"... Dark matter provides the additional gravitational pull to bring model and reality broadly into alignment. Researchers now routinely take this model – Einstein plus dark matter, often called the ‘null hypothesis’ – as their starting point and then perform detailed calculations of galactic systems to test it. ... Most recently, Stacy McGaugh at Case Western Reserve University in Ohio and his team documented that the pattern of rotation in spiral galaxies seems to precisely follow the pattern of the visible matter alone, posing yet another challenge to the null hypothesis."