Waves in the Ether Plenum: The Two Kinds of Gravitational Waves, and What Sources Can and Cannot Emit

The Theory of NeoGravity states a physical cause for gravitation. Space is not an empty void. It is filled by a continuous medium, the Ether Plenum, and it is flooded across the whole electromagnetic spectrum, from radio waves through microwaves, infrared, visible light, ultraviolet and X-rays to gamma rays, by the radiation of every body in it. All matter vibrates and radiates, so matter and medium are in continuous interaction: the outgoing waves carry momentum into the medium, and the medium, by Newton's third law, returns an equal load inward upon the body that drives it. That returned load is gravitational attraction, the Radiative Undertow. It is compressive, so the medium settles denser toward a mass, and a body falls by responding to the state of the medium where it is. Nothing acts across empty space. In this account the curvature of a four-dimensional spacetime metric is a description of the medium's equilibrium profile, not a cause: Newton's potential, Einstein's metric and the gravitational field are three names for one settled state of the Ether Plenum under load.

Linearising the postulates about equilibrium gives the Ether Plenum's wave sector, with every claim verified symbolically. The transverse branch propagates at the speed of light by the construction of the shear modulus. Decisively for the framework, the elastic wave equation admits the transverse-traceless family of solutions exactly: displacement fields whose strain on embedded matter reproduces the plus and cross polarization states of the interferometric record, and whose pulsar-timing correlation is the Hellings-Downs curve.

Two source theorems then close two thirds of the longitudinal problem. Mass conservation forbids monopole compression radiation from bound systems, and momentum conservation forbids centre-of-mass dipole radiation. The leading emission of a binary is therefore quadrupolar and lands in the transverse-traceless sector.

The linearisation also produced a surprise. The longitudinal branch is dispersive across the viscoelastic window, running at the speed of light divided by the square root of three in the fluid regime and at the square root of five thirds times that speed, faster than light, in the elastic regime. That is kinematically permitted in the neo-Lorentzian arena, and it is not a claim that observable gravitational influence propagates superluminally.

It does raise the stakes on the one residual gap. The quadrupole-order compression admixture is open, quantified and assigned, and a scalar component in the nanohertz background that turned out to be frequency-stable would refute the wave sector as derived.

The formulation is five postulates on the medium, with one fitted constant, the optical exponent k = 2/3 (numerically the post-Newtonian parameter gamma), and a medium density of 4.645 x 10^-31 kg/m^3 taken from the cosmic microwave background. From them follow Newton's law, the classical tests of gravitation, Mercury's perihelion advance, transverse gravitational waves at the speed of light, and the double pulsar's orbital decay; in the weak field the formulation cannot be told from general relativity. Where the two accounts diverge, the framework commits in advance to measurements that would confirm or refute it, nearest a black hole shadow diameter 4.63 percent larger than the geometric prediction. Every number in the series is recomputed by an archived verification program (NeoGravity verification suite, https://github.com/worldlibrary-hub/NeoGravity).