Richard Feynman Fire

Caption notes

Feynman pictures a ball crossing a hill and falling into a deep hollow to explain why wood and oxygen can coexist yet release heat during combustion. The hill stands for an energy barrier, and the drop represents the energy released by the reaction. Heat from one reaction can make it easier for nearby reactions to continue. He then asks where the carbon in wood comes from and traces it back to the growing tree, which uses sunlight to turn carbon from atmospheric carbon dioxide into organic matter. In his analogy, the energy released by burning wood is a kind of stored sunlight.