In February, researchers announced that they had made the first detection of gravitational waves from a black-hole merger more than a billion light years from Earth. Sam Gralla, Assistant Professor of Physics at the University of Arizona says the discovery occurred nearly 100 years after Albert Einstein predicted such waves or ripples as part of his general theory of relativity. And that the finding launches the field of gravitational-wave astronomy, in which scientists will "listen" to the waves to learn more about the Universe. In this episode: Sam Gralla, Assistant Professor of Physics at the University of Arizona; Tim Swindle, Ph. D., Director and Department Head of the University of Arizona's Lunar and Planetary Laboratory