# Does the barycenter of the Earth-Moon system change?

• I
• Sven E
In summary, the relative position of the barycenter of the Earth-Moon system can change due to changes in mass distribution, such as the movement of the sun and the potential effects of sea level rise. However, the precise mass distribution of both objects is not well known and it is believed that the Earth's mass distribution is fairly homogenous, while the Moon's may be slightly less so. Additionally, the Earth's gravity has had an impact on the Moon's shape, causing it to deviate from a perfect sphere, but it is still relatively round compared to other moons in our solar system.

#### Sven E

Hi to all!

My question is:
Does the relative position of the barycenter of the Earth-Moon system change due to mass distribution changes in the system and would this affect the Earth-Moon distance?
For example: Could the sea level rise change the Earth-Moon distance?
The only formula I found looks like this one:

But this is obviously a formula which does not take mass distributions of the two objects into account.
Any suggestions for calculations regarding this question are highly appreciated! Thanks in advance!

Best regards,
Sven

It's already changing because it's moving around the sun. If you say "that doesn't count!", fine, but then this discussion will hinge around what "counts" and what doesn't.

Unsurprisingly, the Earth moon barycenter is located about 1000 miles inside the earth. Unsurprising, considering the Earth is about 81 times more massive than the moon. The precise mass distribution of the Earth and moon is not known with great precision. Gravitational studies to date suggest the Earth's mass distribution is very homogenous. the moon/s mass distribution is less well known although the data indicate it too is fairly homogeneous. The Earth is very close to being a perfect sphere, it deviates from spherical only by about 3%. The moon is much less spherical from earth. I think it deviates about 10% from spherical,. The huge gravity of Earth is part of the reason. The moon was largely molten when it first formed and its surface got tugged out of spheroidal by the earth. It also has a much thicker crust on the far side vs the near side thus giving it a lemon-like appearance. Still it is pretty round compared to most moons in the solar system.

## 1. How does the barycenter of the Earth-Moon system change over time?

The barycenter, which is the point where the two objects in a system orbit around, changes constantly due to the gravitational pull of the two bodies on each other. This means that the barycenter of the Earth-Moon system is constantly shifting, but the overall distance between the two bodies remains relatively stable.

## 2. What factors contribute to the change in the barycenter of the Earth-Moon system?

The main factor that affects the barycenter of the Earth-Moon system is the distance between the two bodies. As the Moon orbits around the Earth, the barycenter shifts towards the side of the Moon that is closer to the Earth. Other factors such as the eccentricity of the Moon's orbit and the gravitational pull from other celestial bodies can also play a role in the barycenter's movement.

## 3. How much does the barycenter of the Earth-Moon system change?

The barycenter of the Earth-Moon system can shift up to a few thousand kilometers depending on the relative positions of the Earth and Moon. However, this change is relatively small compared to the overall distance between the two bodies, which is approximately 384,400 kilometers.

## 4. Does the change in the barycenter of the Earth-Moon system affect Earth's orbit?

The Earth's orbit around the Sun is not significantly affected by the change in the barycenter of the Earth-Moon system. This is because the barycenter is still well within the Earth's radius and the Earth is much more massive than the Moon.

## 5. How is the barycenter of the Earth-Moon system measured?

The barycenter of the Earth-Moon system is measured using a variety of methods, including radar ranging, lunar laser ranging, and spacecraft tracking. These techniques involve measuring the distance between the Earth and Moon, as well as their relative positions, to calculate the location of the barycenter at any given time.