Why don't gravitational waves get distorted?

[Naty1]

In BLACK HOLES AND TIME WARPS Kip Thorne writes:

...Light, X-rays and radio waves (produced far outside the hole's horizon)...can be strongly distorted by propagating through intervening matter, they can bring us but little information about the (black) hole...The ripples of curvature (gravitational waves) [from the black hole], by contrast, are not at all distorted by propagating through intervening matter...and as a consequence they can bring us detailed information...and an unequivocal black hole signature...

So why is it that gravitational waves alone are "not at all distorted"??

For example, don't they combine [maybe even non linearly] with other gravitational waves?...they must interact with matter, otherwise we wouldn't be able to detect them...

thanks.

 

[WannabeNewton]

He is saying that because gravitational wave solutions to the linearized EFE's have very low amplitudes. Their interactions with matter are extremely small in magnitude, for example on the order of 10^-21 for certain interactions.

 

[Polyrhythmic]

Gravitational waves can't be "distorted" in the same sense as light, radio and other waves because they are "distortions" of the underlying spacetime. Gravity waves are propagating changes in spacetime, they basically are spacetime.

 

[Bill_K]

Gravitational waves most certainly can be distorted, the same way as light. WannabeNewton is correct in that the interaction is too small to be significant.

 

[Polyrhythmic]

Are you talking about self-gravity distortion? Otherwise I'm not sure we're talking about the same kind of distortion.

 

[Bill_K]

High frequency gravitational waves follow null geodesics, which can produce the effects usually associated with light such as focusing and caustic surfaces.

However what we're talking about here is the lower frequency waves emitted by a collapsing object. And the idea that such waves emerge undistorted is incorrect. As gravitational waves climb out of the surrounding Schwarzschild field they will backscatter, forming a prolonged 'tail' that persists even after the source has stopped.

 

[Polyrhythmic]

Ah, I see. Thank you!

 

[Naty1]

I think Kip Thorne was talking about low frequency gravitational waves...

Bill_K:

Gravitational waves most certainly can be distorted, the same way as light. WannabeNewton is correct in that the interaction is too small to be significant...

High frequency gravitational waves follow null geodesics, which can produce the effects usually associated with light such as focusing and caustic surfaces.

However what we're talking about here is the lower frequency waves emitted by a collapsing object...

Some distortion makes sure makes sense...never heard of any wave that wouldn't be.

So are we saying that lower frequency gravitational waves are distorted less than high, and that distortion of lower frequency waves is "insignificant"...??

When I posted I was particularly thinking about gravitational waves interacting...say from multiple star collapses to black holes across the universe...and gravitational waves from dual pairs of objects...and from rotating massive black holes at galactic centers...Is it believed these types of interactions are insignificant compared to Schwarzschild backscatter??