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The Ancient Astronomers. Ptolemy’s Geocentric model of the Solar System.
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Ptolemy’s Geocentric model of the Solar System Each planet revolves around an epicycle, which in turn revolves around a deferent centered approximately on Earth. As seen from Earth, the speed of the planet on the epicycle alternately (a) adds to or (b) subtracts from the speed of the epicycle on the deferent, thus producing alternating periods of direct and retrograde motions.
Nicolaus Copernicus(1473 – 1543) • Studied canon law and medicine • Developed heliocentric theory of the known universe Born in Torun, Poland • Authored book on his findings called De • RevolutionibusOrbiumCoelestium • Flawed theory in that he thought orbits were circular
Tycho Brahe • Danish born; died 1601. • Danish king built him an observatory • Devised the Tychonic system of • motion of celestial bodies where • Earth was stationary, with the sun • and moon moving around it. All the Planets moved • around the sun.
Johannes Kepler • Born 1571 in Germany • Educated in Germany; math, • philosophy, and theology. • Published a booklet in 1596 • attempting to explain planetary orbits • using math. • Joined Brahe as an associate in 1600 and formed his • three laws of planetary motion using Brahe’s data.
Kepler’s Three Laws 1) Planets have an elliptical orbit. 2) Planets move faster or slower to “keep up” in their orbits. 3) The period of a planet’s orbit squared is the cube of its orbits’ radius. (p2 = a3)
Galileo Galilei(1564 – 1642) • Studied medicine, philosophy • and math. • Developed law of falling bodies • (acceleration due to gravity). Born in Pisa, Italy • Used the telescope in 1609 to observe celestial • bodies giving him reason to question the philosophy • and religious views of the time. • Published Dialogues Concerning the Two Chief World Systems in 1632.
1) Phases of Venus Observations of Galileo 2) Moon mountains! 3) Sun spots 4)Four “Galilean” moons of Jupiter Phases of Venus and the moons of Jupiter helped support the heliocentric model of the solar system
Studied math and science; • specifically optics Isaac Newton(1642 - 1727) • Enjoyed building things that were • mechanical like sundials and water clocks. Born in Woolsthorpe, England • Devised a reflecting telescope and studied light. • Published PhilosophiaeNaturalis Principia Mathematicain 1687 concerning forces and gravitation.
1) Law of Inertia Newton’s Three Laws 2) Acceleration is proportional to force and inversely proportional to mass. 3) Action - reaction The law of universal gravitation, angular momentum, and Newton’s Three Laws helped describe how the planets stay in motion and in their particular orbits.