is it possible to compare Einstein 4D space-time to a fluid ?
A fluid is either a gas or liquid. Since gravity waves result in a transverse shear stress deformation to manifold, and not a pressure (normal stress); then in this respect, such manifold (spacetime) would seem more like a liquid fluid.
Okay, I'll be helpful: in certain cases it kind of acts like a fluid, but it's not. It's a geometry. If you could imagine a 3D grid of flexible metal bars which 'bows in' around mass-energy that's a good picture of spacetime.
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