Detecting the CMB dipole within the earth laboratory.
After the discovery of an anisotropy of the Cosmic Microwave Background (CMB), the idea of a preferred frame is more than a simple possibility. Indeed, the standard interpretation of its dominant dipole component is a Doppler effect due to the motion of the solar system with an average velocity of 370 km/s toward a point in the sky of right ascension 168 degrees and declination -7 degrees. Though, it is usually assumed that this motion cannot be detected inside an earth laboratory by measuring a small difference of the velocity of light in different directions. This belief derives from the ether-drift experiments (from Michelson-Morley until the modern ones with optical resonators) viewed as a sequence of null results in measurements with better and better systematics. However with a preferred reference frame, and if the velocity of light propagating in the various interferometers is not exactly the same parameter "c" entering Lorentz transformations, nothing would really prevent a true non-null result. Therefore, we consider a theoretical model where all measurable effects vanish exactly if light propagates in an ideal vacuum and where, within the analogy of a turbulent flow, there are random fluctuations of the local drift around the average earth motion. In this scheme, a definite instantaneous signal coexists with vanishing statistical averages for all vectorial quantities and the tiny temperature variations of a few mK associated with the CMB dipole represent the key to understand the differences and the analogies among the various experiments (with light propagating in gaseous systems, in vacuum or solid dielectrics). Since, now, the small observed residuals can become consistent with the direct CMB observations with aircrafts and satellites, this open the possibility to definitely reveal the CMB dipole with optical measurements performed entirely within the earth laboratory.
Publisher URL: http://arxiv.org/abs/1801.03775
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