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The moon is indeed slowly moving away from the Earth at a rate of about $3.8$ centimeters per year. This phenomenon is primarily caused by the tidal interactions between the Earth and the moon.

The moon's gravity causes the Earth's oceans to bulge, creating two tidal bulges: one on the side of the Earth facing the moon and the other on the opposite side. The gravity of the Earth then pulls on these bulges, slowing down the Earth's rotation. This process is known as tidal acceleration.

As the Earth's rotation slows down, the length of its day increases. About $620$ million years ago, the length of a day on Earth was only about $21.9$ hours. The slowing down of the Earth's rotation has a secondary effect: it causes the moon to move away from the Earth.

The reason for this is due to the conservation of angular momentum in the Earth-moon system. As the Earth's rotation slows down, the angular momentum of the Earth-moon system must be conserved. This is achieved by increasing the distance between the Earth and the moon, which in turn increases the angular momentum of the moon's orbit.

In addition to tidal interactions, the moon's orbit is also affected by the Earth's slightly ellipsoidal shape. The Earth is not a perfect sphere, and its equatorial radius is about $6,378$ kilometers, while its polar radius is about $6,357$ kilometers. This ellipsoidal shape causes a small torque on the moon's orbit, which also contributes to the moon's recession from the Earth.

It's worth noting that the rate at which the moon is moving away from the Earth is not constant and can vary slightly over time due to various geological and astronomical processes. However, on average, the moon's distance from the Earth increases by about $3.8$ centimeters per year.

This gradual increase in the moon's distance from the Earth has significant implications for the Earth-moon system's evolution. In about $50$ billion years, the moon will have moved far enough away from the Earth that it will no longer be able to stabilize the Earth's axis, which could lead to drastic changes in the Earth's climate. However, by that time, the sun will have already exhausted its fuel and become a red giant, making the Earth's climate uninhabitable anyway.

Space

The moon is indeed slowly moving away from the Earth at a rate of about $3.8$ centimeters per year. This phenomenon is primarily caused by the tidal interactions between the Earth and the moon. The moon’s gravity causes the Earth’s oceans to bulge, creating two tidal bulges: one on the side of the Earth facing the moon and the other on the opposite side. The gravity of the Earth then pulls on these bulges, slowing down the Earth’s rotation. This process is known as tidal acceleration. As the Earth’s rotation slows down, the length of its day increases. About $620$ million years ago, the length of a day on Earth was only about $21.9$ hours. The slowing down of the Earth’s rotation has a secondary effect: it causes the moon to move away from the Earth. The reason for this is due to the conservation of angular momentum in the Earth-moon system. As the Earth’s rotation slows down, the angular momentum of the Earth-moon system must be conserved. This is achieved by increasing the distance between the Earth and the moon, which in turn increases the angular momentum of the moon’s orbit. In addition to tidal interactions, the moon’s orbit is also affected by the Earth’s slightly ellipsoidal shape. The Earth is not a perfect sphere, and its equatorial radius is about $6,378$ kilometers, while its polar radius is about $6,357$ kilometers. This ellipsoidal shape causes a small torque on the moon’s orbit, which also contributes to the moon’s recession from the Earth. It’s worth noting that the rate at which the moon is moving away from the Earth is not constant and can vary slightly over time due to various geological and astronomical processes. However, on average, the moon’s distance from the Earth increases by about $3.8$ centimeters per year. This gradual increase in the moon’s distance from the Earth has significant implications for the Earth-moon system’s evolution. In about $50$ billion years, the moon will have moved far enough away from the Earth that it will no longer be able to stabilize the Earth’s axis, which could lead to drastic changes in the Earth’s climate. However, by that time, the sun will have already exhausted its fuel and become a red giant, making the Earth’s climate uninhabitable anyway.

NewsPepr -

September 26, 2025