1. Bill Nye on Planets and Moons
Lesson 5: Gravity
Bill Nye on Planets and Moons

2. Lesson 5: Gravity
Standard S6E1.e
Explain that gravity is the force that governs the motion in the solar system.

3. Lesson 5: Gravity Gravity
A pulling force that attracts objects to one another.
All objects have a gravitational pull on other objects.
Gravity’s strength depends on 2 factors:
Product of the masses of the objects
Distance between the objects

4. Drawing for Gravity
Gravitational Pull

5. Lesson 5: Gravity
Ex. If mass increases, then the pull of gravity will increase.
If distance increases, then the pull of gravity will decrease.

6. Size Comparison of our Sun & other Stars: “Star Size Comparison HD”

7. Orbits
In our solar system, planets revolve around the sun, and moons revolve around the planets. Their paths are called orbits.
Earth travels in an orbit around the sun.
The Moon travels in an orbit around the Earth.

8. 2nd Drawing for Gravity (increase in distance)
Gravitational Pull

9. Which will have a greater gravitational pull?

10. Which will have a greater gravitational pull?
Distance
Distance

11. Orbit drawing
Orbitt
Earth

12. Orbit Shape *Orbits are not circles.
*Orbits are not circles.
* Orbits are slightly egg-shaped, which is called an ellipse, or elliptical orbit.

13. Orbit shape drawing
Ellipse

14. Inertia
The tendency of objects to keep doing what they are already doing. If an object is already in motion, it will stay in motion at that same speed and direction unless an outside force acts on it.
This is called Newton’s first law of motion.

15. Inertia
Inertia would cause a planet to keep moving in a straight path, but an outside force must act on it in order for it to stay in orbit.
This outside force is gravity.
The gravitational pull of the sun pulls the planet inward while the planet’s speed and directions pushes it outward.
When these are in balance, the planet remains in a curved path around the sun.

16. Inertia drawing Inertia would keep planet moving in a straight path.
Earth
Gravity keeps the planet in orbit.

17. Object’s Motion in the Sky
Lesson 4
Object’s Motion in the Sky

18. Lunar Eclipse Tonight

19. Lunar Eclipse

20. Get out all notes on the solar system:
Introduction to the Universe
Motion of Objects in the Night Sky
Comets, Meteors, Asteroids,
Planets

21. Lesson 4: Object’s Motion in the Sky
Standard S6E1.d
Explain the motion of objects in the day/night sky in terms of relative position.

22. Lesson 4: Object’s Motion in the Sky
The Earth spins from west to east.
Therefore, objects in the sky (planets, the sun, stars) appear to rise in the east and set in the west.
Revolution and rotation cause our view of the night sky to appear to change throughout the year.
Certain constellations might appear to change position in the night sky or look like they disappear.

23. Lesson 4: Object’s Motion in the Sky
1. What 2 words describe the motion of the Earth?
Rotation & revolution
2 Define rotation. ( spinning)
3. Define revolution. (movement of one object around another)
4. How long does it take for the Earth to make one revolution?
365 days

24. Lesson 4: Object’s Motion in the Sky
5. How long does it take for the Earth to make one rotation? 24 hours
6. A day and night is one complete ______rotation___________.
7. A year is one complete ____revolution_________________.
8. The Earth is tilted on a ___axis________________ at an angle of ____23.5*_______.

25. Lesson 4: Object’s Motion in the Sky
Standard S6E1.d
Explain the motion of objects in the day/night sky in terms of relative position.

26. Video showing Constellation Changes in Night Sky