How One of the Universe’s Biggest Secrets Was Discovered

PBS NOVA
PBS NOVAApr 7, 2026

Why It Matters

Gravitational‑wave detections transform astronomy from a purely visual science into a multi‑messenger discipline, unlocking direct insight into black‑hole dynamics and the most energetic processes in the universe.

Key Takeaways

  • LIGO's September 2015 detection proved black‑hole mergers exist.
  • A scientist’s decision to stop early saved the historic signal.
  • The observed wave matched predictions of spiraling black‑hole binaries.
  • Energy released exceeded all stars combined, rivaling the Big Bang.
  • Gravitational‑wave astronomy now lets us ‘hear’ cosmic events.

Summary

The video recounts the serendipitous birth of gravitational‑wave astronomy on September 14, 2015, when LIGO’s two detectors in Louisiana and Washington recorded a fleeting ripple in spacetime. A tired technician, Robert Schofield, chose to shut down the instruments, inadvertently preserving the signal that had traveled 1.3 billion years to Earth.

The waveform, visible to the naked eye in the data, displayed the characteristic “chirp” of two black holes spiraling together—one 29 and the other 36 solar masses—merging into a 62‑solar‑mass black hole. In less than a second, the merger radiated energy equivalent to 50 times the combined output of all stars in the observable universe, a release second only to the Big Bang.

Schofield jokes that his laziness was his biggest contribution, while a colleague’s exclamation, “Holy — ,” captures the awe of the moment. The discovery earned the 2017 Nobel Prize for Kip Thorne, Rainer Weiss and Barry Barish and paved the way for the 2017 neutron‑star event, the first time astronomers both heard and saw a cosmic collision.

These observations opened a new, non‑electromagnetic window on the cosmos, allowing scientists to probe black‑hole populations, test general relativity, and launch multi‑messenger campaigns. As detections multiply, they will reshape our understanding of stellar evolution, galaxy formation, and the ultimate fate of matter in an expanding universe.

Original Description

In 2015, scientists detected the collision of two black holes, confirming a major prediction of Einstein’s general theory of relativity. But the discovery depended on catching a fleeting signal at just the right moment.
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