Human beings can stand still in three-dimensional space, but in the time dimension, they show a one-way irreversible trajectory. Three-dimensional space is obviously not the peak of the universe, and the ultimate dimension can almost only be understood by mythology, from 0 dimensions to 11 dimensions, take you to understand multi-dimensional space, this is zero dimension, it is the basis point of the dimension, it is just a point, there is no space, there is no matter and time, everything is nothing. In zero-dimensional space, the universe itself is a singularity, where all the laws of physics lose their meaning. Connecting 2 points into a line is the so-called one-dimensional space, which has only a length, and the linear motion can thus become popular. Then draw a rectangle, which is a two-dimensional space, you can think of it as a "paper man", at this time it can move vertically and horizontally, left and right, front and back.
This is the three-dimensional space you are familiar with, that is, the place where human beings live, there are lengths, widths and heights in three-dimensional space, but strictly speaking, human beings live in a universe of "3+1" dimensions, 3 refers to the physical dimension, and 1 is the time dimension. "Dimension" refers to the vector of space, is a quantity with size and direction, can be visualized as this kind of line segment with arrows, so that space can only be three-dimensional, as for the four-dimensional should be called space-time, that is, space + time, in essence, time is the product of human self-definition, the concept of time in the universe is not the time of human cognition. So some people began to point out that since space can form a spatial system, time may also create a long river of time. Everything that happens in this universe is recorded in the long river of time, and in contrast to the three-dimensional space, because time is independent of the concept of dimension, human beings cannot see time and touch time.
Will this phenomenon change in four-dimensional space-time? The scientific community believes that in four-dimensional space-time, time is a visual dimension, which means that organisms living in four-dimensional space-time want to touch time, just as people can see the length, width and height of objects in three-dimensional space. You can understand that time has become an entity in the more brain-burning four-dimensional space-time, and the creatures living here can effortlessly see us at each point in time, and in the four-dimensional space-time, the past, present and future can exist at the same time, which is like when you watch a movie, you find that a screen is divided into several pictures, and they are playing different stories. For example, what happened and what is going to happen in the future, but you can only move forward sequentially, and you can't stop and go backwards, which is the four dimensions. What does high dimension do relative to low dimension?
Four-dimensional space-time can achieve absolute invisibility of three-dimensional space, how to understand this? It is essentially different from the invisible existence you think of. For example, suppose an ant can only move on the ground in two dimensions, and you take out an object in three dimensions and hang it over the ant's head. We can see ants and objects from our point of view, but for the ant, it is completely unaware, which can be seen as an absolute invisibility of high-dimensional space to low-dimensional space. Does this make you start to doubt life? In fact, whether it is a multiverse or a parallel universe theory, they can be called multidimensional universes. Multidimensional space is based on mathematical concept imagination, in reality there are only 0-dimensional and 3-dimensional space, objectively speaking, there is no absolute one-dimensional space or two-dimensional space in reality, they are concepts that people imagine by relying on three-dimensional space.
In string theory, it is believed that various elementary particles are composed of very small linear strings, and there are 5 types of superstring theory, although they look very special, but the research of many physicists still points out that there is a subtle correlation between these theories. M Theory is a theory that unifies the formally compatible superstring theory in the physics community. A notable feature of string theory and M theory is that they require additional space-time dimensions to clear up mathematical contradictions. M Theory has 11 dimensions of space-time, how can this be understood?
When you see a straight line, it can be understood that the straight line in front of you extends to the surroundings of the three-dimensional, the French mathematician Poincaré's Poincaré conjecture is based on three-dimensional space, the coordinates of three-dimensional space are three vertical rays emitted by a point, Piero can draw the perspective of three-dimensional objects on a two-dimensional plane, but can not use perspective to draw four-dimensional, five-dimensional or high-dimensional, or that the image of high-dimensional space-time must rely on the Hodge conjecture method, that is, paste. But it is still difficult for people to understand the infinite multidimensional world, because the 360-degree plane is exactly 2 dimensions, you can not insert another dimension, in our opinion, the center of a sphere can only appear 3 two or two connected and perpendicular to each other rays, if under this premise, but also add another ray, it is bound to squeeze the original space, at this time the coordinates can not be 90 degrees of architecture. So how do you rationalize all of this?
Does the dimensional space imagined by physicists really exist? People have moved out of the Möbius belt, which explains compression from a dimensional point of view, and from the point of view of physics, it has 3 dimensions, however, whoever walks on it can only think that it is a dimension. This makes people more convinced that the existence of multi-dimensional space, five-dimensional space-time, what does it look like to them? Suppose you are a creature living in the five-dimensional world, when you take the college entrance examination, you make a judgment, it will determine whether you are a doctor or a lawyer now, if you are now on the timeline of a lawyer, you want to see you as a doctor, at that time, you need to go back to the time of the college entrance examination, and then you need to follow the timeline of the doctor back to the current time. Six-dimensional beings can be understood as parallel spaces, and scientists believe that six-dimensional creatures can intersect any timeline at any point in time in five dimensions due to distortion, after which the six-dimensional creature can directly travel to another possibility, without having to go back to the time point where the decision was previously changed.
The seventh dimension is to see the six-dimensional space as a point, which is equivalent to adding a singularity, that is, the point at which time begins, that is, countless such points, and the lines composed of them create the seventh dimension. The eighth dimension is that at any point on the seventh dimensional line, there will be any universe, they may be similar to us, or they may be completely different from us, but they are the same as the fifth dimension, the possibilities of these countless universes will not intersect, and if the creature living here wants to cross, he first needs to return to any point on the seventh-dimensional line, and then choose another possibility of the universe to re-walk the timeline. Nine-dimensional equivalent of six-dimensional upgraded version, can travel through parallel universes, the role of time here will completely disappear. It seems to lift space upwards, turning the universe into a ten-dimensional space, and at the same time scientists can realize that the two seemingly unrelated fragments of relativity and quantum theory can be seamlessly combined, which is the graphical structure of 10-dimensional space-time.
This is the 10-dimensional space-time imagined by physicists, and it is impossible for humans to feel such space-time, just as human beings cannot hear ultrasonic waves, because they cannot perceive it and think that it does not exist at all.