1. ASTR 1101-001 Spring 2008 Joel E. Tohline, Alumni Professor 247 Nicholson Hall [Slides from Lecture07]

5. Phases of the Moon Entirely depends on relative positions of the Sun, Moon, and Earth. Very predictable! Here are some examples: –At full moon, the moon and sun always appear to be separated by 180 degrees on the sky –The full moon is never visible in the middle of the day –The first-quarter moon will always be on the Eastern horizon at noon –The third-quarter moon will always be directly overhead at sunrise

10. Phases of the Moon Entirely depends on relative positions of the Sun, Moon, and Earth. Very predictable! Here are some examples: –At full moon, the moon and sun always appear to be separated by 180 degrees on the sky –The full moon is never visible in the middle of the day –The first-quarter moon will always be on the Eastern horizon at noon –The third-quarter moon will always be directly overhead at sunrise

12. Phases of the Moon Entirely depends on relative positions of the Sun, Moon, and Earth. Very predictable! Here are some examples: –At full moon, the moon and sun always appear to be separated by 180 degrees on the sky –The full moon is never visible in the middle of the day –The first-quarter moon will always be on the Eastern horizon at noon –The third-quarter moon will always be directly overhead at sunrise

13. Phases of the Moon Entirely depends on relative positions of the Sun, Moon, and Earth. Very predictable! Here are some examples: –At full moon, the moon and sun always appear to be separated by 180 degrees on the sky –The full moon is never visible in the middle of the day –The first-quarter moon will always be on the Eastern horizon at noon –The third-quarter moon will always be directly overhead at sunrise

14. Phases of the Moon Entirely depends on relative positions of the Sun, Moon, and Earth. Very predictable! Here are some examples: –At full moon, the moon and sun always appear to be separated by 180 degrees on the sky –The full moon is never visible in the middle of the day –The first-quarter moon will always be on the Eastern horizon at noon –The third-quarter moon will always be directly overhead at sunrise

21. Other Issues Length of one month: –Sidereal (with respect to the stars) month is 27.32 days –Synodic (with respect to the sun) month is 29.5 days  this is the familiar “lunar” month on which calendars are based What about the spin/rotation of the Moon? –Moon spins exactly once about its axis every month –Consequence: the same side of the Moon faces the Earth at all times!

24. Other Issues Length of one month: –Sidereal (with respect to the stars) month is 27.32 days –Synodic (with respect to the sun) month is 29.5 days  this is the familiar “lunar” month on which calendars are based What about the spin/rotation of the Moon? –Moon spins exactly once about its axis every month –Consequence: the same side of the Moon faces the Earth at all times!