A technician inspects one of the US laboratory's core optics (mirrors) by illuminating its surface at different angles.Caltech / MIT / Ligo LAB
News that elusive gravitational waves - tiny ripples in the fabric of space-time caused by violent astronomical events - have been observed for the first time has been hailed in China.
The discovery, made by the advanced Laser Interferometer Gravitational-wave Observatory in the US, confirms the last outstanding prediction made in Albert Einstein's General Theory of Relativity.
After months of speculation, scientists from the Advanced LIGO project confirmed they had detected gravitational waves caused by two black holes merging about 1.3 billion years ago.
Wang Junjie, an astrophysicist at the National Astronomical Observatories affiliated to the Chinese Academy of Sciences, said, "Besides the direct observation of the gravitational waves, the discovery has another two exciting aspects.
"Both the two black holes observed in this event are way larger than any stellar-mass black holes that have been observed. And it is the first time that astrophysicists have observed a pair of black holes orbiting around each other."
Gou Lijun, an expert specializing in black hole research for the observatories, said, "The surprise I got from this news was like a deaf person who was always envious of those who could hear suddenly finding that they could hear themselves.
"The direct detection of gravitational waves opens a new window for us to understand the world of physics. Even though the information provided by the US observatory is limited, there are amazing discoveries waiting to be made," Gou added.
According to Einstein's prediction in 1915, the universe is like an immense trampoline with countless celestial bodies stretching its surface - the heavier a celestial body is, the larger the ripples - which physicists call gravitational waves - it makes.
Before the discovery, every prediction from Einstein's theory had been proven by direct experimental evidence - except for the existence of gravitational waves.
David H. Reitze, executive director of the US observatory's laboratory, was quoted as saying, "Our observation of gravitational waves accomplishes an ambitious goal set more than five decades ago to directly detect this elusive phenomenon and better understand the universe. Fittingly, it fulfills Einstein's legacy after the 100th anniversary of his General Theory of Relativity."
British scientist Stephen Hawking said on his Facebook account, "It is thrilling to see predictions I made over 40 years ago ... being observed within my lifetime."
Before the discovery, the existence of gravitational waves had only been demonstrated by circumstantial evidence of observed in 1970s and 80s, which was awarded the Nobel Prize in Physics in 1993.