Here’s a date for your diary: 1 January 2017. It’s the day that physicists are predicting for a great scientific breakthrough: the first direct detection of gravitational waves.

Even if you have not yet heard about gravitational waves, you are going to in the coming years. When they are detected, it will revolutionise our investigation of the universe.

It will be the equivalent of astronomers discovering a new sense. With telescopes, they can already see the universe. By detecting gravitational waves, they will be able to ‘listen’ to it as well. We would be able to ‘hear’ stars colliding with one another, the destruction of matter falling into black holes and the catastrophic detonation of distant massive stars.

Ligo Generations tells the story of the 30-year-long hunt for gravitational waves.

Gravitational waves were predicted by Albert Einstein in 1916. They spring from the mathematics of his great theory of general relativity, which seemed to be saying that whenever a mass accelerates, it radiates energy in a form of gravitational radiation that no one had anticipated.

They can be thought of as wave motions that ripple across the universe, causing atoms to bob like boats on a choppy ocean. The difficulty in detecting them comes from the size of the displacement, which is much smaller than the width of an atom.

There was a false alarm last year when cosmologists prematurely announced their detection from an experiment called Bicep2 (Background Imaging of Cosmic Extragalactic Polarisation). Now, however, other physicists working at dedicated gravitational wave observatories around the world are sensing an imminent discovery.

The Bicep2 telescope in Antarctica. Photograph: Steffen Richter/AP

For decades now, physicists and engineers have been developing detectors known as interferometers. Each interferometer consists of two ‘arms’ that stretch for several miles at right angles to one another. Mirrors bounce laser light along these arms repeatedly, increasing the distance travelled to about 62 miles.



The lasers are synchronised to set off along the two arms simultaneously. Any passing gravitational waves will fractionally alter the paths causing the lasers to fall out of synch. The effort has been in developing equipment that is sufficiently sensitive to pick this up.

About 900 scientists from across the world collaborate on Ligo (Laser Interferometer Gravitational Wave Observatory). It has two L-shaped detectors in the US. There is also the Virgo interferometer in Cascina, Italy.

Sometime this year and next year, the research teams believe that the required sensitivity will be achieved in these instruments to strongly increase the chances of a detection. Hence the somewhat tongue-in-cheek statement of the 1 January date (which was decided upon at a conference back in July 2013).

In addition to all this, the European Space Agency will launch LISA-Pathfinder later this year. This mission will test the technology needed to detect gravitational waves from space, opening up new frequencies that are impossible to detect from the surface of the Earth.

To prepare us for these anticipated achievements, the gravitational wave community has come together to engage the public in numerous ways. Ligo Generations is a 25-minute YouTube video funded by the National Science Foundation through the University of Mississippi.

The film aims to show the different generations of scientists that have worked on the project for over 30 years. There is also an excellent TEDx talk online, given by Prof Martin Hendry from University of Glasgow.

Prof Martin Hendry, University of Glasgow, explains gravitational waves.

If watching these whets your appetite, you can also interact directly with the scientists on 13 February. Hendry and other members of the Ligo collaboration will be participating in a Reddit AMA, starting at 6pm GMT (1pm EST). To take part, you must create a reddit account (if you don’t have one already) here.

Make no mistake, the era of gravitational wave astronomy is coming. Let’s just hope we don’t have to cope with its arrival on the same day we are recovering from our New Year’s eve celebrations.



Stuart Clark is the author of The Day Without Yesterday (Polygon). Find him on Twitter @DrStuClark. More from Across the Universe blog