Paradoxical Elastic Squares

A math-magic article I wrote for the German magazine Zeit Wissen: with the 13 triangular and square pieces (fig. 1) it is possible to form two large squares shown in fig. 2. Though the second large square has an extra piece the dimensions of the squares seem to be the same! Can you explain why this is possible?

This puzzle is available as greeting cards from my online store.

Ghost Colors

This is one of my earliest color optical illusions. There is no yellow or green in the diamond shapes, just vertical black lines! (If you don’t believe it, use a eyedropper tool to check it.) This intriguing visual effect is mainly due to “color contrast induction“.

Illusive colors
Ghost Squares / Black Diamonds (2002 – 2007)
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Scintillating Starburst: Seeing rays that aren’t there…

This is one of my oldest illusions I created in the 90s. In the picture you may see ghostlike dark radial beams. This illusion is a variant of the Herman’s scintillating grid illusion. I designed this illusion just by turning 45 degrees the Herman grid and then by applying a polar transformation.

From my book “Eye Tricks“, 2001-2007.
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Is Magenta a Real Color?

Most of us are familiar with magenta — it’s a kind of purplish-red that exists between blue and red on color wheels (color wheels don’t accurately represent the physics of photons, but they represent the philosophical reality: color is a human construct that helps us interpret wavelengths to better understand our world).

The odd thing about color vision is that magenta (or pink) color is not in the spectrum of colors, meaning it cannot be generated by a single wavelength of light. Our brains interpret the color sensation of magenta/pink as ‘absence’ of green.

Source: https://www.archimedes-lab.org/Gallery/new_optical_illusions/pages/10n-Pink_rose.html

magenta