[ HAS A NUKE GONE OFF? ]

This site is a live, always-on watch for nuclear detonations. Two independent, home-built detectors sit in Wiltshire in the UK and report in on their own schedule — the gamma detector every minute, the optical detector every half hour. If either one ever catches the unmistakable signature of a nuclear blast, the answer above flips from No to YES — and the exact moment is logged forever.

[ MONITORING LOCATION ]

Both detectors currently watch the sky from the same spot in Wiltshire. The map below shows exactly where, and the live readout above tells you the last time each one checked in.

[ TWO WAYS TO SPOT A BOMB ]

A nuclear explosion gives itself away in several ways at once — a burst of gamma rays, a double flash of light, a pulse of heat, and finally the blast wave. These two projects each listen for a different clue, so one detector can back up the other:

Bhangmeter V2 detects the invisible gamma-ray flash — the very first signal to arrive.
Bhangmeter V3 watches for the double flash of light that every nuclear fireball produces, and uses its timing to estimate how big the blast was.

[ BHANGMETER V2 · THE GAMMA DETECTOR ]

Bhangmeter V2 is built around an HSN-1000L Nuclear Event Detector — a chip designed to sense the intense gamma-ray burst of a nuclear explosion. That burst travels at the speed of light, so it reaches the detector almost instantly. Behind it come the neutron flux (at roughly a tenth of light speed) and, much later, the blast wave itself — lumbering in at Mach 1.5 to 3, anywhere from milliseconds to seconds afterwards depending on how far away the detonation was.

When the gamma burst hits, the HSN-1000L fires a brief electrical pulse. A Raspberry Pi Pico 2W reads this as a Nuclear Event Detection (NED) and immediately records the precise time it happened.

Every minute the detector checks in over WiFi, uploading its status to the cloud. The instant a real event is recorded, that timestamp is stored permanently — so even if the detector doesn't survive what comes next, the evidence does.

Shortly afterwards — the delay depending on distance — the blast wave arrives and the detector's mission is complete. Its moulded polymer casing is designed to offer a few moments of ablative cooling on the way out.

[ BHANGMETER V3 · THE OPTICAL DETECTOR ]

Every nuclear fireball flashes twice. The first flash is a brief, blindingly bright pulse lasting about a millisecond. The growing shockwave then briefly cloaks the fireball, dimming it to a momentary minimum — before it bursts back into a second, longer and even brighter flash. This double flash is so distinctive that it's how satellites have spotted nuclear tests for decades.

Bhangmeter V3 watches for exactly this pattern with a fast light sensor, and it can do something the gamma detector can't: estimate the yield. The gap between the two flashes grows with the size of the bomb, so V3 turns that interval into an estimate in kilotons — from around 10 kt all the way up to a megaton.

It records two timings: the peak-to-minimum time as a quick cross-check, and the peak-to-peak time as the main yield estimate. Both feed straight into the live readout at the top of this page.

[ BUILD ONE YOURSELF ]

Both detectors are fully open-source — you can build your own. Each design package includes:

• 3D-printed housing
• PCB gerbers, schematic and assembly documents
• Firmware and source code
• Step-by-step build instructions

Full details are on GitHub:
Bhangmeter V2 — gamma detector
Bhangmeter V3 — optical detector