Arrow-right Camera
The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Researchers using Hanford gravitational waves lab win Nobel Prize in Physics

Computer monitoring systems track the LIGO projects performance and data in this file photo from 2006 at the Hanford site. (Jed Conklin / The Spokesman-Review)

It was Christmas, 2015, and Fred Raab had just come home from a long day at the lab.

Raab, the head of the gravitational wave observatory at Hanford, had spent the holiday tinkering with fussy equipment. The system finally appeared to be working correctly when he left around 4 p.m.

The lab, called LIGO, was first conceived nearly 40 years ago to measure infinitesimally small ripples through space and time predicted by Albert Einstein’s theory of relativity. If scientists could measure those waves, it would advance knowledge of black holes, the structure of the universe and how the laws of physics function in the most extreme parts of space.

Raab ate Christmas dinner with his family. Then, he got an alert: the LIGO lab had detected a gravitational wave. It was the lab’s second in less than four months.

“It was a wonderful capstone to an otherwise crummy day,” he said.

On Tuesday, the Royal Swedish Academy of Sciences named three American physicists as winners of the 2017 Nobel Prize in Physics for their work discovering those waves. Barry Barish and Kip Thorne of Caltech and Rainer Weiss of MIT will split the prize for their work setting up the two operating LIGO labs in the U.S. - the one at Hanford, and another in Louisiana.

LIGO stands for Laser Interferometer Gravitational-Wave Observatory. It’s a large, circular underground vacuum that uses lasers and mirrors to measure tiny disturbances gravity caused by black holes more than a billion light years away.

How tiny? Raab said the waves are measured in billionths of the size of a single atom. Noticing such a small disturbance takes big equipment.

LIGO is home to the second-largest vacuum chamber in the world, after the Large Hadron Collider in Switzerland. It holds enough air to inflate 2.5 million footballs.

“We knew the size of the effect would increase with the size of the detector,” Raab said.

Work on LIGO began in 1979, when the National Science Foundation selected Caltech and MIT to pursue research and development. Hanford was selected as a site in 1992, opened in 1999 and began listening for gravitational waves in 2002.

In 2010, LIGO ended its first operation and underwent a retrofit to make the detection much more sensitive. That work was completed in 2014, and a new round of listening began in 2015.

Before long, LIGO detected two waves. The first, on September 14, 2015, was from the tail end of the merger of two black holes, something astrophysicists had predicted, but never observed.

“Having seen them several times, we now know that objects like this merge somewhere in the universe every hour,” Raab said. “We’re only seeing a small fraction of those because our machines are still only serving a very small piece of the universe.”

The ones detected at Hanford and in Louisiana happened quite far away, which means they’re more than a billion years old by the time the gravitational wave reaches Earth.

A second LIGO run from November 2016 to August 2017 picked up a third black hole merger, which was also detected at LIGO Louisiana and a facility near Pisa, Italy.

Raab compares reading the waves to an electrocardiogram that you might get if you were hooked up in a hospital’s intensive care unit. Just as a doctor can see the electrical signals your heart sends out and determine how well it’s functioning, physicists can look at the pattern of a gravitational wave and learn where it came from and what caused it.

“They tell a very exquisitely detailed story of what it is that created the waves,” Raab said.

LIGO is now working to further hone its ability to detect tiny waves. Scientists working at the Hanford site have noticed a limitation at lower frequencies in the detector they’re hoping to correct. Fixes will be made over the fall and winter, and a third run to observe waves will kick off in 2018.