Wen Zhao

The universe rewrites its history again and again. Where ordinary astronomy sees only a point, a black hole, gravitational waves peel back thin layers of the past, like an ancient palimpsest. The idea that black holes can grow by devouring each other, and their offspring can enter new unions, has been discussed by astrophysicists for half a century.

Light bends in a lens — everyone knows that. Gravitational waves passing a massive body also curve their path. But the authors of this work looked further: what happens to the wave's very "color" — its polarization, that is, the direction of oscillation? Gravitational lensing is the deflection of…