A place of utmost gravity.

Byline: Greg Bolt The Register-Guard

RICHLAND, Wash. - To the naked eye, the only waves that splash this V-shaped building set among the remnants of the Hanford nuclear reservation come from wind blowing off the Palouse and pushing piles of tumbleweeds up against anything that stands still.

But inside is one of the most sensitive scientific instruments ever built. Its two shafts each stretch out four kilometers into the Eastern Washington desert, housing laser beams tuned to detect a kind of wave whose crest would rise just a small fraction of the width of the nucleus of an atom.

It is the Laser Interferometer Gravitational Wave Observatory - LIGO for short - one of a pair set up in the United States to detect the exceedingly faint vibrations in the fabric of the universe set off by the most cataclysmic events known to nature. When pairs of black holes or super-dense neutron stars spiral into each other, or when a massive star explodes in a supernova, gravity waves radiate across intergalactic space, stretching and compressing both space and time as they pass.

That's what the theory says, anyway. To date, no one has found a gravity wave, although Albert Einstein's theory of general relativity says they are there, and astronomical measurements support their existence.

The scientists at LIGO, including some from the University of Oregon, hope to be the first to actually detect a gravity wave, either at the Hanford site or its twin near Livingston, La. Ever since the instrument began taking measurements in 2002, after six years of construction, they have steadily been tuning it to sense finer and finer movements and hear farther out into the cosmic sea.

"All we are is a very fancy measuring device," said Robert Schofield, a researcher at the UO who splits his time between campus and LIGO. "All we do is measure a distance."

"Leading edge of technology"

"Fancy" is a bit of an understatement. LIGO is to fancy what a supercomputer is to an abacus.

LIGO is, in fact, the most accurate measuring system ever devised. It can measure a movement of 1 x 10 -18, which is a decimal point followed by 18 zeroes and a 1. That works out to 1/1,000th of the diameter of the nucleus of an atom.

It has to be that sensitive because gravity waves are extremely weak. In fact, gravity is the 90-pound weakling of nature's basic forces, which also include the electromagnetic force and the strong and weak nuclear forces that hold atomic nuclei together.

"Gravity is by far the weakest by many, many, many orders of magnitude," said physics professor Jim Brau, director of the UO's Center for High Energy Physics and a LIGO collaborator. "It is tens of orders of magnitude weaker than any other force."

And yet gravity waves travel millions of light years in ripples that literally stretch and compress the fabric of the universe, the dimension known as space-time. They are too faint to be felt, but it is believed that Earth is constantly being rocked as it floats in a sea of gravity waves spawned by distant spacequakes.

But detecting such a weak force is a challenge, one that until fairly recently was deemed outside the ability of science. Fred Raab, a physics professor at the California Institute of Technology and senior scientist at LIGO Hanford, said it was such a tall order that most scientists scoffed at the idea when LIGO was first proposed.

"It's really on the far, far leading edge of technology at a level to where a lot of people when we proposed it said it just seemed impossible," Raab said. "They would kind of shake their heads and say there's no way to prove you can't do it, but it just seems like you ought not to be able to."

The most perfect color ever

But the potential payoff, if LIGO works, is so huge that the National Science Foundation decided to go for it in a big way. LIGO is the largest and most expensive project ever undertaken by the agency, which covered the $300 million construction cost as well as $20 million a year to operate the observatories.

Scientists and engineers had to take instrumentation to a new level to build LIGO. What they did was build an instrument based on a single laser beam so precisely tuned and amplified it creates what Schofield calls "the most perfect color ever created."

Unfortunately, it's not a color human eyes can see because it's just slightly into the infrared. Scientists see the beam by watching it on a video camera that can see that part of the spectrum.

The LIGO team also had to create the largest vacuum system in the world. It takes four days and three different pump systems to reduce the roughly 24,000 cubic meters inside the laser tubes to a near-perfect vacuum.

The vacuum and the multiple shock absorbers that help isolate the tube are what allow it to detect the tiny changes caused by gravity waves. The laser is so sensitive that Schofield said it registers an uptick in vibrations starting about 6 a.m. on weekdays and running through the day, which he believes is caused by people around the area going to work.

Schofield's main job is trying to reduce or filter out environmental "noise" from the instrument readings. The UO is part of the LIGO Science Collaboration, a network of universities and researchers taking part in gravity wave research, and is one of the few that actually sends scientists to help run the observatories.

The UO also is taking part in the World Year of Physics, a celebration of the 100th anniversary of the year Einstein issued three of his most important theories, including special relativity. His later theory of general relativity, which included the prediction of gravity waves, explained one of the more puzzling experiments of the time that was done with a much smaller interferometer.

In essence, the LIGO instrument works like this: The laser beam goes through a beam splitter to create two beams. Each beam is aimed down a vacuum-filled tube four kilometers long, with the two tubes aimed in a right angle, or "L" shape.

The beams are kept in precise sync so they travel down the tubes, hit a mirror suspended on piano wires at the far end and are reflected back with their waveforms in perfect alignment. Should a gravity wave hit, it literally will push one mirror out by an infinitesimal amount while pulling back the other mirror by the same amount.

That will put the two laser waveforms out of alignment, creating a telltale interference pattern. It may take months of data analysis to separate out a gravity wave signal from thumps generated by the nearby construction and traffic, but when it happens, it will be party time at LIGO.

"I'll make a firm prediction that the announcement that we've detected the first gravity wave will be made within 24 hours of the biggest party I ever attend in my life," said scientist Raab.

An exponential leap forward

What will make that such an important, and festive, moment is the implication it has for science. LIGO has the potential to move astrophysics an exponential leap forward by giving scientists a whole new way to observe the universe.

Some scientists have likened the potential advances to the progress that followed Galileo's invention of the telescope or the advent of radio astronomy, both of which vastly expanded people's ability to see into space. Raab likens it to restoring to someone a sense that he was born without.

"Imagine if you were born unable to hear but only to see. This is the way the world has interacted with the heavens throughout human history," Raab said.

"What LIGO will eventually give us is as if by a miracle cure that person who was born without hearing was given hearing. It will be that dramatic a change once we routinely can detect and hear the universe."

And he means hear. LIGO detects a frequency range of about 40 to 7,000 cycles per second, well within the human hearing range, giving scientists the opportunity to actually listen as, for example, two neutron stars spiral into each other.

Neutron stars pack matter equal to a sun 1.4 times the size of ours into a ball just 10 miles across. They generate intense gravity, and when two are drawn together and collide they are believed to create a black hole.

"You would literally hear them whiz in together and slam together and sound like symbols crashing, and it would all end with a big black hole that would sound like a bell ringing," Raab said. "You can literally take the signals from LIGO, and we do it, and hook headphones in and listen to it or play it on a speaker in the control room."

The events LIGO is listening for are the biggest and most powerful in the universe and are only created by extremely massive objects exploding, spiraling into each other or spinning fast enough to send out gravity waves.

Many involve objects, such as black holes, that are undetectable by the telescopes and antennas used today.

Ray Frey, a physics professor at the UO and a LIGO researcher, said the instrument will open a whole new window on these incredibly powerful events.

"When these binary neutron stars eventually merge, what happens? Nobody really knows. But they'll be emitting gravitational radiation, so we should be able to learn quite a bit about that," he said.

"And the formation of black holes that results from that, we should be able to see how that happens."

Brau said the payoff goes even further. Understanding these events will tell us important things about the very nature of the universe, its structure and even its origin, he said.

"We want to understand the nature of the universe, and we believe the universe has a structure that is rattled by the movement of large masses," he said.

"Once we are actually measuring this rattling that is going on, we will have eyes, new eyes, on phenomena in the universe that we currently do not have."

One thing scientists will be looking for is a kind of echo of the big bang, the cosmic explosion believed to have created the universe. The force of that event was so great that scientists believe they still might hear it, some 14 billion years later.

"With gravity waves we can actually look much, much, much further back to a very small fraction of a second after the initiation of the big-bang explosion," he said.

So far, LIGO has had four "science runs," periods of about one to three months when the lasers are locked in and data is being taken.

The sensitivity of the instrument was probably too low during the first three runs to detect a gravity wave, but the run that ended in March listened far enough into space that within the data collected and yet to be analyzed scientists might already have their first gravity wave detection.

Another science run is expected to begin this summer and could last almost a year, the longest one yet and at the highest sensitivity level ever. If the last run didn't do it, LIGO scientists are optimistic that the next one will finally turn up the proof of Einstein's relativity theory and start to open that new window on the universe they've been seeking for more than 10 years.

"We're just getting to the stage now that it's getting pretty exciting," Schofield said.

CAPTION(S):

One of two enclosures at the Laser Interferometer Gravitational Wave Observatory designed to protect laser tubes. Scientists hope to detect a gravity wave. University of Oregon researcher Robert Schofield: `All we are is a very fancy measuring device.' Help wanted: Science fans sought to help crunch numbers / A9 Chris Pietsch / The Register-Guard Scientist Robert Schofield of the University of Oregon is working to increase the sensitivity of LIGO's measurements. Stephanie Barrow / The Register-Guard Chris Pietsch / The Register-Guard The Laser Interferometer Gravitational Wave Observatory, or LIGO, cost $300 million to build and takes $20 million annually to maintain.