An engine is a machine that converts fuel or electricity into mechanical power. It is the heart of a car, a boat, a generator, or a jet. The principle is simple: burn something or push electrons, create motion. The details are anything but simple.

Internal combustion engines burn gasoline or diesel inside cylinders. Pistons move up and down, turning a crankshaft. Electric motors use magnetic fields to spin a rotor. Jet engines suck in air, compress it, mix it with fuel, and ignite it. Steam engines boil water and use the pressure to push a piston.

Types of engines

• Gasoline: spark ignition, common in cars
• Diesel: compression ignition, trucks and ships
• Electric: battery-powered, no combustion
• Jet: turbines for aircraft
• Steam: historical, still used in power plants

Engines shaped the modern world. They powered the Industrial Revolution, the automobile, and aviation. They also pollute. The shift to electric motors is the biggest change in propulsion since the internal combustion engine was invented.