Explain the law of the moon phases and what is the law of the moon phases

The first moon that appears in the western sky in the first half of the night is the crescent moon, followed by the first quarter moon, which is also in the western sky in the first half of the night, and then, the moon slowly moves eastward, and becomes round, and appears earlier, the full moon at fifteen o'clock, and after the fifteenth month, it slowly becomes smaller, and then it comes to the second quarter moon, which only appears in the second half of the night, and at the twenty-eighth there is no moon in sight, because the moon rises and sets with the sun, and then another cycle begins.

The moon moves from west to east every day, and the phase changes depending on the area of reflected sunlight, which is called the moon phase. The law of change of the moon phase is: new moon - emei moon - first quarter moon - gibbous moon - full moon - gibbous moon - second quarter moon - waning moon.

When the Moon orbits between the Sun and the Earth, and the hemisphere illuminated by the Sun is facing away from the Earth, the Moon cannot be seen on the Earth, and this day is called the "New Moon" or "New Year", which is the first day of the lunar calendar.

After the new moon, with the rotation of the moon, you can see a trace of silver hook-like moon on the earth, appearing on the west side of the sky, with its back arched to the west, called "Momei Moon", which is the beginning of the lunar calendar.

Three, four. to the beginning of the lunar calendar.

On July and eight, you can see half of the moon, with the convex side facing west, which is called the "first quarter moon".

From the ninth to the fourteenth day of the lunar calendar, you can see most of the moon, which is called the "gibbous moon".

Lunar. Ten. Five, ten.

On the sixth and seventeenth, you can see a full moon, which is called a "full moon" or "hope".

to the lunar calendar. Two.

Ten. On the second and twenty-third, only half a moon can be seen, convex facing east, which is called the "last quarter moon".

After a few days, it will become a moth-eyebrow-shaped crescent moon with its arched back facing east, called the "waning moon".

When the Moon moves between the Sun and the Earth again, it starts again and repeats. The whole process of a moon phase change is a "synodic month", about a day, and the length of a lunar month is determined according to the "synodic month".

You can simply memorize the law of the moon phases with a mantra, that is, "up and up and up and down and down and down and down and east and east", which means: the first quarter moon appears on the west side of the sky in the first half of the first half of the lunar calendar, with the bright side facing west. The last quarter moon appears on the east side of the sky in the second half of the second half of the lunar month, with the bright side facing east.

The moon phase change chart is as follows:

From the figure, you can see the law of the moon phase change: from the new moon to the full moon and then to the new moon, it is a cycle of moon phase change. This cycle averages days and is called a synodic month.

The first day of the lunar month is the fifteenth or sixteenth day of the lunar month. Towards the end of the month, the Moon will rotate again between the Earth and the Sun, and the waning Moon will rise again in the east shortly before sunrise. On the first day of the next month, it is Shuo again, and a new cycle begins.

There is a regular pattern in the change of the phases of the moon. The first half of the lunar calendar is missing to the round, and the second half of the month is missing from the round to the short. The change in the phase of the moon is related to the fact that the moon does not emit light, it is related to the sun's irradiation, and it is related to the moon's orbit around the earth. The phases of the moon are cyclical, and its replacement cycle is days, which is about one month.

1. About the 30th day of the lunar month or the first day of the lunar month, the moon is located between the sun and the earth. The moon is not visible on Earth, called the new moon or new moon. Its apparent shape is shown in position a in Figure 1. This phase of the moon is moonrise in the morning and moonset at dusk, and can only be detected during a solar eclipse.

2. About the third and fourth days of the lunar month, the moon leaves the middle of the earth and the sun and deviates to the side by one or more middle, that is, the moon is located in the east of the sun. Some of them can be seen on the earth in the shape of a sickle, convex facing the moon facing the sun to the west, which is called the crescent moon. Its apparent shape is shown in Figure 1 at position b.

This phase of the moon rises after sunrise and sets after sunset, and can only be seen in the western sky some time after the sun sets.

3. About the beginning of each lunar month.

On the seventh and eighth day of the first month, the relative position of the sun, the earth and the moon becomes a right angle, that is, the line between the moon and the earth and the line between the sun and the earth are 90°. On the earth, you can see that the moon is bright on the western half, and the bright side is facing west, and it is called the first quarter moon in a semicircle. Its apparent shape is shown in Figure 1 at position c.

This moon phase is about the moonrise at noon, and the midnight sets in the west, and the first half of the night is visible.

The moon phase change song means that the first quarter moon appears in the first half of the first half of the lunar month, and the moon faces west, located in the western half of the sky (the concave side faces east); The last quarter moon occurs in the second half of the second half of the lunar month, with the moon facing east (the concave side facing west) and is located in the eastern half of the sky.

The phase of the moon is calculated by the difference between the sun and the moon in the yellow longitude (the following degrees are the difference between the sun and the moon in the yellow longitude). The phases of the moon on each day of the lunar calendar have their own special names, the main moon phases are the new moon (the first day of the lunar calendar), the first quarter (around the eighth day of the lunar calendar), the full moon (around the fifteenth day of the lunar calendar), and the second quarter (around the twenty-third day of the lunar calendar), all of which have a definite moment of occurrence and are calculated by precise orbits.

Moon phase recognitionAssuming that the Full Moon is a circle, then no matter how the moon phase changes, the line connecting its upper and lower vertices must be the diameter of the circle (the moon phase is irregular during a lunar eclipse). When we see the outer edge of the moon phase close to the shape of the reverse C, then the moon phase at this time is the moon phase before the 15th day of the lunar calendar, on the contrary, when we see the outer edge of the moon phase is close to the shape of the C letter, then the moon phase at this time is the moon phase after the 15th day of the lunar calendar.