What is the origin of the first and second quarters? What is the First and Last Quarter Moons?

If the earth is the center of the circle, then the upper and lower moons are equivalent to the moon at 12 o'clock and 6 o'clock in a certain radius.

The difference is that due to the different positions of the sun, the earth, and the moon, although the moon is spherical, the upper moon we see is the left half of the circle that is divided into two halves vertically, while the lower moon is the right half that we can see.

The Upper Moon appears on the 7th and 8th of each month, and the Lower Moon appears on the 23rd and 24th of each month.

On the first day of the lunar month, when the moon moves between the sun and the earth, the moon faces the earth with its dark side, and rises and falls with the sun, so people cannot see it. The phase of the moon at this time is called the "new moon" or "new moon".

After the new moon, the moon gradually moves out of the area between the earth and the sun, and then we begin to see a small part of the moon illuminated by the sun, like a curved eyebrow, so the moon phase at this time is called "the moon of the eyebrow". This "crescent moon" can only be seen in the western sky in the evening.

Around the eighth day of the lunar calendar, the moon has moved to a 90° angle east of the sun as seen from the earth. At this time, we can see the bright half of the moon to the west, and the moon phase at this time is called "winding". The first quarter moon can only be seen in the first half of the night, and it submerges into the west in the middle of the night.

After the winding, the moon becomes fuller day by day, and we can see most of the bright hemisphere of the moon, and the phase of the moon at this time is called "gibbous moon".

It's time for the lunar calendar. Ten.

At 5 or 16 o'clock, the moon runs on the celestial sphere to the opposite side of the sun, and the sun and the moon are 180 degrees apart, that is, the earth is located between the sun and the moon. At dusk, the full moon rises in the east.

and at dawn it sinks to the west.

After the full moon, the moon becomes "thin" as the sun and moon positions get closer. It goes through the gibbous moon, the last quarter and the crescent moon in turn, and finally, returns to the position of the new moon. In China, it is customary to call the "Moon" in the second half of the month "the waning moon".

The first and second quarters, the waxing crescent and waning moons are similar in appearance, but they appear at different times, in different positions, and in the direction of their bright surfaces. The crescent moon and the first quarter moon appear in the western sky in the evening and the first half of the night, respectively, and their "faces" are facing west, that is, the western half is bright; The waning and last quarters appear separately.

In the eastern sky at dawn and in the second half of the night, their "faces" are facing east, i.e., the eastern half is bright. Since the date of the lunar calendar in China is arranged according to the phases of the moon, the working people of ancient China sometimes relied on it to judge the date of the lunar calendar and the approximate time of the night.

The average time it takes for the moon to move from the new moon position to the time it returns to the new moon position is days, that is, the average period of change in the phases of the moon is days, which is called a "synodic month". Lunar calendar:

In addition to the sun, the ancient Chinese have long known to calculate the days of each month by observing the periodic changes of the moon phases, which is called the lunar calendar, and the name of the lunar calendar comes from the fact that the ancient Chinese called the moon "Taiyin", so it is also called the "Tailun calendar". The length of the lunar month varies, the big month is 30 days, the small month is 29 days, and the date of the lunar calendar is related to the phase of the moon; As the first day of the new moon is the new moon; Beginning.

The seventh and eighth are the first quarter moons; Ten.

5 and 16 are the full moon; The last quarter moon is in.

Two. Ten. II.XXIII. Because of this, it is easy to determine the date of the moon based on the waxing and waning of the moon's phases.

The first quarter moon appears in the first half of the first half of the lunar month, with the moon facing west, located in the western half of the sky; The last quarter moon occurs in the second half of the second half of the lunar month, with the moon facing east, in the eastern half of the sky.

There is a song "Moon Phase Change Song" that can vividly represent the change of the moon

The first new moon is not visible, only because of being trapped in the sun and the earth. On the seventh and eighth days of the first lunar month, the half full moon faces west.

The full moon rises on the fifteenth or sixteenth, and the earth picks the sun and the moon on one shoulder. Twenty-two and three last quarters, the moon faces east in the second half of the night.

To distinguish between the first quarter and the second quarter of the moon, we first think of the moon as a bow when it is in the shape of a crescent, the first quarter and the last quarter moon means that the string of the bow is on the top of the first half of the lunar calendar, that is, the opening of the crescent moon is facing upward, which is the first quarter moon; The corresponding second quarter moon is the second half of the moon, and the opening of the crescent moon is facing downward, which is the second quarter moon. The moon comes out in the first half of the night and comes out in the west, and the state of the moon facing west is called the first quarter moon, which is a lunar month.

Two. Ten. On the 2nd and 23rd, you can only see the semicircle of the pure pants on the east side of the moon, and this moon phase is called the "last quarter", and the moon at this time is called the second quarter moon.

The first quarter moon is divided into the first quarter moon and the second quarter moon, which is due to the continuous change of the position of the sun, earth and moon, and the moon phase changes in profit and loss. In the first half of the month, the moon's surface towards the earth from the new moon to the full moon is illuminated by the sun and gradually increases, and the moon phase turns from loss to profit. The moon phases change in a period of days.