This week's department colloquium featured the gravitational physics of Andy Lundgren from Penn State, who described the evolving evidence since the Big Bang for dark matter in describing what we don't see in our universe.
Andy overviewed cosmology from the Big Bang to present day as it relates to the contents of our universe and the evidence for existence of much more than just what we see. On the scales of galaxies and larger, 90% of the mass is dark matter which doesn't interact with light or with normal matter.
He also presented a model for dark matter he has helped develop based on a Bose-Einstein condensate of ULTRA-light (~10-29 x the electron mass) dark-matter particles and a sensible thermodynamic history that passes important cosmological tests and provides an interesting solution to some problems with the dark matter story.
Andy's talk concluded with the remark, "The universe is probably a lot weirder than you imagined--if not, you should probably be a cosmologist!"
Andy is also a working member of the international LIGO collaboration and co-chairs with our own Josh Smith the LIGO "Glitch Group" dedicated to helping resolve short-duration spurious events and irregularities in LIGO interferometry with a keen eye towards advanced LIGO.