Whenever Scientific American runs an article on cosmology, we get letters complaining that cosmology isn't a science, just unconstrained speculation. But even if that used to be the case, it is certainly not true anymore. The past several months alone have seen a remarkable outpouring of high-precision observations of the universe on its largest scales. Not only do they give the big bang theory a new quantitative rigor, they hint at secondary effects--perhaps the long-sought signatures of cosmic inflation and cold dark matter. "Previously, cosmology had been independent strands of thought," says cosmologist David Tytler of the University of California at San Diego. "It can now go on to address the next level of detail."

Although the big bang theory has long been supported by three observational pillars--cosmic microwave background radiation, abundance of light elements, and outward velocity of distant galaxies--these pillars uphold different aspects of the theory. Only last year did observations of the first pillar reach the precision needed to cross-check the second one. Two balloon-borne telescopes, Boomerang and Maxima, measured the microwave background with a resolution of better than one degree, revealing small-scale fluctuations. Unlike the larger-scale fluctuations made famous by the COBE satellite a decade ago--which are scale-invariant, occurring with the same relative strength no matter their size--the small ones seem to be strongest on certain scales known as peaks.

This article was originally published with the title The Peak of Success.

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