Paul Richards in his UC Berkeley office, circa 1980. Photo: Roy Katlschmidt
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.
Share your memories of Paul L. Richards
Visit the memories page for Paul L. Richards
Richards’ second CMB instrument was much more powerful — a balloon-borne Fourier transform spectrometer that he built with Mather and graduate students David P. Woody and Norm Nishioka. They realized that only by getting the instrument above the atmosphere and cooling it with liquid helium would they be able to make truly precise measurements of the spectrum of the CMB. At the time, that meant balloon experiments from a launch site in Palestine, Texas. These and experiments by others provided strong support for the theory that the universe began with a Big Bang 13.6 billion years ago, with the cosmic background radiation the cool remnant of that very hot birth.
The details of the microwave background were so important to scientists because they provided “the initial conditions for astronomy” that grew into the galaxies, clusters of galaxies and large cosmic structures we see today, Richards told Science magazine in 1994. “If you want to know why there are big superclusters, why a great wall, why the deep surveys show these gigantic structures,” the answer lies in the details of the background radiation.
Mather later employed similar instruments aboard a satellite, the Cosmic Background Explorer (COBE). In 1992, COBE succeeded in detecting minute variations in the temperature across the sky, a finding Stephen Hawking called the greatest scientific discovery of the century. Mather and George Smoot, then at Lawrence Berkeley National Laboratory and now a UC Berkeley professor emeritus of physics, won the 2006 Nobel Prize in Physics “for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.”