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Keywords:

  • Mach's principle;
  • large number hypothesis;
  • variable speed of light.

Abstract

The separate contributions to cosmology of the above researchers are revisited and a cosmology encompassing their basic ideas is proposed. We study Dirac's article (1938) on the large number hypothesis, Sciama's proposal (1953) of realizing Mach's principle, and Dicke's considerations (1957) on a flat-space representation of general relativity with a variable speed of light (VSL). Dicke's tentative theory can be formulated in a way which is compatible with Sciama's hypothesis on the gravitational constant G. Additionally, such a cosmological model is shown to satisfy Dirac's second ‘large number’ hypothesis on the total number of particles in the universe being proportional to the square of the epoch. In the same context, Dirac's first hypothesis on an epoch-dependent G – contrary to his prediction – does not necessarily produce a visible time dependence of G. While Dicke's proposal reproduces the classical tests of GR in first approximation, the cosmological redshift is described by a shortening of measuring rods rather than an expansion of space. Since the temporal evolution of the horizon R is governed by equation image, the flatness and horizon problems do not arise in the common form.