Universe

Most things get a little bigger when they are heated, even though you probably cannot notice it. If you were to place a glass in a pan of water and heat the water slowly, all the surfaces of the glass would expand evenly, making the whole glass a little bigger. But if you pour boiling … Read more

Have you ever gone camping in the mountains and heated water over an open fire? If so, then you probably discovered that the water boils much more quickly at the higher altitude than at sea level, but at a lower temperature. The one thing that determines the boiling point of water, no matter where you … Read more

There is no record of it ever having rained cats and dogs, but it has rained FROGS. How can this happen? A whirlwind passing over a river or lake, where frogs mate, may scoop up their fertilized eggs and carry them along in the air for a distance. While the eggs are being whirled along … Read more

No. Dark, dirty snow absorbs the heat rays of the sun more quickly than clean, white snow, which reflects these rays back into the air. So dirty snow melts faster than clean snow. Actually, clean snow isn’t white at all. The tiny flakes are frozen, colorless ice crystals which reflect the light and make the … Read more

When you are in a warm house and it is cold outside, you probably have seen the windows steam up. At one time or another, you also probably took your finger and drew a picture on the window and found that your finger came away wet. And did you ever wonder why? Did you wonder … Read more

Since the moon’s mass (the amount of matter it contains) is smaller than earth’s, the moon has a weaker gravity pull, only one-sixth the pull of earth. This means that everything is six times lighter on the moon than it is on earth. A person weighing 120 pounds on earth would weigh only 20 pounds … Read more

First, there was the challenge of the unknown. We have always had explorers of new frontiers who wanted to find out “what’s out there.” Second, these trips have led to the discovery of important information about ourselves. Preparing an astronaut for weightless travel has taught us much about the human body, that man can work, … Read more

Even though there is no air, no wind, and no water on the moon, that is not the major problem in building a moon city. Neither is the engineering that great a problem. The real problem in colonizing the moon is its temperature. Here on earth, we are not accustomed to great variations in temperature. … Read more

The ocean’s depth is measured not by looking, but by listening. This is done with a detection device called sonar. Sonar comes from the words SOund NAvigation and Ranging. Sound waves are sent to the ocean floor and their return time noted. Sound travels through water at the rate of 5,000 feet per second, so … Read more

Just as your parents today might put a fence around your property to keep out unwanted guests or animals, Emperor Shih Huang Ti built a wall to keep out China’s enemies in 221 B.C. But his wall, the longest in the world, was 1500 miles long, or about the distance from New York City to … Read more

All mountains were formed through very slow movements of the earth’s crust. These changes produced four different kinds of mountains, depending on how the crust reacted to these movements. If the earth’s crust formed waves, or upfolds and downfolds, much like an accordian, and layers upon layers of rock pressed on each other, they formed … Read more

When flowing water hits against any kind of barrier, it twists away and spins around rapidly with great force. This creates a whirlpool. Whirlpools can occur in a small area where a piece of land juts out into a river, causing the water to swirl around. They can also occur in the middle of the … Read more

The colorful stone “icicles” which hang from the roof and walls of some caves are called stalactites, and those rising from the floor are called stalagmites. Both these formations build up when water drips through rocks in a cave roof. These rocks contain mineral deposits called calcite. It is this calcite and other minerals which … Read more

The deep, fine sand we call quicksand forms on sand flats at the shore or at the bottom of streams or rivers which flow on top of bases of clay. The smooth, rounded grains of sand slide past each other in wavy movements called swells. This movement is created because the water has no place … Read more

Fossils are the remains of prehistoric plants and animals which were buried in the earth before they decayed and have been preserved in any of several ways. Petrified fossils, those turned to stone, include bones of animals and wood of plants. As they lay in the earth, they filled with minerals and became solid and … Read more

Coal was formed from the remains of ancient, strange looking trees, giant ferns, soft mosses, and grassy plants, all of which grew in swampy jungles hundreds of millions of years ago. When these giant trees and plants died and fell into the swamp, they rotted and became mixed with other decaying plants, forming a spongy … Read more

The Dead Sea, on the border between Israel and Jordan, is really a lake, fed from the north by the Jordan River. Although the Jordan pours 4,740,000 tons of fresh water into the Dead Sea each day, that fresh water evaporates very quickly because of the extreme heat in this part of the world. The … Read more

Caves, or caverns, are holes made in the earth’s surface by the forces of nature. Sea caves were formed by the steady beating of the sea against large rocks on shore. This beating, over thousands of years, hollowed out a cave. The Blue Grotto on the Isle of Capri in Italy is probably the best-known … Read more

Springs form when rain water gets into rocks through cracks. Gravity pulls it down until it finds an opening in the ground in a low place. The spring water escapes through cracks in the rocks along these low places. As it passes through the rocks, the water picks up minerals, which some people consider health-giving. … Read more

Ordinary light seems white as it shines, but it is actually a combination of colors, violet, indigo, blue, green, yellow, orange, and red. Any time the light gets broken up, as in a soap bubble, an oil puddle, a piece of cut glass, or a diamond, we see all or most of these colors. In … Read more

To answer that question takes a lot of “ifs.” If the earth were completely dry, with no oceans separating continents, you, as a person, could walk around our planet, traveling day and night at a steady pace, in less than a year. If, however, you were a tidal wave, you could cross the earth in … Read more

A volcano erupted on August 27, 1883 on the tiny Indonesian island of Krakatoa in the South Pacific. The eruption was so powerful that it caused a tidal wave, or huge wall of water, as tall as a 9-story building. The wave wiped out 163 villages on Krakatoa, killing 36,380 people. It even washed ashore … Read more

In order to avoid airplane collisions because of all the air traffic over our big cities, the sky is carefully mapped. It is actually divided into highways, or airways, which are numbered and have speed limits. As a kind of road sign, radar signals from control towers at check points along the route are beamed … Read more

Man’s deepest journey to the center of the earth was made by a petroleum company in Texas. The hole was dug in search of oil, but when none was found, the hole was plugged. However, drillers worked for two years, at a cost of 3 million dollars, to reach a depth of 25,340 feet, or … Read more

Since the earth is suspended in space, it cannot be put on a scale and weighed. But scientists can estimate its total weight by estimating the weight of each of its parts, the crust, or solid rock, the mantle, also solid rock, and the core, a liquid, because of the great heat at the center. … Read more

What! In the driest place in the world? But the answer is yes! In places like the Sahara Desert in Africa, people can fish in the many underground streams which lie on top of a layer of clay beneath the sand. The water feeding these streams comes from nearby mountains where rain does fall. This … Read more

When a glacier, or river of ice, reaches the sea, a piece of it often breaks off, falls into the sea, and floats. These broken-off pieces of glaciers are called icebergs. Icebergs come in all sizes, from 20 feet across up to 200 miles across. Some icebergs rise as high as 400 feet above the … Read more

When you live in a place like Siberia, in northern Russia, you know what cold means. Ice and snow cover this area for half the year. This is the place of the lowest temperature ever recorded, 90° below 0° Fahrenheit. It is not a good place for people who enjoy outdoor sports. Five minutes outdoors … Read more

Snow is actually water vapor that has frozen in the clouds into shimmering six-sided ice crystals. These ice crystals appear white instead of colorless, as does water, because all the sides of the little ice crystals that make up a snowflake reflect light. The amazing thing is that although billions of snowflakes fall in a … Read more

Most glaciers move very slowly, usually less than a foot a day, although some have been known to move more than 50 feet a day. However, different layers of one glacier also move at different speeds. The bottom moves slowly because it is rubbing against the land, while the middle and top move more quickly … Read more

Scientists studying glacial ice in Greenland drilled down 4,550 feet and concluded that the glacier was formed 2,000 years ago. But that is pretty “new” ice if you compare it with the glaciers in Antarctica. These glaciers are estimated to have formed about 90,000 years ago, and have remained frozen since then! About 250,000 years … Read more

The huge masses of ice flowing slowly over land are what we call glaciers. They form in high mountains and in polar regions, where large amounts of snow build up and freeze into ice. Snow falls in these places during the winter, but not all of it melts in the summer. The remaining snow builds … Read more

Water moves continuously through the ocean in huge rivers called currents. Currents may flow on the surface of the ocean, where they are shallow, or they may flow far below the surface, where they are deeper. Ocean currents are set in motion by the wind. The rotation of the earth moves them clockwise in the … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

There are four basic “ingredients” that go into the “recipe” for making soil: tiny pieces of rock, decayed plants and animals, water, and air. When small pieces of rock break off larger ones, they form the basis of all soil. This breaking can occur in several ways: through the action of glaciers pushing rocks along … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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. … Read more

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 … Read more

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 … Read more

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 … Read more

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, … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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 … Read more

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. … Read more

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 … Read more

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, … Read more