Big-Bang Nucleosynthesis and the Baryon Density of the Universe

• Published in: Science (American Association for the Advancement of Science) Vol. 267; no. 5195; pp. 192 - 199
• Main Authors: Copi, Craig J., Schramm, David N., Turner, Michael S.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 13.01.1995; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Astronomical Phenomena; Astronomy; Average linear density; Baryons; Big Bang theory; Climate; Composition; Cosmology; Dark matter; Dark matter (Astronomy); Density; Deuterium; Deuterium - chemistry; Earth, ocean, space; Elements; Exact sciences and technology; H II regions; Helium - chemistry; Hydrogen - chemistry; Light; Lithium - chemistry; Mathematics; Neutrons; Origin, formation and abundance of the elements; Scientific Concepts; Stars; Stellar nucleosynthesis; Stellar systems. Galactic and extragalactic objects and systems. The universe; Surface temperature; Systematic errors; Temperature; Cosmology; Density; Nucleosynthesis; Baryons; Big bang
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.7809624

For almost 30 years, the predictions of big-bang nucleosynthesis have been used to test the big-bang model to within a fraction of a second of the bang. The agreement between the predicted and observed abundances of deuterium, helium-3, helium-4, and lithium-7 confirms the standard cosmology model and allows accurate determination of the baryon density, between 1.7 × 10$^{-31}$ and 4.1 × 10$^{-31}$ grams per cubic centimeter (corresponding to about 1 to 15 percent of the critical density). This measurement of the density of ordinary matter is pivotal to the establishment of two dark-matter problems: (i) most of the baryons are dark, and (ii) if the total mass density is greater than about 15 percent of the critical density, as many determinations indicate, the bulk of the dark matter must be "nonbaryonic," composed of elementary particles left from the earliest moments.