Throughout the history of the Universe, countless supermassive black holes have engaged in a volatile dance. These behemoths spiral around each other faster and faster until they crash together. Scientists suspect that the resulting collisions are so powerful that they literally generate ripples that spread out into the Universe. To date, detailed measurements only capture how gravitational waves move in a single direction— waves that are either flowing directly toward us or away from us. This new research at the University of Colorado – Boulder is designed to measure how gravitational waves also move from side-to-side and up and down as compared to Earth, since gravitational waves literally operate in three dimensions. The gravitational waves stretch and squeeze spacetime along our line of sight, but they should also cause objects to appear to move back and forth in the sky if the researchers’ hypothesis is correct.