1. Moon phases

3. What causes phases of the moon? The orbit of the Moon around the Earth. The orbit of the Moon around the Earth. We can only see part of the illuminated portion 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 is always illuminated Half of the moon always faces Earth Half of the moon always faces Earth Where the halves overlap, we see phases Where the halves overlap, we see phases

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

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

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

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

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

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

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

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

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

14. Waning moons Waning Crescent Between third quarter and new Between third quarter and new Rises at just before sunrise Rises at just before sunrise Overhead just before noon Overhead just before noon Sets just before sunset 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: Any theory of lunar formation must account for: The moon is as old as Earth, The moon is as old as Earth, is made of the same rock as Earth is made of the same rock as Earth Has no water Has no water Is getting further away from Earth Is getting further away from Earth Has little iron Has little iron

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

18. Fission Theory Moon spun off from a rapidly spinning molten Earth Moon spun off from a rapidly spinning molten Earth Problem – Earth’s gravity should have pulled the bulge back in 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 Moon formed somewhere else and was captured by Earth’s gravity Problem – something would have to slow down the moon Problem – something would have to slow down the moon Doesn’t explain lack of water, or moon moving away Doesn’t explain lack of water, or moon moving away

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

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

22. Giant Impact Theory

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