Adelaide University scientists help detect gravitational waves, proving Einstein right
A CENTURY after Einstein predicted it, scientists — including researchers from Adelaide — say they have finally detected gravitational waves, or ripples in the fabric of space-time.
A CENTURY after Einstein predicted it, scientists — including researchers from Adelaide — say they have finally detected gravitational waves, or ripples in the fabric of space-time.
Head of Physics at the University of Adelaide, Professor Peter Veitch, is at Parliament House in Canberra today for the announcement of the first detection of mysterious gravitational waves, which advances humanity’s understanding of the universe and will open a new field of astronomy.
The faint waves in space and time, caused by cataclysmic events in the distant universe, were predicted by Einstein in his general theory of relativity 100 years ago.
The elusive waves were detected with what Australian scientists say is the biggest experiment ever built to capture evidence of the tiniest signal ever detected.
The gravitational waves detected were produced during the merger of two huge black holes — a region of space with a gravitational field so intense that no matter or radiation can escape — which produced a single, larger spinning black hole over one billion years ago.
The discovery, accepted for publication in the journal Physical Review Letters, was made by the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration, which includes the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA)) and is the culmination of decades of research.
Professor Veitch said the LIGO detectors were a technological triumph and the discovery provided undeniable proof Einstein’s gravitational waves and black holes exist.
“I have spent 40 years working towards this detection and the success is very sweet,” he said. “We are on the threshold of a potential revolution in which gravitational astronomy could dramatically change our understanding of the universe and its evolution.”
The University of Adelaide developed and installed ultra-high precision optical sensors used to correct the distortion of the laser beams within the LIGO detectors, enabling the high sensitivity needed to detect the tiny signals.
The Adelaide team also included Professor Emeritus Jesper Munch, Associate Professor David Ottaway and Dr Won Kim.
Are you excited about #gravitationalwaves like @LKrauss1? #showusyourwave - get creative (video or pics) & tag us! pic.twitter.com/T9Td82rsKk
— RiAus (@RiAus) February 11, 2016
“We’ve been assisting with the assembly and operation of the detectors and one of our PhD students, Elli King, was working at the LIGO Hanford Observatory when the gravitational wave was discovered,” Prof Veitch said.
“She was part of the team that conducted the exhaustive checking to make sure that signal was genuine.”
Other Australian scientists in the project include those based at the Australian National University, the University of Melbourne, the University of Western Australia, Monash University and Charles Sturt University.
ACIGA leader, Professor David McClelland from ANU, said the observation would open up new fields of research to help scientists better understand the universe.
“To detect it, we have built the largest experiment ever ─ two detectors 4000km apart ─ with the most sensitive equipment ever made, which has detected the smallest signal ever measured,” Prof McClelland said.
The gravitational waves were detected on September 14, 2015, by both of the twin LIGO detectors, located in Livingston, Louisiana, and Hanford, Washington, in the United States.
LIGO research is carried out by the LIGO Scientific Collaboration, a group of more than 1000 scientists from more than 90 universities around the world.
Some scientists likened the breakthrough to the moment Galileo took up a telescope to look at the planets.
“Until this moment we had our eyes on the sky and we couldn’t hear the music,” said Columbia University astrophysicist Szabolcs Marka, a member of the discovery team. “The skies will never be the same.”
For many years, scientists have had indirect evidence of the existence of gravitational waves rippling across the universe.
In 1974, student Russell Hulse and his supervisor Joseph Taylor calculated that a pair of burnt-out stars spiralling towards one another were radiating gravitational waves at exactly the rate predicted by Einstein. This earned both researchers a Nobel prize around twenty years later.
But now, an all-star international team of astrophysicists using an excruciatingly sensitive, $US1.1 billion instrument have not only detected one of these waves but they have been able to localise the signal.
The signals seen by LIGO Hanford and Livingston! pic.twitter.com/MHDNxG15mO
— Lawrence M. Krauss (@LKrauss1) February 11, 2016
“Not only did we detect gravitional waves, we can localise the signal. It came from the southern sky,” said Gonzalez.
According to Einstein’s theory, published in 1916, the universe is made up of a “fabric of space-time”: massive accelerating objects in the universe are believed to bend this fabric, causing ripples known as gravitational waves. The colliding of two black holes or merging of two pulsars are among the presumable causes of such waves’ formation.
Being able to observe ripples of space-time as they move across our skies could open up a whole new realm of astronomy. We could ‘see’ invisible objects such as black holes and events such as colliding neutron stars, and perhaps peer back to the dawn of time itself.
To make sense of the raw data, the scientists translated the wave into sound. At a news conference, they played what they called a “chirp” — the signal they heard on September 14. It was barely perceptible even when enhanced.
Detecting gravitational waves is so difficult that when Einstein first theorised about them, he figured scientists would never be able to hear them. Einstein later doubted himself and even questioned in the 1930s whether they really do exist, but by the 1960s scientists had concluded they probably did, Ashtekar said. In 1979, the National Science Foundation decided to give money to the California Institute of Technology and the Massachusetts Institute of Technology to come up with a way to detect the waves.
Twenty years later, they started building two LIGO detectors in Hanford, Washington, and Livingston, Louisiana, and they were turned on in 2001. But after years with no luck, scientists realised they had to build a more advanced detection system, which was turned on last September.
“This is truly a scientific moonshot and we did it. We landed on the moon,” said David Reitze, LIGO’s executive director.
EINSTEIN’S INSPIRED IDEA
Einstein’s famous Theory of General Relativity turned our understanding of space and time on its head. He argued that neither is fixed. Instead, they are dependent upon each other — and the state of one changes with the condition of the other.
Space and time for a single object sitting stationary remains static. But put two objects together, and the matter and energy within them interacts to distort space-time — causing the objects to accelerate and spiral towards each other. This acceleration emits gravitational waves. Their behaviour is thought to be similar to that of light and radio waves, except that they move through space and time itself. They ‘warp’ the very fabric of the universe — shrinking and expanding the distance between two points in the same way a flag billows in the wind.
But gravity is also the weakest force. Gravitational waves cause such a tiny wiggle in space-time that Einstein thought they would never be detected.
COSMIC CLASH
Einstein inferred the energy of an exploding star — a supernova — would be dissipated by relatively huge gravitational waves rushing outward at the speed of light.
He also calculated that two immensely dense neutron stars orbiting each other very closely would also ripple-out immense energy as gravitational waves.
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But it has long appeared that his idea that the titanic fallout from the collision of two black holes would blast across the cosmos like a rock crashing into a still pond was the most likely to bare fruit.
So what’s the problem with seeing gravitational waves produced by such a colossal collision?
On an intergalactic scale, even the incomprehensible energy of colliding black holes translates to the barest vibration of atoms inside our bodies — or a flutter of photons between two lasers.
GRASPING GRAVITY
One of the most advanced (and expensive) efforts to catch gravitational waves in the act began in 2002: The Laser Interferometer Gravitational-Wave Observatory (LIGO). As the complicated name infers, this experiment has been attempting to measure the infinitesimal vibration of perpendicular laser beams reflected along a 4km vacuum tube in a tunnel.
Two such enormous L-shaped tunnels are positioned some 3000km apart — one on either side of the United States.
The theory goes that any true gravitational wave would cause a ripple in the lasers at both locations. Any nearby slamming doors would therefore be cancelled out.
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