the whirligig's motion. String whirligigs have ancient origins. The bamboo-copter or bamboo butterfly was invented in China in 400 BC. While the initial invention did not use string to launch a propeller, later Chinese versions did. The first known depictions of whirligigs are string-powered versions in tapestries from medieval times. Friction whirligigs, also called gee-haws, depend on the holder rubbing a stick against a notched shaft resulting in a propeller at the end of the shaft turning, largely as the result of the vibration carried along the shaft. The motion needed to power a friction whirligig is very similar to rubbing sticks together to create fire. Friction whirligigs are another staple of craft shops and souvenir stores in the Appalachian Mountains. Wind-driven A wind-driven whirligig transfers the energy of the wind into either a simple release of kinetic energy through rotation or a more complicated transfer of rotational energy to power a simple or complicated mechanism that produces repetitive motions and/or creates sounds. The wind simply pushes on the whirligig turning one part of it and it then uses inertia. The simplest and most common example of a wind-driven whirligig is the pinwheel. The pinwheel demonstrates the most important aspect of a blade surface. Pinwheels have a large cupped surface area which allows the pinwheel to reach its terminal speed fairly quickly at low wind speed. Increasing the blade area of the whirligig increases the surface area so more air particles collide with the whirligig. This causes the drag force to reach its maximum value and the whirligig to reach its terminal speed in less time. Conversely the terminal speed is smaller when thin or short blades with a smaller surface area are utilized, resulting in the need for a higher wind speed to start and operate the whirligig. Whirligigs come in a range of sizes and configurations, bounded only by human ingenuity. The two blade non-mechanical model is the most prevalent, exemplified by the classic Cardinal with Wings illustrated at right. History Etymology of the word The word whirligig derives from two Middle English words: whirlen (to whirl) and gigg (top), or literally "to whirl a top". The Oxford English Dictionary cites the Promptorium parvulorum (c. 1440), the first English-Latin dictionary, which contains the definition "Whyrlegyge, chyldys game, Latin: giracu-lum It is therefore likely the 1440 version of whirligig referred to a spinning toy or toys. Origins and evolution