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The Nation | COLUMN ONE

Gravity's Field of Dreams

Forget telescopes. This observatory, built to feel rather than see, aims to find gravitational waves, possible clues to the universe's dark side.

June 10, 2006|John Johnson Jr. | Times Staff Writer

HANFORD, Wash. — Across the tapestry of the night sky, hundreds or perhaps thousands of stars are doing frantic dances of death, spinning wildly around each other and shooting off waves of invisible gravitational energy like interstellar beacons.

In one of the most exotic observatories in the world, Fred Raab is waiting for those waves to wash up on the shoreline of Earth. When they do, they could change our understanding of the universe.

"We've spent 400 years since the invention of the telescope looking at a small portion of what exists," said Raab, head of the LIGO laboratory in the high desert of southeastern Washington.

LIGO -- the Laser Interferometer Gravitational-Wave Observatory -- could reveal the rest.

"This gives us an observational tool to probe the dark, strong-gravity part of the universe, which we've never really done," said Kip S. Thorne, a Caltech physicist who is one of the world's foremost experts on relativity.

Like the first bathysphere diving into deep-sea trenches, the $300-million LIGO project, conceived more than 25 years ago, is expected to uncover exotic creatures, such as dancing neutron stars and binary black holes, circling each other like heavyweight fighters. Physicists also may uncover the mysterious "dark matter" that is believed to be all around us but has never been measured. Some think they might find gateways into extra dimensions.

What makes LIGO different from other observatories is that it doesn't "see" the cosmos by detecting electromagnetic energy in the form of light, radio waves or X-rays. It feels it, measuring waves of gravity that wrinkle space-time like ripples on a lake.

One advantage to gravity-wave science over light-wave science is that whereas light bounces off solid objects, gravity waves go through everything -- planets, stars, people's bodies.

Raab, Thorne and about 500 other scientists around the world caught up in the race to measure the first gravity waves are essentially giving birth to a new science.

It has been gestating 90 years, since Einstein theorized that large bodies moving through space would give off waves of gravity, traveling at light speed, that would shrink and expand space-time itself.

The problem with gravity waves is that they are so difficult to detect that many physicists long doubted they would ever be found. In November, however, LIGO reached a level of sensitivity at which Thorne and other experts believe they might detect waves.

Now excitement has gripped the scientific community as it awaits word.

It can be felt inside the LIGO control room, where Raab studies a series of constantly changing graphs flashed up on the wall. Like a man translating a foreign language, Raab points to one squiggly line that he says is traffic passing on the main road a dozen miles away. Another is construction in the nearby cities of Richland and Kennewick.

If you know what to look for, Raab said, you can pick out the seismic signature of ocean waves hitting the shoreline of western Washington -- 200 miles away.

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Imagine you are an astronaut and you've volunteered, against all sensible medical advice, to expose yourself close-up to gravity waves. What would happen to you?

Presuming that you could somehow survive the violent cataclysms that spawn such waves, you would first be stretched to twice your size, then shrunk to half your size, before you came back to your ordinary height.

A spaceship or planet close enough would be similarly stretched and squeezed by the passing wave.

These effects were predicted by Einstein's theory of relativity, which gave the world an entirely new view of gravity. To Isaac Newton, gravity was a mysterious sucking force between planets and stars.

Einstein said gravity was nothing more than a warping or bending of space and time by large objects. Space to Einstein was not a nothingness but a "fabric" that could be stretched and shaped.

Just as a bowling ball causes an indentation on a trampoline, a planet or star dents the space around it. As the body moves through space, it gives off waves of gravity, as a spoon stirring milk gives off ripples.

The reason we walk around without being constantly stretched out of shape like rubber-band people is that most gravity waves are far too weak. By the time gravity waves reach Earth, even those thrown off by supernovas produce only tiny wrinkles in our world.

So tiny, in fact, that two neutron stars whirling around each other in some distant part of the universe would stretch our world out of shape by a bit more than 10-15 meters -- about the size of an atomic nucleus.

Even so, cosmologists think there is some pretty convincing evidence of the waves' existence.

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