The Dark Universe - Josh Frieman, PhD Presented at the Adler Planetarium on June 9, 2011 Over the last decade, cosmologists have discovered that only 4 percent of the universe is made of ordinary matter — the atoms and molecules that form stars, planets and people. The other 96 percent is dark, existing in a form totally unlike anything scientists have ever encountered.  Dark matter, which makes up approximately a quarter of the universe, holds galaxies together and is the key ingredient in their formation. The remaining three-quarters of the universe is composed of dark energy, a mysterious force that is causing the expansion of the universe to speed up. Frieman is a professor in astronomy & astrophysics at the University of Chicago and a senior staff scientist at Fermi National Accelerator Laboratory’s Center for Particle Astrophysics. He directs the Dark Energy Survey, a collaboration of more than 120 scientists from 20 institutions on three continents. The collaboration is building a 570-megapixel camera for a telescope in Chile to probe the origin of cosmic acceleration.