Qualla: Jiangmen Underground Neutrino Observatory

Jiangmen Underground Neutrino Observatory: Introduction

Fri, 12 Jun 2026 00:00:00 GMT

Two nuclear power plants sit on the coast of Guangdong province, each bristling with reactors. Most of the particles they release never interact with anything. Neutrinos — ghostly, near-massless — pass through the Earth as if it were not there. Every second, trillions of them stream through your body without leaving a mark. Catching even a few requires something extraordinary: a sphere of liquid the size of a ten-story building, buried under a mountain, watched by 43,000 light-sensitive eyes. That is what scientists built 700 meters below the hills near Jiangmen. When the Jiangmen Underground Neutrino Observatory — JUNO — began taking data on 26 August 2025, it became the world's most sensitive instrument for a question that has occupied physicists for decades: which type of neutrino is heavier?

Jiangmen Underground Neutrino Observatory: The Question That Required a Mountain

Fri, 12 Jun 2026 00:00:00 GMT

Neutrinos come in three varieties — electron, muon, and tau — and they oscillate between types as they travel, a quantum behavior with no classical analogue. The pattern of those oscillations encodes something fundamental: the mass hierarchy, meaning which type is heaviest and wh...

Jiangmen Underground Neutrino Observatory: Engineering the Invisible

Fri, 12 Jun 2026 00:00:00 GMT

The main detector is an acrylic sphere containing 20,000 tonnes of linear alkylbenzene liquid scintillator — a compound that emits a faint flash of light when a neutrino interacts with it. Surrounding the sphere, a stainless steel truss supports approximately 43,200 photomultipli...

Jiangmen Underground Neutrino Observatory: First Light, August 2025

Fri, 12 Jun 2026 00:00:00 GMT

Originally projected to begin operations in 2023, JUNO faced the kinds of delays that accompany any first-of-its-kind instrument. The final assembly and commissioning stretched the timeline by two years. When the detector switched on in August 2025, it crossed a threshold: no tra...

Jiangmen Underground Neutrino Observatory: What Lies Beneath Guangdong

Fri, 12 Jun 2026 00:00:00 GMT

The surface above JUNO offers no obvious sign of what is below. Guangdong's hills roll through a landscape of subtropical forest and farmland, unremarkable from a road or from the air. The observatory exists in a civic and scientific context that is easy to miss: China has been b...