This article is about scientific estimates of the age of the universe. For religious and other non-scientific estimates, see Dating creation. In physical cosmology, the age of the universe is the time elapsed since the Big Bang. The best measurement of the age of the universe is 13.798 ±0.037 billion years ((13.798 ±0.037) ×109 years or (4.354 ±0.012) ×1017 seconds) within the Lambda-CDM concordance model.[1][2] The uncertainty of 37 million years has been obtained by the agreement of a number of scientific research projects, such as microwave background radiation measurements by the Planck satellite, the Wilkinson Microwave Anisotropy Probe and other probes. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang,[2] and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time. Explanation The Lambda-CDM concordance model describes the evolution of the universe from a very uniform, hot, dense primordial state to its present state over a span of about 13.8 billion years[3] of cosmological time. This model is well understood theoretically and strongly supported by recent high-precision astronomical observations such as WMAP. In contrast, theories of the origin of the primordial state remain very speculative. If one extrapolates the Lambda-CDM model backward from the earliest well-understood state, it quickly (within a small fraction of a second) reaches a singularity called the Big Bang singularity. This singularity is not understood as having a physical significance in the usual sense, but it is convenient to quote times measured since the Big Bang even though they do not correspond to a physically measurable time. For example, 10−6 seconds after the Big Bang is a well-defined era in the universes evolution. If one referred to the same era as 13.8 billion years minus 10−6 seconds ago, the precision of the meaning would be lost because the minuscule latter time interval is swamped by uncertainty in the former. Though the universe might in theory have a longer history, the International Astronomical Union[4] presently use age of the universe to mean the duration of the Lambda- CDM expansion, or equivalently the elapsed time since the Big Bang in the current observable universe
Posted on: Mon, 08 Sep 2014 10:01:23 +0000
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