Omega_radiation

[hellfire]

What is the currently accepted value for Omega of radiation energy density (photons and neutrinos)? References would be helpful. Thanks.

[Nereid]

This Hyperphysics page (http://hyperphysics.phy-astr.gsu.edu/hbase/astro/expand.html) has an overview of the concepts and relationships. This page from a cosmology lecture (http://instruct1.cit.cornell.edu/courses/astro101/lec31.htm) gives some information in bite-sized bullets. Spergel et al (http://lambda.gsfc.nasa.gov/product/map/pub_papers/firstyear/parameters/wmap_parameters.pdf) present the WMAP team's cosmological parameter analysis and results; this has perhaps the most up-to-date, authoratitive estimate of the neutrino omega, as well as the mass omega. From the latter it should be easy to calculate an estimate of the photon omega.