phy schii periodic

• kepler - formulated three laws of planetary motion
• eudoxus - proposed that the universe has 27 celestial spheres
• aristotle - proposed that the universe has 56 celestial spheres
• galileo - observed the sunspot
• aristarchus - first hypothesized that the sun is the center of the universe
• hipparchus - first measured the discrepancy of sidereal year and tropical year
• plato - proposed that celestial motion is circular and uniform
• ptolemy - added the idea of deferent and epicyclic motions to the geocentric model
• brahe - made detection instruments to produce accurate data regarding the elevation of stars and planets
• copernicus - opposed ptolemic model and paved the way for the heliocentric model