The Earth Is Round
Instead of sending our little Eskimo boy on a long voyage round the world to prove to him that the earth is not flat, we can do better. We can all three go to the seashore and watch the ships sailing away and think about what we see.
This picture shows us what we might really see in any harbor like New York, or Boston, or San Francisco. The ships are sailing away to foreign countries. Some of the ships are near and some far off, and there must be other ships, beyond the edge of the sea, that we can not see at all. They sailed away this morning and are out of sight now. They are already beyond the edge of the sea. There is a name for that line where the sea and the sky meet. It is called the horizon line—the hor-i′-zon, with the accent on the i.
It is the line where the sea and the sky meet. You see that it is a line. At least it looks like one.
Now let us look at the ship that is nearest to us. What do you see? (Look at the picture, which is a true one.) You can see the whole of this ship, with all her masts, her three sails on each mast, and her flag. It is a French flag in the picture—three upright bands of red, white, and blue really, though the colors are not given. Those are the French colors. You can see the hull of the ship—the wooden ship herself, that is—and her tall masts. She is so near the shore where we are that we can see her plainly.
Now look for a moment at the ship next to her. This one is farther away and you do not see her so plainly. She looks smaller, too. And the third ship looks smaller still, and so on. That is something to remember. The farther away a ship, or a house, or a locomotive, is the smaller it looks. You know that already, of course, and so does every Eskimo boy, though very likely he has never said it in plain words like that. The second ship is so far away that she looks smaller. But we can see the whole of her. The hull is there, and the masts and the flag, too.
Now let us look at the third ship in the picture. Recollect that the picture is a true one. Real ships near a real shore would look just so. A photograph of ships would be a true picture, and it would show them just as this drawing does. The third ship looks smaller than the second one because it is farther away. And the hull of this ship is not to be seen. We know that the hull is there, of course.
Let us look at the fourth ship now. It is smaller, of course, and not so plain. But you can not see the hull at all. The sails are there and the masts, but where is the hull? Of course the hull is really there. All ships have hulls, and this one has a hull, surely. But what is the reason we can not see it?
Something has come between our eyes and the hull of this fourth ship. And you must notice that while we can see her topsails, the lower ones are partly hidden too. At the left-hand side of the picture there is another ship almost out of sight. You can not see her hull. Her lower sails are quite out of sight, and even the middle sails are nearly hidden. It looks exactly as if she were going down over the farther side of a hill.
If we should stay here and watch all these vessels we should find that pretty soon the fifth one would vanish entirely. She would seem to slip down over the farther side of some hill. She would go beyond the horizon line—the line which is just at the meeting of sea and sky. Soon she would be quite out of sight. Her middle sails would vanish first, and then her topsails, and she would soon be quite gone and there would be nothing to watch.
We might watch the next ship in the same way; and the same things would happen, in just the same order. The middle sails would vanish first, and then the top ones; and she would be gone too. It would be the same for every one of the ships. When a ship is near we can see the whole of her. We can see her hull, her masts, and the three sails on each mast. As she sails away from us we see less and less of her.
The hull disappears below the horizon line first; then we lose sight of her lower sails; next the middle sails disappear; at last the upper sails are seen no longer, and the ship has vanished from our sight. These things will always happen, in just this order, if you watch for them. The tallest things will be seen longest. The sails that are nearest to the water vanish first. The tallest sails vanish last. No matter when you come to the seashore you will always see this happen.
If the sea were really flat, as it looks, these things would not be so. The hull of a ship is the biggest part of her, and on a flat sea it would be seen longer than any other part. But if the sea is rounded, like a part of the outside of a huge globe, things would be as they are in this next picture.
Suppose we were up in the tower, at the left-hand side of this picture, looking out over the sea, and that there were quite a number of ships, just as the picture shows them. If we took a long stick, like a cane, and held it level we might look along it. If the cane were suddenly to grow miles long it would look like the straight line in the top of the picture. The cane would be perfectly straight, and we should be looking along it. The ships would be sailing over the water just as in the picture.
The nearest ships would be seen completely. The whole of each near ship would be seen. Some of the far-away ships would be hidden, as in the picture, and only the highest parts of these far-away ships would show. The lowest parts would be hidden, so that if the sea were really curved like a globe and not flat, just the same things would happen that really do happen.
The first picture showed exactly what can be seen any day, by any one, anywhere at the seashore. The ships do vanish just that way—the lower parts first, the higher parts next, the highest parts last. The next picture shows that if the sea was curved and not flat these very things would happen just as they do happen. If the sea were rounded the far-away ships would glide away behind the rim of the world.
We have found a reason for what happens. If the sea is really rounded the rim of it will hide ships that sail behind it, just as ships are really hidden in fact. Even a little Eskimo boy can understand that. Let us give him a short time to think about it.