On December 6, 2002 (November 3, 2002 in the lunar calendar), our scientists discovered the disappearance of neutrinos in nuclear reactors. At 5:00 pm on December 6, 2002, scientists in our country and their colleagues in Japan and the United States simultaneously announced their major discovery in neutrino experiments - the discovery of the disappearance of neutrinos produced in nuclear reactors, which means that the neutrinos produced in the reactor oscillated and became another kind of neutrino that was not detected. This important experimental result was obtained by the kamLAND experimental group composed of scientists from Japan, the United States and China. It finally confirmed the oscillation of solar neutrinos and determined the key parameters of neutrino oscillation. Neutrinos are very small elementary particles that do not interact with almost any matter, so they are difficult to detect and detect. The 2002 Nobel Prize in Physics was awarded to the American scientist Raymond Davis and the Japanese scientist Masajun Kosai, who made great achievements in detecting neutrinos in the universe. The sun's nuclear fusion produces a large number of neutrinos. The solar neutrino experiment led by Davis found about 2,000 neutrinos from the sun in 30 years of detection, but compared with the theoretical calculation value, the flow is less than half, which is the famous "solar neutrino loss" mystery. Kosai Masajun confirmed the results of Davis's experiment and also confirmed the disappearance of atmospheric neutrinos. The major significance of the results of the kamLAND experiment completed by scientists from Japan, the United States, and China is that neutrinos disappeared in a new artificial neutrino source with the same characteristics as the disappearance of solar neutrinos, thus finally confirming the oscillation of solar neutrinos, ruling out other explanations for the disappearance of solar and atmospheric neutrinos. This is the first time in the world that an artificial neutrino source has been used to confirm the oscillation phenomenon of solar neutrinos. This experiment also quantitatively gives a unique solution to the oscillation parameters of solar neutrinos for the first time, verifies that the standard solar model is correct, and draws a positive conclusion that the mass of neutrinos is not zero. At the same time, this experiment also observes for the first time the geological neutrinos emitted by the earth itself. The KamLAND detector, built in 1997 under a 1,000-meter-deep mine in Kamioka, Japan, was used by an experimental team of nearly 100 scientists from Japan, the United States and China to detect neutrinos from more than 20 nuclear power plant reactors. The experiment began in February this year. Chinese scientists including Wang Yifang, a researcher at the Institute of High Energy Physics of the Chinese Academy of Sciences, participated in the experiment.