The MIT team members verified their equation by testing centimeter-wide soft hemispheres they made from silicone materials. (So, basically, Barbie implants?) The wrinkling they saw in the hemispheres matched what they predicted from their equation. Of course, not all wrinkly balls look exactly the same. The differences arise from variables such as how steeply curved the surface is, how strong the wrinkling force is, and how thick the wrinkling object's skin is (Grape skin? Human skin?). All of these variables can go into the equation as coefficients.