![]() ![]() A Moon that is to the east of the Sun is called a waxing moon. If you watch the Sun and Moon move across the sky, it will appear that the Sun is ahead and leading while the Moon lags behind. When the Moon is to the east of the Sun, its said to be lagging behind the Sun. The two crescent, quarter, and gibbous moons are further differentiated by on what side of the Sun the Moon is. In this illustration, we are looking down on the Earth’s North Pole, the Sun is off-page to the right, and the Moon is orbiting the Earth counter-clockwise. Figure 1: The phases of the Moon based on the Moon’s position in its orbit. These angles are summarized in Table 2 along with a picture of each phase. A crescent moon is 45 degrees from the Sun, a quarter moon is 90 degrees from the Sun, a gibbous moon is 135 degrees from the Sun, and the Full Moon is 180 degrees away from the Sun. Because the orbit of the Moon is tilted in relation to the Earth’s orbit around the Sun, a New Moon can still be as much as 5.2 degrees away from the Sun, thus why we don’t have a solar eclipse every month. When the Moon is in between us and the Sun, so that there is nearly a zero degree separation, we see a New Moon. Figure 1 will help in understanding the Moon during the different phases, and why we see the phase we do. Each of the phases of the Moon can be defined by the angle between the Moon and Sun in the sky. This is why we see the Moon in different phases throughout the month. However, as the Moon orbits the Earth we see a varying proportion of the sunlight side of the Moon. Since the Moon is a sphere, at any given point in its orbit, exactly half of the Moon is illuminated. From the positions of the Sun and Moon, be able to determine the phase of the moon.Be able to determine the approximate time of day by the position of the Sun.Know the moon-earth-sun angle for all eight phases.Explain what causes the phases of the moon.What causes the different phases is the position of the Moon in its orbit. Sometimes we see a Full Moon, sometimes we see just a sliver of the Moon. Throughout the month, the Moon’s appearance in the night sky changes. ![]()
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