What is the moon phase?

Canyue: The moon or moon phase at the end of the lunar calendar.

Full moon: the moon on the fifteenth night of each month in the lunar calendar.

Convex moon:? December and thirteenth of the lunar calendar.

Chord Moon: In the first half of the month, the part of the moon illuminated by the sun gradually increased from the new moon to the full moon, and the moon phase changed from deficit to surplus.

Extended data:

Moon phase change song

The new moon on the first day is invisible only because it is trapped in the sun and the earth.

On the eighth day of the seventh lunar month, the half moon faces west.

When the full moon comes out on the 15th and 16th, the earth shoulders the sun and the moon.

Twenty-two, three and the last quarter of the moon, the moon faces east until midnight.

A formula (convenient for memory): upper west, lower east-meaning: the first quarter moon appears in the first half of the lunar calendar, and the moon faces west, located in the western half of the sky (the concave surface faces east); The last quarter moon appears in the second half of the lunar calendar, and the moon faces east (concave faces west), which is located in the eastern half of the sky.

Moon phase change law

1. On the first day of the lunar month, the moon lies between the sun and the earth. People on the earth only see the moon deviating from the dark side of the sun, so they can't see the moon on the earth (equivalent to the "black moon"), which is called a new moon or a new moon. See position a in figure 1 for its visual shape. This moon phase almost rises and sets with the sun, that is, it rises in the morning and sets at dusk, and its existence can only be detected during the solar eclipse.

2. After the new moon, the moon rotates eastward around the earth, leaving the middle between the earth and the sun and leaning to one side, that is, the moon is located in the east of the sun.

The half moon illuminated by the sun faces west. On the earth, we can see that part of it is sickle-shaped, and its convex surface faces the western sun. This is the so-called moth eyebrow moon. See position b in figure 1 for its visual shape. Moths rise after sunrise and set after sunset. She and the sun are in the sky, in the bright sky, so she can't see the moon phase. Only after sunset can you see the moth-eyebrow moon in the western sky.

On the seventh and eighth day of the lunar calendar, as the moon continues to move eastward around the earth, the relative positions of the sun, the earth and the moon become right angles, that is, the connection between the moon and the earth is 90 degrees. Observers on the earth just see that the moon is bright in the western half, and the bright side faces west. This is a semicircle called the first quarter moon.

The first quarter moon rises around noon, and it appears in the southern sky at dusk. Suppose the observer is located in the mid-latitude of the northern hemisphere, and midnight falls below the horizon from the west and is visible in the first half of the night.

4. On the 1 1 day and 12 day of each lunar month, observers on the earth see that the western part of the moon is illuminated by the sun for more than half, and the phase of the moon becomes a convex moon. The convex moon rises after noon, in the southeast sky at dusk, the moon faces west, then continues to the west, and sets from the western horizon before dawn, and can be seen most of the night.

On the fifteenth and sixteenth day of the first lunar month, the moon moves to the outside of the earth, that is, the sun and the moon are located on both sides of the earth. Because there is an included angle θ between the ecliptic plane and the ecliptic plane (the average value of θ is 5 09'), under normal circumstances, the earth can't block the sunlight, and the bright side of the moon is all facing the earth, so people can see a bright moon, which is called the full moon or the moon.

When the sun sets at night, the full moon rises from the eastern horizon, lies in the southern sky at midnight and sets on the western horizon in the morning. You can see the moon all night.

Baidu encyclopedia-moon phase