These rows are perfectly horizontal and are not moving. A mind-bending anomalous motion variation of the Café wall illusion by Akiyoshi Kitaoka.
Source: http://www.psy.ritsumei.ac.jp/akitaoka/motion30e.html
Image transcription: Rows of black and white zigzag patterns forming 2x2 checkerboards on a grey background create an optical illusion of warping and motion.
(Originally published on mastodon.social: 2024-02-16)
If you get out an image editor and compare where the pixels fade to the background grey, they are nearly, but not pixel perfect to the same height on the peaks of each row. Different peaks come to different heights. The darker shaded top left ones come up 2 pixels higher than the light ones.
Saying they’re perfectly horizontal is slightly misleading. A sawtooth wave on a oscilloscope is perfectly horizontal also. Technically correct, but also omitting some key detail.