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Il Nuovo Cimento (1955-1965)

, Volume 5, Issue 3, pp 572–578 | Cite as

Sull’età dell’Universo

  • M. Pierucci
Article

Riassunto

In una sua precedente nota l’A. aveva sottolineato una grave discrepanza messa già in evidenza dallo stessoEinstein: l’età dell’Universo, dedotta dalla sua espansione, risultava assai minore dell’età della crosta terrestre, dedotta dallo studio dei minerali radioattivi. L’A. aveva già individuato la causa di ciò in un errato procedimento nel calcolo dell’età dell’Universo, procedimento in cui si faceva ricorso ad una tautologia; ed aveva cercato di girare l’ostacolo, servendosi di invarianti della relatività ristretta, nonchè di formule approssimate di relatività generale. Per una precisa determinazione dell’età dell’Universo occorreva però conoscere la «densità iniziale», della quale, invece, non possiamo avere una conoscenza sicura. Ora, valendosi di una considerazione di natura astronomica, l’A. riesce a fare a meno di tale conoscenza. E la suddetta discrepanza risulta perfettamente sanata.

Summary

Five years ago the author began again to think of the conception of «absolute time» compatible with the Relativity, once introduced byPolvani under the form of «entropic time»; he proved the entropic time coincided with the «expansion time»; then he calculated, in this absolute time, the age of the Universe. The author then pointed out a great discrepance existed at that time, which had already been evinced byEinstein, between the age of the Earth, that was deduced from radioactive transformations, and the age of the Universe, deduced from the expansion; because the latter was shorter than the former. He intended then to abolish such a discrepancy; and he succeeded, by using, in a first approximation, the invariantive quantities of restricted Relativity, and by using, moreover, approximate formules derived from the general Relativity. The method requested a supplementary hypothesis: that is the density of the Universe at the beginning of the expansion. That made the result very insecure; the author arrived in fact, with some hypotheses about the primitive density, to values which were very different from each other and all of them very high. The author now resumes the problem, using an observation of astronomical nature, that allows him to advance, even without knowing the first density of the Universe, and, at the same time, modifies the practical development of the method. As is known, the expansion of the Universe can also be obtained theoretically (Milne) considering the Universe as a gas of particles, that dilates spontaneously. Now astronomical observations inform us that it is necessary to speak about a stellar gas (and about an interstellar particles gas) within every star-cluster, about a gas of star-clusters (and about a galactic particles gas) within every galaxy, about a gas of galaxies (and about an intergalactic particles gas) within every galaxy-cluster, about a gas of galaxy-clusters (and about an intercluster particles gas) within the Universe, all these expanding at the same time. As a quotient between the primitive density and the actual density of the Universe it is enough to put so, in the calculations, the quotient between the actual middle densities of two successive orders, in the disposition that was put before. We arrive, in such a way, at an age of the Universe of about eleven milliards of years, and we are able to show at last that such an age (about twice the age that has been recently given for the Earth) agrees very well with the recent results obtained from radioactive transformations.

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Copyright information

© Società Italiana di Fisica 1957

Authors and Affiliations

  • M. Pierucci
    • 1
  1. 1.Istituto di Fisica dell’UniversitàModena

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