Impossible Fork

ImpossibleForkDevil's pitchfork

The impossible fork (Seckel 2002, p. 151), also known as the devil's pitchfork (Singmaster), blivet, or poiuyt, is a classic impossible figure originally due to Schuster (1964). While each prong of the fork (or, in the original work, "clevis") appears normal, attempting to determine their manner of attachment shows that something is seriously out of whack. The second figure above shows three impossible figures: the ambihelical hexnut in the lower left-hand corner, tribox in the middle, and impossible fork in the upper right.

About the time of the impossible fork's discovery by Schuster (1964), it was used by Mad Magazine as a recurring theme. Their term for it was "poiuyt," which corresponds to the third row of a standard keyboard typed from right to left. The "poiuyt" was commonly used in Mad throughout the 1960s indicating absurdity or impossibility.

Impossible fork columns

Hayward incorporated this figure into a picture of Greek columns (Gardner 1970, Robinson 1998).

See also

Ambihelical Hexnut, Impossible Figure, Impossible Joinery, Penrose Triangle, Tribox

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Ernst, B. Adventures with Impossible Figures. Stradbroke, England: Tarquin, p. 88, 1987.Fineman, M. The Nature of Visual Illusion. New York: Dover, p. 119, 1996.Gardner, M. "Of Optical Illusions, from Figures that are Undecidable to Hot Dogs that Float." Sci. Amer. 222, 124-127, May 1970.Jablan, S. "Set of Modular Elements 'Space Tiles.' ", J. O. The Psychology of Visual Illusion. New York: Dover, pp. 176 and 178, 1998.Schuster, D. H. "A New Ambiguous Figure: A Three-Stick Clevis." Amer. J. Psychol. 77, 673, 1964.Seckel, A. The Art of Optical Illusions. Carlton Books, 2002.Singmaster, D. "Don't Believe Your Eyes." Focus, Dec. 1994.

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Impossible Fork

Cite this as:

Weisstein, Eric W. "Impossible Fork." From MathWorld--A Wolfram Web Resource.

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