It swept over the Earth in thousandths of a second, sending a tiny jiggle through the planet — but it cracked open what scientists are calling a new window on the universe.
US researchers announced Thursday that they have confirmed the existence of gravitational waves, something Albert Einstein predicted in his theory of relativity a century ago. The collision of two black holes 1.3 billion years ago shook the fabric of space and time so violently that the ripples were picked up by specialized observatories in Washington state and Louisiana on Sept. 14, California Institute of Technology physicist David Reitze told reporters.
"What's going to come now is we're going to be able to hear more of these things," said Reitze, the director of the Laser Interferometer Gravitational-Wave Observatory, or LIGO. "And no doubt we'll hear things we expected to hear … but we will also hear things that we never expected."
Yes, hear. The wave that LIGO observatories picked up left behind an audible signal that scientists played for reporters at a news conference in Washington.
"That is one of the beautiful things about this," said Gabriela Gonzalez, a professor of physics and astronomy at Louisiana State University. "We are not only going to be seeing the universe, we are going to be listening to it."
Lawrence M. Krauss, a theoretical physicist and head of the Origins Project at Arizona State University, said Thursday's "spectacular" announcement may allow scientists to peer into things like the edge of a black hole, "where there's a lot of open questions about what may happen."
"It will undoubtedly allow us to see into areas we wouldn't be able to see otherwise," Krauss said. "It's the astronomy of the 21st century, and where it goes is anyone's guess. But its significance is comparable to when we first opened up the telescope, or maybe when we first began to look at the sky with radio waves."
Scientists had observed the effects of gravitational waves only indirectly before now, Krauss said.
The LIGO stations are the most precise measuring devices ever built, using mirrors to bounce a laser beam down an L-shaped system 4 kilometers (2.5 miles) long. A gravitational wave would distort space-time over that by "a tiny, tiny fraction" of the size of a proton, Gonzalez said — but enough to be picked up by the system.
That effect appeared first at the LIGO station in Livingston, Louisiana. It was detected seven thousandths of a second later at the station in Hanford, Washington, confirming the effect, Gonzalez said.
The wave they picked up was unleashed when two black holes — collapsed stars less than 100 miles wide, with gravitational fields so powerful, light can't break out — slammed into each other. The collision happened at half the speed of light, and resulted in the release of a burst of energy equivalent to the complete annihilation of three suns.
LIGO co-founder Kip Thorne said the discovery will allow scientists to view the universe in a new dimension, going beyond the electromagnetic spectrum of light and radiation that's guided astronomy up to now.
"Each time a new window has been opened up, there have been big surprises," said Thorne, also a physicist at Cal Tech. "The universe seen though optical telescopes was very serene. The universe seen through radio telescopes and X-ray telescopes is tremendously violent. Gravitational waves are so radically different from electromagnetic waves that I think we can be rather sure that we will see big surprises."
The announcement caps a 40-year effort to detect gravitational waves. In 2014, scientists hoped they had discovered them in what they were calling an echo of the Big Bang, the sudden, rapid expansion of the universe.
NASA poured a bit of cold water on the prospect in early 2015, reporting that data from two other observatories — one based in space, the other on Earth — failed to pick up the signal. But it said the effort gave researchers a better idea of what that signal should look like, which would help future searches.
"This was truly a scientific moon shot, I believe, and we did it," Reitze said. "We landed on the moon."
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