An article in ANU Reporter in 1991 on the gravitational waves project.
Making sense of the Universe
Professor David McClelland from the ANU Department of Quantum Science reflects on the stunning discovery of gravitational waves.
The technology is impressive, the cost large and the precision of measurement hard to comprehend.
We’ll discover objects we didn’t know existed.
Gravitational waves, predicted by Einstein, are ripples in the curvature of space-time. They propagate at the speed of light from violent events in the Universe such as black hole collisions.
But why go to such effort and cost to detect them? “It’s a new way to sense the Universe,” Professor McClelland says.
“Light tells us about what’s happened outside an object so when we see the light from a star, it has come from the exterior, but we don’t know what’s happened inside.
“If we can measure gravitational waves from a supernova, we can understand the distortions of matter that are happening inside the star; the light tells us what happened from the outside of the star, so we learn complementary information.
“The first discovery of gravitational waves was of two black holes colliding – an event that does not emit light and has never been seen before.
“That’s just the beginning. I believe gravitational waves will revolutionise our understanding of the Universe, we’ll discover objects we didn’t know existed. It’s a major outcome in our quest to understand the Universe.
“When Galileo first turned his telescope to the sky, he saw things we never knew were there – now we’ve got our first gravity telescope.”
While celebrating the achievement, Professor McClelland does not gloss over his disappointment the discovery was not made concurrently in Australia.
However, Australian technology and equipment was installed in LIGO – the Advanced Laser Interferometer Gravitational Wave Observatory – that made the first detection.
LIGO in the USA has two observatories, 3,000 km apart, each built in an L-shape. Light travels along the four-kilometre-long arms and is reflected by mirrors at the ends.
The experiment measures the change in separation between the mirrors – a thousand times smaller than the diameter of a proton.
“In 1992, we first proposed to the federal government that Australia fund a third detector so we’d have a network around the world,” Professor McClelland says.
“They rejected it because gravitational waves had not been detected – to me that was the wrong approach.
“To be involved in the very first detection of gravitational waves was the prize, the holy grail of physics at the time.
“So we were really disappointed that the Australian Government of the time didn’t have the same vision we had. And in hindsight we probably were not ready at that time.
“We decided that while we would continue to strive for an Australian detector, we would work with the American project to learn how to do these things, to be part of that adventure, so that when detection happened, Australia would have a role.”
As a result, LIGO has Australian-made optical components and cameras and techniques that measure minute distortions of space, as part of technology from around the world installed in the $500 million project.
“Direct funding from Australia was about $4 million so we got a lot of bang for our buck,” Professor McClelland says.
“We also got the kudos – we were listed as one of the four countries that were stakeholders – so we gained a lot from that.”
“It might have been beyond us back then but we still need detectors spread around the world – there could very well be a central role yet for Australia.
“If the world says we need a detector in Australia to do the optimum science, then we hope we can bring an international consortium together, so that sometime in the future, that vision we had back in 1992 may well come to fruition.
“In the meantime, we have been well supported by the Australian Research Council and the recent funding of the Centre of Excellence for gravitational-wave discovery will ensure that we remain at the forefront of optical precision measurement and of discoveries from the warped side of the Universe.”