The landmark discovery of the first direct evidence of gravitational waves or ripples in space-time, which Albert Einstein predicted a century ago, will enable mankind to listen to the stars, and not just see them, scientists say.
In a breakthrough announcement, scientists from the Laser Interferometer Gravitational Wave Observatory (LIGO) said that they have finally detected the elusive gravitational waves, the ripples in the fabric of space-time.
Studying gravitational waves will push Einstein's General Theory of Relativity - which originally predicted their existence almost exactly a century ago - to its limits, while revolutionising our understanding of the most violent events in the universe, according to researchers at Massachusetts Institute of Technology Kavli Institute for Astrophysics and Space Research (MKI).
The LIGO project started its first observing run in 2002. Following major upgrades begun in 2010, LIGO re-opened as "Advanced LIGO" in September 2015 and detected its first gravitational waves within days.
Analysis of the waves suggests they originated from a system of two black holes, each with the mass of about 30 Suns, that gravitationally drew closer to each other.
The dense objects whipped up to nearly the speed of light before colliding, sending out a stupendous release of gravitational wave energy that eventually reached the Earth, 1.5 billion light years away.
As the gravitational waves warped space-time within LIGO's gargantuan twin detectors, its exquisitely sensitive instruments registered vibrations on the order of thousands of the diameter of a proton.
The frequency of these waves that LIGO is designed to catch are actually in the audible range for humans.
Accordingly, the signal LIGO received of the black hole merger was played on speakers for eager scientists.
"For this binary black hole system, it made a distinctive, rising 'whoooop!' sound," said Matthew Evans, an assistant professor at Massachusetts Institute of Technology (MIT).
"This detection means that the stars are no longer silent. It's not that we just look up and see anymore, like we always have - we actually can listen to the universe now. It's a whole new sense," Evan said.
To date, virtually all of our knowledge of the cosmos has come from observing electromagnetic radiation, better known as light, including radio waves, visible light and gamma rays.
Now, with the advent of gravitational wave astronomy, otherwise invisible phenomena, such as the black hole system captured by LIGO, will be accessible.
"We could point the best telescopes, sensitive to more or less any electromagnetic wavelength of light, at this system and probably see nothing," said Nergis Mavalvala, a professor of astrophysics at MIT.
"We cannot observe this system with any of the other fundamental forces of nature. It has to be gravity," Mavalvala said.
