The Heat of the Sun

Abstract

Why start a discussion of the future of the universe by looking at the Sun? Two reasons—one obvious, the other less so. The obvious one is that we and the rest of the solar system depend on the Sun to keep us going. If the Sun changes in the future, then everything in the solar system will be affected. So, before looking at what will happen to the various objects in the solar system, we have to predict what the future of the Sun will be. The less obvious reason is that the Sun is one of the basic building blocks of the universe. Wherever you look into space you see stars. All the assorted shapes and sizes of galaxies that the telescope shows us consist mainly of stars keeping company together. In fact, the universe can be pictured as a kind of town, built of bricks. In a town, the buildings vary in size and appearance; they are arranged in a network of streets and roads; but behind all the apparent variety, everything consists basically of bricks. In a similar way, stars, such as the Sun, are the basic astronomical building blocks, which provide much of the structure in the universe around us. As it happens, the Sun is a fairly average sort of star. This means that, if we can predict what will happen to the Sun in the future, we can also say what will happen to vast numbers of other stars. This, in turn, means that we can say something about the future of galaxies. So, starting with the Sun, we can look at the future of the universe in two ways: going down the size scale to smaller things, like the planets, and going up the scale to bigger things, like galaxies.