Chiara Mingarelli is a gravitational-wave astrophysicist and a professor in the Department of Physics at Yale University. She studies supermassive black holes at the centers of galaxies and their mergers using data about gravitational waves that are detected by pulsar timing array experiments. In this episode, Robinson and Chiara discuss PTAs, gravitational waves, black holes, how and why they merge, and the fresh release of NANOgrav’s fifteen-year data set, which gives the first ever evidence of a gravitational wave background in the universe, an unprecedented discovery that marks the dawn of a new era of astrophysical research.Chiara’s Website: https://www.chiaramingarelli.com/Chiara’s Twitter: https://twitter.com/Dr_CMingarelliOUTLINERobinson’s Website: http://robinsonerhardt.comRobinson Erhardt researches symbolic logic and the foundations of mathematics at Stanford University. Join him in conversations with philosophers, scientists, weightlifters, artists, and everyone in-between.