Catching Waves: LSU Scientists, Students Play Major Role in Groundbreaking Gravitational Wave Research
 The Louisiana LIGO facility is located in a remote, flat location, relatively isolated from man-made noise. It has two massive, two-and-a-half mile long arms that form an “L” shape and contain steel pipes emptied of air. Laser light traveling through these arms is used to measure changes in the curvature of space. |
If a tree falls in the woods and no one hears it, does it make a sound?
Most people have heard this well-worn philosophical question, but there is a new variation that may not be as familiar: If black holes collide in deep space, can it be heard in the woods of Livingston Parish, LA?
As it turns out, scientists from LSU, the California Institute of Technology, and several other universities may have an answer to this new question someday soon.
Some 24 miles from the LSU campus, in a location that could be called “off the beaten path,” the sprawling facility known as the Laser Interferometer Gravitational-Wave Observatory, or LIGO, sits on a massive tract of land, hidden from public view by acres of dense forest.
In this unlikely location, researchers and technicians from a group called the LIGO Scientific Collaboration spend their days on the cutting edge of scientific discovery, monitoring parts of the universe that are unquestionably “off the beaten path.” Using lasers rather than telescopes, the staff of this unusual observatory “listens” to the heavens, waiting to “hear” something that will set the scientific world on its ear — gravitational waves.
Produced by violent events in the distant universe, gravitational waves are “ripples” in the fabric of space and time. Though the concept may sound like something from Star Trek, it actually comes from the mind of Albert Einstein, who predicted the existence of these waves in the early 20th century as part of his theory of general relativity.
(left to right) Louisiana State Rep. Dale Erdey, District 71; State Sen. Clo Fontenot, District 13; Gabriela Gonzalez, associate professor of physics at LSU; Joseph Giaime, chief scientist at LIGO and associate professor of physics at LSU; and LSU Chancellor Sean O’Keefe stand on top of the massive LIGO Louisiana facility. |
According to current scientific thought, the waves are the product of massive cosmic events, such as the collision of black holes or shockwaves from the center of supernova explosions. Like waves in a gigantic pond, these ripples in space-time fabric travel toward Earth, carrying information on the very nature of gravity.
“The places in the universe where gravitational waves are emitted, are the most ‘wild’ and interesting,” said Joseph Giaime, LSU associate professor of physics and astronomy and Chief Scientist at LIGO. “Gravity is so strong there that it is twisting spacetime around and things don’t behave in the way we are used to or taught. Thus, Einstein’s theories become necessary (for understanding the phenomena).”
Nevertheless, despite a large amount of scientific evidence supporting their existence, no one has ever actually detected one of these gravitational waves.
That is where the LIGO team comes in, working not only to unravel the mysteries of space, but also, in effect, prove a crucial part of Einstein’s theory.
“It’s absolutely exciting science,” said Giaime. “It’s right here in our back yard and LSU students, faculty, and employees are fully involved.”
What is LIGO?
The LIGO team spends its days trying to unravel the mysteries of space and, in effect, to prove a crucial part of Einstein’s theory of general relativity. |
The LIGO project, first conceived in the 1970s and supported by a grant from the National Science Foundation, is the brainchild of researchers from the California Institute of Technology and the Massachusetts Institute of Technology. A large and growing group of other universities are taking part in the project. This group is known as the LIGO Scientific Collaboration, and LSU is a charter member.
In addition to the LIGO facility located in Livingston Parish, there is another facility in Hanford, WA. Essentially, the two facilities work hand-in-hand as a “single” observatory.
The concept behind the project is based on the effects of gravitational waves. Basically, the waves “warp” space, stretching it in one direction and shrinking it in another. Giaime explained that the LIGO facilities use a process called laser interferometry to detect the tiny changes in the shape of spacetime that occur when gravitational waves pass through the planet.
The detection process involves a laser located in LIGO’s central building that shoots a beam into a splitter. The splitter divides the beam into two identical beams that are fired down two, two-and-a-half mile arms. The beams are bounced back and forth using a system of carefully suspended mirrors and eventually, the two divided beams are recombined into one. Gravitational wave interference in that recombination, as measured by a photodetector, exposes tiny changes in LIGO’s arm lengths
LSU and Gravitational Wave Study
 (View larger image.) |
LSU has been a key player in the LIGO research project for some time, and much of the credit goes to Physics and Astronomy Professor Warren Johnson and Physics Professor Emeritus William Hamilton. These two LSU researchers have been leaders in gravitational-wave-detection research for decades.
Long before the construction of LIGO began, Hamilton and Johnson began developing a wave-detection device of their own. That device is a two-ton, gravity-wave bar antenna known as ALLEGRO, which is one of only five such gravitational-wave detectors in the world and is still located on LSU’s campus.
While Hamilton and Johnson worked to develop the ALLEGRO device, they also became involved in the early stages of the LIGO project. Together with then-LSU Chancellor James Wharton, they were integral in ensuring that one of the LIGO observatories would be built in Livingston Parish.
As part of its involvement in LIGO, LSU’s Physics and Astronomy department began to build a strong group of faculty focused on the experimental and theoretical study of gravitational issues.
On the experimental study side, there is Giaime, an MIT graduate who helped design and install parts of the LIGO detector system. He was named “Chief Scientist” at the Livingston location late last year. In addition, there is Gabriela Gonzalez, who previously worked on the LIGO project at MIT. She specializes in analyzing the data collected by the LIGO detectors and co-chairs one of the LIGO Collaboration’s data-analysis working groups.
LSU’s group of faculty focused on the theoretical study has grown in recent years. The group is led primarily by two physicists, Jorge Pullin and Luis Lehner, who work in the field of numerical relativity. Faculty and students in this arena work to solve some of the difficult equations posed by the theory of relativity, which provides the foundation of LIGO’s research.
“LSU has pursued a harmonious approach to LIGO research, combining experiment and theory,” said Pullin. “Apart from the experimentalists working at the LIGO site, LSU has created the largest numerical relativity group in the United States.”
Other “stars” from the worlds of physics and astronomy have recently arrived at LSU, attracted in part by the proximity of the LIGO observatory. One such star is Edward Seidel, a physicist recognized worldwide for his work on numerical relativity, black holes, and high-performance computing.
“There are an increasing number of LSU people involved in the project,” said Giaime, adding that LSU students and post-doctoral researchers also work at the LIGO facility.
The Future
LIGO carried out its first observational run in 2002. Since then, there have been three additional observational runs, with the last, multi-month run being completed recently. Thus far, the efforts have not resulted in the detection of a gravitational wave.
“We don’t get to choose when the sources for our data come to us, so we need to observe as much as we can,” said Giaime.
The goal of observing more will be met next fall, when LIGO will crank up its technology again and kick off a fifth observational run. This time, however, the goal is to observe for a six-month period. After that, Giaime said, there will be continuous observation for the next several years.
Ultimately, none of the scientists know if they will ever actually detect a gravitational wave, but it doesn’t dampen their enthusiasm. The potential reward for their work is simply too great.
LSU’s Warren Johnson may sum up the attitude of the researchers best.
“We got into this because the scientific payoff, if we succeed, is so great that it’s worth spending our whole careers on it,” Johnson said, referring to his years of work with William Hamilton. “The personal payoff is knowing that we really can build this boat. Whether there’s a new world on the other side of the ocean, we don’t know, but we’re going to sail anyway. The journey alone is enough for me. That’s success.”
Contact Rob Anderson
| LSU University Relations
Highlights Team
Summer 2005
