Penrose staircase

After a drawing by Lionel Penrose and Roger Penrose.

Penrose staircase (plural Penrose staircases)

1. An impossible loop of endlessly ascending and descending stairs, or an optical illusion appearing to be one.
   • 1984 February, Monte Davis, “Profile of Benoit B. Mandelbrot”, in Omni, →ISSN, page 9:

     Can you make a fractal equivalent of the “Auditory Penrose Staircase,” the illusion of a steadily descending tone, by zooming in on a fractal as it branches?

   • 1989, Martin Gardner, Penrose Tiles to Trapdoor Ciphers: ...And the Return of Dr. Matrix, New York: Freeman, →ISBN, →OL:

     They are the inventors of the famous "Penrose staircase" that goes round and round without getting higher; Escher depicted it in his lithograph "Ascending and Descending."

   • 2010, Diana Deutsch, “The Paradox of Pitch Circularity”, in Acoustics Today, volume 6, number 3, →DOI, pages 8–14:

     This pitch paradox has been used to accompany numerous videos of bouncing balls, stick men, and other objects traversing the Penrose staircase, with each step accompanied by a step along the Shepard scale.

• Penrose stairs
• Penrose steps