Wheel

A wheel is a rotating, typically circular component meant to turn on an axle, and together with the axle it forms one of the basic simple machines used to move heavy loads and support transportation. The earliest wheels are recorded in Sumer, in what is now south central Iraq, before roughly 3500 to 3350 BCE, while the oldest surviving wooden wheel and axle found by archaeologists is the Ljubljana Marshes Wheel from Slovenia, dated to about 3130 BCE in the Copper Age. By turning sliding friction into rolling friction, the wheel let people move heavy objects far more easily, carry loads, and drive the mechanisms of other machines, and it is usually ranked alongside farming and metalworking as one of the technologies that reshaped early civilization. Its influence reaches well beyond transport, since water wheels, spinning wheels and countless later mechanical devices all grew out of the same basic principle.