## Kepler's LawsJohannes Kepler, working with data painstakingly collected by Tycho Brahe without the aid of a telescope, developed three laws which described the motion of the planets across the sky. 1. The Law of Orbits: All planets move in elliptical orbits, with the sun at one focus. 2. The Law of Areas: A line that connects a planet to the sun sweeps out equal areas in equal times. 3. The Law of Periods: The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. Kepler's laws were derived for orbits around the sun, but they apply to satellite orbits as well. | Index Gravity concepts Orbit concepts | ||

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## The Law of Orbits## All planets move in elliptical orbits, with the sun at one focus.This is one of Kepler's laws. The elliptical shape of the orbit is a result of the inverse square force of gravity. The eccentricity of the ellipse is greatly exaggerated here. | Index Gravity concepts Orbit concepts | ||

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## Examples of Ellipse Eccentricity
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## The Law of Areas## A line that connects a planet to the sun sweeps out equal areas in equal times.
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## The Law of Periods## The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit.
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## Data: Law of PeriodsData confirming Kepler's Law of Periods comes from measurements of the motion of the planets.
Data from Halliday, Resnick, Walker, Fundamentals of Physics 4th Ed Extended. Table 15-3 | Index Gravity concepts Orbit concepts | ||||||||||||||||||||||||||||||||||||||||

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