What is Cao Fang talking about? How did he know that his father had left him a watch? Shen Yun turned his head and looked blankly at the person who was driving.

Cao Fang smiled and said, "I know a lot more about you than you think. That thing was a birthday present for you when you were fifteen years old, and I applied to the Military Commission on behalf of General Shen to help you prepare it. Now I'm not afraid to tell you the truth, it's not an ordinary, time-watching watch, but a Space Force uniform. ”

"What?!" Shen Yun exclaimed again.

On the way out of Xichang, almost every moment, she was experiencing different degrees of shock, and this shock was better than any time before, even if Cao Fang made it clear, she still couldn't associate a round watch with the uniform she put on her body.

Probably because her confused appearance was a little funny, Cao Fang chuckled twice, but quickly regained his seriousness and explained: "The popular name is military uniform, and the official name is solid-state photon camouflage uniform. ”

"No wonder before my dad left, he quietly told me to protect this watch, because it can save lives at critical moments......"

Fifteen years ago, Shen Yunhong gave his daughter this birthday gift. Fifteen years later, Shen Yun figured out the purpose of the gift and met Cao Fang, the person who prepared the gift back then. Shen Yun once thought that fate was a labyrinth, maybe she could only be trapped in it in this life, but she didn't expect that one day, she would find an exit in the maze.

But as she has always emphasized, she is an atheist, and she should never believe that fictional myths can become reality, just like the Milky Way is not a magpie bridge where the Seven Fairies and Dong Yong meet, and Chang'e who holds a jade rabbit does not live in the moon.

-273.15 degrees Celsius, also known as absolute zero, is the lowest thermodynamic temperature, and when the kinetic energy of particles is as low as the lowest point, the matter formed by the particles will be at this temperature value. For terrestrial humans, absolute zero is the only theoretical lower bound value.

Shen Yun had been with Cao Fang for a few hours, and he had lost the restraint he had when he first met him, and as soon as he heard this unbelievable statement, he immediately expressed his question: "Absolute zero, isn't it a concept that is still difficult for human beings to reach?" ”

"I can understand your suspicions," Cao Fang replied, "but 'unattainable' only refers to the scientific community on the ground, in our new underground world, where all particles exist in the form of bosons, so that world is a sea change compared to where you came from." The best weapon to deal effectively with an incoming enemy is light, which can only be liquid or solid when it is in absolute zero. ”

"So, you have used light to build a world of light in the lower layers of the earth? How is this possible? No matter how strong the light is, it is only a kind of energy, it is not a substance, what kind of medium can make it solidify? Shen Yun wanted to laugh a little, Cao Fang's words were like a fantasy. However, she stopped abruptly and could no longer laugh.

Cao Fang observed her out of the corner of his eye and helped her to tell the truth she had realized: "Yes, Bose-Einstein condensation. ”

Bose-Einstein condensation!

This is a new state of matter proposed by Albert Einstein 80 years ago, "condensation" is not a general term in daily life, but refers to the sudden "condensation" of atoms in different states to the same ground state, thus forming the same type of substance.

When this theory is applied to photons, it is possible to obtain Bose condensed matter light, which is equivalent to a black hole that creates light, and the incident light does not escape, but only forms a liquid in the form of a stream of water. When liquid light encounters obstacles, it does not produce "water waves" or vortices because it has zero friction and zero viscosity, which is superfluid.

Different atoms undergo a property transition at absolute zero to become the same atom, and these atoms are actually in the "fifth state", that is, the "Bo-Ai condensate". The photons emitted from the laser enter the fifth state, and it is theoretically possible to obtain light matter, that is, solid-state light, but that is only a very bold assumption, even if Einstein was alive, the state of synthetic light would only stay in the liquid state. However, in the new world described by Cao Fang, do they really use laser technology to the extent of so-called black technology that cannot be achieved by the existing wisdom of human beings?

Shen Yun couldn't believe it, but Cao Fang's tone and attitude seemed so determined, as if what she was talking about was just ordinary things in daily life, how could she not believe it?

Cao Fang said, "The new world you are about to enter is officially known as the Underground Light Continent. Your father was one of the three people who came up with this idea, and he was the only soldier among the three, the other two being experts in the fields of physics and medicine. At present, the personnel composition of the Light Continent is very simple, only the army and the Federation of Science and Technology. Needless to say, the military is the Federation of Science and Technology, the full name is the Federation of Underground Scientific Communities. Through the joint efforts of scientists in C&T China, in just over 20 years, different bosons from laser beams have been passed through an environment of absolute zero degrees to form a solid photoactive matter. I remember that the first light-based object they created with the help of a particle accelerator collision experiment was a small bench. Since then, fantastic cities of light have been born one after another. However, it is not correct to say that the light continent is close to the lower layer of the earth, the temperature of the earth's core is as high as 6,800 degrees Celsius, and no matter how superb the technology is, it cannot help human beings to live at a depth of 5,000 kilometers underground. The deepest part of the light continent is the upper mantle, about 800 kilometers above the ground. ”

"The realm of human life has penetrated the earth's crust and entered the upper mantle?"

This is a completely new concept, Shen Yun is not unacceptable, but such a beautiful reality suddenly appeared in front of her, and it was difficult for her to adapt quickly.

Cao Fang's topic turned back to military uniforms, "However, because the Light Continent must be in an environment of absolute zero, we have accordingly developed this photon camouflage suit that can protect the human body from low temperature and radiation. If you stay indoors, AI intelligence can adjust the room temperature as comfortable as the ground for the owner, but once you go outdoors, you must be protected by a photonic suit, otherwise you will be frostbitten by low temperatures, or even die quickly. As for the living items on the Light Continent, from buildings to a pencil or a teacup, they are basically synthesized from solid-state light, so it is really a fantasy fairy tale world. ”

One day, will humans be able to turn light into materials, replacing plastic, glass, steel, and even masonry to build city-states and eventually form a new world? This is not a science fiction story for children, but a category that human science has touched on, no, has penetrated into!

In Shen Yun's ears, Qu Zhaodi's voice suddenly sounded, and he was telling her the story of the flying camel.