Sphere from a Circle
Here is a new method for folding an uncut circle into a 'sphere'. 1. Fold concentric circles 2. Divide disk into equal-sized pie-slices (any even number will do) 3. Draw zigzags along the radii 4. Reverse all folds in alternating pie-slices (or in a less elegant version, just crimp the radii) 5. Fold up 6. Secure with pins In this technique the sphere is not hollow. The main difference from the more usual way of making spheroid shapes in origami is that instead of folding up 'walls', one folds polar cross-sections of the sphere. In fact this sphere has the odd mathematical property, that its center is the center of the circle, its "surface" the edge of the circle, and all points in between on the sphere are in the same pair-wise order (in distance from the radius) as in the circle. Greater accuracy and surface coverage can be obtained with some effort by using many 'wedges' (=pie slices in the original circle; looked at side-on they are 'arms'...