Zöllner illusion

The Zöllner illusion is an optical illusion named after its discoverer, German astrophysicist Johann Karl Friedrich Zöllner.

In 1860, Zöllner sent his discovery in a letter to physicist and scholar Johann Christian Poggendorff, editor of Annalen der Physik und Chemie, who subsequently discovered the related Poggendorff illusion in Zöllner's original drawing.

This creates the illusion that the black lines are not parallel.

It may be that the Zöllner illusion is caused by this impression of depth.

All these illusions demonstrate how lines can seem to be distorted by their background.

A version of the Zöllner illusion