1. QQ:
Name the planets in our Solar System in order moving away from the Sun.
What is the largest planet?
What is the smallest planet?
Which planet is closest to Earth’s size?
What is the shape of the path of the planets’ orbits?

3. Today’s Objective:
I can use Kepler’s Laws to explain the way Earth moves through the Solar System.

4. Project Approval Sheet
Projects Due Monday 9/26…

5. Astrolabe data: You can collect it on the weekend if it is easier to get a reading.

6. What’s the big deal about gravity?

7. Gravity
the attraction between every two objects, no matter how big or how small.

8. Balance point is middle
Balance point is not middle

9. Balancing point around
barycenter
Center of mass
between two objects
Balancing point around
which planets orbit

11. Precession
The change in direction of the Earth on its axis.
Changes which stars we see at night depending upon the season
summer
winter

13. What does that mean for Earth?

14. Nutation
The slight wobbling of Earth’s axis as it changes positions ½ degree every 18 years

16. Discovering Kepler’s Work
Follow instructions carefully
Work with your group
Everyone participates equally

17. * Tie string that is 8 cm
long in a circle
* Place white paper board and hold it down with push pins 3
* Place two push pins 3 cm apart
* Wrap string around pencil

19. Kepler’s first law:
1. Planets move in an elliptical orbit (path)

20. Kepler’s First Law
Pin
Pin
String
Orbit
Line

21. Modeling the Shape of an Orbit

22. 2. A planet travel’s faster when it is closer to the sun.
Kepler’s 2nd law:
2. A planet travel’s faster when it is closer to the sun.
Each area is covered
During equal
Time periods

23. Farthest point from Sun
b = 40
h = 10 A = ?
b = 20
h = 20
A = ?
Aphelion:
Farthest point from Sun
Perihelion:
Closest point to Sun
Area is same

24. Earth is farthest from the Sun
Aphelion:
Earth is farthest from the Sun
152 million km
About July 4th

25. Earth is closest to the Sun
Perihelion:
Earth is closest to the Sun
147 million km
About January 3

26. Modeling the Speed of a Planet

27. Kepler’s 3rd law
3. The distance a planet is from the sun affects how long it takes to revolve around the sun.

28. Comparing Speeds of Planets

29. Creating the orbits of other planets
Move the center pins:
4 cm apart
5 cm apart
6 cm apart
7 cm apart

30. When the pins were 3 cm apart, one could represent the Sun
and the other the barycenter between the Sun & Jupiter.

31. Imagine one pin is the Sun
and the other is the barycenter between Sun & Earth.
Would you move the pins further apart or closer together? Why?

32. Test your hypothesis….
Push the pins close together so they are touching. The barycenter between Earth and Sun is near the edge of the Sun. If one pin is the Sun & the other pin is the barycenter, predict whether the orbit of Earth will be more elliptical or more circular.