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Digging Deeper for a Universal Mystery

Mikio Tanabe

Jul. 5, 2016

Researchers in the United States recently detected gravitational waves for the first time, and a Japanese scientist played a key role in their quest to solve the mysteries surrounding the birth of the universe.

Albert Einstein hypothesized about the existence of gravitational waves 100 years ago.

Gravitational waves form when massive objects disturb the fabric of space-time, such as when black holes collide. It's a bit like the ripples that follow your hand when you drag it through water.

Until now, there had been no direct observations made. But recently, an American team detected the presence of multiple waves in rapid succession.

Gravitational waves are said to be a key to solving the mysteries surrounding the birth of the universe.

Seiji Kawamura, a professor at the University of Tokyo, made a significant contribution to the efforts of the American team.

He spent 10 years in the United States researching gravitational waves. He's back in Japan now as a core member of a team working on KAGRA, the Kamioka Gravitational Wave Detector in Central Japan. They aim to put it into operation in 2 years.

"This is a tank for a mirror that the KAGRA system uses," Kawamura says.

To detect gravitational waves, 2 tubes are placed in an L-shape. Each is 3 kilometers long. Laser light travels along them until it hits mirrors at the end of each tube and bounces back.

When gravitational waves distort space-time, there is a slight difference in the time it takes each beam to return. The detection of this difference marks the presence of a gravitational wave.

Kawamura visits the site while testing goes on for the KAGRA device. He focuses on a signal produced by the device.

The wonders of life have fascinated Kawamura since he was a child. He pursued studies on the origins of life in the universe.

Kawamura says that he became completely absorbed by gravitational waves when he first heard about them in graduate school.

"My biggest motivation was how the universe originated," he says.

This year, an American research team working at the Laser Interferometer Gravitational-Wave Observatory, or LIGO, became the first to detect gravitational waves.

And on the June 15, they announced another detection.

Thirty years ago, Kawamura worked with the team, to be at the forefront of research. But at the time, LIGO was still a prototype. Kawamura helped design the system.

The control room at the heart of LIGO is monitored 24 hours a day to catch any tiny signals of a gravitational wave reaching Earth.

Kawamura taught several core members at LIGO. Janeen Romie was one of them and she now heads the development team.

"When I started at CalTech, my supervisor at the time was Seiji Kawamura, and he had prototyped the first collocated sensor-actuator," Romie says.

Even the slightest vibration can throw off the accuracy of sensitive technology like LIGO, so Kawamura developed a device called an Optical Sensor Electromagnetic Actuator, or OSEM. Its internal sensor can eliminate vibrations. LIGO currently has equipped 400 of them.

There's another example of the magnitude of Kawamura’s contribution.

In the beginning, noise and other signals interfered with wave detection. Kawamura studied all types of noise, but he couldn't figure out how to eliminate specific noises. He was wonders where this noise was coming from, and spent months obsessing over a solution.

"I like the challenge, the harder it is, the more I enjoy it," Kawamura says. "So I find the facts that I don’t understand the most interesting. You need to stick to the task until the end and never give up.”

At last, Kawamura had a revelation. No one had expected it. It was the mirrors that reflect the lasers at the ends of the tubes.

Kawamura was sure that the noise could be eliminated by hanging the mirrors on wires and using anti-vibration technology.

But something was still wrong. The anti-vibration device itself vibrated ever so slightly. That caused the mirror to vibrate as well. The movements were only a fraction of the thickness of a human hair, but they created noise.

Kawamura increased the detection accuracy of the device by about 1000-fold. More improvements were made, which culminated in the detection of gravitational waves.

"He talked to me, he talked to a few other scientists and we sort of all came togather and had different ideas of how to do this," said David Reitze, director of LIGO project. "It was Seiji who really got me thinking about how to do interferometry with the advanced LIGO."

Kawamura’s dream is to solve the mystery of the creation of the universe. This has been his life mission, ever since he was a child.

"If we study gravitational waves in depth, we will discover the origins of the universe," he says. "There is a long journey ahead, but I want to live a long life in order to see the solution to this mystery.”


NHK World's Mikio Tanabe joined anchors Aki Shibuya and Sho Beppu in the studio.

Shibuya: Why do you think Professor Kawamura was so successful with his contributions to the LIGO project? What worked in particular?

Tanabe:Kawamura kept asking himself where certain noises in the system were coming from and he never gave up. He says it can take months of thinking to find an answer. And Kawamura has inspired younger researchers. Many now play leading roles in the LIGO project.

Beppu: So with the advances made in gravitational wave research, how much now do we know about the origins of the universe?

Tanabe: There's been some progress. But there's still a lot we don't know about the birth of the universe. All we can do is look at the traces left behind. And, you know, gravitational waves are some of those traces. Observing them could let us see back to the creation of black holes. And scientists also hope to find out how the universe turned into its current form.

Beppu: Mikio, what's the next goal of the scientists?

Tanabe: They want to find the directions of gravitational waves, so that means where they came from. That should give us a clearer map of the universe. Research institutes across the world are using gravitational-wave telescopes to try and pinpoint the sources of the waves. And projects are underway to send such telescopes into space. They could detect even weaker waves. Then we might be able to find out what it was like at the exact moment the universe was born.