1 Fire is an event, not a thing. Heating wood or other fuel releases volatile vapors that can rapidly combust with oxygen in the air; the resulting incandescent bloom of gas further heats the fuel, releasing more vapors and perpetuating the cycle.
2 Most of the fuels we use derive their energy from trapped solar rays. In photosynthesis, sunlight and heat make chemical energy (in the form of wood or fossil fuel); fire uses chemical energy to produce light and heat.
3 So a bonfire is basically a tree running in reverse.
4 Assuming stable fuel, heat, and oxygen levels, a typical house fire will double in size every minute.
Read the rest at Discover. Link -via Not Exactly Rocket Science