# I feel dumb.

I don’t understand this. The animation is pretty cool, and the sculpture is beautiful, but I don’t get the whole fourth dimension thing. I always thought the fourth dimension was time. Can anybody explain this concept to me? Specifically, I don’t get this:

In the three-dimensional world, there are five regular solids — tetrahedron, cube, octahedron, dodecahedron, and icosahedron — whose faces are composed of triangles, squares or pentagons. In four dimensions, there are six regular solids, which can be built based on the symmetries of the three-dimensional solids. Unfortunately, humans cannot process information in four dimensions directly because we don’t see the universe that way. Although mathematicians can work with a fourth dimension abstractly by adding a fourth coordinate to the three that we use to describe a point in space, a fourth spatial dimension is difficult to visualize. For that, models are needed.

In my head, when I put those three-dimensional shapes together, I just get another three-dimensional shape. Like building with blocks. What, exactly, is being built? Does each three-dimensional shape represent a world or dimension or moment in time?

I remember doing arrays back in high school computer science. Mrs. Murphy told us to think of fourth dimensional arrays as putting a “pocket” into the third dimension. I always hated that, because I didn’t think that was accurate, and I didn’t want to base my understanding on a fallacy. I didn’t want to skip the difficult part so I could get my work done. I wanted to understand it.

Am I capable of that?