Will - Thanks Wayne. Fire is the result of the process of combustion. As you rightly point out, in a combustion reaction, a fuel is heated and it reacts with oxygen to produce oxides, compounds that contain at least one oxygen atom and one other element in their chemical formula. But the Sun’s energy comes from a completely different process: nuclear fusion. The difference between fusion and combustion is explained by zooming in to what’s going on inside the nuclei of the atoms of chemicals we’re talking about.