Universe

Fresh water is necessary for human life because it dissolves the nutrients we eat and carries them through our body in the processes of digestion and absorption. Fresh water also helps regulate body temperature. We cannot drink sea water for two reasons. First, the bacterial count may be too high for our health. The second […]

The Bay of Fundy, which separates both Maine and New Brunswick from Nova Scotia in Canada, has the highest tides in the world. They rise and fall anywhere from 10 to 60 feet in an hour! The energy generated by these tides is so great that Canadian engineers are talking about building a dam on […]

If you have ever spent time at the beach, you probably noticed that the water rises slowly on the shore for six hours, then slowly recedes, or falls back, for another six hours. This movement, which happens twice a day, is called tides. Tides are caused by the pull of the moon when it is […]

Dr. James Van Allen, an American physicist, had been studying space satellites for many years, and in 1958 he came to the conclusion that the reason life on earth is not destroyed by radiation from the sun is due to two belts that surround the earth. These belts, named after Dr. Van Allen, are actually […]

A greenhouse gives plants a glass covering which serves two purposes: it conserves the energy they get from the sun and it keeps the air temperature up. The atmosphere surrounding our planet acts the same way. Only a tiny fraction of the heat and energy produced by the sun ever reaches the earth. And that […]

Even though you might think you are standing still anywhere on earth, you are actually moving in five directions, all at the same time! First, the earth is continuously rotating on its axis, which gives us day and night. Second, the earth is continuously orbiting the sun, traveling 600 million miles a year, at a […]

The top of Mt. Everest in the Eastern Himalaya Mountains on the border between Tibet and Nepal takes honors as the highest place on earth. Everest rises 29,028 feet, or 5.5 miles, above sea level. Attempts have been made to climb Mt. Everest since 1921, but it wasn’t until 1953, after eleven men had died […]

Although the highest mountain peaks have been climbed and the densest forests have been visited, there are still about 140,000,000 square miles of unexplored area on earth. Those miles are found on the ocean floor, with its winding valleys, towering mountains, steep canyons, and vast plains. On land, there are still some remote areas that […]

Geysers are underground springs which spout up columns of steam and boiling water from time to time. They form when cold water finds its way from the surface of the earth deep into the rock below. As the water travels, it finds a crack in the rock or wears away a crevice to make its […]

Fog, like clouds, is a collection of water droplets, dust, and ice. Since city air has more dust and soot from factories, chimneys, and traffic, city fogs are thicker than country fogs. London, the city long famous for its incredibly thick “pea-soup” fogs, enacted antipollution laws which actually decreased its fog problem!

Fog is actually a cloud, but it is a low cloud that lies close to the ground or sea. It is formed when warm currents of air hit against cold air resting above land or water. What happens is that the sudden cooling causes moisture in the warmer air to condense, or form tiny droplets […]

No, it doesn’t. Although most substances shrink when they change from a liquid to a solid, this is not true of water. When water freezes, it expands, or gets bigger, actually one-tenth bigger. So nine buckets of water freeze into ten buckets of ice. This explains why water pipes sometimes burst when temperatures are below […]

Amazingly enough, whenever you ice skate, you are doing precisely that, skating on water. Here’s how it happens. When the blade of your ice skate touches the ice, it actually is putting the pressure of your body weight on that thin strip of ice. The ice melts for an instant as a result of that […]

Our planet has up to 1,000,000 earthquakes every year, but most of them occur on the ocean floor and cause very little or no damage. It is only those which occur on land and near big cities that cause damage and loss of life. There are places which have never had a serious earthquake, the […]

The outer layer, or crust, of the earth is made up of plates that are constantly moving past one another in very slow side-to-side and up-and-down movements. These movements cause the earth’s rocks to rub against and slide past each other at their outer edges, creating a break in the crust. This break is called […]

No. Each liquid has its own freezing point. Water, for example, freezes at 32° Fahrenheit (0° Celsius). Mercury freezes at a lower temperature, -38° F. (-39° C), a good reason why it is used in most thermometers. Salt water, or seawater, freezes at about 28.5° F. (-1.9° C), lower than fresh water because of the […]

Dry ice is the name given to carbon dioxide, a gas, when it freezes into a solid state. Dry ice is used to refrigerate food. It is called “dry” ice because when it melts, it doesn’t melt into a liquid like ordinary “wet” ice does. Dry ice melts into a gas. Foods that have to […]

Perhaps you thought that the weather conditions at the Arctic area of the North Pole and the Antarctic area of the South Pole are pretty much alike. Most people think that, but they are wrong. In the first place, the North Pole is mostly water, the Arctic Ocean, with just the edges of the continents […]

Hurricanes are violent storms of wind and rain that can hit areas hundreds of miles across. They usually start in the tropics, with warm, moist air rising in a spiral over the ocean. As the air swirls upwards to colder areas in the atmosphere, the water vapor in the warm air cools and turns to […]

The weight of air pushing against the earth is what weathermen call air pressure. This weight changes from place to place and from time to time in the same place. These changes are sometimes caused by changes in temperature. When the sun’s heat warms the air, it makes the air currents rise skyward. Since warm […]

Although you probably know that liquids and solids have weight, you may not have realized that air has weight too. You can see this weight by taking an “empty” soda bottle, pumping out the air with a small pump, and covering it immediately. Then weigh the bottle. Now, unscrew the cover and let the outside […]

When you drop a straw into a bottle of soda, that straw is filled with air. As you put the straw into your mouth and start sucking in, you begin by sucking the air out of the straw, creating a vacuum, or airless space, inside the straw. Since air pressure is at work all around […]

When electricity is given off through lightning, it heats the air in its path. This heating makes the air expand quickly and often violently. The molecules of heated air fly around in all directions and collide with cooler, distant air. This collision sets up a “wave” of noisy, rumbling air called thunder.

When Ben Franklin came in from the storm with his key and kite, he brought back some important facts about electricity for all the world. We now know that lightning is an electrical current that flows from one cloud to another, or from one cloud down to earth. The tiny droplets of water in clouds […]

Yes, to a very small extent. As the earth rotates on its axis, it wobbles a little because the moon pulls it. This pull is so slight, however, that you cannot feel it, just as you cannot feel the earth rotating. The amount of change in the day’s length will not affect our lives too […]

Grains of sand are really very tiny particles of rock. It takes time and certain kinds of weather to turn rock into sand. Rain, frost, and wind can do the job. At beaches, the tide hitting against the rocks forms sand. Salt water, too, forms sand by dissolving minerals in the rocks. Since rocks are […]

The air moving around the earth, the atmosphere, is heated by the sun. But the sun does not heat this air or the surface of the earth evenly. So, some air is warm and some cold. Warm air rises away from the earth’s surface. When this happens, cooler air flows in to take its place. […]

While geologists disagree as to exactly how diamonds are formed, they do agree that diamonds are formed entirely of carbon and that great heat and pressure were needed millions of years ago for that carbon to change into diamonds. This heat and pressure were believed to have existed in molten rock far below the earth’s […]

Our earth is composed of three main types of rocks, each having been formed in its own special way. The first type, igneus rock, was formed when hot (2,000°F.), melted rock material, magma, deep inside the earth rose to the surface during earthquakes, volcanic eruptions, or other movements of the earth’s crust. This magma cooled […]

Until about thirty years ago, the only people who “made” or claimed to “make” rain were Indian medicine men. How often their magic succeeded, no ale knows. But in the late 1940s, scientists developed a technique to make rain fall. However, this technique can only be used when fluffy cumulus clouds are in the sky […]

Yes. Although we think of it as light, the air has heavy mass. Because the air is held to earth by the strong pull of gravity, it has a total weight of more than 5,600 trillion (5,600,000,000,000,000) tons!

The Polar Lights have got to be among the most fascinating sights in the world. These glowing or flickering colored night lights are known in the Northern Hemisphere as the Aurora Borealis, or Northern Lights, and in the Southern Hemisphere as the Aurora Australis, or Southern Lights. These displays light up the sky with flashing, […]

A comet looks to us like a bright, fuzzy dot in the sky, followed by a long, shiny tail. Although we do not see comets very often, there are about 2 million of them in our solar system. They travel at speeds ranging from 700 miles per hour in outer space to speeds of 1,250,000 […]

The distances that astronomers deal with when they measure the distance between stars, or between stars and planets, are so great that there would be almost no room on this page to express that distance in miles. Astronomers therefore measure those distances in units called light-years. A light-year is the distance light travels during one […]

A star is a huge ball of hot glowing gases whirling in space. Our sun is a star and the only one close enough to earth for us to see its ball shape. Many other stars in the universe are much larger than the sun, some even 1,000 times larger. But all are made up […]

The Milky Way is a huge group of many billions of stars called a galaxy. There are more than a billion other galaxies just like the Milky Way in the universe. The Sun, Moon, Earth, and all the planets form only a small part of our Milky Way. The rest is made up of clouds […]

During the 4,600,000,000 years that the sun has been shining, it has been burning up 22 quadrillion tons of hydrogen and changing it into helium every year. Scientists estimate that the sun has enough of a supply of these gases to keep shining for another 5,000,000,000 years. How do they know this? Astronomers have been […]

Billions of dust and water particles are constantly floating in the air. The sky gets its color from the sun, whose sunlight is a mixture of violet, blue, red, green, yellow, and orange rays, all the colors of the rainbow. When the sun is high in the sky, these red-orange-yellow light rays stream down to […]

When you look up into the sky at the sun and the moon, they appear to be pretty equal in size. But that is far from true. The sun is actually 400 times larger than the moon, with a diameter of 865,000 miles as compared to the moon’s 2,160 miles. Why then do they look […]

Scientists estimate that the sun is 4,600,000,000 years old. They believe that it was formed when the force of gravity pulled gases and dust together in space. As this mass of gases and dust came together, it continuously contracted, or got smaller. As the mass pulled together in a ball shape, the pressure of the […]

Clouds are collections of water droplets or tiny crystals of ice floating in the air high above ground level. They form when warm air containing moisture moves up into the sky and begins to cool. Clouds are not all alike. Some are fluffy and white, while others form gray or black coverings over the earth. […]

To figure out the age of the earth, it is important to know how old the rocks on it are. Scientists can date rocks by measuring the amount it of radioactivity, or rays of energy, they give off. All rocks contain some uranium, which causes radioactivity, and that uranium give off invisible rays of energy […]

If you cut an onion across, you’ll find a series of layers surrounding a central core. A cross-section of our planet would show a similar structure. Studies of earthquakes by geologists, scientists who study the earth, reveal that the earth is made up of three layers: the crust, the mantle, and the core. The crust, […]