LIGO Detects Gravitational Waves for the First Time
Two black holes collide 1.3 billion years ago, and the ripple in spacetime finally reaches two laser tunnels in Louisiana and Washington
Quick facts
- Detected
- September 14, 2015, 5:51 a.m. ET
- Detectors
- LIGO, Livingston LA and Hanford WA
- Source
- Merger of two black holes, c. 1.3 billion light-years away
- Announced
- 11 February 2016
What happened
At 5:51 a.m. Eastern time on September 14, 2015, both detectors of the Laser Interferometer Gravitational-wave Observatory, LIGO, one in Livingston, Louisiana, and one in Hanford, Washington, simultaneously registered a signal lasting a fraction of a second. Caltech's LIGO Laboratory identified the source: physicists concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole, an event roughly 1.3 billion light-years away that came to be called GW150914. NASA's own announcement of the result called it the first time scientists had observed ripples in the fabric of spacetime called gravitational waves arriving at Earth from a cataclysmic event in the distant universe, confirming a major prediction of Albert Einstein's 1915 general theory of relativity a full century after Einstein made it. The discovery was formally announced on 11 February 2016, after months of analysis to rule out instrumental error.
Why it matters
The detection was the first direct evidence that gravitational waves, ripples in spacetime itself predicted by general relativity in 1915, actually exist, and the first ever observation of two black holes merging. Caltech's LIGO Laboratory called it the beginning of a new era, quoting the collaboration's own assessment that the field of gravitational wave astronomy is now a reality, opening an entirely new way of observing the universe that does not rely on light at all.
How we know
The detection was independently registered by two separate LIGO observatories roughly 3,000 kilometers apart, matched against the waveform general relativity predicts for a black hole merger, and published in a peer-reviewed paper by the LIGO Scientific Collaboration and Virgo Collaboration in February 2016, with the discovery later recognized by the 2017 Nobel Prize in Physics.
Sources
- LIGO Laboratory, California Institute of Technology. Gravitational Waves Detected 100 Years After Einstein's Prediction · Primary source (author-declared)ligo.caltech.edu · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- NASA. NSF's LIGO Has Detected Gravitational Waves · Primary source (author-declared)nasa.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
See something wrong? . Corrections with a source get fixed fastest.
Related timelines
- Space Exploration → · Gravitational-wave astronomy opened an entirely new way of observing cosmic events; see the Space Exploration timeline for how it complements telescopes and space probes.