1. Planets’ Motions in Space

2. The planets in the solar system orbit our sun in a specific arrangement.
500 years ago no one even knew that they even went around the sun.
One guy, Johannes Kepler, spent 20 years studying the planets’ orbits.
He came up with his 3 laws of planetary motion…very smart.

3. Johannes Kepler
No…wait…
That’s better
Pretty good looking, huh, girls?

4. Kepler’s Laws of Planetary Motion
1. The path of a planet around the sun is an ellipse.
The orbits are not circular and the sun is not at the center of the ellipse.
So, sometimes the earth is closer to the sun and sometimes it is farther away.
Planets move faster when closer to the sun and slower when farther away.

5. As planets move around the sun, they sweep out equal areas in equal times…

8. 3. The time to go around the sun (orbit) is proportional to the distance from the sun.
- closer planets take less time to orbit the sun.
- closer ones also move faster.
AU=Astronomical Unit=150 million km=average distance from Earth to Sun

9. Mercury (closest to sun) orbits in 88 days, while Pluto (farthest) orbits in 247 years!