Poggendorff Illusion

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adjust upper red line
check by removing rectangle
Can your eyes deceive you? Adjust the position of the upper red line until you think it is aligned with the lower red line. Then check your selection by removing the rectangle.

External Links

Poggendorff Illusion (Wolfram MathWorld)

Permanent Citation

Sándor Kabai
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​"Poggendorff Illusion"​
​http://demonstrations.wolfram.com/PoggendorffIllusion/​
​Wolfram Demonstrations Project​
​Published: August 15, 2008