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Fig.11.—How we compare the Earth and the Sun.

There is a football on the table, shown in Fig.11. We shall suppose it to represent the sun; we shall now choose something else to represent the earth. We must, however, exhibit the proportions accurately. A tennis ball will not do; it is far too large. The fact is, the width of the earth is less than the one-hundredth part of the width of the sun. The tennis ball is, however, only a quarter the width of the football, so we must choose something a good deal smaller. I try with a marble, even with the smallest marble I can find, but when I measure it, I find that one hundred such marbles, placed side by side, would be far longer than the width of the football; I must therefore look for something still smaller. A grain of small-sized shot will give the right size for the model of our earth. About one hundred of these grains placed side by side will extend to a length equal to the width of the football. Now you will be able to form some conception of how enormous the sun really is. Think of this earth, how big we find it when we begin to travel. What a tremendous voyage we have to take to get to New Zealand, and even then we have only got halfway round the globe. Then think that the sun is in the same proportion bigger than the earth as that football is bigger than that grain of shot. If a million of such grains of shot were melted and cast into one globe, it would not be so large as that football. If a million globes, as large as our earth, could be united together, no doubt a vast globe would be produced, but it would not be so large as the sun. Think of a single house, with three or four people living in it, and then think of this mighty London, with its millions of inhabitants. The house will represent our earth, while great London represents the sun!