# How Does Gravity Propagate Through Different Mediums and Energy Fields?

• I
• Gerinski
In summary, there is a small effect on the speed of gravitational waves as they propagate through material mediums, but for observational purposes, this effect is negligible. However, large masses can still affect the path of gravitational waves through gravitational lensing. Our understanding of this propagation is based on linearized equations and the geometrical optics approximation.
Gerinski
It is clear that gravity propagates at the speed of light in the vacuum. But what happens to gravitational waves as they propagate through material mediums? Presumably they get slowed down but, is it known precisely how much and by which factors, density of the medium or any other properties?

And what if the gravitational waves propagate through a region of space which is itself 'warped' by gravity (by say, a neutron star or whatever).

Or are they affected for example by heavy electromagnetic fields, in a similar (reciprocal) way as EM radiation is affected (bent) by gravity?

In summary, how good is our understanding of the propagation of gravity through mediums other than the perfect vacuum, and through other energy fields?

Thanks!

tionis and Dale
Just a quickie: you need to take the weak-field approx. with a non-vanishing energy-momentum tensor of the medium. Could be an interesting exercise to do that for e.g. a simple fluid and see what kind of equation you end up with.

Gerinski said:
But what happens to gravitational waves as they propagate through material mediums?
Really great question.

I don't know the answer, but where I would start is by looking at the linearized equations and see if there is anything that would give an indication.

The following discusses propagation of GW through matter in section five. The overall conclusion is that, in principle, there is a tiny affect on speed, but that it is insignificant in practice. For observational purposes, you can say intervening matter does not scatter, refract, nor diffract GW. However, a large mass can gravitationally lens GW, just as if it were light (this follows from the geometrical optics approximation being valid, as demonstrated in section four of this reference.)

https://www.lorentz.leidenuniv.nl/lorentzchair/thorne/Thorne1.pdf

martinbn and haushofer

## What is the speed of gravity in a medium?

The speed of gravity in a medium refers to the rate at which gravity travels through a substance or material. It is dependent on the properties of the medium, such as density and elasticity.

## Is the speed of gravity in a medium different from the speed of light?

Yes, the speed of gravity in a medium is different from the speed of light. The speed of light is constant, while the speed of gravity in a medium can vary depending on the properties of the medium.

## Can gravity travel faster than the speed of light in a medium?

No, gravity cannot travel faster than the speed of light in a medium. According to Einstein's theory of relativity, the speed of light is the maximum speed at which any form of energy or information can travel.

## How does the speed of gravity in a medium affect the orbit of planets?

The speed of gravity in a medium affects the orbit of planets by determining the strength and direction of gravitational pull between objects. The faster the speed of gravity in a medium, the stronger the gravitational force and the more circular the orbit of the planet will be.

## What is the impact of the speed of gravity in a medium on gravitational lensing?

The speed of gravity in a medium can impact gravitational lensing, which is the bending of light by the gravitational pull of massive objects. A faster speed of gravity in a medium can result in a stronger gravitational pull, causing more significant bending of light and creating a more pronounced lensing effect.

Replies
17
Views
1K
Replies
74
Views
3K
Replies
7
Views
2K
Replies
2
Views
1K
Replies
8
Views
1K
Replies
13
Views
2K
Replies
58
Views
5K
Replies
7
Views
1K
Replies
38
Views
3K
Replies
1
Views
880