Mach discs

What can you see? To investigate the lateral inhibition, the physicist Ernst Mach (1830-1916) used, among other things, rapidly rotating discs with different star patterns (see examples below). When these discs rotate quickly, a grey middle area appears between the black inner area and the white outer area. Shown here is a black star and the corresponding screenshot with the result of the fast rotation, as well as the inverse disk with a white star and the correspondingly changed result:


Note: These examples are very well suited to being shown in real life. To do this, the (enlarged) templates can be set in rotation with the aid of a speed-controlled drilling machine.

What can you do? The project offers a choice of 12 discs, between which you can switch with the up and down arrow keys. The discs are black and white, supplemented by the respective inverse white-black version.

The speed of rotation can be regulated with the slider -360 … tempo … 360 or alternatively with the left-right arrows.

A note on colour enhancements: You can easily colour all discs (saved as costumes) in Snap!’s Paint Editor. Can you see any other effects?

Related topics: Hermann grid illusion, Mach bands, flicker colors