Part 20

"That's right," Uncle Henry replied. "Let's get some scissors and we'll use our big sheet of cardboard to make a cap for Paul's head that will show you just how the slant of the earth's axis makes it hotter in summer and colder in winter."

"Ooh!" exclaimed Paul, "I always thought it was hot in summer because the earth got nearer to the sun then."

"Lots of people think that, too," said Uncle Henry, "but it isn't so. The earth is really farther from the sun in summer."

Betty ran for the scissors, and Uncle Henry cut out a big circle from the stiff cardboard. Then he cut out an opening in the centre of it that fitted Paul's head just as a stiff straw hat would that was a size too big for him. The circle of cardboard dropped down until it rested on Paul's ears and on the bridge of his nose. This cardboard brim represented the "plane of the earth's equator," just as the pane of glass represented the "plane of the ecliptic." Since the "plane of the equator" is always at right angles to the slanting axis of the earth, the "plane of the equator" is always at a slant to the "plane of the ecliptic."

If you will run a long hat-pin through an orange, and sink the orange exactly to its middle in a glass bowl filled with water, holding the hat-pin at a slant, you will see that the equator of the orange is at a slant with the surface of the water. Half of the orange's equator curves up above the water, while half of it curves down under the water's surface. If you fasten a cardboard ring around the orange at the equator the cardboard will then be at an angle with the surface of the water, which represents the "plane of the ecliptic."

Uncle Henry cut two long strips from what was left of the cardboard and crossed the strips over the top of Paul's head, fastening the four ends of them to the round cardboard brim close to his head.

After this Uncle Henry rolled a sheet of the scratch paper round a pencil, put rubber bands tightly around it, cut the end to bend up and make a foot and pinned the foot to the cardboard strips at the place where they crossed. When Paul had it all on he looked very funny with the pencil sticking straight up from the top of his head, and his eyes just peeping over the cardboard brim on each side of the strip down the middle of his nose.

"Now come on, Mr. Earth," said Uncle Henry, "It's time for you to spin round the lamp-sun for another year or two."

So Paul held his head on a slant and kept it so that the pencil always pointed in the same direction as he went round the lamp. These four little pictures show how he looked at the four sides of the sun where the earth is in Winter, Spring, Summer, and Autumn.

"Now," said Uncle Henry, "you see that if we make a black dot on one of the cardboard strips about halfway between the cardboard brim, or the earth's equator, and the pencil, or the North Pole, it will be about as far north as we are in the United States. And when Paul is in his Summer position, with the pencil slanting toward the 'sun,' you see that the sun's rays beat down much straighter on the black dot than they do when he is on the other side of the lamp, with the pole slanting away from the 'sun.' That is why the Winter sun appears to be lower in the sky at noon than the Summer sun, and also why the Summer sun shines hotter on the earth than it does in Winter. Notice, too, that the rays from the lamp light up Paul's head for quite a little way beyond the foot of the 'pole' when it slants toward the 'sun,' while when it slants away from the 'sun' the rays fail to reach the 'pole' at all. This means that in summer the sun shines a longer time upon the part of the earth that slants toward it. If you could look down from the ceiling at Paul's head in his Summer position and in his Winter one you would see why."

Uncle Henry quickly drew these two pictures of the top of a globe to show the children why the days are long in Summer and short in Winter at any point in the United States.

The Summer Day lasts while the black dot on the earth travels from C to D--more than half-way round.]

"It's just like the hot water bottle mother kept in my bed that time I had a chill after swimming," said Paul. "The hotter it was before she put it in the bed the slower it cooled off."

"That's the idea," said Uncle Henry, "the longer the sun shines on any place on the earth the hotter it gets, and when the nights are as short as they are in Summer the place hasn't long to cool off before it is round in the sun's hot rays again. Now do you see why Summer is hotter than Winter?"

The children did.

"There's one thing I don't understand, though," said Peter. "Why are there different stars in the sky in Winter than there are in Summer?"

"That's easy to answer," said Uncle Henry. "Look at Paul again--first when it's 'night' on his face on the 'Summer' side of the lamp, and then when it is 'night' on his face on the 'Winter' side of the lamp.

"At 'night' in Summer Paul looks at the pictures on one end of the room. The cardboard brim, or 'plane of the equator,' is slanted up, above the 'plane of the ecliptic.'"

This picture shows how Paul looked.

"But in Winter, at 'night,' Paul looks at quite different pictures, at the other end of the room. The cardboard brim is slanted down, below the level of the 'plane of the ecliptic.' This is why the path of the Winter Signs crosses the sky higher up than the path of the Summer Signs. In both Winter and Summer you must imagine the cardboard brim to be as transparent as glass, for the 'plane of the equator' is in reality only imaginary."

This next picture shows how Paul looked at the constellations at "night" in Winter.

"Of course the north star and the stars for a considerable distance round the pole never set, and can be seen all night at any time of the year. It is only the ones that rise and set that go and come from our sight with the seasons. In reality they never leave us, for if it wasn't for the sunlight getting in our eyes by day, we could see the Summer night star-pictures in the Winter daytime, and the Winter night star people in the Summer daytime. We are just looking at opposite ends of our big room in the universe on Winter nights and Summer nights, that's all," said Uncle Henry.

Uncle Henry took some folded papers from his pocket and spread them out on the table.

"Here are four maps of the sky," he said, "which show the way it looks at different seasons at 9 o'clock in the evening--on January 1st, April 1st, July 1st, and October 1st. You will see that the groups of stars around the pole are always in view, while the rest of the star people change with the seasons, but even the groups around the pole change their positions with the seasons.

"You have all seen the Swastika. It has been known and used as an ornament for hundreds of years, all over the world--by the American Indians, the Chinese, the East Indians, and many others. I'll show you where I think all these widely separated people got the Swastika, and how it stands for the four seasons."

Uncle Henry drew four little pictures showing the four positions in which the big dipper stands in the four different seasons, with its "pointer stars" always indicating the pole star.

Then he drew all four positions on one sheet of paper, like this:

And when heavy lines were drawn along the handles of the dippers and across the pole star from bowl to bowl the Swastika suddenly appeared like this: