Carl Sagan – The TessaractIn Blog
In geometry, the tesseract, also called an 8-cell or regular octachoron or cubic prism, is the four-dimensional analog of the cube. The tesseract is to the cube as the cube is to the square. Just as the surface of the cube consists of 6 square faces, the hypersurface of the tesseract consists of 8 cubical cells. The tesseract is one of the six convex regular 4-polytopes.
A generalization of the cube to dimensions greater than three is called a “hypercube”, “n-cube” or “measure polytope”. The tesseract is the four-dimensional hypercube, or 4-cube.
In a normal 3D view we can only see the reflective dimensions of the tessaract in 3 dimensional space, where in the sides and angles are not the same as when viewed in 4D space. Like when we project a 3D cube or see its shadow, we see an image which resembles the object but its dimensions appear changed, the sides inclined more and no longer the all-same sides.
The video beside shows Carl Sagan explain this phenomena.