may 9, 1876 - Internal
Throughout the 19th Century, major developments had been made on the engine, which up to this point had been largely steam-based. Rather than heating up water to produce steam that pushed the pistons, several inventors had been working on the idea of combusting fuel to power the engine instead.
The most practical and commercially successful version of this idea was developed by the German Nikolaus Otto in May 1876. Otto's internal combustion engine involved the first "four-stroke" design, meaning the piston inside sucks in the air-fuel mixture, compresses it, which causes the spark, which pushes the piston down again letting out the exhaust fumes.
The benefits of this engine far outweighed the efficiency of the steam-powered versions, particularly it's weight to power ratio. Over the next decade, other inventors would improve upon the idea further, eventually applying it's use to that of transportation, first on boats and then finally on wheeled vehicles themselves.
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History of Human Civilization
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