WASHINGTON: Scientists said today they had for the first time detected gravitational waves, ripples in space and time hypothesised by physicist Albert Einstein a century ago, in a landmark discovery that opens a new window for studying the cosmos.

The researchers said they detected gravitational waves coming from two black holes - extraordinarily dense objects whose existence also was foreseen by Einstein - that orbited one another, spiraled inward and smashed together.

They said the waves were the product of a collision between two black holes 30 times as massive as the Sun, located 1.3 billion light years from Earth.

The scientific milestone, announced at a news conference in Washington, was achieved using a pair of giant laser detectors in the United States, located in Louisiana and Washington state, capping a long quest to confirm the existence of these waves.

The announcement was made in Washington by scientists from the California Institute of Technology, the Massachusetts Institute of Technology and the LIGO Scientific Collaboration.