Gravitational waves are real, they have been observed.
Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light.
There is no consensus whether these GWs' quanta are the hypothetical gravitons or not.
But we do know that EM waves can excerpt pressure on objects. This is how the solar sail works.
Solar sails (also called light sails or photon sails) are a proposed method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. But Solar radiation exerts a pressure on the sail due to reflection and a small fraction that is absorbed
We know that photons do excerpt pressure on matter they interact with.
Yes. Actually photons exert pressure on any surfaces exposed to them. For example, photons emitted by the Sun exert pressure of 9.08μN/m2 on the Earth.
Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength which is absorbed, reflected, or otherwise emitted (e.g. black-body radiation) by matter on any scale (from macroscopic objects to dust particles to gas molecules).
So radiation pressure can move objects.
Radiation pressure can equally well be accounted for by considering the momentum of a classical electromagnetic field or in terms of the momenta of photons, particles of light. The interaction of electromagnetic waves or photons with matter may involve an exchange of momentum. Due to the law of conservation of momentum, any change in the total momentum of the waves or photons must involve an equal and opposite change in the momentum of the matter it interacted with (Newton's third law of motion), as is illustrated in the accompanying figure for the case of light being perfectly reflected by a surface. This transfer of momentum is the general explanation for what we term radiation pressure.
So basically both classicall EM waves and QM photons do excerpt pressure on the matter they interact with, and this is due to conservation of momentum.
Now since GWs are waves too, and there are similarities between them and EM waves, even if we treat GWs classically or in QM as made up of gravitons, GWs should excerpt pressure on matter they interact with.
Due to the weakness of the coupling of gravity to matter, gravitational waves experience very little absorption or scattering, even as they travel over astronomical distances. In particular, gravitational waves are expected to be unaffected by the opacity of the very early universe.
Now the difference between EM and GWs is that basically GWs weakly couple to matter.
- Can GWs move objects (excerpt pressure on matter)?