The secret lies in the fact that the Sun is not just burning. The Sun is not being fed by chemical reactions, for which certain elements are bonded to others which are already present. Its powerhouse is the result of nuclear reactions in which a certain element is transformed into another completely different element: this is the same principle behind the H-bomb, but on an infinitely larger scale. In particular, the Sun transforms hydrogen (which still represents 75% of all the matter in our star) into helium. And where does the energy come from? From this very transformation. In fact, if we weigh the two hydrogen nuclei that are needed to form a helium nucleus, we would find that it weighs 0.7% less than the first two: it is during this hydrogen fusion process that a certain amount of matter is transformed into energy. This is the spectacular mechanism that has kept the Sun going for almost five billion years and will keep it going for another five billion: one element is transformed into another and, according to Einstein's famous equation, matter becomes energy. But the very mechanism that keeps the Sun active, just like for any other star, will also cause it to disappear. In fact, the Sun transforms and loses four tons of matter every second. This is the beginning of the end. If the Sun is a gigantic hydrogen bomb, why doesn't it explode and dissipate into space? The fact of the matter is that the internal pressure generated by the thermonuclear reactions (which would tend to make it explode) is compensated by gravitational attraction, which increases with the amount of matter in the Sun. It is the delicate balance between the "pushing" and "pulling" forces that affect the dimensions and destiny of all stars.
The secret lies in the fact that the Sun is not just burning. The Sun is not being fed by chemical reactions, for which certain elements are bonded to others which are already present. Its powerhouse is the result of nuclear reactions in which a certain element is transformed into another completely different element: this is the same principle behind the H-bomb, but on an infinitely larger scale. In particular, the Sun transforms hydrogen (which still represents 75% of all the matter in our star) into helium. And where does the energy come from? From this very transformation. In fact, if we weigh the two hydrogen nuclei that are needed to form a helium nucleus, we would find that it weighs 0.7% less than the first two: it is during this hydrogen fusion process that a certain amount of matter is transformed into energy. This is the spectacular mechanism that has kept the Sun going for almost five billion years and will keep it going for another five billion: one element is transformed into another and, according to Einstein's famous equation, matter becomes energy. But the very mechanism that keeps the Sun active, just like for any other star, will also cause it to disappear. In fact, the Sun transforms and loses four tons of matter every second. This is the beginning of the end. If the Sun is a gigantic hydrogen bomb, why doesn't it explode and dissipate into space? The fact of the matter is that the internal pressure generated by the thermonuclear reactions (which would tend to make it explode) is compensated by gravitational attraction, which increases with the amount of matter in the Sun. It is the delicate balance between the "pushing" and "pulling" forces that affect the dimensions and destiny of all stars.
