# Chandler wobble: nutation or precession?

• stroustroup
In summary, Wikipedia claims that the Chandler wobble is a precession, while other sources say it is a nutation.
stroustroup
Wikipedia claims that the Chandler wobble (a deviation of the angular velocity vector of the Earth with respect to the principal axis) is a nutation (see http://en.wikipedia.org/wiki/Chandler_wobble).

But suppose we choose our inertial frame so that the Earth's angular momentum points in the +z direction. Then (ignoring gravitational forces from other bodies) the angles of the principal axis and the angular velocity with respect to the z axis are both constant (nutation angle is constant when there are no torques). Moreover, the angular velocity vector, principal axis and angular momentum all lie on the same plane. The principal axis and angular velocity precess around the z axis at a frequency of 2π/day, while the Earth is aditionally spinning (as in change of the third euler angle) about the principal axis at a period of 1/300 days. In the body frame, this corresponds to the precession of the angular velocity vector about the North pole.

If I understand correctly, this is what we call the "Chandler wobble", and it has a period of 435 days (not 300 because the Earth is not a rigid body). But this movement is not a nutation, but rather a precession.

So, what is the nutation in the Chandler wobble? I've also read stuff where "nutation" and "free precession" appear to be synonymous. This is very confusing.

EDIT: Also see http://farside.ph.utexas.edu/teaching/celestial/Celestial/node72.html This also says that the wobble is a precession, but instead it is the precession of the principal axis around the angular momentum, which has a frequency of almost a day.

Last edited:
I'm sorry you are not finding help at the moment. Is there any additional information you can share with us?

Well the trouble is, that the naming of the various effects of the spinning top is a mess. Some textbooks call precession what others call nutation and vice versa. It's also just names. It's much more important and also more fun to do the actual calculations (most elegantly using the least-action principle with Euler angles).

## 1. What is the Chandler wobble?

The Chandler wobble, also known as the axial wobble, is a small variation in the Earth's rotation axis that occurs over a period of approximately 433 days.

## 2. Is the Chandler wobble considered nutation or precession?

The Chandler wobble is considered a combination of both nutation and precession. Nutation refers to the small oscillations in the Earth's rotation axis, while precession refers to the larger, gradual change in the orientation of the Earth's axis.

## 3. How does the Chandler wobble affect the Earth's rotation?

The Chandler wobble causes a small, irregular motion in the Earth's rotation axis, resulting in a slight change in the length of day and the position of the poles. However, these changes are very small and do not have a significant impact on our daily lives.

## 4. What causes the Chandler wobble?

The exact cause of the Chandler wobble is still not fully understood, but it is believed to be primarily caused by the Earth's fluid layers, such as the atmosphere and oceans, shifting and redistributing mass around the rotation axis.

## 5. Can the Chandler wobble be measured?

Yes, the Chandler wobble can be measured through precise monitoring of the Earth's rotation using techniques such as Very Long Baseline Interferometry (VLBI) and satellite laser ranging. These technologies allow scientists to track the Earth's rotation with great accuracy and detect the small variations caused by the Chandler wobble.

• Classical Physics
Replies
7
Views
1K
• Classical Physics
Replies
10
Views
3K
• Classical Physics
Replies
10
Views
1K
• Mechanics
Replies
3
Views
1K
• Classical Physics
Replies
86
Views
4K
• Mechanics
Replies
10
Views
2K
• Astronomy and Astrophysics
Replies
1
Views
2K
Replies
3
Views
1K
• Mechanical Engineering
Replies
10
Views
2K