The 2018 Robert Hofstadter Memorial Lecture: Cosmic Collisions Reveal Einstein's Gravitational-Wave Universe
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein's 1915 general theory of relativity and opens an unprecedented new window onto the cosmos. Gravitational waves carry unique information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Detected gravitational waves were produced during the final fraction of a second of the mergers of two black holes but also during the last hundred seconds of the collision of two neutron stars. The latter is the first ever cosmic event to be observed both in gravitational waves and in electromagnetic waves, shedding light on several long-standing puzzles, like the production of gold in nature and the physics origins of brief gamma-ray flashes. I will review the beginnings of this exciting field of cosmic exploration and the unprecedented technology and engineering that made it possible.