First came dark matter, the gravitational source from within our galaxy that astronomers couldn’t see. Then came dark energy, the undetectable force pushing the expansion of the universe. Now, NASA scientists believe they have confirmed a new player, dubbed “dark flow,” that is dragging hundreds of galaxies along the same path. Even stranger, the researchers believe that dark flow is actually the gravitational pull from matter beyond the edge of the known universe.
The NASA scientists first discovered dark flow in 2008, when they observed numerous galaxy clusters speeding off at 2.2 million miles per hour in the same direction. The results were controversial, so the researchers spent another two years collecting data.