This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
The gravitational waves were detected on September 14, 2015 at 5:51 a.m. Eastern Daylight Time (9:51 a.m. UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT.
The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.
Researchers from the University of Glasgow, the University of Strathclyde and the University of the West of Scotland were involved in the global project to detect gravitational waves.
The University of Glasgow have been working for decades to support the worldwide effort to detect gravitational waves, and co-led the group inside the collaboration which detected the gravitational wave signal.
Scientists from the University of Glasgow’s Institute for Gravitational Research led on the conception, development, construction and installation of sensitive mirror suspensions in the heart of the LIGO detectors in Livingston and Hanford, which were crucial to the first detection. That technology, developed in partnership with the University of Strathclyde, the University of the West of Scotland and other institutes around the UK, Germany and Spain, was based on Glasgow’s pioneering work for the GEO600 detector located near Hannover, Germany.
Those suspensions rely on delicate 400-micron-wide fibres made from silica. Despite their fragility, each suspension fibre is very strong, capable of holding up to 70 kilograms. In the LIGO detectors, the mirror suspensions hold 40kg mirrors and keep them from being interfered with any outside force or vibration except for gravitational waves. The mirrors are held so still by the suspensions that the LIGO detectors can detect movements, caused by gravitational waves, close to one-ten-thousandth the diameter of a proton.
Professor Sheila Rowan, Director of the Institute for Gravitational Research, said: “This is a monumental leap forward for physics and astrophysics – taking Einstein’s predictions and turning them into an entirely new way to sense some of the most fascinating objects in our Universe.
“In the past, we’ve relied the information we collected from the electromagnetic spectrum to help learn more about the cosmos, from the other planets in our solar system to star systems millions of light years away.
“Now gravitational wave astronomy will give us the ability to make many exciting new discoveries. This first detection, in addition to confirming Einstein’s prediction, also gives us the first direct evidence of the existence of black holes, and the first observation of black holes merging, which is a fantastic result. We’re very much looking forward to new data from LIGO in the coming months and years, and to making our detectors even more sensitive.”
Scotland’s First Minister, Nicola Sturgeon, welcomed the announcement. She said: “This is a world leading discovery that again puts Scotland at the forefront of science.
“I’m pleased and proud that scientists from Scottish universities played a key role in the worldwide effort to prove that Einstein’s prediction of the existence of gravitational waves was correct.”
The longest-serving member of the University of Glasgow’s gravitational research community is Professor James Hough, who has worked in the field at the University since 1971.
Professor Hough said: “Alongside Professor Ronald Drever, I was involved in building early gravitational wave detectors here in Glasgow, which monitored outputs from piezoelectric transducers attached to aluminium bars.
“We thought it would take us about a year to make an initial detection, and in 1972, we found what looked very much like evidence of gravitational waves. However, since no other detectors we operating at the same time, we weren’t able to verify our observation. Nonetheless, that finding convinced me that we would one day find the evidence we were looking for.
“This discovery, 43 years later, is the culmination of my career in science. I’m immensely proud to have been involved in the project and I’m very excited to see the fascinating new discoveries gravitational wave astronomy will bring us in the future.”
Physical Review Letters: ‘Observation of Gravitational Waves from a Binary Black Hole Merger‘
University of Glasgow: ‘Gravitational waves detected 100 years after Einstein’s prediction‘
University of Strathclyde: ‘Gravitational waves detected 100 years after Einstein’s prediction‘
University of the West of Scotland: ‘UWS academics contribute to the detection of gravitational waves 100 years after Einstein’s prediction‘