2026 Halley public lecture - 'Black Holes We Didn't Expect' Professor Matias Zaldarriaga

'Black holes we didn't expect: puzzles from gravitational wave observations' The 2026 Halley Lecture was delivered by Professor Matias Zaldarriaga from the Institute for Advanced Study, USA. The public lecture was hosted in person at the Martin Wood Complex, and streamed online via Zoom as well. For those attending in person, the talk was followed by a drinks reception. Abstract: Gravitational waves have opened entirely new windows onto the universe. Ground-based detectors have now observed hundreds of mergers of stellar-mass black holes, revealing a population that is heavier and more diverse than anticipated. Meanwhile, pulsar timing arrays have recently claimed the detection of a low-frequency gravitational wave background, most likely produced by merging supermassive black holes in the centres of galaxies – and its strength appears surprisingly large compared to what we would predict from the known population of these objects. The origin of the heaviest stellar-mass black holes and of the supermassive black holes that inhabit the centres of galaxies remain among the great open questions in astrophysics. As has happened so often in the history of astronomy, new ways of observing the universe have given us not the answers we expected, but new puzzles to marvel at and exercise our imagination. This recording took place on 26 May 2026, Martin Wood Complex, Department of Physics. All copyright Professor Zaldarriaga/Department of Physics/University of Oxford. If you'd like to share part of whole of this material, please seek for written permission from us. --- Welcome to the official YouTube channel of the Department of Physics at the University of Oxford, one of the world’s leading centres for physics research and education. Our researchers investigate the universe at every scale — from cosmology and particle physics to quantum technologies, climate science, medical physics, and advanced materials. Alongside fundamental discoveries, our work contributes to real-world challenges including renewable energy, healthcare technologies, and understanding the Earth’s climate. Each year around 195 students join our undergraduate physics degrees, while around 100 postgraduate researchers from across the world begin doctoral study in our research groups. Together we form a global community dedicated to advancing scientific knowledge and training the next generation of physicists. Learn more about Oxford Physics: https://www.physics.ox.ac.uk/ Study at Oxford Physics Undergraduate degrees (BA, MPhys, MPhysPhil) https://www.physics.ox.ac.uk/study/un... Postgraduate study and DPhil programmes https://www.physics.ox.ac.uk/study/po... Follow Oxford Physics X — https://x.com/oxfordphysics Instagram —   / physics_oxford   Facebook —   / physicsoxford   LinkedIn —   / university-of-oxford-department-of-physics   Bluesky — https://bsky.app/profile/oxfordphysic... Subscribe for research highlights, lectures, student stories, and insights from physicists at Oxford.