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How old is the Universe?

The current best estimate for the age of the universe is 13.7 billion years (13,700,000,000 years), with margin of error reported by NASA to be close to 1%. In other words, the team of astrophysicists who published this estimate in 2003 are confident that the universe is between ~13.5 and ~13.9 billion years old, based on their interpretation of reproducibly obtained observational data.

This age was determined through analysis of data obtained by NASA's Wilkinson Microwave Anisotropy Probe (WMAP), a satellite containing sensitive radiation detectors (radiometers) that is orbiting Earth at a distance of ~1 million miles. The radiometers on this satellite measure the cosmic background radiation (CBR): the radiant heat energy emitted as a result of the Big Bang. The CBR is the oldest light in the universe, emitted ~379,000 years after the Big Bang. The WMAP data reproduces and enhances data sets developed using telescope-based systems at the South Pole, at the Mauna Kea Observatories in Hawai'i, as well as data from the COBE satellite and the balloon-borne BOOMERanG radiometers.

Information about how this age was computed can be obtained directly from the WMAP program via their web site: Web sources for other information about the CMB are listed below.

References and suggested reading

Balloon Observations Of Millimetric Extragalactic Radiation ANd Geophysics (BOOMERanG) home page (

Caltech Observational Cosmology Group home page (, which includes information about BOOMERanG and other projects associated with the study of the birth and evolution of the universe, including measurement and characterization of the cosmic background radiation

NASA's Legacy Archive for Microwave Background Data Analysis (LAMBDA) home page (, with links to active web resources for WMAP, COBE, and other projects and data sets related to the measurement and characterization of the cosmic background radiation.

Penrose, R., 2005, The road to reality -- a complete guide to the laws of the universe: New York, Knopf, 1099 p., ISBN 0-679-45443-8

Raymo, Chet, 2001, An intimate look at the night sky: New York, Walker and Company, 242 p., ISBN 0-8027-7670-1

Smoot, G.F., and others, 1991, Preliminary results from the COBE differential microwave radiometers -- large-angular-scale isotropy of the Cosmic Microwave Background: Astrophysics Journal, v. 371, L1.

Spergel, D.N., and others, 2003, First year Wilkinson Microwave Anisotropy Probe (WMAP) observations -- determination of cosmological parameters: Astrophysics Journal Supplement, v. 148, p. 175.

Weinberg, S., 1988, The first three minutes -- a modern view of the origin of the universe [updated edition]: New York, Basic Books, 198 p., ISBN 0-465-02436-X.

The information on this page was written and approved by the faculty of the Geology Department at Baylor University.