So the furious hurricanes on Jupiter are brought about, partly, at all events, by Jupiter’s own heat, and not by the Sun’s power alone. On the whole, we can hardly look upon Jupiter as a nice and fit place for either animals or men to live in. That does not mean that he can never become nice and fit. Our Earth was a very, very long time being made ready to serve as a home for men. Perhaps Jupiter is being made ready also for some such use. As he is so large he cannot cool down nearly so fast as our Earth. Jupiter’s moons all shine as our moon shines, by borrowed sunlight. The smallest of his four chief moons--which can easily be seen from the Earth--is about the same size as our Moon, and the biggest is larger than Mercury. QUESTIONS. 1. Which is the largest of the planets? Jupiter. 2. How far is Jupiter from the Sun? Nearly fourteen times as far as Mercury is. 3. How much farther still is Saturn? Saturn is as far from Jupiter as Jupiter is from the Sun. So the distance of Saturn is twice the distance of Jupiter. 4. How far is Uranus? Uranus is twice as far from Saturn as Saturn is from Jupiter. 5. Does Jupiter spin on his axis? Yes, in less than ten of our hours. 6. How long is Jupiter’s year? About twelve of our years in length. 7. How fast does Jupiter travel? About eight miles each second. 8. Does Jupiter shine in our sky as brightly as Venus? No, but he is the next brightest planet in our sky after Venus. 9. How many moons has Jupiter? Five moons, four of which can be seen easily. The fifth was only discovered a little while ago. 10. Has Jupiter any markings? He has bands and beautiful coloring when seen in a telescope. 11. Is Jupiter light or heavy? Very light in make; so light that he is thought to be far from solid, and to be wrapped in very thick masses of clouds. 12. Is Jupiter a cooled world like the Earth? Jupiter seems to be only a half-cooled world. 13. Is he hot enough to shine? Jupiter is too cool to shine with his own light; but he seems to be in a very heated and stormy state. 14. How do Jupiter’s moons shine? Like Jupiter himself, by reflected sunlight. CHAPTER XVI. SATURN, URANUS AND NEPTUNE. SATURN is only a little smaller than Jupiter, and very light indeed in weight. Not at all like our firm and solid Earth. He actually weighs _less than water_; which means that if we could make a huge globe, all of water, the same size as Saturn, this water-globe would be heavier than Saturn. This does not look as if Saturn were a very cold or solid globe, does it? A solid globe would surely weigh a great deal more than water.