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Kepler’s Laws. The Man The Myth The Legend. 1. Tycho Brahe. Collected vast amounts of astronomical data (positions of different bodies at certain times) . 2. Kepler (1571-1630). Used Tycho Brahe's precise data on apparent planet motion s and relative distances .
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Kepler’s Laws The Man The Myth The Legend
1. TychoBrahe • Collected vast amounts of astronomical data (positions of different bodies at certain times)
2. Kepler (1571-1630) • Used Tycho Brahe's precise data on apparent planet motions and relative distances. • Deduced three laws of planetary motion. • Took him the last 30 years of his life.
3. Kepler’sFirst Law • The orbits of the planets are elliptical (not circular) with the Sun at one focus of the ellipse. • An Ellipse is an oval shaped geometric figure whose shape is determined by two points within the figure. The Sun is one foci, the other is empty.
4. Eccentricity of Planets • Eccentricity is the amount an ellipse deviates from a perfect circle. • Because an ellipse is not a perfect circle, and a planet’s orbit is an ellipse, the planet’s distance from the sun varies. • Perihelion – closest point to the focus • Aphelion– farthest point from the focus.
5. Kepler's Second Law A. A line connecting the Sun and a planet sweeps out equal areas in equal times. slower faster b. Translation: planets move faster when closer to the Sun.
6. Kepler’s Third Law • The square of a planet's orbital period (p) is proportional to the cube of its semi-major axis (a). • P2 is proportional to A3 • Where P is in Earth years • A is in Astronomical Units (AU) • AU = Astronomical Unit. • 1 AU = 1.5 x 108 km, the distance from the sun to the Earth. • Translation: the further a planet is from the sun, the longer the period.