Tesseract

Everyone knows the image above. It's the surface of a cube. If you cut it out, you can fold it into a cube. A four-dimensional cube has eight three-dimensional cubes as its surface. You can imagine it like this: I'm sitting in a cube with six doors in each wall. Through each door, you can access the opposite cube via a side cube. The starting cube + the end cube + eight side cubes are eight three-dimensional cubes. These eight cubes can be connected to form a three-dimensional surface of a four-dimensional cube.
The problem: To create a four-dimensional cube, I would need a fourth spatial dimension. I could fold this surface into a four-dimensional cube. But that's not possible; there is no fourth spatial dimension.
There doesn't seem to be a second time dimension either. Thus, superluminal speed would be possible in projection.
This raises the question: Is there a curvature of spacetime??

Ludwig Resch