Transcript: The Sun is not burning in a conventional sense. In 1871 Hermann von Helmholtz calculated that if the Sun were burning by chemical reactions it would be the equivalent of seven thousand kilograms of coal for each square meter of its surface. No chemical reaction can produce energy with the efficiency that the Sun does. The Sun is powered by the fusion of hydrogen into helium with two consequences: the release of huge amounts of energy and a gradual change of the chemical composition. For each kilogram processed 0.007 kilograms is released as pure energy. The mass-energy conversion efficiency is therefore 0.7 percent. Each helium nucleus created releases about four times ten to the minus eleven Joules. In the Sun every second four million tons of hydrogen are converted into energy and radiated into space. Over the whole Sun the energy release is four times ten to the twenty-six Joules per second. That’s four hundred trillion trillion Watts which is a lot of light bulbs.