Isotropic CMB has given a convenient zero velocity reference frame for putting kinetic energy into a local field.

Victor Weisskopf wrote in his essay "Contemporary Frontiers Of Physics" published as a chapter by Freeman in 1989 "the observed 3 K radiation determines an absolute coordinate system, at least within the observable universe, the one in which it appears to be isotropic."

PJE Peebles wrote in chapter 6 of his book on "Principles of Physical Cosmology" in 1993 "the CBR acts as an ether, giving a local definition for preferred motion."

Other researchers have suggested CMB is not fundamental only convenient, in which case the basis of zero velocity was not accepted, and kinetic field energy was disputed.

Is Isotropic CMB A Fundamental Reference Frame Or Just A Convenience?