(1) Time is the Structural Relationship

What is time? Philosophers and scientists have pondered this question for thousands of years. Zhang Yuanzhong said, In addition to serving as a timer for other things, they are themselves contained in the answer of "What is time?" but by no means the whole answer. The oversimplified answer that "time is a number of repetitions" equates time with a clock. The aging of plants and animals, the weathering of rocks, and the evolution of the universe do not have a "number of repetitions," but they all occur in time. Regarding the arrow of time, Zhang Yuanzhong said, The examples cited over the centuries include irreversible processes, the "principle of entropy increase" in thermodynamics, the creation and evolution of the universe, and so on. But these are examples, not the final answers to the arrow of time. "What is time?" There is still no complete answer to this question now, how can there be a final answer to its arrow? (Zhang Yuanzhong. "What is time? ". Science World,2009(6))

Some people say that time is a description of the relative speed of motion between objects, or a physical quantity measuring the length of the interval between two moments, these statements are wrong. Because the concepts of "speed of motion" and "moment" themselves need to be defined in terms of time, so the inclusion of these concepts in the definition of time is a circular definition. Some people say that time is the expression of movement and change, but there are many expressions of movement and change, such as images, sounds, symbols, etc., what is the difference between these expressions and time?

In order to explain the nature of time, we first analyze the relationship between two scenes and time. Scenario 1: There are two people in a classroom. Scenario 2: There is one person inside the classroom and another person outside the classroom. What's the difference between these two scenarios? It is obviously the difference between the positions of two people. According to the narrow definition of structure, the difference in position is the difference in structure. Then we look at the time relationship, if two people made an appointment to meet in the classroom at 8 o 'clock, and then by 8 o 'clock both people are in the classroom, scenario 1 occurs. But if one person comes to class on time and the other person is late, scenario 2 occurs at 8 o 'clock.

Therefore, the "same time" is a kind of structural relationship, "before" and "after" are the change in structural relationship. Because of the structural changes of matter, the spatial state of the world as a whole is different. When we compare the spatial states of these different worlds as a whole, we do not say that they are different worlds, but that they are different times of one world. Therefore, the time is the relationship between different spatial states of the world as a whole caused by structural changes in matter. Because structure determines function, the structural change of a clock is also the reference system for all other functional changes. This allows time to represent all structural and functional changes.

Definition: Time is the relationship between the different states of the world as a whole resulting from all structural and functional changes in matter.

We sometimes say, "Let time freeze", "lock this moment", in fact, what we want to freeze or lock is not time, but structure. The so-called "time reversal" actually means that the structure changes of various substances back to the previous state. Physicists tell us that there was no time before the universe came into being. The so-called non-existence of time means that the structure of the universe did not exist. There is no motion or structural change without matter, and there is no time without structural changes.

(2)Calendar and Clock

The changes we usually talk about, such as driving cars, biological growth, social development, etc., are functional changes or structural changes. Functional changes includes progress and degeneration, both of which need to be measured and therefore both need a frame of reference. Time is a frame of reference to measure all functional and structural changes.

Figure 1.1 System b is the time parameter of system a

If the world has only one system, when it changes from structure 1 to structure 2 and then from structure 2 back to structure 1, we can say that the time has gone backwards. In fact, time itself has no direction, the direction of time comes from the interrelationship of different structures. If there are more than two systems in the world, when system A changes from structure 1 to structure 2, some changes also occur in system B. then when system A changes from structure 2 back to structure 1, system B does not change back to structure 1 of system B, then we cannot say that the time has gone back. At this time, the state of system B can be used as the reference frame for the structural change of system A, on which the change process of system A can be recorded. This is the function of the change of system A regarding system B, that is the history of A, and B is the time parameter of A. The order in which the states of system B occur in this history is the direction of time. Conversely, A can also be the time parameter of B.

The direction of time is not necessarily one-way. When system B is taken as the time parameter of system A, if system B changes from state 2 to state 1, it means that time flows backwards. Such a graph is easy to draw. But when we analyze functional relationships, we don't like this kind of graph, we like single-valued functions. So we need to set a fixed time direction. If we think that the sun rises in the east and sets in the west every day, we can go back to the past and cannot calibrate the direction of time, then we can use the change of seasons as a reference to mark the direction of time. If we feel that the change of seasons is not enough to determine the direction of time, we can use slower changes as the coordinate system, such as human growth and aging. If that was not enough, some long-period systems could be artificially programmed, and various calendars were produced. Therefore, time reversal is not impossible, but is not conducive to human understanding of the world.

The movement of clock is the structural change. The time we usually say generally refers to the relationship between the structural change in a small period of a certain substance and the structural change of the clock. Each point on the time coordinate is a position of the clock hands, so the time we say often refers to the position of the clock hands. Before money came into being, people bartered, and later people used some special commodities as general equivalents, so there was money. A clock is also a "general equivalent". Initially, time is the relationship between any two structural changes, and later people use some special structural changes to express time, such as hourglasses, sundials, etc., and finally use clocks to express time, that is to choose a general equivalent which is most convenient and useful in the various structural changes of time. Therefore, the structural change of the clock is the frame of reference for all other structural changes.

(3)Time is not Reversible

Each of us measures the world by our own frame of reference. Clocks and all other equivalents are substitute standards, not the basic standard of time; each self of person is the basic standard of time. Our body changes and our consciousness changes can not go back. The clock can go back. You just need to modify the clock a little, it can go back, because a clock is a simple system. Changes in a certain part of the human body can often go back, such as recovery from injury, fever can be reduced, some of our ideas can go back. However, the human body and the whole consciousness are complex systems, and it is impossible to regress at the same time. This determines that time can not regress.

Theorem: For any complex system, as long as any part of the system cannot go back to the past state at the same time, then the system can not regress.

Regression is not equal to reversion, and non-regression is not equal to irreversibility. Reversion is a special concept in dissipative structure theory, which is related to the change of entropy, while regression is not necessarily related to the change of entropy. Both reversible and irreversible processes are non-regressive.

Now many people like to talk about going back in time and changing history. It may be possible to see the past, but it is completely impossible to change the history. Because to change the histroy means that not only you alone go back to the past, but all people and all things go back to the past at the same time, which is transforming the whole world.

In fact, all our observations are looking into the past, because the light reflected by any matter has a period of motion before it enters our eyes, but the motion of the light is so fast that the observation of nearby things can be regarded as simultaneous, and the observation of distant stars is obviously of the past. Looking at the past doesn't mean we can go back in time, because it takes time for the light we reflect to reach distant stars, so we can't interact with things from the past. If I can see what my great-grandfather is doing, then this observation is only one-way, he can't see me, he seeing me means he can see the future. So looking at the past doesn't mean going back in time.

(4)Definition of Simultaneity and Sequence

According to the previous definition, time is the relationship between different states of the world as a whole resulting from changes in the structure and function of matter. Time relation includes simultaneous relation and sequential relation. Then what is simultaneous relation? If a person sees an object and at the same time sees another object, the two objects produce two senses in the person's consciousness, and the two senses appear in consciousness at the same time, so that the two senses will establish some of the same associations with other consciousness. What is meant by simultaneity is actually the commonality of this conscious association.

So what kind of associations are made in consciousness? People can feel their body changes and their happiness and sorrow every day, people arrange these feelings, this arrangement is a kind of time order. This chronological order becomes a frame of reference, and when the person observes other phenomena, they correspond to the person's feelings about themselves. For example, I started playing football when I was 9 years old, and that year I saw wreaths at Tiananmen Square in memory of Zhou Enlai. These two senses are connected in my consciousness. So time is essentially an associative relationship between consciousness. Or we may say that there is no abstract time in the world at all, but only concrete substances and their changes, when man observes these changes, he sets up a category in order to deal with their interrelations. The category of time is a kind of consciousness.

Definition: The simultaneous relationship is a close connection in mind between two direct experiences.

Everything is moving and changing. If the results of any two direct observations of the same thing are different, then the sequential relationship between the two observations is called the sequential relationship of time.

Definition: The relationships of "before" and "after" are the order of direct experience in consciousness.

Multiple experiences of an object that is constantly changing form a set in which there are specific causal relationships between the elements. Let A be the set of different experiences of several positions of an object in motion, a1, a2,... are elements in this set. There are two such sets A and B for two objects, and there is a one-to-one correspondence between the elements of the two sets. For example, a1 corresponds to b1, a2 corresponds to b2,...... . Each correspondence is derived from one direct observation. When I think of a1, I think of b1. Let a1 precede a2 and b1 precede b2, since a1 corresponds to b1 and a2 corresponds to b2,... then we can deduce that a1 precede b2 and b1 precede a2. Time can therefore refer to the sequence of several things. All the sequence of the manifestations of different things is thus derived. The correspondence and sequence relation between sets can be regarded as a kind of structural relation. So time is a kind of structural relation.

(5)The Subjectivity and Objectivity of Time

Materialism believes that human cognition is a reflection of objective things, and they will say that time, as a category of consciousness, is a reflection of objectively existing time. Empiricism, on the other hand, holds that knowledge and theory derived from experience are only consciousness, and we cannot judge whether there are corresponding objective facts, which are questions forever. Materialism may be right, but we do not need to prove whether consciousness is a reflection of objective facts, we only need to prove whether this knowledge is beneficial to mankind. As long as a theory can be self-justified, predictable and simple, it is a theory that is beneficial to human being.

People have put forward many objective explanations for time, but they can not explain objectively what time is. Simultaneous and sequential in time must be defined by consciousness, and objective definition can never explain the nature of time. The definition must define the unknown with the known. Time, as one of the most basic concept, must be reduced to the most basic knowledge of people. The most basic knowledge of people is direct experience.

Kant was right to note the subjectivity of time, but he said, "Time is not an empirical concept that is somehow abstracted from experience." "Time is given innately." (Immanuel Kant. Critique of Pure Reason(In Chinese). Translated by Li Qiuling. Beijing: China Renmin University Press,2005, 2nd Edition, pp.64-65.) It is wrong to deny the subjectivity of time. Time must be defined by direct experience. But direct experience is not entirely self-generated by consciousness, it has an objective source. And its content is independent of man's will, so time has objectivity.

The relationships of "before" and "after" defined by direct experience is the basic time relation. What scientists tell us about the time relationship of the birth and change of the universe is indirect experience, and indirect experience needs to be tested by direct experience.

The simultaneity of indirect experience is the association after logical reasoning. If two things A and B cannot be observed at the same time, but A and C, B and C can be observed at the same time respectively, and the elements in them are respectively simultaneous, then it can be inferred that some elements of A and B are simultaneous. Then C becomes the intermediary for judging simultaneity. The sun and moon are easy to observe and their positions change continuously, so humans first use them as intermediaries to judge simultaneity. Later, the judgment of simultaneity became more and more precise, and humans created a more easily observed intermediary - the clock. For example, if you tell me that you got on the plane at 1:00 yesterday, and I remember that I was eating at 1:00 yesterday, and then I believe that I was eating when you got on the plane, an association is established between these two experiences. The results of these logical reasoning can all be wrong and need to be checked.

Definition: The clock is the intermediary for judging simultaneous and sequential relationships.

The clock itself is not time, time is the relationship between the multiple direct observations of the same thing. The clock is only a medium for judging simultaneity. People often think of the clock when they say time, because they often observe the movement of the hands of a clock when they observe the movement of other things. In fact, the relationship between the multiple direct observations of anything is time relationship. 

Everything in the universe has the character of simultaneity or time relationship. So the motion of time is the motion of everything in the universe. The fast or slow change of time mentioned by Einstein also refers to the fast or slow change of the movement of various substances, rather than singly refers to the fast or slow of clock. When an object moves faster, its time slows down, which means that when its position changes faster, its other motion slows down. Other motions include changes in position between the parts inside the object, electronic motions, chemical motions, biological motions, etc.

(6)The equivalence relationship between time and space

As a category of consciousness, the expression of time relation in consciousness is similar to that of space relation, or even the same. We often draw coordinate system with time as the horizontal coordinate and other motion changes (e.g., the height of a person, the size of a firm, the GDP of a country, etc.) as the vertical coordinate. On the horizontal coordinate, we can set the unit, that is, what 1 centimeter represents, whether it is 1 minute, 1 hour, or 1 year. If 1 centimeter represents 1 hour, then the spatial relation of 1 centimeter is equivalent to the time of 1 hour. This way of drawing coordinates is actually how we deal with the relationship of time in our consciousness, when we think of a length of time, we tend to think of a length of space. In other words, in consciousness the time relation is the spatial relation.

Theorem: The time relation in consciousness is a kind of spatial relation.

Any point can have a three-dimensional coordinate of space, and can also have a time coordinate as the fourth dimensional coordinate. There are two reasons why two cars can pass through the same point of a intersection without colliding. First, when two cars have the same x and y coordinates, the z coordinates are different because there is an overpass or there is a car that flies. Second, because when their three-dimensional space coordinates are the same, their time coordinates are different. Here the time coordinates and the space coordinates are equivalent.

Since structure is the spatial position relationship between objects or between parts of the system, spatial relations are all structural relations. And time relations are equivalent to spatial relations, therefore, time relations are structural relations.

Any line represents a functional relationship among three-dimensional coordinates of points. When each point on a line has the same time coordinates, the line is a stationary line, and the points on the line are stationary points. But if the time coordinates of the points on the line are different, the line can represent the motion of the points.

Definition: Motion is the function of time for the structure of a system.

There is no absolute stillness in the world, and even if there is absolute stillness, it can be regarded as a special kind of movement. All movements and changes of matter are structural changes. The advance of time means the movement of the system. Structural change includes the change of ordinary structure and the change of generalized structure.

The incoordination of movement between the various parts of the system is a kind of structural error, and the incoordination will reduce the function of the system. For example, when performing arts, lighting, scenery, props, and photography should be synchronized with the performance, if the lights are not bright during the performance, but bright after the performance, which is changing the structure that should be. This structural change will naturally produce functional changes, that is, the performance fails. People are part of groups or social organization, and incoordination between people's behavior and others will also reduce the function of the system. For example, lateness is a kind of structural error, which changes the function of the system.

Eric Jentsch refers to the structural change content represented by time as process structure, and the spatial structure as component structure (Eric Jentsch. "Self-organizing cosmology". Translated by Zeng Guoping et al. China Social Sciences Press,1992,pp.30.) This distinction shows that he paid attention to the relationship between time and structure. I argued in my book "Self-Organized Life Philosophy" that there was no need to use the term "process structure," and now I think it is not only necessary but important to use the term.

The function of system is determined by structure, which includes the spatial structure and the process structure. Time is a kind of structural relationship, and the sequence of events determines the function of a system.