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Dirac large numbers hypothesisThe Dirac large numbers hypothesis refers to an observation made by Paul Dirac in 1937 relating ratios of size scales in the Universe to that of force scales. Dirac noted that the ratio of the size of the visible universe, ct with c the speed of light and t the age of the Universe, to the size of a quantum particle r is about ct / r = 10^{40}. Hence, in units c = 1 and r = 1, this large number can be taken as the age of the Universe, t = 10^{40}. Additional recommended knowledgeThere is another ratio with this order of magnitude: the ratio of the electrical to the gravitational forces between a proton and an electron, (≈ 4.4 × 10^{−40}). Hence, taking the charge e of the electron, the mass m_{pr}/m_{e} of the proton/electron, and the permittivity factor 4πε_{0} as units, the gravitational constant equals G = 10^{ − 40}. Dirac interpreted this to mean that G varies with time as , and built what remains to this day a largely untested cosmology out of this idea. If correct, the connection between gravity and quantum mechanics would be unmistakable and may point in the direction of a theory of quantum gravity. Some scientists believe that the hypothesis is the result of a numerological coincidence, and in 1961, Robert Dicke argued that carbonbased life can only arise when the hypothesis is true lest fusion of hydrogen in stars not occur. A few proponents of nonstandard cosmologies refer to Dirac's cosmology as a foundational basis for their ideas. References

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Dirac_large_numbers_hypothesis". A list of authors is available in Wikipedia. 