A Diamond Universe

Abstract

Cosmology is currently facing some major challenges. In addition to dark matter and dark energy, the issue of ‘impossible’ galaxies has been brought to the fore by the James Webb Telescope. Something simple eludes us, and the various problems mentioned are interrelated. Our proposition is that, on the cosmological scale, it is appropriate to take a value of the speed of light c_c lower than its standard value c_0 in vacuum. This defines an optical index n_c=c_0 /c_c. We account for this ‘refringence’ by a Shapiro effect extended to the scale of the universe (use of Schwarzschild metric), described by its average density ρ_u and its equivalent gravitational radius R_u. Remarkably, universes with indices greater than two are entirely conceivable, and their characteristics are close to those we determine for our own. The velocities v of celestial objects are estimated from redshifts in ratios of the type v/c, where the speed c of light is usually taken to be equal to c_0. With an equal v/c ratio (all things considered, only the v/c ratio has any meaning), dividing c_0 by a certain factor α lowers the velocities v without postulating the existence of dark matter nor dark energy. Taking into account the problems cited earlier suggests a value of α close to 2.4. We are led to a lengthening of the age of the universe: it could reach 33 billion years. This would allow it to host in its relatively young phases objects that are already old and structured.