The 2017 Nobel Prize for Physics has gone to three scientists, two in collaboration, for their work on gravitational waves. These ripples across spacetime echo far-distant cataclysms, giving us a new language with which to interpret the actions of the stars.
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Einstein predicted gravitational waves a hundred years ago, but he was certain we would not be able to measure them. It took 1.3 billion years for the first identified waves, caused by two black holes spiralling into one another, to arrive at the Laser Interferometer Gravitational-Wave Observatory (LIGO) detector in the USA in 2015. LIGO may have picked up an extremely weak signal but its observation will have a powerful impact on research. This is an entirely new way of observing the most violent events in space.
What does it take to measure the infinitesimally small?
LIGO brings together more than 1 000 researchers from over 20 countries and the three winners are described by the Royal Swedish Academy of Sciences as having, ‘(…) with their enthusiasm and determination, each been invaluable to the success of LIGO. Pioneers Rainer Weiss and Kip S. Thorne, together with Barry C. Barish, the scientist and leader who brought the project to completion, ensured that four decades of effort led to gravitational waves finally being observed.’
The L-shaped detectors have two arms, each 2.48 miles (4 kilometers) long, with identical laser beams inside. If a gravitational wave passes through Earth, the laser in one arm of the detector will be compressed and the other will expand. But the changes are tiny—as tiny as one-thousandth of a diameter of a nucleon, reports Live Science.
Thirteen researchers from the EU-funded GRAWITON (Gravitational Wave Initial Training Network) project contributed to the preparation of data leading to the award of the prize and were among the scientists whose work helped in the formulation of the paper ‘Observation of Gravitational Waves from a Binary Black Hole Merger’, following the first observation of gravitational waves. ‘Their work within this project was made possible through European funding which finances cutting-edge science, pushing back the frontiers of human knowledge,’ Carlos Moedas, the Commissioner for Research, Science and Innovation, says.
Improved triangulation thanks to third observatory located in Europe
Until very recently there have been just the two LIGO observatories in Livingston, Louisiana, and Hanford, Washington, USA, but another giant laser interferometer, called Virgo, has been established by the European Gravitational Observatory based Cascina, near Pisa, Italy. On 14 August, 2017, all three stations detected gravitational waves caused by the coalescence of two stellar mass black holes 31 and 25 times the mass of the Sun, located about 1.8 billion light-years away. The ripples rolled out hitting each at a minutely different time: the signal in the Virgo detector arriving a 6 milliseconds after the signals observed in the LIGO detectors.
This bring the total number of times gravitational waves have been observed to four. The team at Virgo explain that having three detectors vastly improves localisation. ‘Overall, the Universe volume which is likely to contain the source shrinks by more than a factor 20 when moving from a two-detector network to a three-detector network.’
‘We’ve entered a new phase of astronomy with Virgo joining, called multi-messenger astronomy,’ Bangalore Sathyaprakash, a physicist at Penn State and Cardiff University and part of the LIGO collaboration, tells The Verge. ‘It is really giving a new direction to our colleagues.’ Welcoming the prize, President of the German Physical Society Rolf-Dieter Huer said the detection of gravitational waves opens, ‘a window into an unseen world that will bring us more information in the future about the universe.’ He told Live Science it was a fantastic discovery.