Word of the Day - Ames Window

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Word of the Day - Ames Window

Friday, June 19th, 2009 | Word of the Day |

The Ames trapezoid or Ames window is a style of window which, when observed frontally, appears to be a rectangular window but is, in fact, a trapezoid.

The window is mounted on a rod connected to an electric motor that rotates it about its vertical axis. When it is observed with one eye from about 3 meters or with both eyes at 6 meters, or more, the window appears to rotate through 180 degrees and then seems to stop momentarily and reverse its direction of rotation. It is therefore not perceived vertically to be rotating continuously in one direction but instead is mis-perceived to be oscillating, reversing its direction once every 180 degrees.

The dark bar on the base seems to indicate when you’re seeing the window head-on. If so then at 0:07 you’re seeing the trapezoid parallel to the plane of the camera’s film or sensor.

LATER: Duh. I had the speakers turned off. With the audio on sure enough the window is being viewed head on at 0:07 and again at 0:37.

See also Ames Room. Hat tip to Jason Kottke.

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Tags: optical illusions