suffering; heaven the place of perfection. Astronomy 20 Universe 15 5 Copernicus Winds of change 1450 – printing press 1492 - Columbus 1520 – Martin Luther 1543 – Copernicus publishes the Sun-centered theory Martin Luther Astronomy 20 16 Copernicus Arguments for the Copernican Theory Puts the largest body (Sun) in the center. Treats all the planets alike. Explains Venus & Mercury simply. Explains retrograde motion of Mars, Jupiter, and Saturn simply. Predicted relative distances of the planets from Sun. Astronomy 20 17 Copernicus Occam’s Razor When choosing between two competing theories, choose the simpler one. "Entia non sunt multiplicanda sine necessitate". - William of Occam Astronomy 20 Universe 18 6 Copernicus Arguments Against the Copernican Theory It contradicted Scripture(?) Lack of effects of Earth’s rotation. Earth would fall to center due to gravity. Failure to observe the stellar parallax. Astronomy 20 19 Copernicus The Controversy Begins Reinhold: Prutenic Tables (1551) Thomas Digges (1576) William Gilbert (1600) Giordano Bruno (1600) Bruno Astronomy 20 20 Copernicus The Execution of Bruno Astronomy 20 Universe 21 7