Knots represents three objects with a one-sided surface, similar to a Möbius strip, named after the German mathematician and astronomer August Ferdinand Möbius (1790-1868). The knot at the upper right is clearly one-sided. The one at the lower centre also has just one side, but appears to have four. To verify this, begin at any point and follow the side around the object. It will take four full turns before your eyes come back to the starting point. To do the same thing with the third knot, at the upper left, you will need to go around eight times.