|MadSci Network: Science History|
Machines can be divided into two categories, simple and complex. Simple machines are tools that redirect force to make work easier, such as levers, pulleys, wedges, wheels, or inclined planes. The first evidence of simple machines dates back to 2 million years ago: fossils from Africa of early hominids called Homo habilis have been found with the first stone tools - hand axes made from chipped rocks which functioned as crude wedges.
The earliest Complex machines appeared much more recently. Machines which convert energy from a natural source into mechanical work are called prime movers. The first evidence of a prime mover dates back to around 100 BC when waterwheels first appeared in the Middle East. These were an adaptation of the older Noria, a wheel with buckets around the rim used by the ancient Egyptians and Sumerians to move water into irrigation canals. Windmills from Persia appeared by 650 AD, and both machines were used extensively throughout the world through to the Industrial Revolution.
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