Monthly Archives: March 2014
25.HOW WAS THE GRAND CANYON FORMED?
The Grand Canyon is one of the greatest spectacles on the face of the earth. At some points it appears like a magic city of rock, with temples, towers, and castles of dazzling colors.
One of the most amazing things about it is that the Grand Canyon was made by a river! The waters of the Colorado River cut out this great gorge in the course of thousands of years. When you consider that it was cut out of solid rock in many places, you begin to appreciate the tremendous force of these waters. Even now, year by year, the rushing Colorado continues to cut deeper into the bottom of the gorge.
24.HOW OLD IS THE EARTH?
This is a question to which we may never have the exact answer. Man has wondered about the age of the earth since ancient times, and there were all kinds of myths and legends that seemed to have the answer. But he couldn’t begin to think about the question scientifically until about 400 years ago.
When it was proven at that time that the earth revolved around the sun (in other words, that the earth was part of our solar system), then scientists knew where to begin. To find the age of the earth, it was necessary to explain how the solar system was born. How did the sun and all the planets come into being?
One theory was called the nebular hypothesis. According to this theory, there was once a great mass of white-hot gas whirling about in space and getting smaller and hotter all the time. As the gas- cloud grew smaller, it threw off rings of gas. Each of these rings condensed to form a planet, and the rest of the mass shrank into the center to become the sun.
Another explanation is called the planetesimal theory. According to this, millions and millions of years ago, there was a huge mass made up of small, solid bodies called planetesimals, with the sun at the center. A great star came along and pulled on the sun so that parts of it broke away. These parts picked up the tiny planetesimals the way a rolling snowball picks up snow, and they became planets.
Whichever theory is right, astronomers have figured out that it all probably happened about 5,500,00O,000 years ago! But other scientists besides astronomers have tackled this question. They tried to find the answer by studying how long it took for the earth to become the way we know it. They studied the length of time it takes to wear down the oldest mountains, or the time needed for the oceans to collect the salt they now contain.
After all their studies, these scientists agree with the astronomers: The earth is about 5,500,000,000 years old!
23.HOW MANY MOONS HAS JUPITER?
Now that we are all reading about satellites and travel to outer space, a great deaf of curiosity has been aroused about the other planets ~ our solar system. With the possible exception of Mars, the most interesting one to us is probably Jupiter.
To begin with. Jupiter is really like a miniature solar system in itself! At present, no less than sixteen satellites, or moons, have been discovered revolving around Jupiter. Four of these are approximately the size of our own moon. Two of them are only about 30 miles in diameter, and some of them are real midgets. They are 15 miles in diameter or less!
Jupiter is the largest of all the planets with a volume more than 1,300 times that of the earth. When you look at it with the naked eye, it appears as a brilliant and beautiful spectacle. Yet it is 367,000,000 miles from the earth at its nearest approach!
Astronomers find a constantly changing “show” when they look at Jupiter through a telescope. It has dark streaks, or belts, separated by bright spaces called zones. The belts don’t keep their shape, but often break up into irregular markings of all kinds. The zones change, too, from time to time, with dark spots and bright white areas suddenly appearing. Sometimes a belt, or part of a belt, will disappear for a few weeks altogether. Astronomers believe that what we see as belts, or zones, are a shell of clouds or vapors which are often in a disturbed condition.
One of the strange things about Jupiter is that it often displays striking colors on its surface. Two of the belts change from very red to brown, grey, or even a bluish color. It is thought that this has something to do with Jupiter’s revolution about the sun. This takes 12 years, and the changes in color seem to follow a cycle that repeats itself every 12 years.
Probably the most interesting and curious thing that has been noticed about Jupiter is its great red spot. It is about 30,000 miles long and about 8,000 miles wide. It varies greatly in color, form, intensity, and motion. In fact, in some years it is brick red, in other years it is grey, and sometimes it seems to disappear altogether. Not only that, but this mysterious red spot actually seems to move about on Jupiter, as if it were drifting.
