The sphere that is placed closest to you looks to be about half the size as the sphere in the background.  Surprisingly, both spheres are exactly the same size.  If you don’t believe it, grab a ruler and measure them both to confirm.

For a similar effect, be sure to revisit the SUV Illusion where three sports utility vehicles parked on the same street appear to be different sizes despite being identical.

Other Optical Illusions You Might Enjoy

Relative Size Animated Optical Illusion

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Major Drapkin Illusion Card #3 – His Own Size?

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Peace 3D Stereogram Optical Illusion Video

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Moving Snakes Motion Illusion

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Delboeuf Illusion

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Dual Axis Illusion

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