CHAPTER I.. This Earth of Ours.

THIS EARTH OF OURS.

Once upon a time--thus runs a certain tale--there was a man who wanted to see what could be found at the other end of the world.

So he left his home behind him, and started off to explore. He had a toilsome journey. He wandered over wide plains; he climbed steep mountains; he forded dangerous rivers; he crossed stormy seas. Through weeks and months, and even years, he kept straight on, steadily on, patiently on, never turning to right or to left. And at last, what do you think he found?

Was it a world of giants? Or a land of fairies? Or a dark ocean, without any further shore? Or a vast range of hills, reaching skyward? Or a profound depth, going downward?

He certainly must have found something, because he came to the end of his journey and travelled no more. He had no need to travel any more. His task was done: the puzzle was found out; and he had arrived at “the other end of the world.”

Only it was no “end” at all, but just the very same spot from which he had started. For he had actually found his way back to his own old home again.

Don’t you think he must have been rather astonished? It was not at all what he had expected.

Suppose that a spider, living in the middle of a very big plain, were to make up his mind to walk to the outside edge of that plain, and see what might chance to be there. And suppose that, having climbed little hillocks, and crossed little brooks, trying always to keep steadily in the same forward direction, he were to find himself all at once back on the very same spot from which he had first set forth!

He would no doubt be a good deal surprised; and if he had sense to think the matter over he would see plainly that he had not managed, after all, to keep going straight forward, but that he must somehow have turned round without knowing it and gone back to his starting point.

The man in the story made no such mistake, however. He did not turn round. He went always on, and on, in exactly the same direction. Yet in the end he found himself at home! There is the curious part of the matter.

If the world were a flat plain, like the top of a large round table, the man could not have done this. It would be out of the question. He might have turned round and walked back; he could not have walked steadily onward and onward, farther and farther away from his home, only to find himself suddenly there again. The thing would be impossible.

Whether any living man ever took such a journey round the world is more than doubtful. But I can assure you of this: that if any man ever did take such a journey it would end just as that man’s journey is said to have ended. By keeping straight forward, always in one direction, and by going on long enough, he would in time get back to his own house again.

How could he? That is the question. If a spider were to walk on for ever, straight across a flat plain, he would never get back to his starting-point.

But the world on which we live is not a flat plain. For a long while men believed that it was; and they made a mistake.

Let us think again of a spider--one of those tiny red spiders often found in a garden--and let us suppose this wee red spider to be standing on a huge round globe, as large as a house. Suppose that the spider, having very short sight, fancied himself to be on a flat table and resolved to take a walk to the further end, to see what he might find there.

You and I, looking on, would know there was no end to the globe: but the spider could not guess this. He would walk on and on, in a straight line, believing himself always to be on a flat surface. And if he contrived to keep a perfectly straight line all round the globe--not an easy thing to do--then, whichever direction he began to go in, the end would be the same: if he kept on long enough he would go round the whole huge ball, and would arrive again at the spot where first he had stood.

If he did not manage to keep quite a direct line, but zigzagged a little to right or left, he would not reach the same spot; though even then he would get back to the same side of the globe as before. He would find no “end” to it, because a globe, properly speaking, has no “ends.”

And this Earth, on which we live, is not flat, like a board or table, but round, like a globe or orange. It is really very like an orange; for an orange is not a perfect globe, but is a little flattened on its sides, or, as we commonly say, “at the ends.” Our Earth also is rather flat in shape at the north and south poles. A round globe, like an orange, or like the Earth, has really no “ends” at all: though we often use the word when speaking of the two poles.

If you were to take such a journey, starting from your home, and keeping a perfectly straight line onwards always in one direction, you too would in time come back to the spot from which you started.

But a journey of this kind would be very hard to manage: far more so than it sounds. Every little hillock, every little streamlet, every house and every tree, to say nothing of rivers and towns, mountains and oceans, would turn you out of your path. By the time you got round the world, although you would return to the same side of the globe from which you first set out, you might be a long way off from the exact spot.

In case you do not know where the two “poles” are, you should ask some one to show you on a school globe. The north pole and the south pole are both very cold parts of our Earth. Ice and snow are there all the year round.

Half way between the north and the south poles is the equator--a line drawn exactly round the whole Earth: and all round the Earth, on or near the equator, are the very hottest countries. About half way between the north pole and the equator, and between the south pole and the equator, are the “temperate” parts of the Earth--not so very cold, or so very hot.

If a man is travelling from near the north pole towards the equator, or from near the south pole towards the equator, he gets into warmer and warmer places.

But if he is travelling from the equator towards the north pole, or from the equator towards the south pole, he gets into colder and colder places.

The right name for a globe-shaped body, like an orange or like the Earth, is a “sphere.” Neither an orange nor the Earth is a perfect sphere, because both have flattened ends; still, the ends are only a little flattened, and we always speak of the Earth as a “sphere.”

A “hemisphere” means a “half-sphere.” If our whole Earth were cut into two equal-sized pieces each of those pieces would be a “hemisphere.”

We always think of the equator as dividing our Earth into two halves. The half towards the north is called “the northern hemisphere;” and the half towards the south is called “the southern hemisphere.”

Since our Earth is said to be a round globe, like a ball, why do we not see over the edge? A fly, standing on an orange, would have, it is true, a rounded surface just under his feet; but he could take a good view downward over the edge. It would look like an edge to him, though there is no edge really to a ball.

If our world were as small as an orange, and we by comparison were each as large as a fly, then we should be able to do the same.

But the Earth is huge in size: and we are very tiny--yes, exceedingly tiny, side by side with the great Earth! And the surface on which we stand curves away so very gently, so very gradually, that it looks like a flat surface to us--just as the large globe would have seemed flat to the wee red spider, only very much more so. For the difference in size between the Earth and a man is far greater than the difference between the globe and the spider.

You may get some idea of how things are, by standing on the sea-shore, and gazing out to sea. Far away the sky and earth seem to meet in a long line, which we call “the horizon.” That line is always around you, on all sides, wherever you are, though often you cannot see it, because of hills or buildings or trees coming between.

Beyond that line the rounded surface of the Earth drops away, so that you can see it no more. It is, in fact, what looked like an edge, to the fly standing on the orange. To us it looks much more as if the ground slanted upwards to meet the sky. But there is no real upward slant. After a certain number of miles, the surface of the ground or the ocean dips downward, out of sight, and all else beyond that line is out of sight also.

Put your eyes close down upon a large schoolroom globe. You will see at once how the solid ball hides from you part of the room. You can see the ceiling, and perhaps the window and the fireplace, but beyond the globe all is hidden. Your horizon, as you stand thus, is just where you seem to see a sort of edge to the globe, beyond which its rounded surface dips away, out of view.

Looking upward into the sky we are able to see enormous distances--hundreds of miles, thousands of miles, millions of miles, billions of miles away! Light travels to earth from far, far distant stars: and we can perceive those feeble gleams because nothing comes between to hide them.

On the Earth it is very different. Here we can commonly see only a few miles off. Not because our eyes are not strong enough: but because the Earth’s rounded surface soon dips away, and all beyond that dip is cut off from us by the solid body of the Earth.

On a flat plain, or close to the surface of the sea, our view is very narrow. If we climb a hill we get a wider landscape, because we can see farther over the “dip,” and from a mountain-top the view is very greatly increased.

Still, no matter how high we go, the Earth’s surface always stretches away to north and south, to east and west. It always seems to rise and meet the sky, making our horizon-line.

If we could get very, very far off indeed, into the sky, we should then see our Earth floating, like an enormous ball--a huge round solid globe. But this we are never able to do. We know our Earth to be a round ball: but we cannot stand apart and see her to be such.

Did you ever notice a ship “hull-down” on the horizon?--that is, with its masts standing up above the horizon, and its body hidden?

This again was caused by the shape of the earth: the hull of the ship having dipped down below the horizon, while the masts still stood up within sight.

When we see the Sun in the sky, he is always a round body. But when he sinks at night below the horizon part of the round surface is hidden first, and then the whole. Hidden in the same way: by the Earth’s rounded surface coming between him and our eyes.

At the moment when the Sun is all but gone, only one glimmer being visible, you might say of him too, as of the ship, that he is “hull-down.”

QUESTIONS.

1. What is a Sphere?

A body in the shape of a rounded ball or globe.

2. What shape is our Earth?

The Earth is a sphere in shape: but not a perfect sphere, because flattened at the north and south poles.

3. What is a hemisphere?

A hemisphere is a half-sphere.

4. Describe the two hemispheres of the Earth, commonly so called?

The northern hemisphere is the whole of the Earth north of the equator; and the southern hemisphere is the whole of the Earth south of the equator.

5. What is the Equator?

A line supposed to be drawn round the whole earth, exactly half-way between the north and south poles.

6. What is the horizon?

The horizon is that line in the distance where the sky and earth seem to meet.

7. What hides all below the horizon?

The solid body of our Earth.

8. How far can a man see on the Earth?

A few miles, usually. On a hill he has a much wider view.

9. How far can a man see in the sky?

He can see stars millions and billions of miles away.

10. What is meant by a ship “hull-down?”

A ship “hull-down” is partly above and partly below the horizon.

11. What becomes of the Sun when he sets?

He goes down below the horizon.

12. Is the Sun then too far off for us to see him?

No: he is only hidden from us after sunset by the solid body of the Earth coming between him and our eyes.

13. Does the Earth’s surface really rise to meet the sky?

No: it really drops away, so that beyond a certain line we can no longer see it.