When the universe was formed during the big bang, the only elements made in the process were hydrogen and heilum (with trace amounts of lithium and beryllium). The elements that we are made from were produced inside of the first stars, in a process called fusion. Though our Sun is not one of these first stars, but a more recent one, it also uses fusion to produce energy.
In this essay tell what fusion is, and how it produces energy in the Sun. How much nuclear fuel is used in a given amount of time, and about how long will the Sun live before it uses up its supply of fuel.