In a world first, scientists have observed ripples in the fabric of space-time called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window to the cosmos.
The University of Western Australia is part of an international project team which has spent the past seven years putting together gravitational-wave detector equipment used to regularly measure gravitational waves. The detectors use powerful lasers to measure vibrations of mirrors suspended four kilometres apart at the ends of huge vacuum pipes.
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 5.51am US Eastern Daylight Time (5.51pm Perth time) by both twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, in Livingston, Louisiana, and Hanford, Washington, US. 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 GEO600 Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.
UWA researchers contributed to the project by using high power lasers at the Gingin Gravitational Research Centre to observe and test newly discovered ways of scattering the laser beams. They developed methods for preventing instabilities in the detectors.
One of the Gingin researchers, UWA PhD student Carl Blair, has been working at LIGO setting up systems, first proposed and tested at Gingin, that involve careful heating of the mirrors to make tiny changes in the mirror shape. Using this method, the new detectors in the US have reached sensitivity able to detect gravitational waves from a distance of approximately 200 million light years.
The UWA project team is headed by UWA’s Professor David Blair, and included researchers Professor Linqing Wen, Professor David Coward, Professor Li Ju, Associate Professor Chunnong Zhao and Dr Eric Howell.
UWA Vice-Chancellor Professor Paul Johnson congratulated the staff and students who have been involved in the discovery.
“The University is extremely proud of the role played by our research staff and students in one of the world’s biggest space discoveries of the past 100 years,” Professor Johnson said. “It is science which will extend our knowledge from the beginnings of our universe – and at the same time develop technologies and processes which will be of practical benefit to industry, business and the wider community.”
Professor Blair said the search for gravitational waves had cost the international science community more than $1 billion but the development of knowledge, spin-off technologies and training would provide huge benefits to outweigh the costs.
“Gravitational wave technology is already being applied to mineral exploration, time standards, quantum computing, precision sensors, ultra-sensitive radars and pollution monitors,” he said.
“We now have proof that the black holes of Einstein’s theory exist and are out there in the universe. We also know that gravitational waves interact with detectors the way physicists had deduced. The theory of detection is correct. And we know that space is populated by black holes – some a direct link to the first stars in the universe.”
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1000 scientists from universities in the US and 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyse data; approximately 250 students are strong contributing members of the collaboration.
The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute (AEI)), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, and other universities in the UK, funded by Science and Technology Facilities Council (STFC). Significant computer resources have been contributed by the AEI Atlas cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin Milwaukee.
LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech’s Richard P Feynman, Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.
Virgo research is carried out by the Virgo Scientific Collaboration, a group of more than 250 physicists and engineers from 18 different European laboratories, six from Centre National de la Recherche Scientifique (CNRS) in France, eight from Istituto Nazionale di Fisica Nucleare (INFN) in Italy, Nikhef in the Netherlands, the Wigner Institute in Hungary, the POLGRAW group in Poland and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo interferometer.
The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first-generation LIGO detectors, enabling a large increase in the volume of the universe probed – and the discovery of gravitational waves during its first observation run.
The US National Science Foundation leads in financial support for Advanced LIGO. Funding organisations in Germany (Max Planck Society), the UK (STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made Advanced LIGO much more sensitive have been developed and tested by the German UK GEO collaboration.
Professor David Blair (UWA School of Physics) (+61 8) 6488 2736 / (+61 4) 09 687 703
David Stacey (UWA Media and Public Relations Manager) (+61 8) 6488 3229 / (+61 4) 32 637 716
Jess Reid (UWA Media and Public Relations Officer) (+61 8) 6488 6876