I recently used another venue to ask about the speed of gravity, specifically if the speed of gravity is constant or if it is subject to diffraction when passing through media, akin to light.

The response stated the speed of gravity was constant. Diffraction in light occurs because it takes time for light to interact with particles and this interaction doesn't occur with gravity.

My understanding is that gravity waves interact with each other. Considering particles have mass and mass has gravity, it seems to me that a gravitational wave passing through media containing mass would interact with the gravity field and that interaction would take time - thus one portion of the wave would interact before another, effectively gravitational diffraction.

Am I mistaken in my assumption that a gravity wave interacts with with a gravity field or that an interaction would be in linear time?

Follow up question - supposing diffraction is possible, does it point toward the existence of the graviton?