Abstract
DIRAC'S cosmology was based on the principle “that any two of the very large dimensionless numbers (of the order 1039 and 1078), occurring in Nature, are connected by a simple mathematical relation in which the coefficients are of the order of magnitude unity”1. From this principle Dirac deduced that the gravitational ‘constant’ G ∝ (epoch)−1. In order to describe a cosmological model according to the principles of the general theory of relativity he then changed the units of distance and time so as to make G constant. With the new units the metric can be written: with R(t) = t2/3. Afterwards I considered this model, and by making certain assumptions, which appeared reasonable, obtained G ∝ 1/t, t ≈ 4 × 109 years2. This gives the values: for Hubble's constant H( = Ṙ/R) and the acceleration parameter q( = RṘ/Ṙ2).
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GILBERT, C. Dirac's Cosmology. Nature 192, 57 (1961). https://doi.org/10.1038/192057a0
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DOI: https://doi.org/10.1038/192057a0
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