Featured image above credit: NASA/C. Henze

For the first time, scientists have observed ripples in the fabric of spacetime 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 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 by twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Louisiana and Washington in the USA. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) and the GEO600 Collaboration) and the Virgo Collaboration.

Australian scientists from The Australian National University (ANU), the University of Adelaide, The University of Melbourne, the University of Western Australia (UWA), Monash University and Charles Sturt University (CSU), contributed to the discovery and helped build some of the super-sensitive instruments used to detect the gravitational waves.

Leader of the Australian Partnership in Advanced LIGO Professor David McClelland from ANU, says the observation would open up new fields of research to help scientists better understand the universe.

“The collision of the two black holes was the most violent event ever recorded,” McClelland says.

“To detect it, we have built the largest experiment ever – two detectors 4000 km apart with the most sensitive equipment ever made, which has detected the smallest signal ever measured.”

Associate Professor Peter Veitch from University of Adelaide says the discovery was the culmination of decades of research and development in Australia and internationally.

“The Advanced LIGO detectors are a technological triumph and the discovery has provided undeniable proof that Einstein’s gravitational waves and black holes exist,” Veitch says.

“I have spent 35 years working towards this detection and the success is very sweet.”

Professor David Blair from UWA says the black hole collision detected by LIGO was invisible to all previous telescopes, despite being the most violent event ever measured.

“Gravitational waves are akin to sound waves that travelled through space at the speed of light,” Blair says.

“Up to now humanity has been deaf to the universe. Suddenly we know how to listen. The universe has spoken and we have understood.”

With its first discovery, LIGO is already changing how astronomers view the universe, says LIGO researcher Dr Eric Thrane from Monash University.

“The discovery of this gravitational wave suggests that merging black holes are heavier and more numerous than many researchers previously believed,” Thrane says.

“This bodes well for detection of large populations of distant black holes research carried out by our team at Monash University. It will be intriguing to see what other sources of gravitational waves are out there, waiting to be discovered.”

The success of LIGO promised a new epoch of discovery, says Professor Andrew Melatos, from The University of Melbourne.

“Humanity is at the start of something profound. Gravitational waves let us peer right into the heart of some of the most extreme environments in the Universe, like black holes and neutron stars, to do fundamental physics experiments under conditions that can never be copied in a lab on Earth,” Melatos says.

“It is very exciting to think that we now have a new and powerful tool at our disposal to unlock the secrets of all this beautiful physics.”

Dr Philip Charlton from CSU says the discovery opened a new window on the universe.

“In the same way that radio astronomy led to the discovery of the cosmic microwave background, the ability to ‘see’ in the gravitational wave spectrum will likely to lead to unexpected discoveries,” he says.

Professor Susan Scott, who studies General Relativity at ANU, says observing this black hole merger was an important test for Einstein’s theory.

“It has passed with flying colours its first test in the strong gravity regime which is a major triumph.”

“We now have at our disposal a tool to probe much further back into the Universe than is possible with light, to its earliest epoch.”

Australian technology used in the discovery has already spun off into a number of commercial applications. For example, development of the test and measurement system MOKU:Lab by Liquid Instruments; vibration isolation for airborne gravimeters for geophysical exploration; high power lasers for remote mapping of wind-fields, and for airborne searches for methane leaks in gas pipelines.

This information was first shared by Monash University on 12 February 2016. Read their news story here.