Cosmological revolutions in sight

Robin Hanson (
Thu, 16 Jul 1998 10:33:39 -0700

>From SCIENCE-WEEK July 17, 1998:

2. COSMOLOGY: THE END OF THE OLD MODEL UNIVERSE Cosmologists are apparently expecting the near-future necessity for profound conceptual alterations in their field. Peter Coles (University of London, UK) presents a short review of the current situation and makes the following points: 1) Observations only recently made possible by improvements in astronomical instrumentation have put theoretical models of the Universe under intense pressure. The standard ideas of the 1980s about the shape and history of the Universe have now been abandoned -- and cosmologists are now taking seriously the possibility that the Universe is pervaded by some sort of "vacuum energy" whose origin is not at all understood. 2) The weakness of the Big Bang model is that the numerical values of certain essential parameters in the model (the Hubble constant, the density parameter, and, in some versions, the cosmological constant) are not predicted by theory, and thus the parameters must be inferred from observations. 3) The Big Bang model does not deserve to be called a "theory" unless and until it can explain how nonuniformities of galaxies and clusters of galaxies came into being and evolved. 4) The Cold Dark Matter model of structure formation, first proposed in the 1980s, is in serious difficulty because the consequent significant gravitational break on expansion is not evident, and in fact expansion may be accelerating. Current observations coupled with current dynamical arguments all suggest a global density of matter in the Universe less than the value required to make the Universe recollapse. 5) The existence of a cosmological constant (or vacuum energy) of the required size necessary to make the basic cosmological models work is not at all explained by current theories of the fundamental interactions of matter. 6) There is every reason to be confident that the important issues will soon be resolved, because a data explosion is about to engulf cosmology, a new generation of galaxy surveys. The Sloan Digital Sky Survey, for example, will encompass more than a million galaxies. The cosmological community is bracing itself for the arrival of these enormous new data sets and the new insights they will surely bring. 7) It is possible that none of the available models will fit all the new data. Coles concludes: "For many of us, that is the most exciting possibility of all, as we would have to move to stranger theories, perhaps not even based on General Relativity."
QY: Peter Coles <>
(Nature 25 Jun 98 393:741) (Science-Week 17 Jul 98)

Robin Hanson RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884 140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-2627