Theoretical physicist. Undergraduate work at Princeton University, graduate work at Stanford University in the early 1980s, where he studied core collapse, Type II supernovae, using them as distance indicators using the Expanding Atmosphere Method. From the mid 1980s to the mid 1990s, he criticized those who would use supernovae as distance indicators. He is the author of the cosmology textbook, First Principles of Cosmology, published in 1997. Was a senior researcher at University of Massachusetts at Amherst when discovery came out in 1998. The papers so impressed him especially the theoretical thoroughness of the SCP paper of 1999, that he was convinced of the accelerating universe, and even asked to join the SCP as a result. Now, collaborates with the SCP at LBL as theoretician.