Steam turbine

A steam turbine extracts power from steam by letting it flow, not by trapping it. High-pressure steam is directed through fixed nozzles onto rows of curved blades fixed around a shaft; the steam, changing direction as it passes, pushes the blades and spins the shaft. Parsons' insight was to do this in *many small stages* — dozens of alternating rows of fixed and moving blades along one shaft — so the steam's pressure and speed step down gradually, each stage taking a modest bite, rather than all at once. The result is a machine with no pistons, no valves, no back-and-forth: just continuous rotation, which is exactly what a generator wants.

The piston steam engine had a ceiling built into its shape. Every stroke it must stop a heavy piston and reverse it, which shakes the machine and limits how fast it can safely run; and it delivers power in pulses that must be smoothed by a flywheel. As demand grew for the *large, fast, steady* rotation that electric generators crave, the reciprocating engine became the bottleneck. The turbine removed it. It could be made far bigger, run far faster and smoother, and pack far more power into far less weight and space — which is why nearly all the world's large-scale electricity, then and now, is generated by turbines.

The turbine is the beating heart of the electrified world. Coal, oil, gas, and nuclear power stations all do the same thing at bottom: make heat, boil water, and blow the steam through a turbine coupled to a generator. Parsons' machine set the pattern and simply grew — from kilowatts to the gigawatt-scale units in modern plants. At sea it displaced the reciprocating engine in warships and ocean liners within a decade, giving the *Dreadnought* battleship (1906) and the great liners their speed. And the same principle of a bladed wheel driven by a hot gas stream, run on combustion gases instead of steam, became the gas turbine and the jet engine.