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Definitions

Definitions. Epicycle = a small rotation on which a planet is placed. The epicycle then moves on a larger orbit. Used to explain retrograde motion. Deferent = the larger orbit on which the epicycle moves. Hipparchus(190-120BC). Developed many of the ideas included in the Ptolemaic model.

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Definitions

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  1. Definitions • Epicycle= a small rotation on which a planet is placed. The epicycle then moves on a larger orbit. Used to explain retrograde motion. • Deferent= the larger orbit on which the epicycle moves.

  2. Hipparchus(190-120BC) • Developed many of the ideas included in the Ptolemaic model. • Sorted the stars into 6 orders of brightness • Along with Aristarchus, measured the Earth-Moon distance by timing lunar eclipses.

  3. Ptolemy (100-170AD) • Refined Aristotle’s world view… • Created a linear sequence of uniform orbits. • Argued that each planet also revolved in a small circle (EPICYCLE) • His GEOCENTRIC model remained for 1400years

  4. Ptolemaic Model

  5. THE COPERNICAN REVOLUTION

  6. What we now consider “science” arose during the European Renaissance • The dramatic change now known as the “Copernican Revolution” spurred the development of virtually all modern science and technology

  7. Nicholaus Copernicus (1473-1543) • Proposed a sun-centered (HELIOCENTRIC) universe. • There were now 2 types of planets: those inside Earth’s orbits and those outside • Held onto the idea of epicycles and constant perfectly circular motion • Proposed that stars were very far away • Proposed that the Earth rotated on an axis

  8. Feared criticism from the Catholic Church. • Early supporters were drawn to the aesthetic advantage of his model. • Belief in circular orbits made it no less complex than the Ptolemaic • As a result it won few converts for 50 years

  9. Why was is it considered such a big deal? • It was a strange and even rebellious notion • It was a time of major upheaval: Columbus had sailed to “the new world”, Martin Luther has proposed radical revisions in Christianity • The present PARADIGM (or prevailing scientific theory) is a way of seeing the universe around us. Questions, Research and interpretation of results is all in the context of this theory. Viewing the universe in any other way requires a complete shift in thinking. • Replacing a theory that had been believed to be correct for nearly 2000 years is not easy • Only when the old theory’s complexity made it beyond usefulness was the intellectual environment at a point that the concept of heliocentric universe was possible

  10. By his time, tables of planetary motion based on the Ptolemaic model were noticeably inaccurate. But few people were willing to undertake the difficult calculations required to revise the tables. • He was probably motivated in large part by the much simpler explanation of retrograde motion offered by a Sun-centered system.

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