The so-called four-dimension, simply put, is to add a time axis to the axis of length, width and height, that is, the length is the first dimension, the width is the second dimension, the height is the third dimension and the time is the fourth dimension. A four-dimensional space composed of these four dimensions.

People in the three-dimensional space world seem to have found the existence of four-dimensional space-existence may be perceived. People's knowledge grows in three-dimensional space. It may be difficult to explore high dimensions under the existing conditions. For example, a bug that can only know two-dimensional space crawls in a square box. In this three-dimensional box with limited space, you can never climb to the end. For it, this is an infinite two-dimensional space.

People like us in three dimensions now. When you are in four dimensions, you can't change the limited perception of three dimensions. Where is the four-dimensional space? Our universe should be! (proposed by physicists).

Einstein's theory of relativity explains the universe: before the Big Bang, the chaotic state was a point in zero dimension. The energy released by the Big Bang led to the birth of various substances, which were reflected in various dimensions in turn. The so-called four-dimensional space is the three-dimensional space we face in life and time. Time and space are inseparable and are different parts of a unified whole. Because we are moving at a macro low speed on the earth, we can't perceive the deviation of phenomena in time, so we won't obviously feel the existence of four-dimensional space. If we can look around at a high speed close to the speed of light, then we can see that the ball enters the basket first, and then the player shoots.