Definition
The energy revolution is the historical transition from biological sources of power — human muscle, animal labour, wood, wind, water — to concentrated mineral fuels: coal, oil, and natural gas. Steam engines, internal combustion, and electricity multiplied the work an hour of human time could command by orders of magnitude.
Harari treats this transition as the precondition for everything else that defines modernity. Pre-industrial societies were constrained by the rate at which sunlight could be converted into plants, food, and labour. Fossil fuels lifted that ceiling and made industrial-scale production thinkable.
Why it matters
How it works
Energy revolutions proceed by discovering how to convert one form of energy into another more efficiently — chemical to mechanical (steam engines), chemical to electrical (generators), nuclear to thermal (reactors). Each conversion expands the total useful work available and lowers the cost per unit.
The political economy follows. Cheap energy makes labour relatively expensive, which drives mechanisation, which raises productivity, which feeds capital back into more energy infrastructure. The cycle is the productive engine of modernity — and the source of the carbon emissions destabilising the climate it produced.