Watch the video: Optical illusion – flickering grid puzzles science.
This grid has an intriguing property. If we look longer at the graphic and move our eyes a little over it, black dots flicker at the intersections of the grid lines.
The image is a simple black area divided into small squares by gray lines. At the intersections of the lines there are white dots, which begin to flicker when viewed for a long time. This optical illusion is called a scintillation grating, named after the flickering or glittering effect of stars in the night sky. But while the glittering effect of the stars is caused by air turbulence and altered refraction of light in the atmosphere, the flickering effect of the scintillation grid is created solely in our brain. Curious: if the lines are curved, the effect disappears. The scintillation grating is a variant of the more popular Hermann grating. In both cases, the perceptual illusion could not be explained beyond doubt.