Probing the Early Universe with the SZ Effect

The cosmic microwave background radiation (CMBR) is providing important clues into the evolution of the early universe. In their Perspective, [Joy and Carlstrom][1] discuss one feature of the CMBR, the Sunyaev-Zel'dovich effect, which can be used to determine the abundance and evolution of clusters of galaxies, thereby constraining key cosmological parameters such as the matter density of the universe and its expansion rate. [1]: http://www.sciencemag.org/cgi/content/full/291/5509/1715