Sumanta Chakraborty

In general relativity, a black hole has long been regarded as a perfect mirror: no matter what fields fall onto it, it does not deform. The tidal Love numbers, which measure how a body deforms under an external tidal field, turned out to be zero for scalar, electromagnetic, and gravitational perturbations.

Two neutron stars whirl in a close dance, each feeling the tidal field of its partner. It's like the Moon raising oceans on Earth, but here it's spacetime itself and the star's matter that deform. Astrophysicists call this tidal deformation — a measure of how much an object 'bends' under the gravitational pull of its companion.