This program is a study of the interaction of clusters of galaxies with the cosmic microwave background radiation. Both theoretical calculations and a series of observations will be made. The principle investigator has been largely responsible for the observational evidence for the existence of the Sunyaev- Zel'dovich effect, which predicts small irregularities in the background radiation due to the effect of clusters of galaxies. These observations and their interpretation are very difficult, and this investigator is widely regarded as the leading expert on these studies. If successful, this work will lead to a greater knowledge of the constituents of clusters of galaxies, and a new method of determining the Hubble constant.
