Joel R. Primack is a professor of physics and astrophysics at the University of California, Santa Cruz and is a member of the Santa Cruz Institute for Particle Physics. 

Primack specializes in the formation and evolution of galaxies and the nature of the dark matter that makes up most of the matter in the universe. After helping to create what is now called the "Standard Model" of particle physics, Primack began working in cosmology in the late 1970s, and he became a leader in the new field of particle astrophysics.  His 1982 paper with Heinz Pagels was the first to propose that a natural candidate for the dark matter is the lightest supersymmetric particle.  He is one of the principal originators and developers of the theory of Cold Dark Matter, which has become the basis for the standard modern picture of structure formation in the universe.  With support from the National Science Foundation, NASA, and the Department of Energy, he is currently using supercomputers to simulate and visualize the evolution of the universe and the formation of galaxies under various assumptions, and comparing the predictions of these theories to the latest observational data.

With Nancy Abrams, he is the author of The View from the Center of the Universe: Discovering Our Extraordinary Place in the Cosmos (Riverhead/Penguin, 2006) and The New Universe and the Human Future: How a Shared Cosmology Could Transform the World (Yale University Press, 2011).