In September 2015, a vibration lasting just one-fifth of a second changed the history of physics. It was the first direct detection of gravitational waves — perturbations in the geometry of space-time that move across the Universe at the speed of light.
Astronomers say it was like gaining a new sense — as if, until 2015, they had only been able to ‘see’ cosmic events, and now could ‘hear’ them, too. Since then, it has become almost a matter of daily routine to record the passage of gravitational waves at the two massive facilities of the Laser Interferometer Gravitational-wave Observatory (LIGO) in Louisiana and Washington state, along with their sibling Virgo observatory near Pisa, Italy.
The detection of gravitational waves has provided new ways to explore the laws of nature and the history of the Universe, including clues about the life story of black holes and the large stars they originated from. For many physicists, the birth of gravitational-wave science was a rare bright spot in the past decade, says Chiara Caprini, a theoretical physicist at the University of Geneva in Switzerland. Other promising fields of exploration have disappointed: dark-matter searches have kept coming up empty handed; the Large Hadron Collider near Geneva has found nothing beyond the Higgs boson; and even some promising hints of new physics seem to be fading. “In this rather flat landscape, the arrival of gravitational waves was a breath of fresh air,” says Caprini.
That rare bright spot looks set to become brighter.
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