Lever, Pulley, Screw, Gear

The simple machines — lever, inclined plane and its cousin the wedge, pulley, screw, and gear — are the irreducible parts from which every other machine is assembled. Each performs the same bargain: it exchanges force for distance, so a small push applied over a long path becomes an enormous push over a short one. None creates energy; they only reshape effort into a form human muscle can actually supply.

These were the first technologies that let people exceed the strength of their own bodies without simply adding more bodies. Earthen ramps and wooden levers raised the multi-tonne blocks of the Egyptian pyramids; pulleys and capstans let a handful of sailors control forces that would defeat a mob pulling bare-handed. A small crew with the right mechanism could do the work of a crowd, which is the seed of all engineering.

Nothing exotic was required: a hardwood pole and a rock make a lever, a mound of packed earth makes a ramp, a grooved wheel and a rope make a pulley, and a wheel with pegs meshing into another makes a gear. Builders used these tricks for millennia on instinct and rule of thumb. Only in the 3rd century BC did Archimedes prove the law of the lever and put numbers to mechanical advantage, turning craft knowledge into a science that could be extended deliberately.

Cranes, olive and wine presses, ships' rigging, the screw pump, siege engines, and mills all fall out of these five elements combined. Gearing in particular made it possible to change the speed, direction, and axis of rotation — the key to the water wheel's millstones and, much later, to clockwork. Every engine since, from Newcomen's beam to a jet turbine, is simple machines in combination.