Of what is the universe made?  Recent observations suggest surprising results. Not only is most of the matter in the universe dark and unconventional but, more surprisingly, the major component of the universe may be what's called "dark energy"—a form of energy that opposes the pull of gravity and causes the universe's expansion  to accelerate. By combining recent observations of clusters and large-scale structures, distant supernovae, and the cosmic microwave background radiation, we find evidence for a universe comprised of  5 percent  normal atomic matter, 20 percent non-atomic dark matter, and 75 percent  "dark energy." The observations suggest a universe that is lightweight. With only 25 percent of its critical mass-density needed to halt the universal expansion, the universe will likely expand forever. Dr. Bahcall will discuss the observations of the dark side of the universe and their implications.

Dr. Neta A. Bahcall: Eugene Higgins Professor of Astrophysics, Princeton University

This talk celebrates the legacy of Vera Rubin and is associated with a symposium in her honor.

The program is co-hosted by the Carnegie Institution for Science with Stockholm University, via the Oskar Klein Centre for Cosmoparticle Physics, with additional support from the National Science Foundation and the Heising-Simons Foundation.