Paper detail

The Precession Caused by Gravitational Waves

We show that gravitational waves cause freely falling gyroscopes to precess relative to fixed distant stars, extending the stationary Lense-Thirring effect. The precession rate decays as the square of the inverse distance to the source, and is proportional to a suitable Noether current for dual asymptotic symmetries at null infinity. Integrating the rate over time yields a net rotation -- a `gyroscopic memory' -- whose angle reproduces the known spin memory effect but also contains an extra contribution due to the generator of gravitational electric-magnetic duality. The angle's order of magnitude for the first LIGO signal is estimated to be $Φ\sim 10^{-35}$ arcseconds near Earth, but the effect may be substantially larger for supermassive black hole mergers.