Why and how does the moon phase change?

As the moon moves a large distance from west to east in the starry sky every day, its shape is constantly changing, which is called the moon phase. "People have joys and sorrows, and the moon has clouds and sunny days", here the circle and deficiency refer to the "moon phase change": the different images of the moon illuminated by the sun as seen on the earth.

Since the moon itself does not emit light, the half of the sphere facing the sun is a bright area, and the other half of the sphere is a dark area. As the position of the Moon changes relative to the Earth and the Sun, the illuminated side of the Moon is sometimes facing the Earth and sometimes facing away from the Earth; Sometimes the part of the moon facing the Earth is larger, sometimes it is smaller, so that different phases of the moon appear.

Whenever the moon orbits between the sun and the earth, and the hemisphere illuminated by the sun is facing away from the earth, people cannot see the moon on the earth, and this day is called the "new moon", also called the "new moon", which is the first day of the lunar calendar.

After the new moon, the moon follows the direction of the earth's rotation, and the bright area gradually turns to the earth, and the moon can be seen on the earth showing a trace of slender silver hooks, appearing in the western sky, bowing its back towards the sunset, this moon phase is called "moth eyebrow moon", which is the beginning of the lunar calendar.

Three, four. Subsequently, the moon moves away from the sun in the sky day by day, at the beginning of the lunar calendar.

On July and August, half of the bright area facing the Earth, one can see the half moon (convex facing west), and this phase of the moon is called the "first quarter moon".

When the Moon moves in the direction of the Earth's back sun, the lunar calendar.

Ten. Five, ten.

On the sixth and seventeenth, the bright areas of the moon are all facing the earth, and we can see a full moon, and this phase of the moon is called the "full moon", also called "hope".

After the full moon, the west side of the bright area begins to deficit, and it is the lunar calendar.

Two. Ten. On the second and twenty-third, you can see the half moon (convex facing east), and this phase of the moon is called the "last quarter moon". During this period, the Moon moves closer to the Sun and rises in the east in the middle of the night.

After another four or five days, the moon turns into a moth-eyebrow-shaped moon bud with its back arched towards the rising sun, and this moon phase is called the "waning moon".

When the Moon moves between the Sun and the Earth again, the Moon returns to the "New Moon".

This is how the phases of the moon change over and over again. If calculated by the cycle of the moon phase change (that is, the entire process of a moon phase change), from the new moon to the next new moon, or from the full moon to the next full moon, it is a "synodic month", with an interval of about a few days, and the length of a month in the Chinese lunar calendar is determined according to the "synodic month".

Because the moon itself does not emit light, but reflects the sun's rays. In this way, when the moon rotates, because the moon is at different angles relative to the earth and the sun at different positions, the size of the circle reflected on the earth will be different, which forms the moon phase change. Here's what happened:

On the first day of the new year, the moon is not visible, and then the west side of the moon is seen first, and then gradually expands to the east side. to the beginning of the lunar calendar.

On the seventh and eighth days of the lunar month, the visible part of the moon appears semicircular, and then continues to expand eastward, and by the fifteenth day of the lunar calendar, it expands to the entire circle. After the fifteenth, the western part of the moon begins to gradually become invisible, and gradually expands to the east to the lunar calendar.

Two. Ten. At 2 and 23 o'clock, only half of the circle on the east side remained. Then the shadow part continued to expand eastward, and was completely invisible from the 30th lunar month to the first day of the next lunar month. At this point, the one-month phase change cycle is completed.

By the way, no matter what the phase of the moon is, the round side of the moon is always pointing towards the sun.

When the Moon orbits the Earth, sunlight will shine on the Moon from different angles, so the Moon will take on a different shape when viewed from the Earth.

Why does the moon change differently

Whenever the moon runs between the height of the solar belt and the earth, and the hemisphere illuminated by the sun is facing away from the earth, people cannot see the moon on the earth, and this day is called the "new moon", also called the "new day", which is the first day of the lunar calendar.

After the new moon, the moon follows the direction of the earth's rotation, and the bright area gradually turns to the earth, and the moon can be seen on the earth showing a trace of slender silver hooks, appearing in the western sky, bowing its back towards the sunset, this moon phase is called "moth eyebrow moon", which is the beginning of the lunar calendar.

Three, four. Subsequently, the moon moves away from the sun in the sky day by day, at the beginning of the lunar calendar.

On July and August, half of the bright area facing the Earth, one can see the half moon (convex facing west), and this phase of the moon is called the "first quarter moon".

When the Moon moves in the direction of the Earth's back to the sun, that is, the lunar calendar.

Ten. Five, ten.

On the sixth and seventeenth, the bright areas of the moon are all facing the earth, and we can see a full moon, and this phase of the moon is called the "full moon", also called "hope".

After the full moon, the west side of the bright area begins to deficit, and it is the lunar calendar.

Two. Ten. On the second and twenty-third, you can see the half moon (convex facing east), and this phase of the moon is called the "last quarter moon". During this period, the Moon moves closer to the Sun, and only rises in the east at midnight on the second quarter of the month.

After another four or five days, the moon turns into a moth-eyebrow-shaped moon bud with its back arched towards the rising sun, and this moon phase is called the "waning moon". When the Moon moves between the Sun and the Earth again, the Moon returns to the New Moon.

This is how the phases of the moon change over and over again. If we use the cycle of moon phase change (i.e., the whole process of a moon phase change) to calculate, from the new moon to the next new moon, or from the full moon to the next full moon, it is a "synodic month", with a time interval of about a few days, and the length of a month in the Chinese lunar calendar is determined according to the "synodic month".

The Moon shines by reflecting sunlight, and it takes on a variety of shapes depending on its position relative to the Sun (ecliptic longitude). As the moon moves a large distance from west to east in the starry sky every day, its shape is constantly changing, which is called the moon phase change.

1. Shuo: The difference between the sun and the moon and the yellow longitude is 0°, at this time the moon is located between the earth and the sun, facing the earth with a dark side, and almost at the same time as the sun, so it cannot be seen on the ground, this is Shuo, this day is the first day of the lunar calendar.

2. Quarter Moon: The moon continues to rotate forward until the beginning of the lunar calendar.

Seven, eight, the yellow longitude difference is 90 °, the sun sets, the moon is already overhead, in the middle of the night, the moon sets, at this time the moon illuminated by the sun, exactly half of it is for you to see, called the "first quarter moon".

3. Full Moon: It's the lunar calendar.

Ten. 5. 16. When the moon turns to the other side of the earth, the earth is in the middle of the sun and the moon, and the half of the moon illuminated by the sun is facing the earth, which is called "looking". Since the moon is exactly opposite the sun, the sun sets in the west, and the moon rises in the east, and when the moon sets, the sun rises again in the east, and a bright moon is visible all night.

As we all know, the moon is different every day of the month, and we call this change in the moon's "cloudy and sunny" "moon phase change". The phases of the moon mainly include: the change in the position of the moon in the sky and the change in shape.

Do you know the reason for the change of the moon phase? Check it out!

Reasons for the change in the phases of the moon.

The reason for the change in the phases of the moon is related to the nature of the moon itself and the relative position of the moon, the earth, and the sun. The moon itself does not emit light, and when illuminated by the sun's rays, half of the sphere facing the sun is a bright area, and the other half of the sphere is a dark area (blocked by itself). As the position of the Moon changes relative to the Earth and the Sun, the illuminated side of the Moon is sometimes facing the Earth and sometimes facing away from the Earth; Sometimes the part of the moon facing the earth is larger, sometimes it is smaller, so there are different phases of the moon.

The new moon is 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, and the moon is not visible on the earth, called the new moon or new moon, and its existence can only be detected during solar eclipses.

The moon is about the third or fourth day of the lunar month, the moon leaves the middle of the earth and the sun and deviates to the east, and the sickle-shaped part of it can be seen on the earth, called the crescent moon, only when the sun sets and can be seen in the western sky.

The first quarter moon is about the beginning of the lunar month.

On the seventh and eighth day of the first month, the moon continues to orbit the earth to the east, and the moon-earth line is 90 degrees connected with the sun and the earth, and the western half of the moon can be seen on the earth, and it is called the first quarter moon in a semicircle.

The gibbous moon is about every month in the lunar calendar.

Ten. 1. 12. On the earth, more than half of the part of the moon illuminated by the sun can be seen, that is, the gibbous moon, which can be seen in most of the night.

The full moon is about every month of the lunar calendar.

Ten. 5. 16. The moon moves to the outer side of the earth, that is, the sun and the moon are located on both sides of the earth, and all the bright surfaces of the moon can be seen on the earth, which is called the full moon or hope.

The second quarter moon is about the month of the lunar calendar.

Two. Ten. 2. 23, the relative position between the sun, the earth and the moon becomes a right angle again, the moon is 90 degrees west of the line between the sun and the earth, and the eastern half of the moon can be seen on the earth in a semicircle, and the moon is facing east, which is called the last quarter moon, and it is visible in the second half of the night.