We all know that the moon itself is not luminous, the reason why we can see the moon is that the moon can reflect the light from the sun.

If the relative positions of the Sun, the Moon, and the Earth change, we can see the Moon in different shapes.

The moon becomes a crescent because the angle of its rotation and revolution around the earth changes, making us see the surface of the moon illuminated by the sun to a different extent.

When the Moon is completely between the Earth and the Sun, we see a full Moon, when the Moon is outside the Earth and the Sun, we see a crescent Moon.

Specifically, when the angles of the moon's rotation and revolution around the earth differ by 45 degrees, we see a half-moon shape, when they differ by 60 degrees, we see a one-third moon shape, and when they differ by 90 degrees, we see a half-moon shape or crescent.

The crescent usually appears when the moon is rising or falling, that is when the moon is positioned close to the horizon.

In addition, the crescent can also appear in other positions of the Moon, but this requires special conditions, such as in special light conditions or on nights when the air is very clear.

The moon will gradually turn from a curved moon on the first day to a full moon. Around the 15th day of the first lunar month, the moon reaches its fullest. After that, the moon will slowly become curved.

At the end of the month, the moon appears when it is almost dawn, when the moon is hard to be found, because at this time the light of the moon reflecting the sun will not reach our eyes anymore, and even if it does, the moon's light will be dulled in front of the sun.

There is another special sight - a total lunar eclipse. The surface of the moon turns dark red, and the moon is invisible to the eye from Earth.

The number of lunar eclipses per year is usually two, up to three, and sometimes not even once.

In general, the Moon either passes above or below the Earth's umbra and rarely passes through or partially passes through the Earth's umbra, so lunar eclipses do not usually occur.

In general, the moon has many forms each month and we can observe the moon at different times of the month and under different weather conditions.