What does the universe sound like? Scientists describe cosmic ‘background hum’

Scientists on Wednesday unveiled evidence that gravitational waves, the ripples in the fabric of space-time predicted by Albert Einstein more than a century ago, are permeating the universe at low frequencies - creating a cosmic background hum. The new findings show that space is awash with these gravitational waves, which oscillate over years or longer and appear to originate primarily from pairs of supermassive black holes spiraling together before merging. The gravitational waves actually stretch and compress space-time itself as they travel through the universe," said Oregon State University astrophysicist Jeff Hazboun, a member of the scientific collaboration that conducted the research and lead author of one of the papers describing the findings in the Astrophysical Journal Letters. The discovery was announced seven years after researchers announced that they had first detected the existence of gravitational waves generated by two distant black holes - extraordinarily dense objects with gravity so strong that not even light can escape.