That’s right, friends, like all of our troubles, gravity comes in waves. For us earthlings they are so subtle that we don’t feel them and so on Earth gravity seems comfortably stable. Far out in space though, black holes and neutron stars spiraling out of control produce waves in the gravitational field which astrophysicists believe we will soon be able to detect. In the fantastic realms of the universe, orbiting bodies and cataclysmic supernovae are causing the rubbery fabric of space-time to quivering.
My wife, Stephanie, and I traveled to the LIGO Hanford Observatory on the Hanford Nuclear Reservation for the February 28 public drop-in tour and March 1 Family Science Day. These events to promote science education remind us that the scientists are reaching out in the spirit of learning. Our Plowshare friends hope to change nuclear weapons for peaceful use of resources. Notice! This is what has begun to happen at Hanford!
One of the world’s great scientific experiments is right here in Washington state. LIGO stands for Laser Interferometer Gravitational-Wave Observatory. Their website says, “[LIGO] is an instrument for sensing the presence of matter, whether shining or dark, in the distant reaches of the cosmos.” The project, funded by the National Science Foundation , is jointly operated by the California Institute of Technology and Massachusetts Institute of Technology.
Gravity is so familiar that we rarely think about it. “Down” means toward the center of the Earth, “up” is directly away from the center. The Moon and other satellites orbit Earth in the same way that Earth orbits the Sun. When I throw a baseball up, guess what it will end up doing? As the Earth makes its way around the orbit, the gravity field changes with the Earth’s changing position. Scientists speculate that the changing gravity field sends waves outward from here at the blazing speed of light. However, LIGO won’t measure waves from mild processes such as planetary orbits; only high mass, high acceleration events like black hole mergers. Only high frequency waves will register on LIGO machines.
High frequency waves are so delicate and subtle that no experiment has yet to measure them. We can infer the effect a gravitational wave will cause because of the tides on Earth, which is so familiar to us here in Olympia. The tide results from the Earth spinning under the alternating pull of gravity from the Moon and Sun. But other stars and planets are so far away that we would need a very sensitive detector. A great collaboration among scientists have built the device called LIGO at the Hanford site, and a twin facility at Livingston, Louisiana, which is on the brink of making this long sought measurement. If you have surplus computing power you may even participate in this adventure with the Einstein@home project where volunteers help analyze the collected data.
There are a few other detectors and teams around the world that form a (sort of) network. The European Space Agency is making a gravitational wave detector for outer space that will cover lower frequency wave events and is expected to be more sensitive and certain to get that measurement.
The best sources of gravitational waves are massive objects in rapid orbits. Astronomers are confident that neutron stars and perhaps black holes in close orbit create strong gravitational waves. In addition, supernova explosions, thought to emit a pulse may actually produce some type of gravitational wave. The Nobel Prize in physics in 1993 was awarded to Russell Hulse and Joe Tyler for finding a pair of neutron stars, one of which is a pulsar, in close orbit which are spiraling inward toward eventual collision. Using Albert Einstein’s equations of Relativity, scientists have calculated the energy of these waves and they expect that LIGO is close to sensing them.
Dale Ingram was our tour guide of this wonderful facility and he is a great spokesperson for the project. With a small group (six other visitors) we were shown around the entire place. Because LIGO is nearing the end of a tremendous upgrade, some components left from the initial science run are displayed around the visitor center for guests to study. Magnificent isolation tables steady the apparatus from earthly vibration and some extraordinary mirrors are there to see. We toured the clean room where instruments are being prepared at a fantastic degree of cleanliness. And we spent time in the brilliant control headquarters (like being aboard the bridge of the Starship Enterprise) where myriad of scientists were busy at testing the upgrade status. Even the lunch room was full of science demos and the air of professionalism of the whole place was the best I’ve ever seen—the Washington LIGO is a hub of astronomy at its finest.
At my request a veteran LIGO scientist made time for an interview and he enthusiastically described the project to Stephanie and me. Micheal R. Landry, Ph.D., explained the project from a knowledgeable perspective. Though the science of gravitational wave astronomy is well explained on the LIGO website, to meet a lead scientist who has dedicated his career to making sense of the world was a great honor (he even helped edit this copy and drew on his chalk board for us!) I paraphrase some of his answers here:
What is the economic value of this experiment?
“The manufacture of the finest quality instruments in the world creates work for an engineering industry that is a worldwide collaboration. The Hanford site—once a production area for nuclear weapons–now serves as one of the production areas for LIGO’s quest for new knowledge. This work is primarily driven by curiosity and physics so we may understand the universe better. This additional window into the cosmos makes for better astronomy.”
Isn’t University of Washington involved?
“There is an excellent gravity group at University of Washington which is working on its own short range gravity measurement experiment. That device is testing the universal constant of gravity to refine its known value and for modifications to Newtonian gravity. Their work compliments ours but is a separate operation.”
Has India recently joined the LIGO group?
“Here at Washington LIGO we are building an additional set of devices for the nation of India which is planning to set up the detector and join the network. Having another detector at a distant location will help triangulate the signals so we can better pinpoint wave sources in the sky. The distance also helps us separate seismic and other local noise sources from actual gravitational waves.”
How certain are we of detecting waves soon?
“Our upgrade is nearing completion; the new device, called Advanced LIGO is ten times more sensitive and as we continue to refine the device our detection power continues to improve. Depending on the mass and distance to some in-spiraling neutron stars the theory predicts wave strength close to our ability. As they are about to collide the signal strength increases to a chirp. When we will detect these chirps we can inform optical astronomers where to look in the sky to observe exciting events. Later this year we expect to begin test operations of the Advanced LIGO. These experiments are valuable tests of our understanding of nature according to General Relativity.”
Thank you, Mike and Dale and all the staff at the LIGO Hanford, for the hospitality and time. Saturday, March 1, we returned to attend the special event, Family Science Day. Some twenty volunteers gave demonstrations around the facility of the scientific principles being tested. I was excited to see many of these volunteers were local high school students. The crowds of visitors (two to four hundred guests) were local families with children of all ages enjoying the hands-on exhibits and interaction with science enthusiasts. It was a festive learning experience of the highest order. The sincere researchers at LIGO are trying to make a difference in the lives of people.
The specter of nuclear history and background radiation did not deter these brave people. The LIGO Hanford holds accessible, free public tours one Friday and one Saturday each month, several special public events throughout the year, and additional group tours available by appointment. The scenic drive from Olympia is around 250 miles and the considerate professionalism of the staff made this tour a memorable learning experience. We wish the scientists the best of luck in their upcoming science run. Lee Smolin in his latest book Time Reborn claims “Unprecedented measurements [may] not be governed by any prior law.” The folks at LIGO have done their homework, I’d bet they are on the brink of finding out.
And, extra special thanks to Works in Progress for supporting science learning and citizen journalism in our community.
Russ Frizzell is an activist living in Olympia since 2010 and a graduate of The Evergreen State College where he studied Physics and Cosmology.