A Note on the Fly-by Anomaly: A Null Prediction from Momentum-First Gravity   

This note clarifies the prediction of the Momentum-First (M-First) framework regarding the anomalous velocity shifts observed during spacecraft fly-bys of Earth. The framework's foundational conservation laws, derived from the time-isometry of a stationary spacetime, are shown to mandate that the novel kinematic mechanisms of M-First are strictly conservative with respect to a particle's asymptotic speed. While the standard gravity-assist energy exchange is correctly described within the framework via a change of reference frame, the residual anomaly cannot be explained by these new gravitational effects. M-First thus makes a sharp, falsifiable null prediction for its own contribution, constraining the source of the fly-by anomaly to non-gravitational physics or effects beyond the stationary spacetime model.