In ancient times, time meant time. Time is divided by human beings according to the movement of matter, and it is not inherently existent, and the "time" in the universe is inherently indispensable.

The reason why we can think is because thinking can name the material world, things are real, thinking is virtual, and thinking things are imaginary and used by thinking.

The "time" that has not been divided cannot be named and cannot be distinguished, and only after it has been divided into "time" can it be used by the mind, because it can be named after the division.

For example, we divide the movement of the earth around the sun into one year, and the movement of the earth in one rotation into one day.

If you don't live on Earth, you will never be divided by the movement of the Earth. Therefore, time is just a division of the movement of matter by man in order to facilitate his thinking about the universe, and it is a rule set by man, not some natural rule.

It is artificially divided, and it can be divided in any way.

Time is an objective existence. The concept of time is the result of human cognition, induction, and description of nature.

In ancient China, its original meaning originally referred to the change of seasons or the reincarnation of the position of the sun on the ecliptic. "Guanzi Mountain Quanshu" said: The time, so remember the year.

With the deepening of understanding, the concept of time covers all visible and intangible movements. "Visible time is used to describe the uniform property of all motion processes, and this is the connotation of time.

Since the problems studied by ancient people were basically macroscopic, rough, and slow-paced, they only paid attention to the problem of "time". Later, due to the need to study rapid and instantaneous objects, the concept of "between" was added.

Thus, time encompasses both the continuous and instantaneous states of the process of motion, and its connotation is finally enriched and perfected, and the word "time" is finally finalized.

So what exactly is time?

Even today, we still can't define time in the same way that we define anything practical. We can measure time, but we don't know what time is, and we hang "time" on the wall or on our wrist.

According to Einstein's theory of relativity, we know that time can be extended or shortened. That's why physicists simply use time as a sequence of events and mark them with time. For example, a person's birthday or the expiration date of food, etc.

Does time flow like a river or is there an intermittent succession?

Unfortunately, there is no theory or experiment that can prove whether time flows in a continuous manner or whether it gives the impression of continuity, as in each frame of a movie, with a continuous succession.

The study of the continuity or discontinuity of time also involves the question of whether time has a beginning. There is no definite answer to this question yet. Because the famous Big Bang theory holds that time-space has a beginning; Other scientists point out that the "time" scale does not have a momentary beginning, which is unnecessary.

Then things are complicated. Because according to the principles of quantum mechanics, time intervals smaller than the so-called Planck time are undetectable. Planck time units are on the order of seconds. So it is impossible to calculate the state of the nascent universe in a very short period of time.

In short, as far as current theories are concerned, the first cry of the universe will always be unknown.

Now let's return to the "coherence" of time. Curiously, it flows in a continuous or intermittent fashion, but the smallest, calculable interval is the same as Planck time. In conclusion, time is a continuous band, and physicists treat it as an interlocking, discontinuous necklace.

A few years ago, scientist David Finklerstein proposed a theory, but it did not gain much support in the scientific community. This physicist postulates the existence of time atoms. These time atoms may exhibit their discontinuity.

Does time pass in the same way for everyone?

Einstein's theory suggests that the answer is no. In fact, like space, time is relative.

What does relative mean?

That is, in order to describe an event in its entirety rather than ambiguously, then the event should be placed in a frame of reference.

For example, if I go on a date with someone at the end of the road, the "end" may be the beginning of the road for the other person. If I add "in the square behind the end of the road", then this "date event" is accurate.

The same goes for things that come with a time factor. If I say that 10 years have passed, then I must indicate to which frame of reference 10 years have passed. Obviously, there is no need to be obsessed with details in everyday life.

But who knows if we will organize interstellar travel or communicate with aliens in the future? At that point, the time interval will no longer be so simple, and the relativity of time will be felt.

A well-known example explains it all. Alpha and Beta are twin brothers, 30 years old, both astronauts. In 2000, Beta began traveling in a spacecraft with a speed of 240,000 kilometers per second to a planet 8 light-years from Earth. At this rate, it would take 10 years for the beta to make a round trip each way.

The fact is that in order to reach the desired average speed, Beta needs to speed up and slow down when it reaches its destination. Because their frame of reference is no longer the same, we can separate the alpha and beta times by simply changing the direction of motion.

When Beta returns to Earth in 2020, Alpha will be seen celebrating his 50th birthday, just over 12 years for himself, and he is only 42 years old. This is not an intelligence test. The expansion and contraction of time has been measured by real watches.

In 1971, two physicists, Huffeler of the University of Shengtonhua and Richard Keating of the U.S. Naval Observatory, made a trip around the world and measured four atomic clocks on the plane. The speed of an airplane cannot be compared to the speed of light.

But scientists have confirmed that the elasticity of time has been captured: at the end of the trip, the clock on the plane indicates 59 nanoseconds later than the clock on the ground.

In addition, altitude also affects the passage of time, and Einstein's theory suggests that due to gravity, time passes more slowly the closer it is to the ground. In fact, time passes more slowly in the basement than on the top floor of the building.

Someone once calculated that in a person's life, if they live on the first floor, they can live a microsecond longer, of course, this is too insignificant for longevity.

If time is a scale, then why can't it go forward and backward as in space?

Traveling in time in the future and in the past falls under science fiction. As the Austrian mathematician Kurt Goedel proved in 1949, travel in the past time was not forbidden by the laws of physics, but the conditions were very specific: the universe had to be able to turn (which was impossible in reality), and the seeker of time had to move at a speed greater than 71% of the speed of light.

Anyway, the recipe is there, but there are no ingredients.

As physicist Stephen Hawking has argued, this could be a way for nature to protect itself, while preventing time travel would avoid possible paradoxes, such as encountering oneself or changing history.

Are black holes really time machines?

One of the possibilities offered by black holes is that they fall into them after passing through a space-time tunnel and reappear in the past.

What is a tunnel? There are all sorts of hypotheses, from gravity defying the world to mirroring the world, to cosmic replacement.

While there are many hypotheses, none of them are feasible. Suffice it to think about the super-gravity of a black hole: time is like a rubber band that ends up being stretched, and in such a situation it is hopeless to come out alive. Time is a permanent topic, and people are constantly exploring and trying other methods.

Modern cosmological theories hold that there was no time "before" the Big Bang. "Always forward" means that the increment of time is always positive. Time expresses the arrangement of life and death of objects. "Time" is abbreviated as "time". Time is the movement of matter and the transfer of energy.

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So what is there to be space?

According to the Big Bang theory, after the universe exploded from the singularity, the state of the universe was split from the initial "one", so that there were different forms of existence, states of motion and other differences, the difference in the position of things is called "space", and the change in position is measured by "time".

Space is represented by length, width, height, size. It usually refers to the four directions (directions) up and down.

Space includes cosmic space, cyberspace, ideological space, digital space, physical space, and so on, all of which belong to the category of space. Geography and astronomy refer to a part of the earth's surface, which is divided into absolute space and relative space. Space is made up of different lines, and lines form different shapes, and space is within the line.

Space is a relative concept that constitutes the abstract concept of things, and the abstract concept of things exists with reference to space

The place where objects exist and move (finite or infinite), i.e., the three-dimensional area, is called (three-dimensional) space.

The emergence of non-Euclidean geometry has broadened people's horizons, and the existence of non-Euclidean geometry systems that are different from Euclidean geometry has given new meanings to geometry and space.

In general, a collection of "points" (i.e., elements) or a collection with some kind of geometric structure is called space, such as dimensional space, Riemannian space, and so on.

After the establishment of Riemannian geometry and the concept of dimensional space, the concept of space in the intuitive sense is usually abstracted into a "spatial form" with a certain quantitative relationship in the real world.

Space is defined according to the axioms of space.

Axiom of space: space is unbounded and forever. Logical expression: U=r∈[0,+∞)∧r=ct.

The axiom of space is divided into two parts: the point theorem and the space-time relation theorem.

Point Theory: r∈[0,+∞) is "unbounded", which means "any point in space is centered".

The number of points is infinite, and it is the nature of space that the points are continuous, the points are different, and the points are equal. Here the point P = (r,θ,φ ) [spherical coordinates], r is the distance from the point P to the origin of the spherical coordinate system, and its measured value is a non-negative real number, θ∈[0,π], φ∈[0,2π].

Space-time relationship theory: r=ct is "forever", which means "space is always present in the current moment".

Any point in space must appear in the present moment, which is the basic relationship between space and time. where c is the speed of light constant. Because according to the four-dimensional concept of space-time in the special theory of relativity, the space-time interval ct-r=0 is invariant, that is, there is no interval between time and space, so r=ct means that point P is the point where light arrives instantly, that is, "space always appears at the current moment".

Space is divided into "the space of love" and "the space of knowledge". The horizontal space of sitting side by side is the "space of love"; The vertical space where you sit facing each other is the "space of knowledge". The former makes people feel the need to cooperate and communicate emotionally; The latter makes people feel that there is a sense of competition and oppression, and there is no room for affection to enter.