The Milky Way measures 100 to 120 thousand light-years across, a distance that defies imagination. But clusters of galaxies, which comprise hundreds to thousands of galaxies swarming under a collective gravitational pull, can span tens of millions of light-years. These massive clusters are a complex interplay between colliding galaxies and dark matter. They seem impossible … Continue reading "Mapping Dark Matter 4.5 Billion Light-years Away"