Lecture 8: The Phases of the Moon

The moon circles the earth and goes round the earth.

The rotation of the moon and the synchronization of the orbit are caused by a strong tidal power from the Earth, which effectively "locks" the direction of the moon towards the Earth.

[Note: The degree of synchronization is not complete for two reasons. First, because the moon's orbit is not a circle but an ellipse, the moon's orbit speed is fast in the near point and slow in the far field. This discrepancy between accurate orbital speed and rotational speed reduces the Moon's apparent east-west "shaky" movement by about nine degrees per month. The second is that the axis of the moon is tilted about 7 degrees relative to its orbital plane (as at 23.5 degrees of the earth). This led to the additional north-south nodding movement of the moon. The combination of tremor and nodding movement is called "liberation". You can see the liberation in the movie of the lower month. ]

[Lunation movie. This movie shows the phases of the moon's moon. The moon looks big at the near point and it looks small at the far field. Also pay attention to the obvious nod and shaky movements caused by "release" above.

The time of ascending and descending depends on the Earth seen from the surface of the rotating Earth. Details of composition of the sun and the moon

Other examples are given in the class (better calculate the approximate monthly and monthly time of the current phase of the month and go outside to see if your forecast is correct! )

A certain week of the month is the time it takes for the moon to travel around the earth against the moon.

Note: Although the background constellation is the same after 27 days (Gemini), the moon is in another early stage (Wanning Gibbs before the last quarter stage).

The Islamic calendar is indicated by the first appearance of the new moon at the beginning and end of the new moon.

Sidereal comes from the Latin star (sidus). A fixed week indicates the time it takes for objects (such as the moon) to return to the same position as the stars.

Synodic is derived from the Greek Shinod and means "to gather" (for example, the "meeting of the church"). Therefore, the synchronization period of the month is the time between consecutive months and the time the sun and moon appear on the same side of the sky.

In the synchronization cycle, you always have to combine two star cycles. In this case, we will calculate the synchronization period by combining the orbit of the moon around the earth (the star period of the moon) and the orbit of the earth (the star period of the earth) around the sun.

The full moon is the phases of the moon when the whole moon is illuminating the earth. This phase occurs when the earth is between the moon and the sun. About a week later, the moon entered the quarter of the lunar month. At this point, half of the moon can be illuminated from the ground, so the moon looks like a semicircle. When the moon moves between the earth and the sun, the side facing the earth is completely dark. This is called the New Moon Phase, and we usually do not see the moon at this point. Sometimes, you can hardly understand the outline of the new moon in the sky. This is because a part of the sun reflects off the Earth and hits the moon. Before and after the quarter moon phase are uplift and new moon phase. During the expanse of the lunar moon, the moon was illuminated more than half, but it was not full. At the new moon stage, the moon is considered to have less than half the brightness, having only one sliver or crescent shape.

Probably the easiest is to understand the cycle of the month in this order. New month and full moon, first and third quarter, and the stage between them. As shown above, when the moon is above the earth and the sun. These three objects are approximately aligned (why "approximation" is explained later). The entire illuminated part of the moon is behind the moon, half not visible. In the full moon, the earth, the moon, and the sun are roughly aligned like a new moon, but since the moon is on the other side of the earth, the whole part illuminated by the sun of the moon turns toward us. Shaded part is not to be seen completely. Satellites in the first quarter and the third quarter (sometimes referred to as "half moon") occur when the moon is at 90 degrees to the earth and the sun. The term new moon refers to the stage where the moon is less than half of the light. Therefore, in the following decreasing step