Poggendorf’s mirror

In the second century BCE, the Sicilian–Greek scholar Archimedes provided a theoretical explanation for the action of a lever, the early force amplifier that was one of key technologies of the ancient world. He showed that two weights would be in equilibrium on a lever arm if their distances from the fulcrum were in inverse proportion to their weights. With this Archimedes introduced a mathematical approach to the analysis of the physical world that would transform science across Europe when his books began to be widely read in the 17th century.

Levers could amplify not just forces, but their measurement too. At the end of the 18th century Charles Augustin Coulomb and Henry Cavendish introduced the torsion method to measure electrical and gravitational interactions. The exquisite sensitivity of the method led to the development of numerous highly accurate instruments, not least to measure the earth’s magnetic field which, rather mysteriously, did not align with geographical north.