In the central part of the Vichten Mosaic, various elements of the geometrical tessellation are separated by braids. These braids consist of endless ropes (closed loops). Notably, the central braid encircling the octagon is composed of just one rope: although it appears as three separate ropes, it is actually a single rope that wraps around the octagon three times.
The additional braids are separate from the central braid and (locally) consist of two ropes. Interestingly, these braids converge at various corners, where two or even three braids come together. Excluding the central braid, there appear to be five ropes arranged in a non-symmetrical manner. See this linked image.
Whirls
In the Vichten mosaic, there are two rectangular stripes that contain a pattern made with a "whirl" shape.
Describe the whirl shape.
The whirl is the union of four congruent figures that differ by rotations of 90°.
Each figure consists of two parts: The first part is
a half-circle without two half-circles (of half the size).
The second part is a half-annulus that continues as a rectangle.
Describe the optical illusion concerning the two "identical" stripes of whirls from the Vichten mosaic.
The two rectangular stripes have the same area.
The different number of whirls contained in the two rectangles is noticeable by comparing the orientation of the first and the last whirls in a row. The orientation of the whirls alternates. In the stripe above (respectively, below) there is an odd (respectively, even) number of whirls.
