WHAT CAUSES THE WAVES? If you've ever spent some time near a body of water, then you noticed that on a calm day there are very few waves in the water, and on a windy or stormy day there are many waves. This, of course, explains what causes waves in the water. It is the wind. A wave is a way in which some form of energy is moved from one place to another. Some sort of force or energy must start a wave, and the wind provides that energy in the water. When you watch the waves move, one after the other, the water seems to move forward. But if there is a piece of floating wood in the water, it will not move forward as the waves seem to do. It will only bob up and down with the waves. It moves only when the wind or tide moves it. Then what kind of motion is taking place in a wave? A water wave is mostly the up-and-down movement of water particles. The movement passes on toward the shore, but not the ...
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WHICH IS THE DEEPEST OCEAN? In many ways, the oceans still remain a great mystery to us. We don't even know how old the oceans are. It seems certain that in the first stages of the earth's growth no oceans existed. Today, man is exploring the bottoms of the oceans to learn more about them. Covering the floor of the ocean to a depth of 3,660 metres is a soft, oozy mud. It is made up of the limy skeleton of tiny sea animals. The floor of the deep, dark regions of the sea, where the water is more than four miles deep, is covered by a fine, rusty-colored ooze called "red clay." It is made up of tiny parts of skeletons of animals, the coverings of tiny plants, and volcanic ash. ...
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WHY IS THE OCEAN SALTY? Every now and then, we come across a fact about our earth which mystifies us and for which no answer has yet been found. Such a fact is the existence of salt in the oceans. How did it get there? The answer is we simply don't know how the salt got into the ocean! We do know, of course, that salt is water-soluble, and so passes into the oceans with rain water. The salt of the earth's surface is constantly being dissolved and is passing into the ocean. But we don't know whether this can account for the huge quantity of salt that is found in oceans. If all the oceans were dried up, enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator! Or put another way, the rock salt obtained if all the oceans dried up would have a bulk about 15 times as much as the entire con...
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WHY ARE THERE DIFFERENT KINDS OF CLOUDS? Here is how clouds are formed: Warm air, laden with moisture, rises into the sky. When it gets to a certain height, the warm air cools. At the cooler temperatures it can no longer hold all its moisture in the form of water vapor. So the extra moisture changes into small drops of water, or bits of ice, and this forms clouds. No two clouds are exactly alike, and they are always changing their shape. The reason we have different types of clouds is that cloud formation takes place at different heights and temperatures. And clouds will be com- posed of different particles, depending on their height and temperature. The highest clouds are called "noctilucent" clouds. They may be up as high as 30 to 50 miles! The next highest are called "nacreous," or "mother-of-pearl" clouds. They're 12 to 18 miles high. They are very thin, beau...
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WHAT IS A COMET? At one time, the appearance of a comet caused people to tremble with fear. They believed that comets were evil omens foretelling plagues, wars, and death. Today, we have a pretty good idea of what comets are, though we still don't have all the answers about them. When a comet first appears, it is seen as a tiny point of light, though it may be thousands of miles in diameter. This point of light is "the head," or nucleus, of the comet. Scientists think it is probably made of a great swarm of bits of solid matter, combined with gases. Where this matter originally came from is what is still a mystery. 21 [8:19 am, 24/11/2024] Sher Singh: As the comet approaches the sun, a tail usually appears behind it. The tail consists of very thin gas...
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WHAT ARE FALLING STARS? F or thousands of years men have looked up at "falling stars" and wondered what they were and where they come from. At one time it was believed that they came from other worlds. Today we know that they are not "stars" at all. We call them "meteors." They are small, solid bodies which travel through space, and which may also pass through the earth's atmosphere. When meteors come within our atmosphere, we can see them because they leave a fiery train of light. This is caused by the heat made by the friction, or rubbing, of air upon their surfaces. Strangely enough, most individual meteor particles are quite small, about the size of a pinhead. Occasional meteors weigh many tons. Most meteors are destroyed entirely by heat as they pass through the earth's atmosphere. Only the larger meteor ...
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WHAT IS THE BRIGHTEST STAR? Have you ever looked up at the sky and tried to find the brightest star? You may imagine that the number of stars you can see is countless. But the most that can be seen without a telescope are about 6,000 stars, and one-quarter of them are too far south to be seen in North America. Ever since the days of the Greek astronomers, 2,000 years ago, the stars have been divided into classes according to their magnitude or bright- ness. Until the invention of the telescope, only six magnitudes, or degrees of brightness, were recognized. Stars of the first magnitude are the brightest, and stars of the sixth magnitude the faintest. Stars fainter than the sixth magnitude cannot be seen without a telescope. Today, stars can be photo- graphed with modern telescopes down to the 21st magnitude. A star of any given magnitude is about two and a half t...