Paul Steinhardt
Princeton University

A decade ago, the composition of the universe appeared to
be a simple story: five per cent ordinary matter and
ninety-five percent dark matter, where the latter most likely
consists of weakly interacting massive particles.  Today,
growing evidence suggests that matter, both ordinary and
dark combined, is but a minor player in the universe.  Most
of the energy consists of some ubiquitous dark energy with
the remarkable property that it is gravitationally self-repulsive,
causing the expansion of the universe to accelerate outwards.
Also, some evidence suggests that the dark matter itself  may
have more complex properties than previously supposed.
This talk will discuss the evidence and some of the theoretical
explanations that are being explored.