1. Warm up:
With your group determine your advice to the general on the aerial attack and beach landing dates and time. Be ready to justify your choice!!

2. ORBITAL MOTIONS OF PLANETS AND SATELLITES
Kepler 
-Kept asking why the Sun changed in diameter?
Developed the Laws of Planetary Motions:
1. The orbit of every planet is an ellipse with the sun at one focus
2. Planets sweep out equal areas of their elliptical orbit in equal time periods
3. A planet’s period of revolution squared is proportional to its distance from the sun cubed
This means every orbit is an ellipse, not circular.

3. All our planets orbit with the sun at one focus
1st law
drawing the orbit

4. Warm up review: Tell the person to the right of you:
Why we see different phases of the moon
Why the moon rises 50 mins later each night
Why it takes longer to see one complete phase cycle than it does for the moon to make one revolution
Why we see the same side of the moon.

5. Law 1: All planets orbit in an elliptical fashion
Eccentricity tells how “elliptical’ the orbit is
Eccentricity is how elongated (oval) the orbit is .
eccentricity = distance between foci length of major axis

6. The bigger the eccentricity the more elliptical the orbit
The bigger the eccentricity the more elliptical the orbit.   Earth’s orbit is very round, it’s eccentricity (little wonder the early astronomers thought the orbit was circular)

7. Eccentricity of planet orbits
Examples of Ellipse Eccentricity
Mercury .206
Venus
Earth
Mars
Jupiter .048
Saturn .055
Uranus .047
Neptune.008
Pluto

9. Warm up: Check the board to see if you owe any labs.
Complete the first three questions on the handout.

10. Comets are highly elliptical

13. Law 2: Planets sweep out equal areas of their elliptical orbit in equal time periods keplers law of equal areas
keppler 2nd law

14. The Law of Equal Areas
A line that connects a planet to the sun sweeps out equal areas in equal times.
This arises from conservation of angular momentum.
When the planet is closer to the sun, it moves faster, sweeping through a longer path in a given time

15. 3rd Law: A planet’s period of revolution squared is proportional to its distance from the sun cubed

16. The 3rd Law: R2 (year) is proportional to d3 (distance)
The closer to the sun, the shorter the year both because the distance is shorter and because the planet moves faster.
Earth 30km/sec,
Mercury 49km/sec,
Pluto 5km/sec
3rd law

17. Forces that keep satellites in orbit:
Gravity:
Inertia

18. Forces that keep satellites in orbit around their primary:

19. Velocity and Gravitational force change with distance
Velocity and Gravitational force change with distance. The satellite moves faster when closer because the gravitational force is greater. The satellite’s kinetic energy is greater when velocity is faster. The sun’s apparent diameter looks larger when the satellite is closer

21. How to draw an ellipse

22. Another view of the laws….
carl sagan explains the laws
1st law
drawing the orbit
keppler 2nd law
3rd law

23. Procession of the axis https://www.youtube.com/watch?v=0qHjtp4cdCA

25. Climate change