The biggest discovery of 2016 was gravitational waves, but what’s next?

Wednesday 7 December 2016

Have more been found, what is Australia’s role, and why should we care?

Back in February 2016 it was Professor David Reitze who announced to the world that gravitational waves had been discovered at LIGO, 100 years after Einstein predicted them.

Credit: Matt Heintze/Caltech/MIT/LIGO Lab

Credit: Matt Heintze/Caltech/MIT/LIGO Lab

And now they want to find more. Last Thursday LIGO resumed the search for gravitational waves and the world is eagerly awaiting the results.

Today in Brisbane David Reitze will give a first-hand account of what it is like to make a potentially Nobel-prize winning discovery, which is being hailed as the beginning of a new era in astronomy.

Tiny ripples in space and time caused by the most violent events in the universe, such as black holes colliding, were predicted by Einstein 100 years-ago in his theory of relativity, but he thought they would be too small for humans to ever detect.

Undeterred, Reitze, along with Kip Thorne, Rainer Weiss, Gabriela González, and others spearheaded the international efforts to build a gravitational wave detector called LIGO (the Laser Interferometer Gravitational-wave Observatory) that would use laser light to detect gravitational waves as they travelled from distant cosmic upheavals, warping space on their way.

Almost as soon as they turned it on in September 2015, LIGO scientists detected a tiny ripple, a thousandth the diameter of a proton, caused by two enormous black holes colliding, over a billion years ago, the most violent event ever directly witnessed by humans.

He’ll tell the story of the four months of checks and double checks that the data was not a mistake while rumours abounded. When the news finally broke, physicists celebrated a new era of astronomy, discovering things that were previously invisible.

Australia’s role

To detect gravitational waves, LIGO needed an entire generation of instruments to be created, such as powerful, stable lasers and ultrasensitive detectors. Australia played a significant role with researchers from the University of Adelaide, ANU, Charles Sturt University, Monash University, The University of Melbourne, and UWA developing LIGO instrumentation, developing theoretical frameworks underlying gravitational-wave detection, and analysing LIGO data.

  • At the ANU, Dr Robert Ward and his team designed and installed the complex control system which brings LIGO into operation, at the Congress he’ll describe the optical measurement techniques that enable the extraordinary sensitivity of these detectors, and how they extract the signals necessary to control the interferometer – highlighting the Australian contributions.
  • Dr Bram Slagmolen’s team, also at the ANU, developed and installed small optic suspension systems to steer the laser beam around inside the interferometer. He’ll tell the Congress about the role of detector characteristics on the detection of gravitational waves.
  • Carl Blair from UWA will relate how the University of Western Australia developed a system which prevents powerful lasers from causing the mirrors to ‘ring’ which would have masked the minute gravitational wave signal.
  • Peter Veitch and David Ottaway at the University of Adelaide developed a system that measured warps in the mirrors caused by the powerful lasers.

Where to from here?

Australia has been a leader in the search for gravitational waves for decades – already a new research centre, OzGrav has been funded to launch us into the Gravitational Wave era. The $31.3 million ARC Centre of Excellence for Gravitational Wave (OzGrav), led by Swinburne University, will open in early 2017.

Deputy Director David McClelland from the ANU is excited by the possibilities.

“Long term funding for OzGrav will enable us to be world leaders in developing core technologies for future generations of LIGO and detectors in space.  We will develop quantum technologies which could ultimately improve sensitivity by a factor of 10,” says David.

“Techniques for measuring and suppressing the direct effect of objects moving near the interferometer mirrors will not only have a big payoff for gravitational wave astronomy but may have application to earthquake early warning systems.  We can take the lead in searching data for signals from rapidly spinning neutron stars or neutron stars colliding into each other.”

“Ultimately, we will position Australia as a prime location for a future gigantic interferometer using advanced technologies, allowing us to observe every black hole binary system in the universe and discover new objects residing in the dark side of the universe.”

Australian gravitational wave research being presented at the Congress:

  • Dr Eric Thrane from Monash University is already exploring the new horizons opened by LIGO’s discovery. He believes gravitational waves leave scars on the cosmos, too small to see individually, but a pattern may emerge as more gravitational wave detections occur.
  • Georgia Mansell from ANU is building a quantum light source which can triple the sensitivity of LIGO. She’ll tell the Congress about light sources for future gravitational wave detectors.
  • Associate Professor Chunnong Zhao from UWA will present a new idea for extending the band of frequencies over which detectors can be sensitive to gravitational waves.
  • Parth Girdhar from the University of Sydney hopes gravitational wave technology may give clues to the grand unification theory. He is using LIGO’s extraordinary sensitivity to listen to the Universe, hoping he may hear the secrets of quantum gravity like the sea inside a shell.
  • Two giant detectors each with twin 4 km long arms found gravitational waves. Now ANU researchers are testing a new technique on ‘fridge-sized prototype’. David McManus and Perry Forsyth tell how this system could be used for gravitational waves, seismic waves, and atmospheric disturbance mitigation.

The APCC-AIP Congress is the Joint 13th Asia Pacific Physics Conference and the 22nd Australian Institute of Physics Congress incorporating the Australian Optical Society Annual Conference. It’s on at the Brisbane Convention Centre from 4 to 8 December 2016.