The great sun is very glorious and beautiful, and is always pouring out floods of light and of fierce heat. His light gives day to all the planets; and his heat enables corn to grow upon our Earth, and men to live there; and makes warm summer days when children may play in the fields.

But his fiercest heat does not come to our Earth; we are far, far away from the great fire of the sun; and only get the gentle warmth which makes our world pleasant. Some parts of the world get much more of the sun's heat than others; why they do so, you will know soon; but it is nowhere scorching hot. Everywhere, nearly, people and animals may live, and plants grow; and the sun is a kind friend which gives life and pleasure to all living things.

Day and night, never resting for a moment, the eight planets are continually moving around the sun. When the journey is finished they begin again, silent, punctual, never tired; so punctual are they, that astronomers (the wise men like Galileo who study the stars) know just in what part of the sky to look for a planet at any time. And it comes—more true to time than a railway train, but without any blowing of whistles or ringing of bells, without any bustle or noise or smoke. And the astronomers are filled with delight to see how well these wonderful works of God obey the laws of the universe.

The eight planets do not travel around the sun side by side. Some are much farther from the sun than our Earth. Some are nearer to Earth. As each one keeps at a distance from the sun all through its journey, the more distant the planet is, the longer is the time it takes to finish its course.

The length of our year is 365 days, but the planet Saturn, which is much farther from the sun than the earth is, has a year nearly thirty times as long as ours. That is to say, he has a far larger circle to move around, so it takes him nearly thirty times as long as it takes the earth to go around the sun.

Supposing each of the planets left a shining track which we could see as it went on its course, there would be eight shining circles around the sun at different distances from him. These would show us the orbits or paths of the planets. The path our Earth takes through space in her journey around the sun is her orbit. Not that there is any real path or waymark of any kind for her to follow. Yet, year after year, she journeys over the same course, and never gets nearer to the sun or farther from him.

Should Earth lose her way by any chance, and get nearer to the sun, terrible things would follow. Trees, grass, and houses would all blaze up; the very hills and ground would burn; and our whole world would become a great fire, kindled by the fierce heat of the sun. But there is no chance in the matter. The earth and the other planets keep moving around in their own places by two wonderful laws which cannot be broken. But you are too young to understand about these yet.



Notebook Work: Write the answers to the questions.

1. What discovery did Galileo make?

2. What is a planet?

3. How do planets shine? Do they glow from within or reflect light?

4. How does the size of our world compare to that of stars and other planets?

5. What is our world's name as a planet?

6. How long is our year?

7. Is there any reason why our year should be 365 days in length?

8. What is the path Earth takes around the sun called?