A sun fuel burning effect could not have been so for more than a few million years. But man has existed for about 4 million years on planet earth was formed almost 5 billion years, it was necessary then, to find another explanation to the radiation from the sun. Various theories advanced by the end of the last century and in 1905 to Albert Einstein who finally found the solution: the sun and all stars, is a huge mass of gas is changed, the original gas (hydrogen) becomes progressively the other gas (helium) by fusion of atoms, in the course of this process part of the mass is lost. The difference in that every second, is the equivalent of 4 million tons (!) Is converted into energy which is the radiation from the sun. You gentlemen physicists call this operation the thermonuclear fusion. The most powerful nuclear bombs (bombs H) operate on the same principle. In other words, the sun is a giant pump that operates continuously.
Empedocles mentions that the stars and planets are genuine fire, which Empedocles did not know is that its much-admired sun was but a single star, because astronomers are very interested in the sun because it is the only star we can study in detail, by reason of its proximity, we must know that there is only a very small star in relation to all that inhabit the sky. There are some smaller than him, but also and in more quantity, others older. The colder there, but also other much more lacking.