The moon is a satellite of the planet Earth. Rotating around the Earth, the Moon reflects sunlight, so people think that it shines. The relative position of the Earth, the Moon and the Sun changes slightly from day to day, which is why the Moon is illuminated by the Sun in different ways, these stages are called phases.
The phases of the moon are due to the movement of the so-called terminator - this word denotes the border between the dark and lighted sides of the moon. Since the moon has a spherical shape, then if it is not fully illuminated, a month appears - a part of the celestial body is simply closed from the inhabitants of the Earth by the shadow of its own planet. Even when the Sun is below the horizon, the illuminated side always shows which side it is on.
The lunar month - the time during which the moon manages to go through all its phases (they are also called synodic month) - lasts approximately 28-29 days. The moon's orbit is not perfectly round, it is an ellipse, so the exact number of days in the lunar month changes slightly from time to time. On average, the duration of the lunar month is 28.5 Earth days.
The following phases of the moon are distinguished: new moon, new moon, first quarter, waxing moon, full moon, waning moon, last quarter and old moon. During the new moon, the Moon is completely hidden behind the Earth, it is not visible. The nights are very dark, but all the stars are clearly visible. New Moon is the best time to observe the starry sky through a telescope or photograph it if you are fond of something like that.
The young moon is the first days when the night star just appears in the sky. Only a thin sickle is visible. This phase is quickly replaced by the next one: the first quarter. During the first quarter, the illuminated portion reaches half the surface of the lunar disk. The moon is already clearly visible. After that, she still arrives and soon already shines in all her splendor: round as a ball. The full moon begins. At this time, the entire moon is visible. The time is very good in order to examine its surface, study the craters or troughs of the moon through a telescope.
A full moon lasts 3-4 days, after which the moon begins to wane. Soon this state is replaced by the last quarter, only half of the moon is visible. When the moon decreases even more, it is called old. Sooner or later, she completely disappears from the firmament, the time of the new moon comes.
There is a mnemonic rule by which it is easy to determine whether the moon is growing or decreasing. You need to put a stick to the non-circular side of the moon. If the sign turns out to be similar to "y", then the moon is decreasing, and if to "p", then it is growing. This method is not suitable if you are in the equator, where the moon almost always lies on its side. But in the Southern Hemisphere, the moon is oriented in the opposite direction: if, according to the above rule, you determine that it is growing, it means that it is actually decreasing.