China at cutting edge of dark matter search

"Imagine that you are driving your car in the pollution haze, and each time a pollutant particle hits into your car it makes a weak sound. What we are doing in the underground laboratory is trying to figure out these sounds," said Liu Jianglai, a professor at the Shanghai school and a member of the PandaX team.

How difficult would that be? In Liu's word, it's like "trying to hear the sound of a mosquito waving its wings 30 meters away while you are sitting in the front row of a concert".

The laboratory was built deep underground to help researchers avoid as much interference as possible.

In 2014, Tsinghua's CDEX project got experimental results with the highest sensitivity in the world. The same year, PandaX released results from the first stage of its experiment.

Later, Tsinghua began to upgrade the Jinping lab from 4,000 cubic meters to 30 times that size.

"The underground experiments have been carried out in a number of countries for nearly two decades, and the technology is becoming mature," Ji Xiangdong, a professor at Shanghai Jiao Tong, was quoted as saying earlier by Xinhua News Agency.

"We are close to the edge of dark matter, and we are eager to make sure it is Chinese people who give the answer to this cutting-edge scientific question," Ji said.

Bi Xiaojun, a researcher from the science academy's Institute of High Energy Physics, said the decadeslong search has been narrowing the range in which to look for dark matter.

"This is like searching for a missing plane at sea. We search the energy ranges in which dark matter could possibly exist, and rule out those we already checked," he said. "Now we are working on a range with high possibilities. If we do not find dark matter here, maybe we will be lucky in the adjacent waters."

No matter what is discovered by the new instruments, the physics field is ready to embrace revolutions in the theory of dark matter, said Wu Xiangping, an astrophysicist at the National Astronomical Observatory of the Chinese Academy of Sciences.

"Whether or not you believe in the existence of dark matter, the development of physics has reached a phase that it needs an update. Either a new theory or new phenomena with breathe in new life," he said.

Physics has evolved from Newton's classical mechanics to quantum mechanics and the theory of relativity because scientists managed to expand their observations to things that could not be observed before, such as atoms, or stars flying at close to the speed of light, he said. If we were able to further extend our vision to new matter about which we know little, a new revolution in physics will follow.

"Now is the time," he said.