Rotating Grid Optical Illusion

This is pretty trippy: David OReilly found that a large grid rotating at a certain speed will appear to group itself into smaller grids, rotating independently.

It appears the persistence of vision effect overrides our knowledge that this is a single grid and divides it up optically. This only seems to work on a uniform grid (I also had interesting results with a brick formation), but the effect is lost when using a checkered texture.

http://www.davidoreilly.com/blog/2008/07/rotating-grid-illusion/