By Lauren Puckett
WASHINGTON, D.C – Colliding black holes have a heartbeat. It just took scientists 1.3 billion years to hear it.
Fresh from the announcement Feb. 11 that researchers had detected gravitational waves, ripples in spacetime itself, a triumphant Gabriela González appeared at the AAAS Global Science Engagement in Washington, D.C. February 12. González, spokesperson for the LIGO Scientific Collaboration and a professor of physics and astronomy at Louisiana State University, has spent years working with the Laser Interferometer Gravitational-Wave Observatory (LIGO), scouting for undulations in spacetime.
As she explained the implications of such a discovery, González played an audio clip of the gravitational waves hitting Earth. The noise only lasted a moment, but the sound was undeniable: a low thump, as if someone had dropped a heavy box on a wooden floor. Then, after increasing the frequency, she played it again: this time, a higher-pitched blart.
Grinning, González repeated the clip. “Isn’t it amazing?” she asked the audience. “I can’t stop playing it.”
González explained the waves were created by a collision of two black holes. The black holes circled one another, picking up momentum, until they finally slammed together while nearing the speed of light. At the last fraction of a second, waves burst from the gravitational fields, immediately before the two joined to form one humongous black hole.
LIGO scientists estimate these black holes were about 29 and 36 times, respectively, the mass of the sun, according to a LIGO press statement, and that this catastrophic crash happened around 1.3 billion years ago. Ever since then, those waves – equalling three times the mass of the sun – have been hurtling through the universe.
Earth finally recorded them on Sept. 14, 2015, first at the LIGO detector in Livingston, Louisiana, and seven milliseconds later at the detector in Hanford, Washington. This finding was announced to much fanfare on Thursday and published in the journal Physical Review Letters.
González explained that what makes this finding so incredible is what it means.
There was a time many people didn’t believe in black holes, González said. While the collision of black holes had been predicted, it had never been observed until now, according to a LIGO press statement.
These waves not only give the world unequivocal evidence that black holes exist, but they confirm a prediction of a famous figure of physics: Albert Einstein.
“Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” Caltech’s David H. Reitze, executive director of the LIGO Laboratory, said in a press statement.
Einstein’s theory describes the effect of mass changing to energy through the equation E=mc^2. First-hand observations of black hole mass converting into energy (gravitational waves) are a powerful testament to Einstein’s work.
“It would have been wonderful to watch Einstein’s face had we been able to tell him,” said Rainer Weiss, professor of physics, emeritus, at MIT, in a press statement.
Einstein doubted any instrument could ever detect gravitational waves, according to a LIGO press release.
At each observatory, a LIGO detector measures minuscule changes in the time it takes a laser to bounce between mirrors housed inside 4-kilometer long chambers. The detector recorded the teeny tiny tremors made as gravitational waves passed through. And to get a better idea of just how tiny: Scientific American reported that the change is “smaller than one ten-thousandth the diameter of a proton, or less than a size of a soccer ball compared with the span of the Milky Way.”
This discovery not only supports the understanding of gravity, but it opens the door to all sorts of exciting aerospace adventures.
“You will be hearing about this data every year,” González said. “This is a new window to the universe.”