It appears that everybody is interested in cosmology. In one anthropological study, every one of the more than 60 separate cultures examined was found to have several common characteristics, including "faith healing, luck superstitions, propitiation of supernatural beings, … and a cosmology." Apparently, to be human is to care how the physical world came to be, whether it has boundaries and what is to become of it. Modern cosmology is a highly sophisticated subject funded by governments with hundreds of millions of dollars a year. It is unquestionably interesting, but is it, even in its modern guise, convincing?

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The current Big Bang paradigm has it that the cosmos is expanding out of an initially dense state and that by looking outward into space, one can, thanks to the finite speed of light, look back to much earlier epochs. This understanding owes much to two accidents: astronomers' discovery of redshifts in the spectra of distant nebulae and the fortuitous detection of an omnipresent background of microwave noise, which is believed to be the remnant of radiation from a hot and distant past. Set in the theoretical framework of Einstein's general theory of relativity, such observations lead to a model that makes predictions and can thus be tested.

Of late, there has been much excitement over precision measurements of the cosmic background radiation and the discovery of very distant galaxies of great antiquity. There is even talk of a "concordance model" in which all of the observations come together to paint a coherent picture of how the universe must be constructed.

It is true that the modern study of cosmology has taken a turn for the better, if only because astronomers can now build relevant instruments rather than waiting for serendipitous evidence to turn up. On the other hand, to explain some surprising observations, theoreticians have had to create heroic and yet insubstantial notions such as "dark matter" and "dark energy," which supposedly overwhelm, by a hundred to one, the stuff of the universe we can directly detect. Outsiders are bound to ask whether they should be more impressed by the new observations or more dismayed by the theoretical jinnis that have been conjured up to account for them.

My limited aim here is to discuss this dilemma by looking at the development of cosmology over the past century and to compare the growing number of independent relevant observations with the number of (also growing) separate hypotheses or "free parameters" that have had to be introduced to explain them. Without having to understand the complex astrophysics, one can still ask, at an epistemological level, whether the number of relevant independent measurements has overtaken and comfortably surpassed the number of free parameters needed to fit them—as one would expect of a maturing science. This approach should be appealing to nonspecialists, who otherwise would have little option but to believe experts who may be far too committed to supply objective advice. What one finds, in my view, is that modern cosmology has at best very flimsy observational support.