99.8 MB (2.3 MB compressed)
5906 x 5906 pixels
50.0 x 50.0 cm ⏐ 19.7 x 19.7 in (300dpi)
SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Ehrenstein's illusion - a square in concentric circles. This is one of a number of illusions studied by Walter Ehrenstein. The sides of a square placed inside concentric circles appear to curve inwards when in fact they are straight. This is due to the apparent perspective created by the concentric circles. The brain interprets this picture as having depth and alters its perception of the red square accordingly.
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