Bakerian Prize Lecture
By Professor Joseph Silk FRS, University of Oxford
The emergence of cosmic structure is an outcome that has been studied by peering back through the mists of time to the remote depths of the universe as well as by deciphering the fossil structure of nearby galaxies. One of the greatest mysteries in the cosmos is that it is mostly dark. That is, not only is the observed night sky dark, but also most of the matter in the universe whose existence is directly inferred from the observations is dark. For every atom visible in planets, stars and galaxies today there exists at least five or six times as much ``Dark Matter'' in the universe. Astronomers today are seeking to unravel the nature of this mysterious, but pervasive Dark Matter, and determine whether it can be detected. Nor does the mystery rest only with dark matter, as there is also a dark force, dubbed ``Dark Energy'' and originally postulated by Einstein in the form of the cosmological constant, that is systematically accelerating the universe. Indeed, Dark Energy accounts for two-thirds of the mass-energy density of the Universe, and understanding its origin and nature presents one of the greatest challenges in physics. Joseph Silk will review the status of ongoing searches for the dark components of the universe.