There is now evidence dark matter fills what would otherwise be considered to be empty space. 'Cosmologists at Penn Weigh Cosmic Filaments and Voids' http://www.upenn.edu/pennnews/news/cosmologists-penn-weigh-cosmic-filaments-and-voids "Dark matter ... permeate all the way to the center of the voids." '"No Empty Space in the Universe" --Dark Matter Discovered to Fill Intergalactic Space' http://www.dailygalaxy.com/my_weblo...-discovered-to-fill-intergalactic-space-.html "A long standing mystery on where the missing dark matter is has been solved by the research. There is no empty space in the universe. The intergalactic space is filled with dark matter." In the following article the dark matter which fills 'empty' space is displaced by the particles of matter which exist in it and move through it. 'Comment on the higher derivative Lagrangians in relativistic theory' http://arxiv.org/abs/1305.5759 "Einstein theory of gravitational fields and this gives a new perspective on the Mach principle revisiting the “absolute” acceleration concept as a natural motion in space-time deformed by the matter-energy contained therein. We refer the reader to the paper of Einstein on a related topic . The relativistic theory of an Aether was discussed several time, see for e.g. , . In this paper, our hypothesis is different and gives a relativistic theory of the deformation of continuous media (for which the geometry is described by the metric field)." Any chance the Milky Way's halo is the deformation of continuous media?