Black holes colliding in the distant reaches of the universe release energy in the form of gravitational waves. These waves pass through space-time, causing ripples similar to those created by a dropped pebble on the surface of a pond.
While one might expect the fabric of space-time to return to normal after the gravitational wave passes, it does not. According to Einstein’s general theory of relativity, gravitational waves subtly shift the structure of space-time as they pass, creating a phenomenon known as “gravitational memory.” Although this effect is incredibly weak, some astrophysicists are determined to demonstrate its existence.
The discovery of gravitational memory would have significant implications. It would provide evidence of a hidden form of symmetry that saturates the entire universe. This would offer valuable insights into a quantum theory of gravity and the fundamental makeup of space-time.
Joseph Weber, a physicist in the late 1960s, was one of the first to propose the idea of gravitational memory. Since then, optimistic astrophysicists have been working to measure and understand this phenomenon, hoping that the recent influx of gravitational wave detections will lead to a breakthrough.
