During the month, the Moon changes from a full circle to a narrow crescent. There is a myth that this is due to the obstruction of the moon by another celestial body. However, if you look closely, you can understand that this is just a delusion.
The nature of moonlight
As you know, the Moon does not emit light, but only reflects it. And therefore, only that side of it, which is illuminated by the Sun, is always visible in the sky. This side is called daytime. Moving across the sky from west to east, the Moon overtakes and surpasses the Sun during the month. There is a change in the relative position of the Moon, the Earth and the Sun. In this case, the sun's rays change the angle of incidence on the lunar surface and therefore the part of the moon visible from the Earth is modified. The movement of the moon across the sky is usually divided into phases directly related to its modification: new moon, young moon, first quarter, full moon and last quarter.
Moon observation
The moon is a spherical celestial body. That is why when it is partially illuminated by sunlight, the appearance of a "sickle" appears from the side. By the way, by the illuminated side of the Moon, you can always determine which side the Sun is in, even if it is hidden behind the horizon.
The duration of a complete change of all lunar phases is usually called a synodic month and ranges from 29, 25 to 29, 83 Earth solar days. The length of the synodic month varies due to the elliptic shape of the lunar orbit.
On a new moon, the disc of the Moon in the night sky is absolutely not visible, since at this time it is located as close to the Sun as possible and at the same time faces the Earth with its night side.
This is followed by the waxing moon phase. During this period of time, the Moon for the first time in a synodic month becomes visible in the night sky in the form of a narrow crescent and can be observed at dusk a few minutes before its sunset.
The first quarter follows. This is the phase in which exactly half of its visible part is illuminated, as in the last quarter. The only difference is that in the first quarter, the proportion of the illuminated part at this moment increases.
The full moon is the phase in which the lunar disk is visible clearly and completely. During the full moon, for several hours, you can observe the so-called opposition effect, in which the brightness of the lunar disk noticeably increases, while its size remains the same. This phenomenon is explained quite simply: for an earthly observer, at this moment all shadows on the surface of the Moon disappear.
There are also phases of the waxing, waning and old moon. All of them are characterized by a very narrow crescent moon of a grayish-ash color typical for these phases.
From all of the above, we can conclude that, in fact, nothing obscures the Moon. The angle of its illumination by the sun's rays simply changes.
