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Physics of the Solar System. Kepler’s Laws. Planetary Paths. Learning Target: Define planetary orbit and describe its shape Define eccentricity and compare planets to each other Explain Kepler’s 3 Laws in simple language and give examples. Activity 1. Draw a simple orbit below.
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Physics of the Solar System Kepler’s Laws
Planetary Paths • Learning Target: • Define planetary orbit and describe its shape • Define eccentricity and compare planets to each other • Explain Kepler’s 3 Laws in simple language and give examples
Activity 1 • Draw a simple orbit below
Activity 1 • What do you know? • What is an orbit? • What are some things that orbit? • What is the shape of an orbit? • Do all orbits have the same shape? • Are orbits natural or human made?
Johannes Kepler • One of the fathers of early astronomy • Along with…
Kepler’s Laws of Planetary Motion • The planets move in elliptical orbits with the sun at one focus • In their orbits around the sun, the planets sweep out equal areas in equal times • The squares of the times to complete one orbit are proportional to the cubes of the average distances from the sun
Ellipses • Construct an ellipse
1: Law of Ellipses • Planets orbit in an ellipse • The sun is at one focus • The other focus is not occupied
Eccentricity of Orbits Planetary orbit eccentricities
2: Law of Equal Areas/Equal Time • A planet takes the same amount of time to move through any same area • So area A=B=C • But t (time) is the same for each one • What does it mean? A B C
3: Law of Harmony • Orbital Period: time it takes to go around the sun once • Semi-major axis: the line from the center of the ellipse to the end
3: Law of Harmony • So, what does it mean? • The further the orbiting body, the longer it takes to orbit • Yep, that simple