12.3 The Moon: Phases, Eclipses, and the Tides 1. The Motions of the Moon a. Rotation i. Period of Moon’s rotation = 27.3 days b. Revolution (orbit) i. Period of the Moon’s orbit around the Earth = 27.3 days ii. Lunar cycle = 29.5 days (time that the calendar month is based on) 1. Time needed for the moon to return to the same place in the sky 2. Since the Earth is orbiting as well as the Moon, the Moon needs the extra 2 days to “catch up to the Earth” in its orbit c. Orbital period of the moon = the rotational period of the moon = 27.3 days i. Synchronous rotation ii. Reason that we only see one side of the Moon 2. Phases of the Moon a. Order of the phases i. Based on the Moon appears to us on Earth ii. New moon, waxing crescent, 1st quarter, waxing gibbous, full moon, waning gibbous, 3rd/last quarter, waning crescent b. The sun’s light moves from right to left across the face of the moon c. Moonrise and moonset i. Time when one’s location on Earth can see the moon 3. Eclipses a. Any time one celestial body passes between another celestial body and the Sun b. Lunar eclipse i. Partial lunar eclipse; when the any part of the Moon falls within the penumbra (partial shadow) of the Earth ii. Total lunar eclipse; when the Moon falls entirely within the umbra (total shadow) of the Earth c. Solar eclipse i. Partial solar eclipse; when any point on the Earth falls within the penumbra (partial shadow) of the Moon ii. Total solar eclipse; when any point on the Earth falls entirely within the umbra (total shadow) of the Moon 4. Tides a. Caused by the gravitational pull of the Moon (primarily) and the Sun on the Earth’s oceans b. Daily tidal changes i. Caused by the rotation of the Earth underneath the Moon ii. 2 highs and 2 lows during a 24-hour period c. Monthly tidal changes i. Caused when the Moon and the Sun affect the Earth’s oceans ii. Spring tide 1. Sun and Moon work together to create unusually high and low tides 2. New and full moon phases iii. Neap tide 1. Sun and Moon work against each other to create high tides that aren’t as high and low tides that aren’t as low 2. 1st and 3rd quarter phases .