The most recent Star Talks meeting of the Prescott Astronomy Club featured a familiar face to many Embry-Riddle Aeronautical University students. Physics professor, Michele Zanolin dropped by the Prescott Public Library on Thursday, Feb. 21 to talk about his recent research into measuring gravity waves.
The title of the presentation was aptly titled, “Is General Relativity Correct? Tests of Gravity with Gravitational Waves.” Dr. Zanolin started off explaining that the aim of his research was not necessarily to prove Albert Einstein wrong, but to learn how gravity waves act. Gravity waves have become popular in recent years since a team of scientists won the Nobel Prize for discovering evidence that indicates that gravity waves exist.
When an object moves relative to another object, according to the theory of general relativity, miniscule ripples travel through the fabric of space and time in the form of gravity waves. For instance, one object moving around another will produce gravity waves, while a spinning sphere like a planet will not. To illustrate this point, Dr. Zanolin used the example of two stars orbiting one another. According to Newtonian Physics, the two stars should stay in the same orbit around each other. However, this is not the case.
According to the theory of general relativity put forth by Einstein, the stars should emit tiny amounts of energy in the form of gravitational waves. This means that the stars will not orbit each other forever, but will one day eventually collide as their orbits grow smaller and smaller. This behavior has already been seen by telescopes looking to the stars.
Although scientists can see evidence that points to Einstein being correct, there are a number of competing theories as to how gravitons behave. One competitor with Einstein’s theory is the Brans-Dicke theory of gravitation. The formula for calculating graviton waves for the two theories is mostly similar, however, instead of there being a constant value for gravitational force between two bodies, the Brans-Dicke theory predicts that the gravitational force changes depending on where you are in the universe.
This field of study is relatively new to the scientific community because of the almost negligible effect gravity waves have on us. Until recently, the technology to measure that effect did not exist. Dr. Zanolin went on to explain his work in recent years to measure gravity waves.
His story started in the swamps of Louisiana where one of the United States’s Laser Interferometer Gravitational-Wave Observatory (LIGO) is located. The stations have a main building with pipes running for four kilometers out of adjacent sides at right angles. In the center of the facility, a single laser beam is split into two pieces and travels down each leg where, it bounces along mirrors. The laser beam eventually meets back up in the center. If nothing is affecting the beam when it meets back up, then it will cancel itself out. However, because of the small influence of gravitational waves, the beam is not destroyed, and scientists can look at the remnants to get an idea of what gravitational waves are like.
The measurements involved have to be extremely precise. The current LIGO arrays can measure the changes in the laser beam down to 10x-20 meters. To get such a precise measurement, Dr. Zanolin explained how scientists are able to sift through all of the noise caused by other radiation to find evidence of gravity waves.
The next facility that the United States will build to measure gravity waves, Advanced LIGO, should be even more precise than LIGO. It is scheduled to be ready in the next few years, and will hopefully prove the existence of gravity waves.