24.118 Paradox and Infinity, Fall 2006

At each corner of the figure depicted, two rectangular prisms join at a 90 degree angle. If any of the triangle's three corners is obscured, the resulting image is consistent, but if all three are left visible, the image is geometrically impossible. The illusion relies on the inevitable loss of information that results from projecting a three-dimensional figure onto a two-dimensional plane. (Image by MIT OCW.)