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The Anisotropy of the Universe at Large Times

Published online by Cambridge University Press:  07 February 2017

S. W. Hawking
S. W. Hawking*
Affiliation:
Institute of Astronomy, Cambridge, U.K.

Extract

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The most important cosmological observation in the last forty years has undoubtedly been the discovery of the microwave background. As well as confirming the existence of a hot early phase of the Universe, by its spectrum, its remarkable isotropy indicates that the Universe must be very nearly spherically symmetric about us. Because of the revolution of thought brought about by Copernicus, we are no longer vain enough to believe that we occupy any special position in the Universe. We must assume, therefore, that the radiation would appear similarly isotropic in any other place. One can show that the microwave radiation can be exactly isotropic at every point only if the Universe is exactly spatially homogeneous and isotropic, that is to say, it is described by one of the Friedmann models. (Ehlers et al., 1968). Of course, the Universe is neither homogeneous nor isotropic locally. This must mean that the background radiation is not exactly isotropic, but only isotropic to within the very good limits set by the observations (about 0.1%). One would like to know, however, what limits the observations place on the large-scale anisotropies and inhomogeneities of the Universe. One would also like to know why it is that the Universe is so nearly, but not exactly, isotropic.

Type
Part V: The Structure of Singularities
Information
Symposium - International Astronomical Union , Volume 63: Confrontation of Cosmological Theories , 1974 , pp. 283 - 286
Copyright
Copyright © Reidel 1974 

References

Carter, B.: 1970, The Significance of Large Numbers in Cosmology, Cambridge University, unpublished preprint.Google Scholar
Collins, C. B. and Hawking, S. W.: 1973, Astrophys. J. 180, 317.Google Scholar
Collins, C. B. and Hawking, S. W.: 1973, Monthly Notices Roy. Astron. Soc. 162, 307.Google Scholar
Dicke, R. H.: 1961, Nature 192, 440.Google Scholar
Ehlers, J., Geren, P., and Sachs, R. K.: 1968, J. Math. Phys. 9, 1344.Google Scholar
Ellis, G. F. R. and MacCallum, M. A. H.: 1969, Commun. Math. Phys. 12, 108.Google Scholar
Estabrook, F. B., Wahlquist, H. D., and Behr, C. G.: 1968, J. Math. Phys. 9, 497.Google Scholar
Misner, C. W.: 1968a in deWitt, C. M. and Wheeler, J. A. (ed.), Battelle Rencontres, W. A. Benjamin, New York.Google Scholar
Misner, C. W.: 1968b, Astrophys. J. 151, 431.Google Scholar
Rees, M. J. and Sciama, D. W.: 1968, Nature 217, 511.Google Scholar
Sachs, R. K. and Wolfe, A. M.: 1967, Astrophys. J. 147, 43.CrossRefGoogle Scholar
Zel'dovich, Ya. B.: 1970, Zh. Eksper. Teor. Fiz., Letters 12, 443; Transl. in JETP Letters 12, 307 (1971).Google Scholar