Wheels and Axles

The wheel and axle is probably the most important invention of all time. A wheel is usually a solid disk or spoked-ring, designed to turn around a smaller rod (the axle) passing through its center. The idea of a wheel to help move heavy objects has been around for more than 5,000 years. Wheels with spokes were invented around 2,000 years ago in Egypt for use on chariots.

The figures on the left show the probable progression in the invention of the wheel. Rollers and sledges are two ancient tools used to move heavy loads. After a few steps, people figured out how to adapt a roller and attach it to the sledge as a wheels and an axle.

The figure on the right is a picture of the oldest known wheel. It is about 5,200 years old. This early model of wheel did not rotate around the axle. Instead, the wheels were attached to the axle and the axle rotated with the wheels.