Gamma-ray bursts are the most powerful explosions in the Universe: a dying star collapses into a black hole, ejecting streams of energy. Often this happens after a supernova flare. But astronomers caught a strange rhythm — in the emission of 34 such bursts, clear pulsations appeared, like beats of a cosmic heart. The secret of this rhythm hides in the twisted spacetime around the black hole. The effect discovered by Josef Lense makes even empty space rotate, dragging along superheated gas that alternately compresses and stretches, giving rise to periodic bursts. This resembles a heartbeat — only the size of a solar system. Some pulsations speed up or slow down, as if a heart changes rhythm from excitement. These studies confirm the ideas of John Archibald Wheeler, who coined the term "black hole." The pulsations open a window into the very core of the gravitational funnel, where matter performs its farewell dance before vanishing.