Spinning your wheels isn't just going around in circles. In fact, it's revolutionary--literally. The history of civilization has turned on the wheel, and we have traveled as far as we have because of it. One of the six simple machines and perhaps the... (more) most important invention in the history of mankind, the wheel has been essential in all aspects of life--from farming to fighting, traveling to trading. Features interviews with scientists, historians, philosophers, millers, potters, and spinners.