Why does Japan store 50000 tons of water under 1000 meters? “Ghost of the universe” to explain

In Japan, there is a mysterious building with the official name of “super kamoka detector”, which is equivalent to 15 stories high, 1000 meters underground. Since 1996, this detector with 50000 tons of 100% pure water has made several achievements of Nobel prize level in physics for Japan, and what it detects is neutrinos, which are called “ghosts of the universe”.


Today’s physicists tell us that the material world where human beings live is composed of various basic particles, and neutrinos are also one of the basic particles. However, neutrinos have a very strange property, that is, although its number is extremely large, it is one of the largest particles in the universe.

But because it’s a neutral particle, it doesn’t participate in electromagnetic interaction, which leads to 10 trillion neutrinos per second passing through your body, but you don’t know. The neutrinos that the sun shoots at the earth are only one in a billion, which are absorbed by the matter on the earth. The rest of the neutrinos pass through the earth and fly to the depths of the universe.


However, it is very difficult for neutrinos to interact with other substances, but when they move in water, they still have a very small probability of reacting with hydrogen or oxygen atoms, and because the speed of light in water is only 75% of that in vacuum, neutrinos flying near the speed of light in water are faster than that of light. In this way, just like the sonic boom generated by supersonic aircraft, neutrinos in the water will emit unique Cherenkov radiation due to “superluminal speed”.


The reason why Japan wants to store 50000 tons of ultra pure water underground at a depth of 1000 meters is to avoid the interference of other cosmic rays except neutrinos as far as possible, and to ensure that the Cherenkov radiation generated by neutrinos can be accurately recorded.

The calculation of stellar physicists shows that every three photons produced by the sun will be accompanied by two neutrinos. But for a long time, the number of neutrinos detected on the earth is only one-third of the theoretical calculation. Where are the remaining two-thirds? No one knows.


On February 23, 1987, the astronomical community witnessed a supernova explosion in the Large Magellanic nebula, which occurred 160000 light-years away. But the number of neutrinos produced by this supernova explosion is not as good as that of the solar neutrinos. Two thirds of them disappear.


So physicists guess that there are three kinds of neutrinos, not one. And the three kinds of neutrinos will transform each other, which is called the theoretical prediction of neutrino oscillation. In 1998, it was confirmed for the first time by Japan’s super Shenkang detector. This breakthrough also won the Nobel Prize in physics in 2002 for the neutrino project.

From the prediction of existence, discovery and confirmation of neutrino oscillation, it took nearly a century for the physics community, but other information about neutrinos is still unknown. Because of this, neutrino related research has become one of the hottest topics in physics.


By 2027, Japan’s super Shengang upgrade, the top Shengang detector, will start collecting neutrino data. The top Shengang with 260000 tons of water storage will have several times the detection capacity of super Shengang. China’s Jiangmen neutrino experiment will begin to collect data as early as 2022. This neutrino detection facility, located at a depth of more than 700 meters underground, will further uncover the mystery of neutrinos, and may produce scientific research achievements of Nobel physics level.


In science fiction works, neutrinos are the most ideal means of information transmission, because they almost do not interact with other substances, so in theory, a bunch of neutrinos carrying information can transmit information to any place in the universe, without distortion and loss of information like electromagnetic waves.

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