By Ron Cowen
Analyzing the faint glow left over from the Big Bang, scientists report measuring the age of the cosmos with unprecedented accuracy. They claim the age they calculate, 14 billion years, is accurate to within half a billion years.
Astronomers previously had calculated cosmic age by measuring distances to galaxies to deduce the Hubble constant–the current expansion rate of the universe. They then used models to calculate how the rate might have differed in the past. The age obtained this way hovers around 13 billion years. Since measurements of the distances to galaxies are uncertain, however, the Hubble constant isn’t known to an accuracy better than 10 percent, and the age of the universe derived using this method is plagued by the same uncertainty.