Physics Colloquium

The Universe is thrumming with gravitational waves. Last year brought the first evidence for an all-sky background of nanohertz-frequency gravitational waves, discovered by collaborations including the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) and groups in Europe, Australia, India, and China. This was an endeavor decades in the making, requiring painstakingly precise timing observations of scores of millisecond pulsars across the Milky Way using flagship radio telescopes. While the results from separate groups are consistent with one another—and the leading interpretation of a population of supermassive black-hole binaries as the source—the observations provoke many new questions. Do the results imply a population of binaries more massive than expected? What are the observational milestones as the first resolvable binary signals come into focus? Can we link these signals to host galaxies through ranking protocols and by leveraging electromagnetic counterparts? And will our understanding of the gravitational-wave background hit a cosmic-variance barrier? In this talk, I will chart the path to discovery, reflect on what we have learned during our first year since our announcement, and explore the exciting opportunities ahead—including the role of next-generation instruments like DSA-2000 in expanding our pulsar network to explore the low-frequency gravitational-wave landscape.

Join via Zoom:
https://caltech.zoom.us/j/89860951893
Meeting ID: 898 6095 1893

The colloquium is held in Feynman Lecture Hall, 201 E. Bridge.