 Gravitational memory effect

The gravitational memory effect, also known as the "gravitational memory" or "memory effect in gravity," refers to a phenomenon predicted by general relativity in the context of gravitational waves. It describes how the passage of a gravitational wave can leave a permanent change in the separation between two freely falling test masses after the wave has passed. When a gravitational wave propagates through space, it creates a ripple in spacetime, causing spacetime to stretch and compress.