Scientific milestone as gravitational waves are discovered

Graphic depicting two circling black holes giving off gravitational waves Credit: Caltech/MIT/LIGO Laboratory.

Video report by ITV News' science correspondent Alok Jha

Scientists have said they have for the first time detected gravitational waves, a landmark discovery in physics which may allow us to gain insight into the nature of the early universe.

Predicted by Albert Einstein a century ago, gravitational waves are ripples in the fabric of spacetime, which move away from huge objects at the speed of light.

Read more: What are gravitational waves?

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.

Professor Stephen Hawking said the discovery could "revolutionise astronomy" as he congratulated the scientists on their work.

Listen: the 'sound' of gravitational waves emitted by black holes

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.

ITV News' science correspondent Alok Jha says the discovery is the "first direct information" humans have ever received from a black hole.

Why it matters

By studying gravitational waves scientists hope to gain insight into the nature of the very early universe, which has remained mysterious. Because the waves don't encounter interference like radio waves and visible light as they travel across the universe, they can tell more of the story.

Scientists also said gravitational waves may allow us to gain knowledge about enigmatic objects like black holes and neutron stars.

An aerial view of the LIGO Hanford Observatory Credit: Caltech/MIT/LIGO Laboratory.

How the waves were discovered

The discovery was achieved using a pair of giant laser detectors in the United States, located in Louisiana and Washington state.

The two laser instruments work in unison to detect remarkably small vibrations from passing gravitational waves. After detecting the gravitational wave signal, the scientists said they converted it into audio waves and were able to listen to the sounds of the two black holes merging.

Detecting the gravitational waves required measuring 2.5-mile (4 km) laser beams to a precision 10,000 times smaller than a proton.

Credit: LIGO

Gravitational waves are sent rippling through space by a huge object, such as a black hole.

Credit: LIGO

The LIGO instrument has two laser beam detectors of equal length. The time between the firing of the laser and the laser being received is monitored.

Credit: LIGO

Gravitational waves cause one laser beam to hit the detector before the other, as the waves cause objects to get closer at one axis and farther at a perpendicular axis. It's a miniscule difference in time, but one the scientists say proves the existence of gravitational 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.