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The Double Flash Meets the Bhangmeter

The bhangmeter was named for an intoxicant, but the U.S. Nuclear Detection System relies on this technology in satellites to detect a nuclear blast anywhere on Earth.
July 1, 2015
The Double Flash Meets the Bhangmeter

A bhang shop in Jaisalmer, Rajasthan, India. (Photo: Tom Maisey, Flickr. Licensed under CC BY-SA 2.0 via Wikimedia Commons)


  • Managing Editor
  • Clay Dillingham
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You had to be “high on something” to believe such a simple instrument would work.

One of the sensors on satellites in the U.S. Nuclear Detonation System uses a relatively simple device to detect the “double flash” of a nuclear detonation anywhere on earth. That simplicity earned a jokey name when researchers in the late 1940s called it the bhangmeter, because you would have to be “high on something” like bhang, which is cannabis, to think it could work.

But it does work. Deployed on Vela satellites, the bhangmeter has a track record of spotting 41 confirmed nuclear tests and one puzzling anomaly—a mysterious double flash over the far-southern Indian Ocean.