Pulsar Timing Array (VIDEO) University of Wisconsin - Milwaukee This video is under embargo. Please login to access this video. Caption This animation demonstrates interacting supermassive black holes in merging galaxies and how this generates low frequency gravitational waves. As these waves propagate through space, they cause coordinated changes in the arrival times of radio signals from pulsars, the universe's most stable natural clocks, as seen from Earth. These telltale variations can be detected by powerful radio telescopes, like the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia. Credit John Rowe, Swinburne University of Technology Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.