This golden chamber buried under a mountain in Japan contains water so pure it can dissolve metal.

This place is hidden 1,000 metres under Mount Ikeno in Japan.

Super-Kamiokande (or “Super-K” as it’s sometimes referred to) is a neutrino detector. Neutrinos are sub-atomic particles which travel through space and pass through solid matter as though it were air.

Studying these particles is helping scientists detect dying stars and learn more about the universe. Business Insider spoke to three scientists about how the giant gold chamber works — and the dangers of conducting experiments inside it.

Seeing the sub-atomic world
Neutrinos can be very hard to detect, so much so that Neil deGrasse Tyson dubbed them “the most elusive prey in the cosmos.” In this video, he explains that the detection chamber is buried deep within the earth to stop other particles from getting in.

“Matter poses no obstacle to a neutrino,” he says. “A neutrino could pass through a hundred light-years of steel without even slowing down.”

How Super-K catches neutrinos

A diagram of Super-Kamiokande. Kamioka Observatory, ICRR, The University of Tokyo

Buried 1,000 metres underground, Super-Kamiokande is as big as a 15-story building.

The enormous tank is filled with 50,000 tonnes of ultra-pure water. This is because when travelling through water, neutrinos are faster than light. So when a neutrino travels through water, “it will produce light in the same way that Concord used to produce sonic booms,” said Dr Uchida.

“If an aeroplane is going very fast, faster than the speed of sound, then it’ll produce sound — a big shockwave — in a way a slower object doesn’t. In the same way a particle passing through water, if it’s going faster than the speed of light in water, can also produce a shockwave of light.”

The chamber is lined with 11,000 golden-colored bulbs. These are incredibly sensitive light-detectors called Photo Multiplier Tubes (PMTs) which can pick up these shock-waves.

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