# Four-dimensional creature is what? They may be all around us, but we can not perceive

Einstein believed that we live in a four-dimensional space-time being. Mentioned here refers to the four-dimensional three spatial dimensions plus a time dimension, Einstein unified the two together that time and space are inseparable. But string theory suggests that there may also be higher spatial dimensions of the universe.

If you consider such a case, the spatial dimension to add a one-dimensional, four-dimensional space will become what? Four-dimensional biological and what is it? If someone enters a four-dimensional space, he will face consequences?

Since no one has gone four-dimensional space, so no one knows exactly what kind of four-dimensional space, we can only be understood by analogy dimension. Is a zero-dimensional point; when numerous points in a row, it will give a straight line, which is one-dimensional; myriad dimensional line may be combined into a two-dimensional plane; numerous two-dimensional plane will be combined into a three-dimensional space; Similarly, we can not perceive a certain direction, and then add a dimension, numerous three-dimensional space will be combined into a four-dimensional space.

So, how to imagine the fourth dimension it? On the fourth dimension, you can look as follows Klein bottle:

for what we consider a closed three-dimensional space, in four dimensions, the fourth dimension can be inside and outside the three-dimensional space communicate with each other, so that the concept of three-dimensional space lost inside and outside. About this, we can use two-dimensional space for illustration.

draw a box on a two-dimensional plane, two-dimensional space human plane (as applicable), the two-dimensional block divided into inner and outer spaces. But for living in three-dimensional space for us, there is a third dimension of very interesting things inside and outside the box is connected, it will appear.

in the eyes of the plane, we like the same as the existence of "God." If we take a plane person (let's call Xiaoming) within boxes take up outside into the box, then other people will see Xiaoming plane from a dimension that they can not be perceived slowly disappear, then mysteriously appear out of the box. As a three-dimensional space creatures, we can see what is directly behind the two-dimensional wall.

Likewise, for a four-dimensional space in biological terms, it does not matter inside and outside the three-dimensional space, they can see directly behind the wall stuff, you can see all the faces of a cube at the same time. Biological dimensional windows or doors without opening, the article can be taken out of the room from the fourth dimension. In this process, we will see the items in the room slowly disappear, then reappear outside the room. For us, the four-dimensional biological with super powers incomprehensible.

when light shines into three-dimensional objects when the body, it will cast a shadow on the two-dimensional plane. In fact, we can only see two-dimensional projection of the three-dimensional object produced. Imagine, when the four-dimensional object is irradiated with light, will cast a shadow in the three dimensional space, four dimensional creature can see three-dimensional projection.

Four-dimensional biological perhaps on our side, they may be hidden in the fourth dimension, we can not perceive that dimension, so we can not see the four-dimensional creatures. Biological or four-dimensional shadow projected onto the three-dimensional space, we can not identify what is a three-dimensional object, which is four-dimensional creatures projection.

for the three-dimensional biological terms, enter the four-dimensional space will not be a good thing. Because in four dimensions, the fourth dimension will we communicate inside and outside the body, resulting in the original body of all the things exposed, viscera and blood in the fourth dimension can not be supported, so we can not survive in the four-dimensional space .