A visual of gravitational waves from two converging black holes is depicted on a monitor as Interferometer Gravitational-Wave Observatory (LIGO) Exectutive Director David Reitze speaks during a news conference at the National Press Club in Washington
It was just a tiny, almost imperceptible “chirp,” but it simultaneously opened humanity’s ears to the music of the cosmos and proved Einstein right again.
In what is being hailed as one of the biggest eureka moments in the history of physics, scientists announced last week that they have finally detected gravitational waves, the ripples in the fabric of space and time that Einstein predicted a century ago.
The news exhilarated astronomers and physicists. Because the evidence of gravitational waves is captured in audio form, the finding means astronomers will now be able to hear the soundtrack of the universe and listen as violent collisions reshape the cosmos.
It will be like going from silent movies to talkies, they said.
“Until this moment, we had our eyes on the sky and we couldn’t hear the music,” said Columbia University astrophysicist Szabolcs Marka, a member of the discovery team. “The skies will never be the same.”
An all-star international team of astrophysicists used an exquisitely sensitive, USD1.1 billion set of twin instruments known as the Laser Interferometer Gravitational-wave Observatory, or LIGO, to detect a gravitational wave generated by the collision of two black holes 1.3 billion light-years from Earth.
“Einstein would be beaming,” said National Science Foundation director France Cordova.
The proof consisted of what scientists called a single chirp —
in truth, it sounded more like a thud — that was picked up on Sept. 14. Astronomers played the recording at an overflowing news conference last week.
“That’s the chirp we’ve been looking for,” said Louisiana State University physicist Gabriela Gonzalez, scientific spokeswoman for the LIGO team. Scientists said they hope to have a greatest hits compilation of the universe in a decade or so.
Some physicists said the finding is as big a deal as the 2012 discovery of the subatomic Higgs boson, known as the “God particle.” Some said this is bigger.
“It’s really comparable only to Galileo taking up the telescope and looking at the planets,” said Penn State physics theorist Abhay Ashtekar, who wasn’t part of the discovery team.
Physicist Stephen Hawking congratulated the LIGO team, telling the BBC: “Gravitational waves provide a completely new way of looking at the universe. The ability to detect them has the potential to revolutionize astronomy.”
Gravitational waves, postulated by Albert Einstein in 1916 as part of his theory of general relativity, are extraordinarily faint ripples in space-time, the continuum that combines both time and three-dimensional space. When massive objects like black holes or neutron stars collide, they generate gravitational waves that stretch space-time or cause it to bunch up like a fishing net.
Scientists found indirect proof of gravitational waves in the 1970s by studying the motion of two colliding stars, and the work was honored as part of the 1993 Nobel Prize in physics. But now scientists can say they have direct proof.
“It’s one thing to know sound waves exist, but it’s another to actually hear Beethoven’s Fifth Symphony,” said Marc Kamionkowski, a physicist at Johns Hopkins University who wasn’t part of the discovery team. “In this case, we’re actually getting to hear black holes merging.”
In this case, the crashing of the two black holes stretched and squished Earth so that it was “jiggling like Jell-O,” but in a tiny, almost imperceptible way, said David Reitze, LIGO’s executive director.
The dual LIGO detectors went off just before 5 a.m. in Louisiana and emails started flying. “I went, ‘Holy moly,'” Reitze said.
But the finding had to be verified, using such means as conventional telescopes, before the scientists could say with confidence it was a gravitational wave. They concluded there was less than a 1-in-3.5-million chance they were wrong, he said.
LIGO technically wasn’t even operating in full science mode; it was still in the testing phase when the signal came through, Reitze said.
“We were surprised, BOOM, right out of the box, we get one,” Reitze said.
Reitze said that given how quickly they found their first wave, scientists expect to hear more of them, maybe even a few per month.
Detecting gravitational waves is so difficult that Einstein figured scientists would never be able to hear them. The greatest scientific mind of the 20th century underestimated the technological know-how of his successors. By Seth Borenstein, AP Science Writer
From left: Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration Spokesperson Gabriela Gonzalez, and Laser Interferometer Gravitational-Wave Observatory (LIGO) Co-Founders Rainer Weiss and Kip Thorne, applaud during a news conference at the National Press Club in Washington
faq: just what are einstein’s gravitational waves?
WHAT IS A GRAVITATIONAL WAVE?
Gravitational waves are extremely faint ripples in the fabric of space and time that come from some of the most violent events in the universe. In this case, it is from the merger of two black holes 1.3 billion light-years away. The way to think of this is to imagine a mesh net and visualize pulling on its ends. Those kinks are sort of like what a gravitational wave does.
WHAT IS SPACE-TIME?
Space-time is the mind-bending, four-dimensional way astronomers see the universe. It melds the one-way march of time with the more familiar three dimensions of space.
General relativity says that gravity is caused by heavy objects bending space-time. And when massive but compact objects like black holes or neutron stars collide, their immense gravity causes space-time to stretch or compress.
HOW IS THIS “HEARING” THE COSMOS?
Scientists mostly use the word “hear” when describing gravitational waves, and the data does, in fact, arrive in audio form. The researchers can don headphones and listen to the detectors’ output if they want. To prove they found a gravitational wave, the researchers played a recording of what they called a chirp.
HOW CAN THEY BE CERTAIN THIS IS REAL?
Astronomers sat on the discovery for nearly five months, since Sept. 14, checking back and forth to make sure it was right. They considered all sorts of Earth-bound interference or noise, examined the possibilities and eventually dismissed them.
The astronomers are so cautious that they routinely have other scientists deliberately inject false data to test their abilities. In those tests, the observatory team was able to show that the injected data wasn’t real. In the case of the discovery announced last week, they are extra certain they are not seeing injected or hacked data because the system that allows false information to be inserted was down at the time.
In addition, the team of 1,004 scientists on the project looked over the data, and the results were then peer-reviewed by even more experts and published in the journal Physical Review Letters.
WHAT’S NEXT?
Expect more waves. It could be as many as a few a month or as little as a few per year. The observatory is also being further upgraded to hear even fainter, more distant waves.
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