When Daoist Hong saw that the Yin Devouring King had turned into a cloud of black qi and fled, he was about to chase after him, but his Dao method was limited, he couldn't fly, and he didn't have a weapon in his hand, so he had to give up for the time being. The frozen old sow opened her mouth and looked like an ice sculpture floating in a pool. Mao Bowu really regretted that the old sow who froze to death at home took a shovel and jumped into the pool to dig ice to get the old sow out. The ice was very hard, and Mao Bowu tinkered for a while, only digging a few small pits on the ice.

"Now that the temperature is in the teens, how can the water freeze? I don't think this ice is ordinary ice, it should be attacked with fire. The Floodmaster told a few young men to carry bundles of firewood and pile them in the pool, pour kerosene on them, and set them on fire, and smoke billowed from the pool. After a while, the ice melted, and Mao Bowu and a few strong men salvaged the old sow.

"Can you eat this female pork?" A young man asked, looking a little hungry for him.

"This old sow has been around for more than ten years, with thick skin, old meat, and a lot of toxins accumulated in her body, which she can't eat." Mao Bowu said. He and a few young men dug a deep pit on the slope and found an old pig cage at home to carry the sow up the slope and bury it. In order to prevent someone from digging up the old sow, Mao Bowu flattened the place where the pigs were buried, and then piled up dead branches and leaves, leaving no traces. It is said that in ancient times, those adulterers and adulteresses would be punished by immersing themselves in the pig cage, and Hong Daoshi's grandfather told him these living examples.

The peachwood sword had to be hung at the door of Xie Juying's bedroom for three days, and it was inconvenient for Hong Daoshi to take it away. When he returned home, he carried the ancient knife given to him by Hu Kehao, and wanted to search for the Yin Devouring King and eliminate harm for the people. The Yin Devouring King had already turned into a cloud of black gas, and he was nowhere to be found. According to the northwest direction where the black gas disappeared, the Hongdao master looked for clues.

Unconsciously, Daoist Hong came to Professor Yang Shimo's newly built laboratory to see if Professor Yang could find the Yin Devouring King. Professor Yang hired a moving company and has moved the experimental equipment from the warehouse in U City. The laboratory claims to be a vegetable greenhouse, and there are usually no idlers to disturb it. The village telephone pole passed by outside the laboratory, and Professor Yang got the laboratory energized and is now functioning normally.

Daoist Hong asked Professor Yang about the whereabouts of the Yin Devouring King, but Professor Yang didn't have advanced spells, so he naturally couldn't figure it out, and only used high-tech experimental equipment. Professor Yang took Master Hong to the Magic Mirror Room of the laboratory. In the center of the mirrors arranged in the eight directions of Qian, Kan, Gen, Zhen, Xun, Li, Kun and Dui, there is a large Taiji mirror, which controls the operation of these eight mirrors.

Professor Yang opened the Tai Chi Mirror and saw a cloud of black qi inside, which was the image left by the Yin Devouring King when he fled. Just like what Hong Daoshi saw by the pool that day, this black qi kept running in the northwest direction, and reached the edge of the Taiji Mirror, which was equivalent to the edge of Hong Daoshi's line of sight that day, and the black qi of the Yin Devouring King in the mirror also disappeared and disappeared. The sensing range of this Taiji Mirror is limited, and the Yin Devouring King moves outside its sensing range, and the Taiji Mirror cannot sense it.

"Master Hong, don't worry, although the Taiji Mirror can't reveal the hidden place of the Yin Devouring King, I can find a way to test it." Professor Yang saw Master Hong's anxious appearance and comforted him.

"What's your best idea? I've tested it several times with the Water Transformation Technique, and the Brownian motion of the Scented Ash particles in the water doesn't show any trace of the Yin Devourer. Hong Daoshi said.

"The Yin Devouring King has high mana and has anti-reconnaissance capabilities. You're a bit behind in that method, and now we're using the cloud room to find his hiding place. Professor Yang said.

The Tai Chi Mirror is connected to a transparent cloud room. Master Hong Dao saw that there was a seven-colored rainbow in the cloud room, which was very beautiful, and this was the landscape that Professor Yang made with the cloud room. Professor Yang activated the button, and a beam of electrons flew into the cloud room, and the image in the Tai Chi mirror was displayed in the cloud room. I saw a cloud of mist appear in the cloud room, exactly the same as the black gas left behind when the Yin Devouring King fled.

In general, for the vapors in the cloud chamber to condense, each fog bead must have a dust core. Professor Yang improved the experimental setup to observe the trajectory of electrons by simply emitting electrons into the cloud chamber to form clouds. This is Professor Yang's improvement of the very famous Wilson cloud room in history, which can be used in conjunction with the Tai Chi Mirror to detect the movement of the Yin object.

"Are the electrons in the cloud chamber particles or waves?" Master Hong asked. He often communicated with Professor Yang and learned some physics knowledge, and he often applied various physics knowledge in the process of practicing Taoism.

"Waves are ethereal, scattered, and if electrons were waves, they would not leave any trail in the cloud chamber. If the electron is a particle, there must be a trajectory. What we see in the cloud room is the trajectory of the electron, the trajectory of the electron's wave function after collapse! Professor Yang said.

"The electron itself is invisible, and your trajectory is so clear, which means that the 'trajectory' is much more than the electron itself! Why is it able to make a trajectory that is hundreds of thousands of times wider than itself? Hong Daoshi asked.

"It is supposed that when an electron passes by, the molecules that have come into contact with it are ionized and turn into ions, attracting the surrounding water molecules and gathering into water droplets. So, we see the trajectory of the electron. The problem now is that we can't accurately track the velocity and coordinates of electrons, making it difficult to trace the whereabouts of the Shadow Eater. Professor Yang looked at the trajectory of the electrons in the cloud chamber and saw that the electrons were moving in a northwesterly direction, but he could not specify a definite coordinate.

"It can improve the accuracy of the electron trajectory test! According to the principle of similarity, as long as the approximate location of the Yin Devouring King is converted, I can find him within a range of five hundred meters! Hong Daoshi said.

In order to obtain the definite trajectory of the electrons and find out where the Yin Devourer King is hiding, Professor Yang uses photons to track them. Photons have wave-particle duality, they have frequency, and the wavelength (frequency) of the photon directly determines the accuracy of the measurement. The shorter the wavelength and the higher the frequency of the photon, the more precise the measured position. But at the same time, since the energy of the photon is equal to Planck's constant multiplied by frequency, the higher the frequency of the photon, the greater the energy, the greater the change in the speed of the electron when it hits the electron, and the less accurate the measured speed is. If you want to maximize the speed of the electron, you can only reduce the photon frequency, but the frequency decreases and the wavelength increases, and the accuracy of measuring the position of the electron decreases! Therefore, when measuring the position of electrons, there must be interference. Measuring one value must interfere with another. Professor Yang used different frequencies such as infrared, orange, yellow, green, blue, indigo, etc., to test the electron trajectory in the cloud chamber, and found that the more accurate the momentum of the electron, the more inaccurate the position is. The more accurate the position, the more inaccurate the momentum is, which is really difficult to balance!

When Professor Yang speculated on the whereabouts of the Yin Eater, he came up with this paradox: the shorter the wavelength of the test photon, the more accurate the position of the Yin Eater, but the more imprecise the measured flight speed of the Yin Eater. The longer the wavelength of the test photon, the more accurate the speed of the Shadow Eater's flight, but the less precise the measured position. In either case, there are always uncertain parameters that make it difficult to accurately track the Yin Devourer. This is the uncertainty principle proposed by the German physicist Heisenberg in 1927.

The uncertainty principle tells us that you cannot know the position of a particle and its velocity at the same time, and that the product of the uncertainty of the particle's position and the uncertainty of the momentum must be greater than or equal to Planck's constant divided by 4π(ΔxΔp≥h/4π), which indicates that particles in the microscopic world behave very differently from macroscopic matter. In the macroscopic world, for example, if you use a photon to test a running puppy, the photon hits it, it basically has no effect, its position and speed (or momentum) can be measured, and the measurement error is completely negligible. In the microscopic world, Professor Yang is unable to accurately measure the position and velocity of electrons using photons, so he cannot accurately predict the whereabouts of the Yin Devourer. Just like a running puppy, you know its precise location, but you don't know its precise speed, you can't know where it will be in a few minutes; In the same way, you know its precise speed, you don't know its precise location, you can't know where it will be in a few minutes, you can only get an approximate range.

Based on the principle of uncertainty, Professor Yang calculated that starting from the laboratory, fifteen kilometers northwest is the center of the circle, and within a radius of two kilometers, it is the hiding place of the Yin Devouring King. If time drags on, the Yin Devouring King will still have to move around, and it will be even more difficult to find him if he is not within the detection range of the Taiji Mirror.