“It was a sleepless night,” says Distinguished Professor Susan Scott recalling the first gravitational wave discovery in 2015.

“The collaboration at this stage was around 1000 people across the world. And I got an email at 9.15pm and it said there’s been this extraordinary signal. 

“I dropped everything.”

The thrill of detecting the first gravitational waves, which originated from the collision of two black holes, is still front of mind for many at The Australian National University (ANU) Centre for Gravitational Astrophysics.

“It was just so exciting. I had been working on this project for 20 years and, finally, it happened!”

Researchers at ANU played a pivotal role in this discovery by providing key instrumentation, including steering mirrors and stabilisation systems, to the Laser Interferometer Gravitational-Wave Observatory (LIGO).

“Teams from ANU spent months and years in the United States, installing systems into LIGO that were designed and tested here,” adds Distinguished Professor David McClelland. 

But despite the precision capabilities of LIGO, the team needed to analyse the data from the first detection with a healthy dose of scepticism. 

“We needed to prove that, beyond a shadow of a doubt, that it really was a signal from outer space,” he says.

“As that reality grew, so did the excitement, until we could finally reveal this first detection to the world.”

Almost 10 years later that excitement is continuing to grow as researchers at the ANU Centre for Gravitational Astrophysics dig deeper into the Universe’s violent past.

“It was an exciting moment that was the beginning of a new era in astronomy,” says Dr Lilli (Ling) Sun explaining the impact of the first detection of gravitational waves.

“But in addition to those exciting moments of discovery and detection, there are also a lot of challenges.”

First predicted by Albert Einstein, gravitational waves were long assumed impossible to detect due to their inconceivably minuscule effects here on Earth. 

“Gravitational waves are essentially ripples in space-time,” explains Dr Sun.

“You can imagine very massive, compact objects like black holes and neutron stars orbiting each other. This triggers ripples in space-time that spread out travelling at the speed of light.”

As the gravitational waves move through the Universe they change the physical distance between objects.

“The ripples are tiny, making them hard to detect,” says Dr Sun. 

Because they are so tiny, gravitational wave detectors require some of the most precise measurements ever made.

“A passing gravitational wave will change the separation between two objects that are 4kms apart by less than 1000th the size of a proton,” says Distinguished Professor McClelland. “That’s ridiculously small!”

Thankfully, here at ANU, our gravitational astrophysicists are ridiculously good at measuring ridiculously small things.

“We’re always pushing the boundaries of what is currently available,” says Associate Professor Bram Slagmolen. “We’re pushing those boundaries because we want to have the science to understand the Universe.

“These are new fields of research and we’re very proud and very keen to keep going.”

From developing new laser and quantum optical technologies that provide even more precision, to integrating telescope observations with real-time gravitational wave observations, and investigating compact binary mergers; the team are enabling us to explore some of the most fundamental laws in the universe.

“The centre is uniquely placed in Australia and in the world, because we have such a broad range of activities that we do,” says Associate Professor Slagmolen. 

“This is just the starting point of gravitational wave astronomy,” adds Dr Sun. “It’s not like we detected that and that’s it. It’s just the beginning.”

Humans have been seeking answers in the night sky for hundreds of thousands of years. And ultimately, it’s this curiosity to answer fundamental questions that are driving this new field.

“We have been looking to the sky using light, and eventually radio waves,” says Distinguished Professor Scott. “But gravitational waves are not part of that spectrum. It’s an entirely new spectrum, allowing us to observe all these things we couldn’t see before.”

Distinguished Professor Scott, and the interdisciplinary team of researchers at the ANU Centre for Gravitational Astrophysics, plan to keep pushing boundaries and unravelling the mysteries of how everything begun.

“We can go the whole way,” she says. “It can be an absolute probe of the very earliest universe.”