Paul L. Richards, an experimental physicist who built some of the first highly sensitive detectors to probe the faint radiation left over from the birth of the universe, died peacefully at his home in Berkeley on Monday, Sept. 16. A professor emeritus of physics at the University of California, Berkeley, Richards was 90.
Richards got his start as a solid-state physicist, studying the properties of superconductors. But after the discovery of the cosmic microwave background (CMB) in 1965, he shifted to astrophysics and cosmology, employing instruments he had developed to measure the properties of very cold materials to also measure cold radiation from space. He built the first of these instruments — a Fabry Perot spectrometer — in the early 1970s with graduate student John Mather and postdoctoral fellow Michael Werner, who took it to a high peak in the White Mountains of California to measure the temperature of the radiation. Werner went on to the Jet Propulsion Laboratory in Pasadena to lead the Spitzer Space Telescope as project scientist.