After decades of searching, scientists Thursday announced they have directly detected gravitational waves for the first time, caused by a cosmic clash of black holes so violent that its shock waves rippled the ethereal fabric of space and time across a billion light years of distance.
Confirming rumors roiling the scientific world for months, the scientists said their find verifies an unproven portion ofEinstein’s Theory of General Relativity and, because the waves are largely unimpeded by matter, offers a new way for astronomers to probe hidden recesses of the universe. Einstein first predicted the existence of gravitational waves in 1916.
“It is one of the most spectacular verifications of Einstein’s theory,” said Columbia University astrophysicist Zoltan Haiman, who wasn’t involved in the research effort. “This is like a new window into the universe.”
The team of more than 1,000 researchers in 15 countries, led by scientists at the California Institute of Technology and the Massachusetts Institute of Technology, published their work in Physical Review Letters. The scientists discussed their work Thursday at a news conference convened by the National Science Foundation in Washington, D.C., which has spent $1.1 billion on the effort over the past 40 years.
“They picked up this minute tremble in space, but it is totally shaking up the field of science,” said physicist Robbert Dijkgraaf, director of the Institute for Advanced Study in Princeton, N.J., where Einstein once worked. “It is confirming the ideas of one of the most brilliant minds that ever lived.”
By Einstein’s reasoning, any object with mass warps the curvature of space and time, like a bowling ball on a trampoline. It stirs space and time, generating waves that radiate at the speed of light.
The hunt for evidence of gravitational waves has consumed researchers world-wide for decades. Princeton University researchers in 1993 won a Nobel Prize for their discovery of an unusual pulsar star that offered indirect evidence of gravitational waves. In 2014, astronomers at the Harvard-Smithsonian Center for Astrophysics announced they had spotted gravitational waves from the earliest moments of the universe. Within a year, they had to admit they were wrong.
In the work announced Thursday, researchers said they detected gravitational tremors from a pair of spiraling black holes about 1.3 billion light years away from Earth. To do so, they used an elaborate measuring device called the Laser Interferometer Gravitational-wave Observatory, or LIGO. It is composed of two mammoth laser installations—one set in Hanford, Wash., and the other in Livingston, La.—operating in tandem to cross-check their results.
The LIGO detectors measure how long it takes controlled laser light to travel between suspended mirrors. Passing ripples in space-time alter the distance measured by the light beam, causing the amount of light falling on the LIGO photodetectors to vary infinitesimally.
As originally designed, the detectors could detect distortions in local space-time as small as 1/1000th of the diameter of a proton—equal to measuring the distance from Earth to the nearest star outside the solar system to within the width of a human hair. But even that precision wasn’t enough to capture the faint perturbations caused by gravitational ripples.
After searching fruitlessly for a decade, researchers shut down the LIGO installations for a redesign in 2010. They renewed the search last fall after a $200 million overhaul to boost the detectors’ sensitivity.
Last September 14th, they detected the waves generated by the paired black holes as they crushed together and merged into a single black hole, the researchers said.
In that moment, they released 50 times the energy of all the stars in the universe put together. That event “created a violent storm in the fabric of space and time, a storm in which the shape of space was bent this way and then that way,” said Caltech theoretical physicist Kip Thorne, a co-founder of the LIGO project.
Astronomers hope to use gravitational waves to probe some of the most mysterious objects in the cosmos. As they travel, gravitational waves stretch and compress space, encoding the physics of the event that produced them. They can be translated into signature sounds.
“This discovery will illuminate what we can learn about merging black holes, neutron stars and other exotic astronomical phenomena that raise so many questions about the evolution of our universe,” said NSF director France Córdova, who is herself an astrophysicist.
Gravitational waves from the merger of black holes, neutron stars or other massive objects would produce a chirp much like the increasing pitch of a slide whistle, the researchers said. Those likely produced by supernovae or gamma ray bursts produce telltale pops and crackles. The oldest—relics of the Big Bang—simply sizzle.
“Not only can we explore the universe with neutrinos and cosmic rays, see it with light across a huge range of wavelengths, but we can now hear it too with gravitational waves,” said Caltech physicist Chiara M. F. Mingarelli, who studies them. “Imagine hearing the universe for the first time.”