In a much-anticipated press conference, astronomers announced Thursday that they have found the first direct evidence of gravitational waves.
Gravitational waves — first theorized by Albert Einstein 100 years ago in his general theory of relativity — are ripples in space-time. These waves travel faster than light and are indicative of massive cataclysmic processes in our universe. Detecting them requires highly sensitive instruments such as that at the Laser Interferometer Gravitational-Wave Laboratory (LIGO), which made the announcement Thursday morning.
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“Ladies and gentlemen, we have detected gravitational waves,” said Dave Reitze, LIGO’s executive director. “We did it.”
The LIGO detectors are incredibly sensitive: they can measure a ripple in space-time by as little as 1/1,000 the diameter of a proton.
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The waves — detected on Sept. 14, 2015 — were made by two merging black holes 1.3 billion years ago. The first signal was detected by the Livingston detector and then seven milliseconds later by the Hanford detector and lasted just .2 seconds.
These plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. LIGO
These plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington.
“It’s exactly what you would expect … with two black holes spiralling into each other,” said Reitze.
After the discovery, it took months of analysis to confirm the data.
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Scientists believe that the collision occurred between two black holes about 30 times the mass of the sun, 150 km in diameter and moving about half the speed of light. The collision also proves that there are binary black holes in our universe. As the black holes merged, there was a burst of gravitational waves that took 1.3 billion years to arrive at Earth where LIGO detected the stretch in space as well as its compression.
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“That’s what we saw here. It’s mind boggling,” said Reitze.
The detectors also measured the vibrations of the waves, which produced sounds.
“It’s the first time the universe has spoken to us through gravitational waves,” Reitze said. “That’s just amazing to me.”
The collision of two black holes holes—a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO—is seen in this still from a computer simulation. LIGO
The collision of two black holes holes—a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO—is seen in this still from a computer simulation.
There is a Canadian connection to the discovery, as well: a team of astrophysicists from the University of Toronto assisted in the calculations necessary in the confirmation.
Astronomers know the general direction of the source, toward the Magellanic clouds, two neighbouring galaxies to our own, visible from the Southern Hemisphere. However, because there are only detectors with the extreme sensitivity of LIGO, they cannot pinpoint the source. That will change when the VIRGO interferometer comes online later this year.
The approximate location of the source of gravitational waves detected on September 14, 2015, by the twin LIGO facilities is shown on this sky map of the southern hemisphere. LIGO
The approximate location of the source of gravitational waves detected on September 14, 2015, by the twin LIGO facilities is shown on this sky map of the southern hemisphere.
“What’s going to come now is we’re going to hear more of these things. We will also hear things that we never expected,” Reitze said.
“This discovery has taken a long time,” said Gabriela González, LIGO spokesperson. “It’s been a very long road, but this is just the start.”
“Now we’ll begin listening to the universe.”
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