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By adjusting the relative intensity and delay of the light beams entering the two channels, remarkably, researchers consistently altered the light's radiation pattern outside the cavity.

When played as an audible sound, the waves make an unmistakeable ‘chirp’ — a rapidly rising tone — followed by a ‘ringdown’, the radiation pattern from the merged black hole.

“Some of that could be a radiation pattern effect,” he said, with the seismic waves being stronger in certain directions than others.