Earth’s Moon

1. Earth’s Moon Chapter 7, Section 3 Pages 197-207

2. Rotation & Revolution • Moon revolves around the Earth • It takes 27.3 days (a sidereal month) for the Moon to revolve once around Earth and line up with the same star again • Because the Earth revolves around the Sun, it will take the Moon two more days to line up with the Earth and the Sun again • Complete lunar cycle takes 29.5 days, known as a synodic month

3. The Moon does not appear to rotate because it keeps the same side facing Earth – this is not true • Moon keeps the same side facing Earth because it takes 27.3 days to rotate once on its axis – the same amount of time it takes to revolve around the Earth

4. The Moon’s Effect on Tides • Tide: rise and fall of sea level • Tide on Earth is caused by a giant wave produced by the gravitational pulls of the Sun and the Moon • As the crest of the wave approaches the shore, the level of the water in the ocean rises – high tide • About six hours later, the sea level drops, causing a low tide

5. As Earth rotates and the Moon revolves, different locations on Earth’s surface pass through the high and low tides • The Sun can strength or weaken the tidal effect • When the Moon and Sun are lined up – the high tides are much higher and the low tides are much lower – Spring Tide • When the Sun and Moon are at right angles, the high tide is not as high and the low tides are not as low – Neap Tide

6. Moonlight • The Moon shines because it reflects sunlight from its surface • Half of the Moon is lighted while the other half is dark • As the Moon revolves around Earth, different portions of the side facing Earth are lighted causing the Moon’s appearance to change

7. Moon phases are the changing appearances of the Moon as seen from Earth • The phase that you see depends on the relative positions of the Moon, Earth, and the Sun

8. Phases of the Moon • New Moon • Occurs when the Moon between the Earth and the Sun • The side of the Moon facing away from the Earth is light and the side facing the Earth is dark • The Moon cannot be seen in the sky

9. Waxing Phases • After the New Moon, the phases are said to be “waxing,” the lighted portion gets a larger each night • 1st phase after New Moon: Waxing Crescent

10. About a week after a new we see one-half of the Moon’s lighted side, which is one quarter of the Moon’s surface • First Quarter Moon

11. From the point of a first quarter to a full moon, this phase is called a Waxing Gibbous

12. When we see all of the Moon’s light side when the Moon is on the side of the Earth opposite of the Sun • Full Moon

13. After a Full Moon, the light portion gets smaller and smaller each night – the phases are said to be waning • When only half of the side of the Moon facing Earth is light: Third-Quarter Moon

14. Waning crescent occurs before another new moon – only a small slice of the Moon is lighted facing the Earth

15. Eclipses • Moon and the Sun have close to the same size diameters • The Sun is about 400 times larger than the Moon, but it is also about 400 times further away from the Earth than the Moon • Eclipses occur when the Earth or the Moon temporarily blocks sunlight from reaching the other object

16. Occurs only when the Sun, the Moon, and the Earth are lined up perfectly • Only happen a few times each year

17. Solar Eclipse • Occurs when the Moon moves directly between the Sun and the Earth • Occurs during a New Moon and the Moon casts a shadow on the Earth • Darkest part of the Moon’s shadow: umbra – if standing here you will experience a total solar eclipse • Surrounding the umbra is a lighter shadow on Earth’s surface called the penumbra – partial solar eclipse

18. Only part of the Sun that is visible is a pearly white glow around the edge of the Moon • Can occur twice a year, although most people live their entire lives without seeing one • In order to see the eclipse, you must live in the small portion of the Earth where the umbra strikes and there must be clear skies

20. Lunar Eclipse • Earth’s shadow falls on the Moon • Begins when the Earth moves into the Moon’s penumbra • As the Moon continues to move it enters the Earth’s umbra and a curved shadow on the Moon is seen • When the Moon is completely in Earth’s umbra, this is a total eclipse

21. Moon sometimes becomes red because light from the Sun is scattered and refracted by Earth’s atmosphere • Partial eclipse: a ;portion of the Moon moves into Earth’s umbra • Almost certain everybody will have a chance to see a lunar eclipse • Anyone on the night side of Earth can see an eclipse

22. The Moon’s Surface • Craters were formed by meteroids, asteroids, and comets • There are lighter-colored patterns around the craters, which are resulted from debris from the impact settling around the crater • Cracks formed from the impact, which allowed molten to fill in the cracks from the molten center - this formed Maria

23. Maria - dark colored relatively flat regions on the Moon’s surface • 3-4 billion years old • Mountain ranges are also present on the surface

24. Regolith • When spacecrafts land on the surface of the Moon, the spacecraft actually bounces • Regolith - layer of debris on the Moon that formed by the accumulation of metoric material

25. The Moon’s Interior • At on time, the interior of the Moon was molten lava • When the molten lava cooled, if formed layers • Moonquakes occur and the Moon and by studying the moonquakes, we can find out information about the Moon’s history