1. Moon phases

2. Moon Phases Terms Waxing – moon getting bigger
Waning – moon getting smaller
Crescent – moon less than half full
Gibbous – moon more than half full

3. What causes phases of the moon?
The orbit of the Moon
around the Earth.
We can only
see part of the
illuminated
portion

4. What do we see? Half of the Moon is always illuminated
Half of the moon always faces Earth
Where the halves overlap, we see phases

5. What do we see? It takes 28 days for the moon to make a complete orbit
This means the cycle repeats about once a month

6. Waxing and Waning Waxing - Moving towards a full moon
Waning – Moving towards a new moon

7. New Moon New moon When the near side is totally in shadow
Rises at sunrise
Overhead at noon
Sets at sunset

8. Waxing moons Waxing crescent Between new and first quarter
Rises after sunrise
Overhead in the afternoon
Sets after sunset

9. Waxing moons First quarter Between new and full
We see half of the illuminated half
Half of half = ¼
Rises at noon
Overhead at sunset
Sets at midnight

10. Waxing moons Waxing Gibbous More than quarter but less than full
Rises after noon
Overhead in evening
Sets after midnight

11. Full Moon When the near side is totally illuminated Rises at sunset
Overhead at midnight
Sets at sunrise

12. Waning moons Waning Gibbous Less than full, more than third quarter
Rises after sunset
Overhead after midnight
Sets after sunrise

13. Waning moons Third quarter Between full and new
We see half of the illuminated half
Half of half = ¼
Rises at midnight
Overhead in early morning
Sets at noon

14. Waning moons Waning Crescent Between third quarter and new
Rises at just before sunrise
Overhead just before noon
Sets just before sunset

15. Formation of the Moon
Where did it come from?

16. Points to keep in mind Any theory of lunar formation must account for:
The moon is as old as Earth,
is made of the same rock as Earth
Has no water
Is getting further away from Earth
Has little iron

17. Did the moon.. Spin off from Earth? Form somewhere else?
Form alongside Earth?
Form from an impact?

18. Fission Theory Moon spun off from a rapidly spinning molten Earth
Problem – Earth’s gravity should have pulled the bulge back in

19. Capture Theory
Moon formed somewhere else and was captured by Earth’s gravity
Problem – something would have to slow down the moon
Doesn’t explain lack of water, or moon moving away

20. Coformation Theory
Moon and Earth formed side by side from same accretion disk.
Problem – lack of iron, lack of water, moon moving away
Earth would have cleared its orbit

21. Giant Impact theory Mars sized planetoid impacted Earth.
Moon formed from debris cloud.
Most accepted theory

22. Giant Impact Theory

23. How do they stack up Theory Age Composition No water Moving away
No iron
Fission
Capture
Coformation
Impact