Related Experiment Video
Updated: Aug 10, 2026

Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Big-bang nucleosynthesis and the baryon density of the universe
C J Copi1, D N Schramm, M S Turner
1Department of Physics, University of Chicago, IL 60637-1433.
Abstract:
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 x 10(-31) and 4.1 x 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 "non-baryonic," composed of elementary particles left from the earliest moments.
More Related Videos
14:11Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
Published on: March 29, 2016
10:57Mapping Absolute DNA Density in Cell Nuclei using Single-molecule Localization Microscopy
Published on: November 11, 2025
Related Concept Videos
Atomic Mass
Radioactivity and Nuclear Equations
A nuclide of an element has a specific number of protons and...
Nuclear Stability
To hold positively charged protons together in the...
Nuclear Binding Energy
Detection of Black Holes
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Atomic Nuclei: Nuclear Spin State Population Distribution