Sound of gravity, a middle C, vindicates Einstein
● Expressing joy over the historic detection, PM Modi said, ‘ Immensely proud that Indian scientists played an important role in this challenging quest’
Scientists said on Thursday they have for the first time detected gravitational waves, ripples in space and time hypothesised byphysicist Albert Einstein a century ago, in a landmark discovery that opens a new window for studying the cosmos.
The researchers said they detected gravitational waves coming from two black holes — extraordinarily dense objects whose existence also was foreseen by Einstein — that orbited one another, spiraled inward and smashed. They said the waves were the product of a collision between two black holes 30 times as massive as the Sun, located 1.3 billion light years from Earth.
The scientific milestone, announced at a news conference in Washington, was achieved using a pair of giant laser detectors in the United States, located in Louisiana and Washington, capping a long quest to confirm the existence of these waves.
The announcement was made in Washington by scientists from the California Institute of Technology, the Massachusetts Institute of Technology and the LIGO scientific collaboration.
Like light, gravity travels in waves, but instead of radiation, it is space itself that is rippling.
Detecting the gravitational waves required measuring 2.5- mile ( 4 km) laser beams to a precision 10,000 times smaller than a proton.
[ The New York Times quoted a scientist as saying that the cosmic chirp rose to a middle C note.]
The wave that made history snuck up on them. David Shoemaker will never forget the date — September 14, 2015 — when he woke up to a message alerting him that an underground detector had spotted a 1.3- billion- yearold ripple in the fabric of space- time.
A gravitational wave, predicted to exist a century ago by Albert Einstein, had been glimpsed directly for the first time by a pair of US- based detectors. “It is seared in my brain,” said Shoemaker, a top scientist at the Massachusetts Institute of Technology and head of the Advanced LIGO Project, an international effort to uncover evidence of gravitational waves. Such waves are a measure of strain in space, an effect of the motion of large masses that stretches the fabric of space- time, a way of viewing space and time as a single, interweaved continuum. The “chirp,” as Shoemaker described the long- awaited wave, had arrived while he was asleep. But since the data analysis works in quasi- real- time, scientists watching the data stream early in the work day in Europe saw it immediately. Two black holes spiralling into each other became a single black hole, and the joining of these two giants curved the fabric of space- time around them, ever so briefly. “When the signal finally got to the Earth on September 14 we knew within three minutes that our instruments had seen something really different,” said Shoemaker.
“I was sitting at home, with a cup of coffee in my hand and opening up my email at around 7 am,” he told AFP. An instant message had arrived from a close colleague in Germany. The message said: “I think we are in trouble now,” he recalled. But Shoemaker, a leading scientist in the search for gravitational waves since the early 1980s, did not leap out his chair or shout expletives. He just took a deep breath. “My immediate reaction was, ‘ That’s fascinating. Let’s see what the instruments did wrong.’” In fact, the team had only just turned on the pair of underground detectors, one in Louisiana and one in Washington state, for a series of final checks before formally starting the observation experiment, which would run from mid September until January. “It was just at the beginning of this run, when we were all ready to go, to press the button to start the observing run, that the gravitational wave was observed,” he said. “So it was a very exciting moment for us and it took us perfectly by surprise.” Immediately, Shoemaker and colleagues began running through a checklist of possible failures. One by one, they ruled out electromagnetic storms, lighting strikes, earthquakes, or interference by people near sensitive parts of the instruments. Further- more, the timing matched up. The detector in Hanford, Washington picked up the signal 7.1 milliseconds after the Livingston, Louisiana instrument, some 1,800 miles away. “The travel time of light between the two instruments is 10 milliseconds,” said Shoemaker.