# Gravitomangetic B-field units

• stubbypeeps33
In summary, the gravitomagnetic B-field has units of frequency, and it describes how a particle near it will spin around its own axis.

#### stubbypeeps33

Does the gravitomagnetic B-field (from the GEM equations) have units of frequency (1/s)? And if so, what exactly does the B field describe?

I guess what I'm really trying to find out is whether the B field around say a rotating spherical object describes the rate of frame dragging, or does it describe how a particle near it will spin around its own axis, or something entirely different?

And also why is it that because gravity is a spin-2 field, the gravitomagnetic charge is twice that of the gravitoelectric charge?

Thanks,

stubby

Hi stubby,

can you give a reference to put this in context ? I don't know about GEM but in GR the field around a rotating body will induce rotation in test bodies. See Hamilton and Lyle arXiv:gr-qc/0411060v2.

M

stubbypeeps33 said:
Does the gravitomagnetic B-field (from the GEM equations) have units of frequency (1/s)? And if so, what exactly does the B field describe?

I guess what I'm really trying to find out is whether the B field around say a rotating spherical object describes the rate of frame dragging, or does it describe how a particle near it will spin around its own axis, or something entirely different?

And also why is it that because gravity is a spin-2 field, the gravitomagnetic charge is twice that of the gravitoelectric charge?

Thanks,

stubby

There are various different conventions for the gravitomagnetic B-field, differing by factors of 2. However, they all effectively represent an angular velocity. Basically, if you are in such a field, you feel as if you are rotating, in the same way as if you're in the E-field component, you feel as if you are accelerating. The rotation can be detected for example by rotational frame-dragging of a gyroscope.

The gravitomagnetic equations can't be matched up exactly with the electromagnetic equations; one way or another there's always a factor of 2 needed somewhere, and different sources use different conventions. (Last time I looked, the Wikipedia entry on the subject was not even self-consistent). This does seem to relate to the need to use a tensor rather than a vector as part of the description of the force between relatively moving objects. However, I don't personally know how this relates to "spin 2".

For more details on GEM, I suggest you Google "gravitomagnetism" and have a look at the 2000 review paper by Mashhoon. There seems to be a more recent paper too, but I haven't looked at that.

## 1. What are Gravitomagnetic B-field units?

Gravitomagnetic B-field units are a theoretical unit of measurement used to describe the strength of the gravitomagnetic field. This field is a relativistic effect of gravity that is similar to the magnetic field created by a moving electric charge.

## 2. How are Gravitomagnetic B-field units calculated?

Gravitomagnetic B-field units are calculated by taking the product of the speed of light, the gravitational constant, and the mass of the object creating the field. This calculation is similar to how magnetic fields are calculated using the speed of light, the electric constant, and the charge of the object.

## 3. What is the difference between Gravitomagnetic B-field units and magnetic field units?

The main difference between Gravitomagnetic B-field units and magnetic field units is the source of the field. Gravitomagnetic fields are created by the movement of mass, while magnetic fields are created by the movement of electric charge. Additionally, the strength and behavior of these fields can vary due to the unique properties of gravity and electromagnetism.

## 4. Do Gravitomagnetic B-field units have practical applications?

Currently, Gravitomagnetic B-field units are purely theoretical and have not been observed or measured in real-world scenarios. However, some scientists believe that the study of gravitomagnetism could lead to new insights and technologies in the future.

## 5. How are Gravitomagnetic B-field units related to general relativity?

Gravitomagnetic B-field units are a concept that arises from the principles of general relativity. This theory describes how gravity is caused by the curvature of space and time by massive objects. Gravitomagnetism is a consequence of this curvature and is an important aspect of understanding the behavior of gravity on a larger scale.