2 Just as the Sun appears to change its position in the sky, so too, does the Moon.This is a result of the movement of the Moon around the Earth and our changing viewpoint on Earth relative to the Sun.
3 2. The sequential changes in the appearance of the Moon are called lunar phases.
4 3. The Moon does not emit visible light; instead we see the Moon’s reflection of the Sun’s light.
5 4. The new moon is the phase created when the Moon is positioned between Earth and the Sun.
6 5. As the Moon moves along in its orbit, the amount of reflected light that we can see increases. The increase in the portion of the sunlit side of the Moon is called waxing. When we can see half of the sunlit side, it is called the first quarter.
7 6. The full moon is the phase created when Earth is between the Moon and the Sun, and we are able to see the entire sunlit side of the Moon.
8 7. The decrease in the amount of the sunlit side of the Moon is called waning. During this phase, when we see half of the sunlit side, it is called the third quarter.
9 8. As the Moon orbits Earth, the same side faces Earth at all times because the Moon is rotating with a period equal to its orbital period, so it spins exactly once each time it goes around Earth.
10 9. The lunar month is the length of time it takes for the Moon to go through a complete cycle of phases. The length of a lunar month is about 29.5 days.
11 10.One of the Moon’s effects on Earth is the formation of tides, which occur roughly every 12 hours.
12 The basic causes of tides are the gravitational attraction among Earth, the Moon and the Sun.
13 2. The Moon does not actually orbit Earth 2. The Moon does not actually orbit Earth. Rather, both Earth and the Moon orbit around a common center of gravity. As a result of their motions, both Earth and the Moon experience differing gravitational forces. The unbalanced forces generate tidal bulges on opposite sides of the Earth.
14 3. Lunar tides are more than twice as high as those caused by the Sun because the Moon is much closer to Earth. Earth’s tidal bulges are always aligned with the Moon.
15 4. Solar tides can either enhance or diminish lunar tides 4. Solar tides can either enhance or diminish lunar tides. Spring tides are large tidal ranges that occur when the Moon is either full or new and the Sun, Moon, and Earth are aligned. Spring tides have high tides that are higher than normal and low tides that are lower than normal.
16 5. Neap tides occur when there is a first- or third- quarter Moon 5. Neap tides occur when there is a first- or third- quarter Moon. During these times, the Sun, Moon, and Earth form a right angle.During neap tides, high tides are lower than normal and low tides are higher than normal. Spring tides are, on average, three times higher than neap tides.