Why do we only see one side of the moon?

The moon is probably one of the most beautiful heavenly bodies we can see here from Earth, and as a kid, we are often baffled about the great mysteries the moon has.

But as the years went by, scientists are continuously gaining more and more knowledge about the moon. Like in the year 1969, when the American Astronaut, Neil Armstrong landed on the moon, unraveling some mysteries, and learning more information about it.

That is why today, the moon is no longer a big question to us, as it is already a part of our education as a child. However, there are still some queries about how the moon works, and particularly, why do we only see one side of the moon?

This question is famous for some people who are starting to have an interest and curiosity about the moon. That is why in this article, let’s look into the reason behind this phenomenon, and other interesting facts about the moon.

How does the moon work?

For starters, the moon acts as the Earth’s natural satellite that provides light during the nighttime, as well as causing tides and helps in moderating the planet’s place on its axis.

At night, we can see the bright circular moon reigning at the top of the sky. And after several nights of observing the night sky, we could notice that the moon’s appearance is the same.

This appearance is called the near side of the moon, which usually takes up about 59% of its surface. The remaining 41% of the moon is what we call the dark side, which is not entirely dark; it’s just a name derived from the side of the moon that is continuously facing away from Earth.

The near side, however, is not stuck only to one side as others conclude. The main reason behind this phenomenon is what we call tidal locking or synchronous rotation. This tidal locking is a result of the moon’s rotation, which takes the same amount of time to rotate around its axis and Earth. Meaning to say, it will take 27.3 “Earth days” to spin around its axis and the same amount of time to make a complete revolution around the Earth. With this synchronous rotation, it allows the moon only to display its one side, which gives the appearance that it is stuck.

This activity is vital to our planet as it helps Earth to maintain balance. If the rotation rate of the moon and Earth are even slightly different, then we could see the entire surface of the moon. However, the tidal locking between Earth and the moon is present since the beginning of the known history.

The detailed explanation for this phenomenon is called tidal friction, wherein gravity is the major contributor to its effects. The Earth and Moon exert a gravitational force, and this mutual force causes tidal bulges to each body. One bulge faces towards the other entity, and the other bulge faces in the opposite direction. Throughout the years, they siphon energy away from the rotational momentum of both bodies, which produces a breaking-effect.
Since that the Earth on the moon has a considerably higher gravitational force than that of Moon on Earth – about six times, the moon experiences a more significant breaking-effect. The Earth attracts the moon towards it while it tries to go on a straight line.

Initially, the rotation speed of the moon is much faster – this is from millions of years ago. Over time, the moon’s rotation has gradually slowed until the rate of rotation matches the speed at which the tidal bulges move around the body; that has tidal locking.

Today, we can find the tidal bulges at a fixed position to the rotation of the moon, forming a sort of equilibrium. Now the moon is locked into this period, with the same hemisphere always turned towards Earth.

Even though we should only be able to see half of the surface according to this theory, we get to see 59%, as mentioned earlier. This discrepancy is because of the moon orbits around Earth in an elliptical trajectory rather than a perfectly circular one, and it creates differences in angular and linear velocities.

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