The “writing on the cosmic wall”: Is there a straightforward explanation of the cosmic microwave background?

The C osmic M icrowave B ackground (CMB) is taken today as reflecting the thermodynamical state of the universe at these early cosmic times. Based on this assumption and standard cosmological principles meanwhile many fundamental cosmological facts have been deduced from the CMB state which, however, to some surprise reveal that the universe should be dominated by dark energy and dark matter, while for its energy content the usual baryonic matter is nearly negligible. Thus the question which we want to raise in this article is, whether this standard interpretation of the CMB phenomenon is solid and unequivocal enough to support the standard cosmological claims. We shall show, however, that in many details the standard explanation is not straightforward, but allows for important alternatives which seriously should be looked at. Especially arguments for a vanishing cosmic curvature (k = 0) are shown to be weak, and, contrary to the usual claim, the light distance to the recombination horizon is in fact strongly model‐biassed. We also show that the CMB dipole which is generally understood as a consequence of a peculiar motion by about 680 km/s with respect to rest system of the CMB can as well, and perhaps even better, be understood as indication of differerent cosmological expansion dynamics seen in an anisotropically expanding universe in different directions of the sky. We also discuss that the power amplitude (i.e. effective Planck temperature) in the dipolar CMB structure depends on wavelength even inverting the dipole maximum orientation in the Wien's branch. In addition unexpected properties of the lowest CMB multipoles could mean that we are at least partly seeing an unquantifyable foreground in the background. Only after its removal the CMB interpretation could at all then, but then on a completely new basis, become a subject of cosmological terms. At the end of this article we shall briefly discuss an alternative explanation of the CMB radiation which helps to better understand the mysterious cosmic photon‐to‐baryon ratio of about 10 9 .