I am a Professor of Physics and of Astronomy at the University of California, Berkeley. I received my Ph.D. in physics at Berkeley under the supervision of George Field in 1970. After a brief stay at Lawrence Livermore National Laboratory, I spent a year as a postdoctoral fellow in theoretical astrophysics at Caltech. I was an assistant professor of astronomy at Harvard from 1971-1974 before returning to Berkeley in 1974. At Berkeley, I helped to establish the Theoretical Astrophysics Center , and served as the Director of the Space Sciences Laboratory from 1985-1998. I chaired the Physics Department from 2000-2004. Joseph Taylor and I co-chaired the 2000 Astronomy and Astrophysics Survey Committee, which conducted the most recent decadal survey in astronomy and astrophysics. I am a member of the National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences, and a Fellow of the American Physical Society.

Much of my research focuses on the theory of physical processes in the interstellar medium, the diffuse gas between the stars. How do stars form out of this tenuous gas, and what effect do the stars have back on the interstellar medium? Jerry Ostriker and I developed the three-phase model of the interstellar medium, which has been widely used to organize and interpret observations of the diffuse interstellar medium. With my colleagues and students, I have worked on the theory of the evaporation of clouds by both hot gas and ionizing radiation, the evolution of supernova remnants and stellar wind bubbles, the structure and emission spectrum of interstellar shocks, the evolution of interstellar dust grains, the structure of molecular clouds, and on the theory of active galactic nuclei, particularly the study of reverberation mapping and of Compton-heated coronae and winds above accretion disks. I am currently concentrating on the theory of star formation, including the formation of the first stars. My students and I use both analytic and numerical techniques to address these problems. Richard Klein and I have established the Berkeley Astrophysical Fluid Dynamics Group to develop the technique of adaptive mesh refinement for numerical simulations of astrophysical fluid dynamics, particularly star formation.