Mathematica(@mathemetica):AB = BC = CA Three square beams meet pairwise at right angles and appear to bound an equilateral triangle, yet no such solid can exist in ordinary Euclidean three-space. Each corner, taken by itself, is an entirely ordinary joint; the closed circuit assigns incompatible depths and therefore cannot close. Oscar Reutersvärd first assembled the figure from cubes in 1934; Roger Penrose, independently in 1954, called the resulting tribar impossibility in its purest form. A real construction can still produce the identical image, but only from one carefully chosen viewpoint.

2026.09.23 06:19

AB = BC = CA Three square beams meet pairwise at right angles and appear to bound an equilateral triangle, yet no such solid can exist in ordinary Euclidean three-space. Each corner, taken by itself, is an entirely ordinary joint; the closed circuit assigns incompatible depths and therefore cannot close. Oscar Reutersvärd first assembled the figure from cubes in 1934; Roger Penrose, independently in 1954, called the resulting tribar impossibility in its purest form. A real construction can still produce the identical image, but only from one carefully chosen viewpoint.