Computer simulations carried out by astronomers from the University of Groningen in collaboration with researchers from Germany, France and Sweden show that most of the (dark) matter beyond the Local Group of galaxies (which includes the Milky Way and the Andromeda galaxy) must be organized in an extended plane. Above and below this plane are large voids. The observed motions of nearby galaxies and the joint masses of the Milky Way and the Andromeda galaxy can only be properly explained with this "flat" mass distribution. The research, led by Ph.D. graduate Ewoud Wempe and Professor Amina Helmi, is published in Nature Astronomy.
… that’s not how it works, though. In science, a theory is a proven hypothesis that can be used to make predictions and successfully does so. Just because we don’t know what happened in the very first fraction of an instant doesn’t mean the theory (that the universe was in a very hot, compact and dense state that rapidly expanded out and formed the universe as we know it today) isn’t correct, just that it’s incomplete.