Age of the universe

This article is about scientific estimates of the age of the universe. For religious and other non-scientific estimates, see Dating creation.

In Big Bang models of physical cosmology, the age of the universe is the cosmological time back to the point when the scale factor of the universe extrapolates to zero. The age is about 13.8 billion years, with the latest models estimating it more precisely as 13.787 billion years. Astronomers have two different approaches to determine the age of the universe. One is based on a particle physics model of the early universe called Lambda-CDM, matched to measurements of the distant, and thus old features, like the cosmic microwave background. The other is based on the distance and relative velocity of a series or "ladder" of different kinds of stars, making it depend on local measurements late in the history of the universe. These two methods give slightly different values for the Hubble constant, which is then used in a formula to calculate the age. The range of the estimate is also within the range of the estimate for the oldest observed star in the universe.

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