The Dark Side of the Universe: Dark Matter and Dark Energy

In the last decade or so, astronomers have been forced to accept two mysterious observations. About a quarter of the universe is made of "dark matter," which attracts things with its gravity, but is otherwise invisible. And roughly two-thirds of the universe is composed of "dark energy," which causes space itself to expand at an ever-increasing rate. That means only a small fraction of the universe is made of ordinary matter -- the stuff we understand! In this non-technical presentation, Dr. Patricia Burchat of Stanford University explores the evidence for the dark side of the cosmos, and the experiments that are being developed to investigate it further. Recorded May 20, 2009.