# Penrose triangle

### From Wikipedia, the free encyclopedia

The **Penrose triangle**, also known as the **Penrose tribar**, is an impossible object. It was first created by the Swedish artist Oscar Reutersvärd in 1934. The mathematician Roger Penrose independently devised and popularised it in the 1950s, describing it as "impossibility in its purest form". It is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it.

The tribar appears to be a solid object, made of three straight beams of square cross-section which meet pairwise at right angles at the vertices of the triangle they form.

This combination of properties cannot be realized by any 3-dimensional object in ordinary Euclidean space. Such an object can exist in certain Euclidean 3-manifolds.^{[1]} There also exist 3-dimensional solid shapes each of which, when viewed from a certain angle, appears the same as the purple, green, and yellow 2-dimensional depiction of the Penrose triangle on this page. The term "Penrose triangle" can refer to the 2-dimensional depiction or the impossible object itself.

M.C. Escher's lithograph *Waterfall* depicts a watercourse that flows in a zigzag along the long sides of two elongated Penrose triangles, so that it ends up two stories higher than it began. The resulting waterfall, forming the short sides of both triangles, drives a water wheel. Escher helpfully points out that in order to keep the wheel turning some water must occasionally be added to compensate for evaporation.

If a line is traced around the Penrose triangle, a 3-loop Möbius strip is formed.

## [edit] Other Penrose polygons

While it is possible to construct a Penrose triangle with other regular polygons to create a Penrose polygon, the visual effect is not as striking, and as the sides increase, the image seems to be warped or twisted.

Penrose square |
Penrose pentagon |
Penrose hexagon |

## [edit] References

**^**Francis, George (1988).*A topological picturebook*. Springer. ISBN 0387964266. In the chapter on the Penrose tribar, Francis attributes this observation to John Stillwell.

## [edit] External links

Wikimedia Commons has media related to: Penrose triangle |

- An article about impossible triangle sculpture in Perth
- Escher for Real constructions
- Three-dimensional model of a Penrose triangle for SketchUp
- Build an impossible triangle
- Impossible sculptures by Francis Tabary
- A large Tribar in Austria/Europe At Camping Rosental Roz in Carinthia/Austria
- A 3D computer solid model of the so called impossible triangle