Blivet
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The blivet is an undecidable figure, an optical illusion and an impossible object. It is an object that appears to have three cylindrical prongs, but at the base is only divided into two rectangular prisms: the top surface of the furthest prism becomes the furthest prong while the surface facing the viewer becomes empty space, and vice versa for the closer prism; the third, central prong is formed from the empty space between the prisms.
It was known in 1964, and one was shown on the March 1965 cover of Mad magazine (who dubbed it the poiuyt), and has appeared numerous times since then. An anonymously-contributed version described as a "hole location gauge" was printed in the June 1964 issue of Analog Science Fact/Science Fiction, with the comment that "this outrageous piece of draughtsmanship evidently escaped from the Finagle & Diddle Engineering Works".
It is also called a three pronged blivet, poiuyt, widget, two-pronged trident, three-legged widget, Devil's pitchfork, Devil's tuning fork, or trichotometric indicator support.
The word blivet is sometimes used as a cadigan.
External links
- An Impossible Fork (http://www.cut-the-knot.org/Curriculum/Geometry/ImpossibleTrinomial.shtml)fr:blivet