You may have heard references made to the “dark side” of the Moon. This popular term refers to the fact that the same physical half of it, the “near side”, is always facing Earth, which in turn means that there is a far side or so-called “dark side” that is never facing Earth and can only be seen from space.
This phenomenon has nothing to do with illumination or the periodic light and dark we see as the phases of it change. Sometimes people refer to a New Moon as a “dark moon” because it is fully in shadow as viewed from Earth and we can’t see it, but that’s not the same thing as the dark side of it.
The side of it facing us during a New Moon is the same as any other phase, such as a Full lunar activity when we can see the entire face.
So why can we only see one side of the moon from Earth? We all know that the Earth rotates on its own axis, so theoretically, it should also do the same, allowing us to get a full picture of the planetoid. Why are we limited to seeing only 50 percent? It turns out that the speed at which the Moon rotates has led to this particular phenomenon.
Millions of years ago, the Moon spun at a much faster pace than it does now. However, the gravitational influence of the Earth has gradually acted upon the it to slow its rotation down, in the same way that the much smaller gravitational influence of it acts upon the Earth to create tides. This influence slowed the rotational period of it to match that of its orbit – about 27.3 days – and it is now “locked in” to this period.
Each time you see a full moon you always see the same side
Finally, one reason that the far side of it is frequently referred to as the “dark side” is because many people mistakenly think that it never sees any light from the Sun. In that sense the term “dark side” is wrong and misleading.
In fact, since the Moon is constantly rotating on its own axis, there is no area of the planetoid which is in permanent darkness, and the far side of it is only completely devoid of sunlight during a Full Moon – when the Sun is facing it with the Earth in between.