How gravitational waves attracted a Nobel Prize | Human World

 In Science

Artist’s concept of the collision of two black holes, an event predicted theoretically to produce gravitational waves. And indeed these elusive waves were detected – for the first time ever – by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Image via The SXS (Simulating eXtreme Spacetimes) Project

By Eric Thrane, Monash University; Paul Lasky, Monash University, and Yuri Levin, Monash University

The 2017 Nobel prize for physics, awarded overnight in Sweden by the Royal Swedish Academy of Sciences, began with a discussion 42 years ago between two scientists in a hotel room in Washington DC.

Kip Thorne, a theoretical physicist from Caltech, and Rainer (Rai) Weiss, an experimentalist from MIT, debated what would have seemed to most physicists like a far-fetched, borderline crazy idea: the detection of ripples in the fabric of spacetime called gravitational waves.

But the two young men were serious. Weiss had written a detailed technical paper outlining a proposal for an experiment that would go on become LIGO (the Laser Interferometer Gravitational-wave Observatory).

Read more: Gravitational Waves arrive in Europe

Thorne, meanwhile, had thought a lot about potential sources of gravitational waves and had developed a deep appreciation of just how much their detection would tell us about exotic astrophysical objects such as black holes and neutron stars.

A great collaboration was forged that night. And it was soon strengthened by Ronald Drever, a brilliant experimental physicist who joined the faculty at Caltech. The three came from very different cultural backgrounds.

Thorne grew up in a Mormon family in the US state of Utah. Weiss was born in Berlin, Germany, and when he was a child, his half-Jewish family escaped the Nazis by first moving to Prague and then fleeing Czechoslovakia just before it was invaded. Drever hailed from Glasgow, in Scotland, and had a thick Scottish accent.

Ronald Drever, a LIGO co-founder. Image via American Physical Society.

They were united by their passion to “hear” the universe with gravitational waves.

Gravitational waves are emitted from some of the universe’s most catastrophic events such as exploding stars and colliding black holes. Every source emits gravitational waves differently. For sources detectable by LIGO, these waves have the same frequencies as the sound waves we can hear.

By studying the precise “sound” of a gravitational wave, it is possible to reconstruct the event that created it. They offer a unique window on the universe, allowing us to probe black holes and other extreme objects.

Together, they developed the ideas behind LIGO, obtained the support of Caltech and MIT, and secured research funding from the US National Science Foundation. Most importantly, they inspired two generations of physicists around the world to devote their lives to the quest for gravitational waves.

The chirp heard round the world

It took many years of dedicated teamwork to realise the vision of LIGO. The laboratory took shape under the leadership of experimental physicist Barry Barish, now an emeritus professor at Caltech.

He created the LIGO Scientific Collaboration, an international team now numbering more than 1,000 scientists working on all aspects of LIGO science and technology, from laser physics to data analysis algorithms to astrophysics.

Australia was an early international partner in the consortium, and Australian scientists made important contributions to LIGO instrumentation, theoretical modelling and data analysis.

The instrument was so complex that it had to be built in two stages. The first stage of LIGO operated through the 2000s, demonstrating the technology that would be needed to detect gravitational waves. Not until the second stage, Advanced LIGO, was the equipment sensitive enough to detect the gravitational waves themselves.

The newly refurbished Advanced LIGO was ready to go in late 2015. Then, on September 14 that year, days after Advanced LIGO was switched on, a burst of gravitational waves shook the mirrors used to monitor the curvature of spacetime by a distance of about one-thousandth of the size of a proton.

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