One litre of fuel can match a day of many workers' toil
A human labourer turns only about 1 to 5.5 percent of the energy in food into useful work. Burn a single litre of fossil fuel in an engine and you get roughly what 50 hands could deliver working around the clock for 24 hours. That lopsided arithmetic explains why machinery spread into nearly every trade.
Mechanisation means moving from doing work by hand or with animals to doing it with machines. An early engineering text described a machine as something placed between a source of power and a job, adapting one to the other. In modern usage the word implies more than hand tools: devices that change speed, or turn back-and-forth motion into rotation, using gears, belts, cams or cranks. Once machines also correct themselves using feedback from sensors, the step up is called automation.
The roots run deep. Water wheels ground grain and lifted irrigation water in Roman times, and Chinese blast furnaces used water-powered bellows by 31 AD. By the thirteenth century water drove sawmills and trip hammers that pounded flax and rags into paper pulp. Clockmakers pushed precision forward, building gear- and screw-cutting machines, and around 1650 the French mathematician Desargues built the first mill with mathematically shaped gear teeth. The Newcomen steam engine began pumping a mine in 1712, and textile inventions like the spinning jenny of 1764 launched the Industrial Revolution.
Farming changed too. Jethro Tull's seed drill, from around 1700, spaced and buried seed evenly, raising yields while wasting less. Horse-drawn reapers and threshers followed, then steam tractors, and by the 1930s self-powered combine harvesters. In factories, a glass-bottle machine of 1905 replaced well-paid glassblowers and the children who assisted them.
Electricity reshaped the factory floor after 1900. Previously a single line shaft carried power from one engine to every machine. Giving each machine its own motor, known as unit drive, let owners arrange equipment sensibly and run tools at different and much higher speeds. Industrial electric motors now reach efficiencies in the low 90 percent range, and big ship diesels approach 50 percent. Set against even a very low wage of one dollar a day, human muscle works out at around four dollars per kilowatt-hour, dearer than solar panels.
Source: Mechanization
