Acceleration due to Energy

The 2011 Nobel Prize in Physics was awarded "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae." Nobody yet understands what causes this (the acceleration, not the expansion), but the cause, whatever it is, has been given the name dark energy. The UC Berkeley page on Saul Perlmutter (awarded half the prize, with the other half jointly awarded to Brian P. Schmidt and Adam G. Riess) has some interesting discussions on the subject. Among other things, Prof. Perlmutter's passion for physics shines through.