There’s a new cosmological background in town. In June, researchers from the North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, published the results of 15 years of observations, finding evidence for a constant, universe-wide hum of gravitational waves.

The scientists at NANOGrav don’t yet know for sure where these gravitational waves are coming from. But if what's past is prologue, scientists need only look to another pattern imprinted across the universe—the cosmic microwave background—for clues as to where research into the gravitational-wave background might be headed.

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