Gravitational waves: what they are and why everyone is so excited about finding them – maybe.

For the past three days the scientific Twitterverse has been all worked up about a possible major breakthrough with regard to our physical universe – the detection of gravitational waves. Such a discovery would be a direct verification of Albert Einstein’s last prediction from his theory of general relativity.

But wait. The few scientific facilities capable of detecting gravitational waves have made no claim of discovery. Instead, the excitement began with a tweet by Lawrence Krauss, an astrophysicist from Arizona State University.

And here is Krauss’s earlier tweet from September 2015.

Krauss’s tweet on gravitational waves has triggered a tsunami of reactions on social media. Scientists are discussing the possible causes of the as yet unconfirmed gravitational wave, either commenting that the discovery is a guaranteed Nobel Prize winner, or upbraiding Krauss for irresponsible speculation.

So, what are gravitational waves and why is this possible discovery such a big deal? A hundred years ago, Einstein proposed that the universe is in the form of four-dimensional space-time. Planets or stars cause the fabric of space-time to curve and their relative movements cause ripples in that fabric. These ripples are gravitational waves.

The biggest gravitational waves would be caused by neutron stars – also called black holes – spinning around each other, merging or colliding. These are rare events happening millions of light years away from earth and very, very difficult to detect.

The Laser Interferometer Gravitational-wave Observatory (LIGO), with detectors across the US, has been built for the precise purpose of catching that elusive gravitational wave. The experiment involves splitting a laser beam, projecting the twin laser beams perpendicular to each other over distances of 4 kilometres, bouncing them off mirrors, merging them and then looking for a signal of a G-wave in the merged beam. LIGO was upgraded to become the Advanced LIGO last year, just a week before Krauss posted his first G-wave rumour.

LIGO scientists have refused to comment on Krauss’s rumour and will want to reconfirm and verify their findings many times over before making any announcement. There may be several reasons for seeing a signal, including a test signal created by LIGO scientists themselves to check how well their systems work.

In 2014, astronomers from the Havard-BICEP2 collaboration made an announcement with great fanfare about having found a signal from gravitational waves created by the Big Bang, but when their work was peer-reviewed the signal seemed to be from space dust.

However, if LIGO has indeed found its first gravitational wave, it will mean that we are on the verge of a whole new understanding of how the universe was formed and what its fundamental laws are; about black holes, neutron stars and supernovae; about what’s out there in the far reaches of space.