Everyone is familiar with pinwheels, and few of us haven’t crafted one from a square of paper, a stick, and a pin. Pinwheels are pretty optimized from a design standpoint, and are so cheap and easy to ...

Introduction Have you ever played with a toy pinwheel—or seen larger real-life versions, such as a windmill or wind turbine? Have you wondered why they look the way they do—with multiple blades, ...