The theory of spatiotemporal relativity is expressed in a coordinate system as

The theory of relativity introduces a four-dimensional coordinate system, ie.

Lorenz coordinate system.

Added a T-axis and a timeline to the original XYZ axis, linking space and time!

The absolute view of time and space holds that time and space are two independent concepts, unrelated to each other, and each has absoluteness. The absolute view of space-time holds that the measurement of time and space has nothing to do with the state of motion of the inertial frame of reference, and that the kinematics (e.g., coordinates, velocity) observed by the same object in different inertial frames of reference can be related to each other through the Galilean transformation.

The principle of relativity of mechanics: all laws of mechanics are invariant under the Galilean transformation. However, modern science has confirmed that there is no such thing as absolutely static space and matter in the universe, and there is no such thing as absolute elapsed time.

In Einstein's theory of relativity, time and space are both relative, and time and space are interrelated and mutually conditioned.

Background: However, classical physics (Newtonian mechanics) before the 20th century believed that time and space have no connection with moving matter, and that they exist a priori in human consciousness, and it is only after the establishment of the theory of relativity that people realize that time and space are closely related to moving matter.

The classical view of space-time was first clearly put forward by Newton, who made a clear statement on absolute time and absolute space in his famous book "Mathematical Principles of Natural Philosophy", the so-called absolute, refers to time and space have nothing to do with the observer's state of motion, in fact, the absolute view of space-time is a summary of people's experience in a low-speed state.

The specific properties of time and space vary with the form of matter, and the specific properties of time and space change with the change of the speed of movement of matter.

Time and space, as the form of existence of moving matter, exist independently of human consciousness; All matter exists in time and space, without exception. This shows that the existence of time and space is unconditional and absolute. The absoluteness of matter and its motion determines the absoluteness of time and space.

In the relative view of time and space, time and space are linked, they are interconnected and mutually restricted, and the movement of matter has a certain influence on time and space. Einstein also regarded time as the fourth dimension, which, together with three-dimensional space, forms a four-dimensional space-time.

Time and space exist absolutely with respect to (metaphysical) man, and man who exists relatively is the absolute existence of time and space. (Human-oriented).

We have now observed the fact that there is indeed a connection, but why no one can do it. Just like in the past, people only knew that the earth revolved around the sun, but they didn't know why it revolved around the sun. In the theory of relativity, it is said that an increase in speed slows down relative time, and no one can say why this is the case, because no one can say why the speed of light in a vacuum is a constant and cannot be changed.

Space is considered to be a spatial extent as long as there is matter or force. As for the change of space caused by massive objects, it is not the property of space, but the property of massive matter, and space is only a structure. If the universe is closed, then there must be a closed field surrounding the universe, and this field has no matter, no motion, and no time, but it still belongs to the spatial category of the universe.

It is impossible for matter to fill all the space of the universe, so matter is full of forces. So space is just a structure. Time, on the other hand, is a property of matter, and space is completely different.

Matter can produce force, which is also the property of matter, and matter produces velocity, displacement and time due to the mutual movement of forces, which are all material properties. Whereas there is only space where the force acts, because there is no body matter, time is not generated.

The electrons moving around the nucleus, both the nucleus and the electrons produce time, but the space between them has no time. Of course, the frame of reference is different, and from a human perspective, we can look at the nucleus and electrons as a whole, so the particles have time, but we need to know what time is caused by. The sun can also be seen as a whole, but a large part of the sun's interior does not produce time.

Traditional physics studies believe that when a person stands on a train and shoots, the speed of the bullet is the original velocity plus the speed of the vehicle. And so on a person standing on a train emitting light, and the speed of light is the original speed plus the speed of the train. But experiments have shown that the speed of light is constant regardless of the measurement of any frame of reference.

So what has changed is time and space.

In physics, it is said that time and space become a variable, and they can be reversed by certain factors, or other time changes.

In my opinion, space-time is originally a four-dimensional thing, which is constructed through a variety of concepts, and we can see it in three dimensions, but we cannot see it in four dimensions.

It is still very difficult to understand, in fact, relatively speaking, it represents the motion and bending of matter, and the main analysis is also about some motion of objects.

I think the concept of space-time in general relativity means that space-time is eternal and unchanging, and there are a lot of fixed matter.

The theory of relativity does not have a concept of space-time. What is a concept? A concept is a generalized idea.

There is no such thing as the earth, the sun, and Marx does not have such a concept. We can't say what the Earth is. The concept is in a general sense, for example, a fruit, which is a generalized abstraction of apples, pears, plums, etc., and a fruit is the fruit of a plant with more moisture, which is the concept.

A house is a place to live, and this is the concept of a house, which is a generalized abstract thing. In the same way, what is the concept of time, that is, the process of movement and change of material things, all things are gone and never look back, so time is gone forever. This is the concept of time.

Now that we have the concept, we know what time is. What do you mean, you can't just talk about it. The concept must be compounded.

For example, can time expand and contract? No! Time is generalized, and commonality exists, so why expand and contract!

Is there a size of fruit? You get me a big fruit? Isn't that nonsense?