Scientists have released what is perhaps the most important sound heard this century.

Gravitational waves spew out from places like black holes and dying stars. Eventually they might allow us to look into those same strange parts of the universe, giving us clues about how it began.

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The particular sound heard this time around emerged millions of years ago when two black holes careered into one another.

Einstein predicted the sound almost exactly a century ago. And scientists have spent decades proving that it exists, and searching for it.