Is It True That The Moon Is Getting Away From Earth?

When the Moon first formed, it is thought to be closer to Earth than it is today. Computer simulations show that the distance was once 22,500 km. Today this distance is 402.336 km. The reason for this departure is the tides. The tides both reduce the rotational speed of the Earth and cause the Moon to move away from Earth. Measurements made thanks to the devices placed on the Moon with Apollo tasks show that the Moon moves away from the Earth by an average of 3.8 cm per year.

Since the gravitational effect between the two objects is inversely proportional to the square of the distance between them, the gravitational effect between the objects close together is more pronounced. Therefore, a relatively large satellite like the Moon causes the changes we know as the tide on Earth. The parts of the Earth facing the Moon feel this effect more, while the more distant parts feel less. The gravity of the Moon on Earth is quite evident in the oceans. Therefore, some changes occur in the shape of the Earth. This effect causes an ellipse-like stretching in the direction of the Earth facing the Moon, and these bulges that cause temporary increases in the mass distribution of the Earth are called tidal bulges.

As in systems where the rotation time of a planet around itself is longer than its orbital period, the Earth completes its orbit around the Earth in 24 hours, while the Moon completes its orbit around the Earth in about 27 days. For this reason, the mass center of tidal bulge is not on the line between the moon and the mass centers of the Earth, it is ahead of the Moon according to the direction of Earth's motion. Due to the gravitational interaction between this bulge and the Moon, the Moon pulls the Earth in the opposite direction of movement, slowing it down. Therefore, while the angular momentum of the Earth decreases, the angular momentum of the Moon increases and the Moon moves away from the Earth. Part of the angular momentum of the Earth is lost as a result of friction due to the ocean hitting the land.