What are gravitational waves?
Long predicted but never directly seen, gravitational waves are ripples in the fabric of the universe.
Albert Einstein compared the universe’s shape to a single fabric, hewn from space and time. According to his theory of general relativity, the force of gravity is the result of curvature in this space-time, and gravitational waves are ripples in it, produced when massive objects like black holes collide.
Who has found them?
If rumours are to be believed, researchers working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) experiment. This pair of detectors, sitting 3000 kilometres apart in Livingston, Louisiana, and Hanford, Washington, use lasers to pick up tiny variations in space-time that could be caused by a passing gravitational wave. The LIGO team have scheduled a press conference on Thursday, and an exclusive New Scientist analysis suggests they may have seen as many as three such signals.
Why does it matter?
Einstein’s theory of general relativity revolutionised our understanding of gravity and is one of the great pillars of modern physics. But we know it can’t fully describe the universe because it disagrees with another major theory, quantum mechanics. By studying gravitational waves, the final unconfirmed prediction of Einstein’s theory, physicists may be able to figure out a way to extend it.
What else can they do?
Besides putting Einstein to the test, the first confirmed observation of gravitational waves will mark the beginning of a new kind of astronomy. Just as we use various electromagnetic wavelengths such as visible light, infrared and X-rays to study the cosmos, gravitational waves will act as a brand new eye on the universe, potentially giving us greater insight into objects like black holes and neutron stars.
Has anyone tried to see them before?
In 1974, astronomers Russell Hulse and Joseph Taylor detected a binary pulsar, a pair of two dead stars emitting pulses of radio waves. Hulse and Taylor realised that the two pulsars were losing energy and slowly spiralling towards each other in a way that was exactly consistent with Einstein’s equations of general relativity: the missing energy is thought to be emitted as gravitational waves. The finding earned the pair the Nobel prize for physics in 1993.
Wasn’t there a big fuss over gravitational waves a few years ago?
In 2014, researchers on the BICEP2 telescope announced they had seen signs of primordial gravitational waves, ripples created not from modern-day black hole collisions but from the big bang itself. But the team later had to backtrack on these claims, after it turned out they hadn’t accounted for the effects of galactic dust. If LIGO is indeed announcing a discovery later this week, they’ll want to be sure to avoid any similar mistakes.