Elements of Astronomy

When we look at the sky by day we see the sun; by night we see the moon and stars. These, and all other objects which we see in the heavens, are called heavenly bodies. Astronomy is the science which treats of these bodies. The heavenly bodies are all of immense size, most of them larger than the earth. They look small because they are so far away. If we could fly from the earth as far as we please, it would look smaller and smaller as we went farther, until at a distance of many millions of miles it would appear as a little star. If we kept on yet farther, it would at last disappear from our sight altogether. If we lived on one of the heavenly bodies, it would be to us as the earth, and the earth would be seen as a heavenly body. In trying to think of the relation of the earth to the heavens, we may liken ourselves to microscopic insects living on an apple. To them the apple is a world, than which nothing bigger can be conceived. As this continent is to their apple, so is the universe of stars to our world. We may fancy how their ideas would have to be enlarged to make them comprehend the relations of the Atlantic and Pacific oceans; and then we may try to enlarge ours in the same way to understand the relations of the heavenly bodies.