James Turrell is widely acknowledged as one of the most important artists working today. From the mid 1960s onwards his principal concern has been the way we apprehend light and space. His study of mathematics and perceptual psychology, as well as his Quaker upbringing and background as a pilot, inform his practice. His first exhibition in 1967 of projection pieces' used high-intensity light projectors to give the illusion of a solid geometrical object, often seemingly floating in space. From these investigations of light, Turrell went on to begin his series of Skyspaces'. These are enclosed...