I had no idea the insides of bowling balls could be so strange

Popular Science:

No matter how hard you try to spin the house balls at your local bowling joint, they rarely curve. That’s because they are simple spheres built for durability, not fancy moves. But a small handful of companies—among them Storm Bowling—create gear that is surprisingly complex inside. Precisely shaped, meticulously balanced weight blocks leverage the laws of physics to help skilled alley jockeys throw a strike on most rolls. This clever engineering allows the projectiles to hook inward as they approach the end of the 60-foot lane, where the invisible oil slick on the boards thins. The spin an expert gives the globe (as fast as 600 rpm) will find purchase there as the friction increases, putting the orb right next to the headpin. Here’s a look at what’s going on under the surface.