On December 12, 2010 (November 7, 2010 lunar calendar), China's first ultra-deep underground "dark matter" laboratory was put into use. Computer simulation of dark matter. This diagram demonstrates how invisible dark matter is combined in the halo. China's first ultra-deep underground laboratory - "China Jinping Underground Laboratory" was unveiled and put into use today at Jinping Hydropower Station on the Yalong River in Sichuan. The vertical rock coverage of Jinping Underground Laboratory reaches 2,400 meters, making it the deepest laboratory in the world. Its completion marks that China has a world-class clean low-radiation research platform, capable of independently carrying out international cutting-edge basic research topics such as dark matter detection. At present, the dark matter detector of the experimental group of Tsinghua University has taken the lead in entering the laboratory and started the detection work. Next year, research teams such as Shanghai Jiao Tong University will also enter here to carry out dark matter detection research. The picture shows the ultra-low energy valve high-purity germanium detector used for dark matter detection in the "China Jinping Underground Laboratory". Explanation of terms: Dark matter In cosmology, dark matter refers to those substances that do not emit any light or electromagnetic radiation. At present, people can only know that there is a large amount of dark matter in the universe through the effect of attractive force. The earliest evidence of the existence of dark matter comes from observations of the rotation speed of spherical galaxies. Modern astronomy studies through attractive force lenses, the formation of large-scale structures in the universe, and microwave background radiation show that the part we currently know accounts for only about 4% of the universe, dark matter accounts for 23% of the universe, and 73% is a kind of dark energy that causes the accelerated expansion of the universe. Underground Laboratory In the process of building the Ertan Hydropower Station in Sichuan Jinping Mountain, an 18-kilometer tunnel was built at the bottom of Jinping Mountain that can pass cars, and above it is a mountain rock more than 2,500 meters thick. This will become the site of the first experiment after the establishment of the institute, dedicated to "hunting" dark matter. At present, this is the best environment in the world to detect dark matter. According to Ji Xiangdong, head of the Department of Physics at Jiaotong University and director of the Institute of Particle Physics Cosmology, the laboratory uses the underground tunnel built when the local hydropower station was built, and excavates 40 meters long, 6 meters wide and 6 meters high on its side. Therefore, compared with some underground laboratories "born out" of mines abroad, it is more convenient to use, and you can "enter the ground" without taking an elevator up and down, and taking a car. And tunnels buried 2,500 meters deep are even more rare, because the deeper they are buried, the less interference from cosmic rays. "Underground work" is not uncomfortable. "It takes about 20 minutes to drive from the ground, and you can reach the underground laboratory." Ni Kaixuan, a special researcher at the Institute of Particle Physics Cosmology at Jiaotong University, still remembers the feeling of "entering the ground" for the first time. Wearing a hard hat and hard-soled shoes, he entered the laboratory with all kinds of equipment. "The temperature is constant in the four seasons, warm in winter and cool in summer, and there is no need to use air conditioning. The only difference from the ground laboratory is that there are no windows, it is windy and rainy, and it is easy to make people confused about whether the outside world is day or night after entering for a long time." "Underground work" for a long time, will people feel uncomfortable? "The ventilation equipment in the underground laboratory is very good, and you will not feel stuffy at all. If you stay down for half a day, you will not feel any strange feelings. Mr. Ni said that once the instruments were stable, he could simply monitor the operation of the detector from his office on the ground, and all the data from the underground laboratory would also be transmitted to the ground, so that researchers did not have to "guard" the detector 24 hours a day.