简介

Irwin Shapiro, the former Director of the Harvard-Smithsonian Center for Astrophysics, has had a very localized geographical career - all in Cambridge - but has wandered widely in research, from study of the core of the Earth, through remote-sensing exploration of the solar system, to observation of the most distant known objects in the universe. He also originated and carried out solar-system tests of the general theory of relativity. The common thread tying these various topics together is his use of radio or radar techniques in all of these efforts. Most recently, Shapiro has been concentrating on radio studies of gravitational lenses and supernovae, seeking to determine the size scale and age measure of the universe-the Hubble constant-free from the errors affecting more conventional such estimates. For example, the first gravitational lens system discovered, 0957+561, is on the verge of yielding to sustained attack; robust models of the lens' mass distribution, coupled with radio, optical, and x-ray observations of the system's brightness variations appear to imply a Hubble constant of 65 km s-1 Mpc-1, with a standard error estimated to be about 10 percent.