Abstract
The dominant CMB dipole anisotropy is a Doppler effect due to a particular motion of the solar system with a velocity of 370 km/s. Since this derives from peculiar motions and local inhomogeneities, one could meaningfully consider a fundamental frame of rest Σ associated with the Universe as a whole. From the group properties of Lorentz transformations, two observers, individually moving within Σ, would still be connected by the relativistic composition rules. However, the ultimate implications could be substantial. Physical interpretation is thus traditionally demanded in order to correlate some of the dragging of light observed in the laboratory with the direct CMB observations. Today, the small residuals—from those of Michelson–Morley to present experiments with optical resonators—are just considered instrumental artifacts. However, if the velocity of light in the interferometers is not the same parameter “c” of Lorentz transformations, nothing would prevent a non-zero dragging. Furthermore, the observable effects would be much smaller than what is classically expected and would most likely be of an irregular nature. We review an alternative reading of experiments that leads to remarkable correlations with the CMB observations. Notably, we explain the irregular 10−15 fractional frequency shift presently measured with optical resonators operating in vacuum and solid dielectrics. For integration times of about 1 s and a typical Central European latitude, we also predict daily variations of the Allan variance in the range (5÷12)·10−16.
Highlights
Soon after the discovery [1] of the Cosmic Microwave Background (CMB), it was realized that the observed temperature of the radiation should exhibit a small anisotropy as a consequence of the Doppler effect associated with the motion of the Earth [2,3] (β = V/c): T(θ) = To 1−1 − β2 β cos θ (1)Accurate observations with satellites in space [4,5] have shown that the measured temperature variations correspond to a motion of the solar system described by an average velocity V ∼ 370 km/s, a right ascension α ∼ 168◦, and a declination γ ∼ −7◦, pointing approximately in the direction of the constellation Leo
The isotropy of the CMB could just indicate the existence of this fundamental system Σ that we may conventionally decide to call “ether”, but the cosmic radiation itself would not coincide with this form of ether1
Due to the present interpretation of the dominant dipole anisotropy of the Cosmic Microwave Background as a Doppler effect, one may wonder about the reference system in which this dipole exactly vanishes
Summary
Soon after the discovery [1] of the Cosmic Microwave Background (CMB), it was realized that the observed temperature of the radiation should exhibit a small anisotropy as a consequence of the Doppler effect associated with the motion of the Earth [2,3]. Some general arguments (see [41,42]) suggest instead that the physical vacuum might behave as a stochastic medium that resembles a turbulent fluid in which large-scale and small-scale flows are only indirectly related This means that the projection of the global velocity field at the site of the experiment, say vμ(t), could differ non-trivially from the local field vμ(t), which determines the direction and magnitude of the drift in the plane of the interferometer. Whatever its precise value is, this typical magnitude can help with intuition It can explain the quantitative reduction of the effect in the vacuum limit, where gas → 0 and the qualitative difference with strongly bound solid dielectrics, and where such small temperature differences would mainly dissipate through heat conduction without producing any particle motion and directional refraction in the rest frame of the medium.
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