Figure 2: Position of the Sun in the sky for the eight different times we will use in the lab. This will make determining the moon-earth-sun angle easier. These eight different positions are all 45 degrees apart from each other, just like the eight positions for the moon in its different phases are 45 degrees apart.
Figure 2 shows the Sun’s position in the sky for these eight different times. The Sun during these times is below the horizon, but we can still locate its position. Note that three of these times are at night. In this lab, we will only consider eight different times of day, 3:00am/pm, 6:00am/pm, 9:00am/pm, and 12:00am/pm. The exact location of the Sun in the sky varies from season to season, but for this lab we will assume that we are near one of the equinoxes so that the Sun will rise right from exactly due east at 6:00am and set exactly due west at 6:00pm. Since the time of day is determined by the position of the Sun, where a given phase of the moon will appear in the sky at a specific time of day can also be determined. Table 1: Illustrations of the phases of the Moon and their angles from the Sun. As a waning moon continues to move in its orbit, we see less and less of the sunlight side of the Moon, so it appears to shrink in the sky. When the Moon is to the west of the Sun, it’s said to be ahead of the Sun, and the Sun lags behind. As a waxing moon continues to move around in its orbit, we see more and more of the sunlight side of the Moon, so it appears to grow in the sky. 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.
LUNAR CYCLE DIAGRAM FULL
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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