FYI -- very interesting lecture about Dark Matter, which may just be stuff predicted by supersymmetry which is quite plentiful, but which interacts extremely weakly with normal stuff that we can see. In particular, there may be an average of on the order of 1 of these heavy particles per liter of space, but these things move right through us (and the Earth) almost like a neutrino, but much more massive. According to Dr. Arkani-Hamed, exploring the Dark Universe doesn't require higher energy accelerators, since the interactions should happen well within the reach of the accelerators we've had for several decades. The problem is that the interactions with normal matter are 1/1000'th the strength of other interactions, so we just need to look a bit harder/longer. Perhaps we decommissioned some of our older accelerators too quickly ?? This talk is 3 years old, so there must already be some answers to some of the questions he posed. http://online.kitp.ucsb.edu/online/plecture/arkanihamed/ Dec 16, 2009 Exploring the Dark Universe Nima Arkani-Hamed, Institute for Advanced Study There is strong evidence that most of the mass and energy dominating the dynamics of the universe at the largest scales is not made of ordinary matter, but is something new Âdark energy and Âdark matter. Understanding the dark sector poses fascinating challenges to theoretical physicists. More excitingly, a slew of experiments ranging from satellites to particle accelerators to deep-underground detectors are poised to shed a great deal of light on this subject in the very near future. In this talk I will describe these developments, and explore what we might learn about the dark universe in the next five years. http://online.kitp.ucsb.edu/download/plecture/arkanihamed/snd/ArkaniHamed_Pu... (VLC 2.0.5 _can_ play this movie, but you have to set the "file caching" parameter to an absurd value -- around 40 _seconds_ = 40000 msec.)