I can remember attending a colloquium talk in the 1970s by Joseph Weber on his pioneering attempts to measure gravitational waves. I also recall a talk later in the 1980s on the concept of a giant Laser Interferometer Gravitational-Wave Observatory (LIGO) for detecting such waves. It’s sure has been a long search, but two LIGO detectors in Livingston, Louisiana, and Hanford, Washington have now observed for the first time the gravitational waves signal created by two black holes rotating around each other and then colliding and merging into one big black hole.
- Found! Gravitational Waves, or a Wrinkle in Spacetime – National Geographic
- Gravitational Waves Detected 100 Years After Einstein’s Prediction – LIGO Lab/Caltech
- Cosmic breakthrough: Physicists detect gravitational waves from violent black-hole merger – The Washington Post
Here is a brief video about the discovery
This clip illustrates how the waves are detected by monitoring the interference pattern of two laser beams that have traveled to the ends and back of 4 km (2.5 mile) long tunnels at 90 degrees to each other. A gravitational wave will alter the length of those tunnels slightly, which in turn will alter the interference of the two beams :
Here is a video of the entire briefing held today:
And here is the scientific paper: LIGO-P150914-v14: Observation of Gravitational Waves from a Binary Black Hole Merger.