On September 14, 2015, the scientific world witnessed a monumental breakthrough: the first-ever detection of gravitational waves. This landmark achievement, a century in the making, confirmed a key prediction of Albert Einstein's General Theory of Relativity and opened a new window into the universe's most extreme phenomena.
Einstein's theory posited that massive accelerating objects, such as colliding black holes, would create ripples in spacetime – gravitational waves. However, he doubted their detectability due to their minuscule size, far smaller than an atom. The Laser Interferometer Gravitational-Wave Observatory (LIGO), a project spearheaded by Rainer Weiss, Kip Thorne, and Barry Barish, was designed to overcome this challenge.
LIGO's ingenious design employed interferometers, splitting laser beams and sending them down long arms (2.5 miles each) before recombining them. The passage of a gravitational wave would subtly alter the lengths of these arms, causing a measurable phase shift in the recombined beams. The use of two detectors, located in Livingston, Louisiana, and Hanford, Washington, helped eliminate local disturbances and pinpoint the source of the waves.
Years of painstaking work, including significant upgrades to enhance sensitivity and mitigate environmental noise, were necessary before the upgraded LIGO detectors finally captured a signal. That signal, detected on September 14, 2015, was a distinct 'chirp' – a fluctuation corresponding to the collision of two black holes 1.3 billion light-years away. This event, initially detected only by LIGO, was later confirmed by the European Virgo detector.
The discovery marked the dawn of multi-messenger astronomy, allowing scientists to observe the universe through both light and gravitational waves. Since 2015, LIGO, Virgo, and the Japanese KAGRA detector have detected hundreds of cosmic collisions, including triple black hole mergers and the collision of black holes with neutron stars. Further discoveries, such as the detection of a faint gravitational wave background and the validation of Stephen Hawking's black hole theory, continue to build on this groundbreaking initial detection.
The immense impact of this work is undeniable, earning Weiss, Thorne, and Barish the 2017 Nobel Prize in Physics. The detection of gravitational waves represents not only a triumph of scientific ingenuity but also a profound expansion of our understanding of the cosmos, promising exciting new discoveries in the years to come.
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Originally published at: https://www.livescience.com/space/black-holes/science-history-gravitational-waves-detected-proving-einstein-right-sept-14-2015
