They observed the orbit of the pulsar to decay ever so slightly, one full rotation taking 76.5 microseconds less every year, and deduced that energy must be drained from the orbit to cause the dissipation. The energy loss is precisely as predicted by Einstein’s theory of gravity. The orbiting neutron stars drag the curves in spacetime around with them and pump energy into waves in the spacetime geometry. Or, more plainly, the lost energy is carried off in gravitational waves, in the sound of spacetime. Theory and experiment fit together snugly in this fortunate observation.
