First, there was light. Then, there was sound. Gravitational waves have reverberated across the universe and registered on planet Earth. Astrophysicists at the two Laser Interferometer Gravitational-Wave Observatories (LIGO) in Louisiana and Washington recorded the waves, also known as gravitational radiation or “chirps,” on September 14, 2015 around 2:30 am PST. However it took several months of double-checking testing methods to confirm that massive gravity waves can traverse, shape and warp the fabric of space-time. This marks the first time in history that space-time alterations have been detected by LIGO teams and confirms Albert Einstein’s general theory of relativity.
For centuries, astronomers could only see light emanating from the cosmos. Now, however, astronomers can also hear gravitational waves coming from deep in the universe. The event that registered at LIGO was a collision located approximately 1.3 billion light years away from Earth. With LIGO’s data from mid-September, astronomers and physicists will be able to determine the mass, timing and rough location of the merging bodies—in this case, two super massive binary black holes.
“What LIGO saw is actually pretty stunning,” said Seattle Central College Astronomy Instructor Doug Faust. “We have two LIGO detectors, so in the same way you can echolocate something with two ears, LIGO can pinpoint the origin of the gravitational wave. The two detectors were able to roughly locate it, and it came from somewhere in the Southern Sky about where the Magellanic clouds are.”
In an unprecedented stroke of luck, the gravitational waves were detected shortly after a $200 million upgrade of the LIGO facilities’ laser light projection. This upgrade increased LIGO’s quantum-limited sensitivity, which is the laser power increasing from the initial value of 10 Watts to just underneath 200 Watts, in turn enhancing sensitivity and accuracy from one thousandth of a proton to one ten thousandth of a proton.
Researchers can rule out the possibility that the waves were a mere blip registered from geological activity, or the result of a semi truck rolling by on the nearby freeway, because the event was recorded by two independent stations. The two LIGO locations are two thousand miles apart—and when traveling at the speed of light approximately seven milliseconds in time—and according to Faust, the Louisiana site received the signal first.
As the waves reach Earth, they gently wobble our planet. “Gravity isn’t this weird mysterious force. What’s actually happening is each celestial body is curving space-time,” said Faust. “The frequencies LIGO is built to hear are characteristic of really compact objects doing really exotic things. Like in this case, two moderately size black holes, one eating the other one—which is weirdly tame as far as the universe’s standards go. But these things happen in the course of a fraction of a second.”
The exciting announcement is the culmination of one hundred years of research, theory and study, dating back to Albert Einstein’s publication of “The Foundation of the Generalized Theory of Relativity” in 1916. When originally published, Einstein’s theory was so ahead of its time, it took 60 years for the first gravitational wave detection prototypes to be developed.
Currently, the machines in Washington and Louisiana are the most sensitive in the world. However a new gravitational wave detector, the Laser Interferometer Space Antenna (LISA), is under consideration in Europe. Despite plans to use similar laser detection technology as LIGO, LISA is expected to be much more reliable and sensitive because it will be space-based: orbiting around Earth’s atmosphere instead of being stuck on the—relatively shaky and noisy—ground.
While the future of gravitational wave detection may be up in the air, one thing is for certain: the LIGO data thrilled researchers and astrophysicists around the world. Faust claims the entire Seattle University Department of Physics partied while he was being interviewed. The LIGO team’s press conference was quickly shared throughout social media and even dominated international news reports.
For millennia, humanity has sought new methods to cultivate observation and scientific explanation for astronomical phenomena. Humans on planet Earth have always been fascinated with seeing deeper into space, but now, for the first time, we can hear it too.
By Jack Pappin