The Nanohertz Background Without Gravitational Waves: An Ether Plenum Interpretation of Pulsar Timing Array Observations, and the Decisive Test It Faces

In June 2023 five pulsar timing array collaborations independently reported evidence for a stochastic nanohertz signal in the arrival times of millisecond pulsar pulses. The standard interpretation attributes it to a background of spin-two gravitational waves radiated by inspiraling supermassive black hole binaries. This paper develops the alternative interpretation the Theory of NeoGravity requires, in which the timing residuals are refractive fluctuations produced by pressure and density oscillations in the Ether Plenum, driven by the periodically varying load force returned upon orbiting binaries whose electromagnetic emission is modulated by orbital phase. Under this reading the source population is unchanged, the frequency band is reproduced from first principles, since supermassive binaries at separations of one hundredth to one tenth of a parsec drive oscillations at approximately one to one hundred nanohertz, and the pulse delay is a refractive effect of precisely the kind used elsewhere in this series to derive the Shapiro delay. The paper then confronts the decisive difficulty without minimizing it. The signature the collaborations regard as definitive is the Hellings-Downs angular correlation, whose distinguishing property is that it becomes negative, reaching approximately minus 0.152 at a pulsar-pair separation of 82.6 degrees and crossing zero at 49.2 and 121.8 degrees. That anticorrelation is the geometrical fingerprint of transverse-traceless spin-two radiation. A compressible medium supporting scalar density waves predicts the scalar-transverse correlation, which declines monotonically from 0.500 to 0.250 and is positive everywhere. The two predictions differ in shape rather than in coefficient, and the reported data favour the tensor pattern. This paper states that plainly and then examines its strength: the published Bayesian preference is a factor of approximately two, the weakest recognized category of evidence on the conventional scale, in contrast to the same data favouring a correlated background over uncorrelated noise at a Bayes factor exceeding ten to the fourteenth. The detection is overwhelming; the polarization determination is not. The paper documents that the preceding twelve-and-a-half-year data set preferred the scalar-transverse mode at odds of approximately twenty to one before that preference reversed, and that no medium-based interpretation of pulsar timing results exists in the literature. It closes by committing in advance to the conditions under which the interpretation should be withdrawn.