China opens the world's deepest and largest underground laboratory 7,800 feet below a mountain to hunt for dark matter

• China has just opened the deepest and largest underground laboratory in the world.
• The China Jinping Underground Laboratory-II will seek to uncover the secrets of dark matter. 
• At about 7,800 feet underground, it should be shielded from cosmic radiation. 

China has opened the biggest and deepest underground laboratory in the world in a bid to uncover the secrets of dark matter.

The China Jinping Underground Laboratory-II (CJPL-II) laboratory in southwest China's Sichuan Province opened in December 2023, an expansion of the original CJPL facility, which was first launched in 2010.

CJPL-II stands at 7,874 feet underground with a surface area of more than 11.6 million cubic feet, per a press release. That makes it bigger than Italy's Gran Sasso National Laboratory, which previously held the record, Nature News reported.

Thanks to its extensive mountainous cover, the facility aims to provide the perfect conditions to study the elusive stuff that makes up an estimated 95% of the universe — dark matter.

Dark matter is really hard to see

Visible matter's gravity is too weak to explain why fast-moving galaxies don't fly apart, Nature News explained.

That leaves us with one overarching theory; that there is another type of matter acting on the universe, or so-called dark matter.

By its very nature, scientists think dark matter doesn't want to interact with the matter we can see and feel or even light.

That makes it very difficult to pick up on physical detectors, and any type of observation is easily foiled by background radiation that can contaminate the experiment.

Going inside the Earth to protect from space

Even extremely weak radiation can ruin the hunt for dark matter.

Cosmic radiation, for instance, is very faint and doesn't affect humans, but it can cause background noise that can alter the experimental results.

That's why scientists are digging deep to protect their detectors. The thick mountains of the Sichuan province should help fend off up to 0.000001% of the radiation that hits the Earth from space, per Nature News.

Weak radiation that comes off of concrete or the water and rocks in the mountain itself can also prove damaging. So the experimental chambers have been lined with a mix of concrete and rubber that should protect them from the radiation of the mountain, per Nature News.

A video, below, provides more views of the inside of the facility.

New detectors to match the new facility

The new footprint of the lab has allowed CJPL to expand its experimental equipment. CJPL hosts the Particle and Astrophysical Xenon Experiments (PandaX) and the China Dark Matter Experiment.

PandaX now sits inside a water tank of about 32,000 cubic feet to protect its 8,800 pounds of liquid xenon detector from background interference. That's a big improvement on their previous detector, which only held 264 pounds of liquid xenon.

This upgrade puts PandaX-4T in a similar league to the detectors in Italy and at the Sanford Underground Research Facility in Lead, South Dakota, per Nature News.

"With better sensitivity, we can play with the detector and test the different types of interactions," said team member Ning Zhao, a physicist at Shanghai Jiao Tong University in China, per Nature News.

Whether the detector will transform the field of dark matter physics remains to be seen, Juan Collar, a physicist at the University of Chicago in Illinois, told Nature News.

PandaX is similar to other detectors seen around the world, and it's not clear whether better sensitivity will yield better results.

"There is enough replication already," he said, adding that it may be better to try to find a new approach in the hunt for dark matter.