> According to #general #relativity, every #gravitational #wave should leave an indelible #imprint on the structure of space-time. It should permanently strain space, displacing the mirrors of a gravitational wave detector even after the wave has passed.
Since that first detection almost six years ago, physicists have been trying to figure out how to measure this so-called “memory effect.”

> First consider what happens when a gravitational wave passes by a gravitational wave detector. The Laser Interferometer Gravitational-Wave Observatory (LIGO) has two arms positioned in an L shape. If you imagine a circle circumscribing the arms, with the center of the circle at the arms’ intersection, a gravitational wave will periodically distort the circle, squeezing it vertically, then horizontally, alternating until the wave has passed. The difference in length between the two arms will oscillate — behavior that reveals the distortion of the circle, and the passing of the gravitational wave.
According to the #memory #effect, after the passing of the wave, the circle should remain permanently deformed by a tiny amount.

https://www.quantamagazine.org/gravitational-waves-should-permanently-distort-space-time-20211208/