Rainer Weiss and the CMB

Rai Weiss was a pioneer in measuring both the absolute temperature and anisotropy of the CMB. In 1973, Dirk Muehlner and Weiss showed that the CMB spectrum turned over at frequencies above 200 GHz, and was thereby consistent with a 2.7 K Planckian curve. This was an important milestone in the discovery phase of the CMB spectrum. Starting in about 1974, working again with Muehlner, Weiss did the first CMB anisotropy experiments with bolometers. These days, most measurements of the CMB are made with bolometers in contrast to coherent receivers. Also in 1974, Mike Hauser, John Mather, Dirk Muehlner, Bob Silverberg, Pat Thaddeus, Rai Weiss, and Dave Wilkinson got together to start the COBE satellite mission. While Mather became the satellite and FIRAS PI, Hauser the DIRBE PI, and Smoot the DMR PI, Weiss became the leader of the COBE Science Working Group. The results from COBE are legendary. In this talk I will review Rai's contributions to the foundations of CMB science mixed together with some anecdotes from that phase of his remarkable career.