EFFECT OF THE MOON’S DISTANCE ON ITS APPEARANCE.
We are now about to take a good look at the moon and examine the different objects which are marked upon it. There is a peculiar interest attached to this particular orb, because it is much the nearest of all the heavenly bodies to our globe, and therefore the one that we can see the best. Every other object—sun, star, or planet—is hundreds, or perhaps thousands, of times as far off as the moon. It is right that we should desire to learn all we can about the bodies in space. We know that the earth is a great ball, and we see that there are many other such bodies. Some of them are much larger, and some of them are smaller than the globe on which we dwell; some of them are dark bodies like the earth, and among them the moon is one. Is it not reasonable that we should make special efforts to find out all we can about this interesting neighbor?
Though the moon is so close to us relatively to other objects in space, yet when we express its distance in the ordinary methods of measurement it is a very long way off—about 240,000 miles—a length nearly as great as that of all the railways in the world put together. An express train which runs forty miles an hour would travel 240 miles in six hours, and the whole distance to the moon would be accomplished in 6000 hours, so that travelling by night and day incessantly you would accomplish the journey in 250 days. To take another illustration, if you wrapped a thread ten times round the equator of the earth, it would be long enough to stretch from the earth to the moon. Or suppose a cannon could be made sufficiently strong to be fired with a report loud enough to be audible 240,000 miles away. The sound would only be heard at that distance a fortnight after the discharge had taken place.
The moon is too far for us to examine the particular features on its surface by the unaided eye. Suppose that there was a mighty city like London on the moon, with great buildings and teeming millions of people, and you went out on a fine night to take a look at our neighbor. What do you think you would be able to see of the great lunar metropolis? Would you be able to see its streets full of omnibuses, or even its great buildings? Would you see St. Paul’s and Westminster—the great parks and the river? Of all these things your unaided eye would show you almost nothing. I can give you a little illustration. Suppose that you made a tiny model of London; imagine this little structure all complete, so that the streets, the buildings, the bridges, the railways, the parks, and the Thames were placed in their true proportions; suppose that the miniature city was so small that it could stand on a penny postage stamp, surely everything would look very insignificant, even if you had the model in your hand and looked at it with the aid of a magnifying glass. But suppose it were put on the other side of the table or on the other side of the room, or the other side of the street. Even St. Paul’s Cathedral itself would have ceased to be distinguishable; but yet the distance is not nearly great enough. You would have to put the little model a quarter of a mile away before it would be in the right position to illustrate the appearance of a lunar London to the unaided eye.