Na Linwan glanced around, and saw that the children who were fascinated by both comrades-in-arms and comrades were very relieved and continued: Actually, here, we have to face a few facts to speak. First of all, because time exists, space also exists. They exist at the same time. If time can be turned back, there are several ways to look at time.

First, let time stop. How to understand it? From conception, birth, experience to death, the period of time from a person's conception and birth to death is a fact, and it has been rushing forward, because the sun and the moon are still changing day by day, and it is impossible to stay for a moment, and time has been advancing; This person is always active in the space. And when the person dies and the life ends for the person, it means that time has stopped in the person. If the mother who gave birth to the person had been alive, she would have seen that time had not stopped. I'll leave this topic for now, and I'll talk about it later.

Second, make time reversible, that is, turn back time. This makes it clear that going back in time is turning back in time. To turn back time is to allow a person to go back in time. I'll leave this topic for now, but I'll talk about that later. Third, let the time turn off. To emphasize, what is a shutdown, and closure cannot be understood as a stop. That is to say, time itself does not stop, it does not flow backwards, it does not close, but it is just artificially participating in the intermittent activity of time through another means. To further illustrate these ways of time, I have to talk about gravity.

Among the gravitational forces, there is one problem that we may have noticed or thought about, or even experienced, that is, two objects will produce gravitational attraction no matter how far apart they are. This gravitational pull travels from one place to another, and it doesn't take time. So what is the transmission of this force? If anything, the transmitter must be faster than the speed of light. For now, all we know is that light is the fastest. We customize time at the speed of light.

There is also an interesting phenomenon, which is also controversial in the scientific community. That is, why is gravitational force inversely proportional to the square of distance? As we all know, gravitational force is proportional to mass, and gravitational force is generated between objects without repulsion, but in the vast universe, it is obvious that there is not only gravitational force, but in terms of relativity, there should also be a universal repulsive force. We know that the irradiation of light is inversely proportional to the square of the distance, because the irradiated sphere is directly proportional to the square of the radius, and the irradiance per unit area is naturally inversely proportional to the square of the radius.

There is a question that the scientific community cannot explain, that is, is gravity also a gravitational field that radiates outward? Also, Why is the gravitational constant constant in the universe? What are the factors that determine the origin of this cosmological constant? This brings us to cosmic forces. The world of chaos can be said to be a world full of power. After I have explained the cosmic forces clearly, we can go back to the question of time. Now let me ask you a question, how many forces are there in the universe that you can see, feel, and even think of?

Li Zhuangzhuang immediately replied: "Uncle, let me tell you, this has been known for a long time in the physics class of our middle school, and force has gravity, elasticity, pressure, buoyancy, resistance, and electricity.

You're not entirely right, but also magnetism, friction, explosiveness, hydraulics, and firepower. Zhao Shiyan hurriedly added.

Xin Ruofei immediately objected: What you said is not complete: there should still be ability, field force, intelligence, strength, mechanical force, external force, and internal force.

Liu Yiyi suddenly smiled and pointed at Xin Ruofei: What kind of power are you? Is there still tension, manpower, ox power, and horsepower? That's all right! No matter how many forces you name in the universe, they can be summed up into four: gravitational force, electromagnetic force, strong force, and weak force. The discovery of gravity was the earliest and was Newton's outstanding contribution. Electromagnetic forces include electricity and magnetism. We Chinese know that the compass is the earliest application of magnetism. In fact, the strong force is the nuclear force, which refers to the force inside the nucleus of the atom. Like the atomic bomb and the hydrogen bomb, both are the release of nuclear power. Weak force belongs to the advanced research category of physics, and it is more difficult to perceive it.

Right! Yiyi's answer is very good! Na Linwan praised with great interest: If we want to figure out the weak force, we must start with the strong force. We all know that matter is made up of molecules, molecules are made up of atoms, and atoms are made up of electrons and nuclei. The most beneficial and excellent thing about the development of science today is the use of atomic energy. Atomic energy is the nuclear energy that uses atoms. The nucleus is made up of protons and neutrons.

The proton is composed of two upper quarks and one lower quark; Neutrons are made up of 2 lower quarks and 1 upper quark. Quark: It is an elementary particle and at the same time the basic component of matter. Quarks combine with each other to form a composite particle called hadrons; The most stable of these are protons and neutrons, which are the building blocks of the nucleus. Let's talk about hadrons in a nutshell, which is a composite particle that is tied together by a strong force from a quark or an antiquark. Hadrons are divided into two categories, baryon and meson. The baryon consists of 3 quarks or 3 antiquarks; The meson is composed of an upquark and an antiquark.

The nucleus of an atom has a strong energy, and when there is energy, light is produced. Light is formed from photons. Photons, also known as light quanta, move at the speed of light and have energy, momentum, and mass. That is, photons have velocity, energy, momentum, mass, and also condensation. It is impossible for a photon to be stationary. This must be emphasized. The photon also has the property that it can change into other matter, but it exhibits conservation of energy and conservation of momentum.

Going back to weakness, I'll explain it in detail. Because the weak force is different from the macroscopic visible forces such as gravitational and electromagnetic forces, it is only present in the range of extremely small particles, so it is more difficult to perceive it. However, scientists have discovered that the weak force has a very wonderful decay process, that is, from neutrons to protons to electrons to neutrinos, in this process, there are no photons involved, so it is not caused by electromagnetic force. Again, it is not caused by gravity because the mass of the particle is too small for its gravitational force to cause decay.

Finally, because the strong forces between nucleons are attracted to each other, it is even less likely to cause decay. This is where weak forces come into play. However, there is a question, scientists have been tracking, how does the weak force come about? Don't say it, but let scientists really find the fifth force, which is the supercharged force. So, the question arises again, under what force does the supercharged force occur?

Dad, I have understood, you are saying that there is still a substance in the universe that we don't know, since there is a substance that we can see, let's call it positive matter for the time being, then according to the principle of relativity, there must be invisible matter negative matter.

(End of chapter)