Is the Moon moving away every year?

When you look up at the night sky, the "Moon" appears to be in the same place all the time.
Currently, the Moon is moving away from the Earth at a rate of about 3.8 cm per year.
You might think, "Only 3.8 cm a year?"
However, over the course of hundreds of millions or billions of years, the relationship between the Earth and the Moon changes significantly.
What is even more interesting is that this recession of the Moon is deeply related to the high and low tides that we see every day.

In this article, we will look at:

• Why the Moon is moving away

• The relationship between tides and the Moon

• Will the Moon ever escape from the Earth?

We will explore these topics.

The Moon is moving away

Currently, the average distance between the Moon and the Earth is about 385,000 km.
And from observations using laser ranging, it is known that the Moon is currently moving away from the Earth at a pace of about 3.8 cm per year.That is
3.8 cm in one year.
However, in reality, it does not continue to move away at a constant rate of 3.8 cm/year forever.
Because the effects of tides change as the Moon gets further away, the current speed cannot be used as is for long-term calculations.

Why is the Moon moving away?

The answer is closely related to the ebb and flow of the tides.
The Moon has strong gravity.
That gravity pulls the seawater on Earth, creating a "tidal bulge" on the Earth.
This is one of the major causes of high and low tides.
However, the Earth is rotating.
Moreover, the Earth's rotation is faster than the Moon's orbital motion around the Earth.
Therefore, the tidal bulge of seawater is not directly under the Moon, but forms slightly ahead of it.
Then, the gravity of that seawater bulge pulls on the Moon.

What is important here is that it pulls the Moon in the same direction as its orbital motion.
As a result, the Moon gradually receives orbital energy, and its orbit grows larger.

The "spring tides" of the full moon and new moon are also related to the Moon and the Sun

Not only the Moon but also the Sun is involved in the ebb and flow of the tides.
During a full moon or new moon, the Sun, Earth, and Moon are aligned in a nearly straight line.
Then, the tidal effects of the Moon and the Sun overlap, and the difference between high and low tide becomes larger.

This is a spring tide.

On the other hand, during the first and last quarter moons, the Moon and the Sun are at an angle of approximately 90 degrees as seen from the Earth.
At this time, the tidal effects partially cancel each other out, so the difference between high and low tide becomes smaller.

This is a neap tide.

In other words, the changes in tides that we see casually every day also change significantly depending on the positional relationship between the Moon, the Sun, and the Earth.

Summary: The Moon is running away. But it won't disappear anytime soon

The Moon is currently moving away from the Earth at a rate of about 3.8 cm per year.
The cause is the tides generated by the Moon and the Earth's rotation.
When you look at the Moon floating in the night sky, just knowing that "the Moon is moving away by about 3.8 cm every year" might give you a slightly different perspective.

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Thank you for reading until the end.
I hope today's article was helpful to you.
If you'd like, please let me know your thoughts in the comments.
See you in the next article!