Johannes Kepler

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Johannes Keplers Three Laws of Planetary Motion
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Aim What are Johannes Keplers Three Laws of
Planetary Motion?
I. Keplers Three Laws of Planetary Motion

1. Ist Law of Planetary Motion

1. Planets travel in elliptical orbits with the
sun at one focus. a. Planets distance from the
Sun will change throughout its orbit
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1. Aphelion point in planets orbit where it is
   furthest from the Sun.
2. Perihelion point in planets orbit where it is
   nearest the Sun.

B. 2nd Law of Planetary Motion (Equal Area Law)
1. States that each planet moves around the Sun
in such a way that an imaginary line joining the
planet to the Sun sweeps over equal areas of
space in equal periods of time.
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Kepler's Second Law
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C. 3rd Law of Planetary Motion (Harmonic Law)

1. Period time it takes a planet to travel one
   orbit around the Sun.
2. 3rd Law states that the period (P) of a planet
   squared is equal to the cube of its distance (D)
   from the Sun. P2 D3

1. Period must be in earth years
2. Distance from the Sun is expressed in AU
   (astronomical units)

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3. The further a planet is from the Sun, the
longer its period of revolution.

• Orbit is larger
• Planets further away move slower.
• (ex Earth moves 30 km/sec, Mercury moves 49
  km/sec, and Pluto moves 5 km/sec.)