5.3 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Dirac large numbers hypothesis | 2/2 | https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis | reference | science, encyclopedia | 2026-05-05T09:33:55.823362+00:00 | kb-cron |
== Later developments and interpretations == Dirac's theory has inspired and continues to inspire a significant body of scientific literature in a variety of disciplines, with it sparking off many speculations, arguments and new ideas in terms of applications. In the context of geophysics, for instance, Edward Teller seemed to raise a serious objection to LNH in 1948 when he argued that variations in the strength of gravity are not consistent with paleontological data. However, George Gamow demonstrated in 1962 how a simple revision of the parameters (in this case, the age of the Solar System) can invalidate Teller's conclusions. The debate is further complicated by the choice of LNH cosmologies: In 1978, G. Blake argued that paleontological data is consistent with the "multiplicative" scenario but not the "additive" scenario. Arguments both for and against LNH are also made from astrophysical considerations. For example, D. Falik argued that LNH is inconsistent with experimental results for microwave background radiation whereas Canuto and Hsieh argued that it is consistent. One argument that has created significant controversy was put forward by Robert Dicke in 1961. Known as the anthropic coincidence or fine-tuned universe, it simply states that the large numbers in LNH are a necessary coincidence for intelligent beings since they parametrize fusion of hydrogen in stars and hence carbon-based life would not arise otherwise. Various authors have introduced new sets of numbers into the original "coincidence" considered by Dirac and his contemporaries, thus broadening or even departing from Dirac's own conclusions. Jordan (1947) noted that the mass ratio for a typical star (specifically, a star of the Chandrasekhar mass, itself a constant of nature, approx. 1.44 solar masses) and an electron approximates to 1060, an interesting variation on the 1040 and 1080 that are typically associated with Dirac and Eddington respectively. (The physics defining the Chandrasekhar mass produces a ratio that is the −3/2 power of the gravitational fine-structure constant (analogous to the electromagnetic fine-structure constant), 10−40.)
=== Modern studies === Several authors have recently identified and pondered the significance of yet another large number, approximately 120 orders of magnitude. This is for example the ratio of the theoretical and observational estimates of the energy density of the vacuum, which Nottale (1993) and Matthews (1997) associated in an LNH context with a scaling law for the cosmological constant. Carl Friedrich von Weizsäcker identified 10120 with the ratio of the universe's volume to the volume of a typical nucleon bounded by its Compton wavelength, and he identified this ratio with the sum of elementary events or bits of information in the universe. Valev (2019) found an equation connecting cosmological parameters (for example density of the universe) and Planck units (for example Planck density). This ratio of densities, and other ratios (using four fundamental constants: speed of light in vacuum c, Newtonian constant of gravity G, reduced Planck constant ℏ, and Hubble constant H) computes to an exact number, 32.8·10120. This provides evidence of the Dirac large numbers hypothesis by connecting the macro-world and the micro-world.
== See also ==
Dimensionless physical constant – Physical constant with no units Hierarchy problem – Unsolved problem in physics Time-variation of fundamental constants – Hypothetical conflict with the laws of physics as currently known
== References ==
== Further reading == P. A. M. Dirac (1938). "A New Basis for Cosmology". Proceedings of the Royal Society of London A. 165 (921): 199–208. Bibcode:1938RSPSA.165..199D. doi:10.1098/rspa.1938.0053. P. A. M. Dirac (1937). "The Cosmological Constants". Nature. 139 (3512): 323. Bibcode:1937Natur.139..323D. doi:10.1038/139323a0. S2CID 4106534. P. A. M. Dirac (1974). "Cosmological Models and the Large Numbers Hypothesis". Proceedings of the Royal Society of London A. 338 (1615): 439–446. Bibcode:1974RSPSA.338..439D. doi:10.1098/rspa.1974.0095. S2CID 122802355. G. A. Mena Marugan; S. Carneiro (2002). "Holography and the large number hypothesis". Physical Review D. 65 (8) 087303. arXiv:gr-qc/0111034. Bibcode:2002PhRvD..65h7303M. doi:10.1103/PhysRevD.65.087303. S2CID 119452710. C.-G. Shao; J. Shen; B. Wang; R.-K. Su (2006). "Dirac Cosmology and the Acceleration of the Contemporary Universe". Classical and Quantum Gravity. 23 (11): 3707–3720. arXiv:gr-qc/0508030. Bibcode:2006CQGra..23.3707S. doi:10.1088/0264-9381/23/11/003. S2CID 119339090. S. Ray; U. Mukhopadhyay; P. P. Ghosh (2007). "Large Number Hypothesis: A Review". arXiv:0705.1836 [gr-qc]. A. Unzicker (2009). "A Look at the Abandoned Contributions to Cosmology of Dirac, Sciama and Dicke". Annalen der Physik. 18 (1): 57–70. arXiv:0708.3518. Bibcode:2009AnP...521...57U. doi:10.1002/andp.20095210108. S2CID 11248780.
== External links == Audio of Dirac talking about the large numbers hypothesis Full transcript of Dirac's speech. Robert Matthews: Dirac's coincidences sixty years on The Mysterious Eddington–Dirac Number