Ency123

Learn how to make a  Megaphone  -  Cardboard Megaphone - excerpt from the book "The Scientific American Boy" by A. Russell Bond A sheet of light cardboard 30 inches square was procured. At the center of one edge a pin was stuck into the cardboard, then a piece of stout thread was looped over the pin and the two ends were knotted together just 5 inches from the pin. Another knot was also made 29 inches from the pin. Now, with a pencil hooked into the loop, and resting first against the inner knot and then against the outer one, two arcs were drawn on the paper, one of 5-inch radius and the other of 29-inch radius. A line was now drawn from the pin to the point where the longer arc met the right hand edge of the paper, and a dotted line was drawn from the pin to a point 1-1/2 inches from the edge at the other end of the arc. From a point 1 inch to the left of the pin we then drew a line to the left end of the arc. With a scissors we cut the cardboard along the arcs and s...

Why do Boats Float on Water - Do you know why some things float while others sink? It isn't just because of their size or their weight. If you can float when you go swimming, why does a small pebble sink? The answer is that floating or sinking depends on an object's density. If an object is more dense than water, it sinks. If it is less dense than water, it floats. An object is more dense than water if it weighs more than the same amount, or volume, of water, Pebbles are made of gritty particles, which are very heavy and packed together tightly. This is why they sink. They are more dense than water. Steel has a higher density than water, so why doesn't a steel boat sink? The answer is that the inside of a ship is hollow and contains air. It also contains other materials which are less dense than water. The density of the whole ship is less than that of water.

What to do During a Tornado - Tornado Safety rules  - While different kinds of storms bring different kinds of danger, some basic safety rules apply to all storms. To be safe you should learn what kinds of storms affect the area where you live or are visiting, and you should become familiar with the safety rules for those storms. You can use the Federal Emergency Management Agency’s (FEMA) Project Impact Web page to find the hazards for any part of the United States. If you are in the United States, you should buy a special weather radio, which picks up broadcasts of regular weather reports and storm watches and warnings from the National Weather Service. When the Weather Service announces a watch, it means that a particular kind of storm is possible. A warning means that a storm is headed for your area. The best weather radios automatically turn on and sound an alarm when the nearest Weather Service office issues a warning. The online Federal Emergency Management Agency Library in...

All storms have two things in common: low atmospheric pressure at the storm’s center, and winds that are created by the flow of air from higher pressure outside the storm toward the low pressure at the center. Wind, in other words, is air that’s being pushed by high pressure toward low pressure. Areas of low air pressure occur because the Sun heats the Earth unequally. The Sun shines down almost directly on Earth’s tropical regions near the equator, heating this region more than the polar regions around the North and South poles and the middle latitudes between the poles and the tropics. Storms, along with ocean currents, redistribute heat from the tropics to the middle latitudes and the poles. Without storms and ocean currents, the tropics would grow hotter and hotter until the oceans boiled. In other words, the Sun’s heat powers the weather. Air pouring into an area of low pressure from all sides rises because it doesn’t have any place else to go. As air rises, it cools, and...

One of the most common blood diseases worldwide is anemia, which is characterized by an abnormally low number of red blood cells or low levels of hemoglobin. One of the major symptoms of anemia is fatigue, due to the failure of the blood to carry enough oxygen to all of the tissues. The most common type of anemia, iron-deficiency anemia, occurs because the marrow fails to produce sufficient red blood cells. When insufficient iron is available to the bone marrow, it slows down its production of hemoglobin and red blood cells. In the United States, iron deficiency occurs most commonly due to poor nutrition. In other areas of the world, however, the most common causes of iron-deficiency anemia are certain infections that result in gastrointestinal blood loss and the consequent chronic loss of iron. Adding supplemental iron to the diet is often sufficient to cure iron-deficiency anemia. Some anemias are the result of increased destruction of red blood cells, as in the case of sickle...

Blood is produced in the bone marrow, a tissue in the central cavity inside almost all of the bones in the body. In infants, the marrow in most of the bones is actively involved in blood cell formation. By later adult life, active blood cell formation gradually ceases in the bones of the arms and legs and concentrates in the skull, spine, ribs, and pelvis. White blood cells, Red blood cells and platelets grow from a single precursor cell, known as a hematopoietic stem cell. Remarkably, experiments have suggested that as few as 10 stem cells can, in four weeks, multiply into 30 trillion red blood cells, 30 billion white blood cells, and 1.2 trillion platelets—enough to replace every blood cell in the body. The majority of white blood cells have a relatively short life span. They may survive only 18 to 36 hours after being released from the marrow. However, some of the white blood cells are responsible for maintaining what is called immunologic memory. These memory cells retain knowled...

Blood is produced in the bone marrow, a tissue in the central cavity inside almost all of the bones in the body. In infants, the marrow in most of the bones is actively involved in blood cell formation. By later adult life, active blood cell formation gradually ceases in the bones of the arms and legs and concentrates in the skull, spine, ribs, and pelvis. Red blood cells, white blood cells, and platelets grow from a single precursor cell, known as a hematopoietic stem cell. Remarkably, experiments have suggested that as few as 10 stem cells can, in four weeks, multiply into 30 trillion red blood cells, 30 billion white blood cells, and 1.2 trillion platelets—enough to replace every blood cell in the body. Red blood cells have the longest average life span of any of the cellular elements of blood. A red blood cell lives 100 to 120 days after being released from the marrow into the blood. Over that period of time, red blood cells gradually age. Spent cells are removed by the s...

What is Blood Plasma? Plasma consists predominantly of water and salts. The kidneys carefully maintain the salt concentration in plasma because small changes in its concentration will cause cells in the body to function improperly. In extreme conditions this can result in seizures, coma, or even death. The pH of plasma, the common measurement of the plasma’s acidity, is also carefully controlled by the kidneys within the neutral range of 6.8 to 7.7. Plasma also contains other small molecules, including vitamins, minerals, nutrients, and waste products. The concentrations of all of these molecules must be carefully regulated. Plasma is usually yellow in color due to proteins dissolved in it. However, after a person eats a fatty meal, that person’s plasma temporarily develops a milky color as the blood carries the ingested fats from the intestines to other organs of the body. Plasma carries a large number of important proteins, including albumin, gamma globulin, and clotting factors. A...

Have you ever swum in the sea and accidentally swallowed some sea water? It probably made you gag and cough. Sea water contains a lot of salt and this makes it very unpleasant to taste, as well as unhealthy to drink. If you were to drink salt water, you would become thirsty. Do you know why? You already have lots of salt in your body— everybody has! If you take in even more, you would feel the need to drink some liquid to water down, or dilute, the extra salt. We can make good use of both the water and the salt in the sea, but we need to separate them first. People in some countries in the world are so short of fresh water that they are even thinking about towing icebergs from Arctic regions to their own dry lands! Ninety-seven per cent of the world's water is found in the oceans and seas. Fresh water can be made by taking salt out of sea water. Desalination process This process, called desalination, is expensive because it needs large amounts of energy, and the salt ...

In mountainous regions, a river of ice may flow down a valley. This is called a valley glacier.  A glacier can move at different speeds, from a few inches (centimeters) every year to as much as 660 feet (200 meters) every year. Glaciers begin in small dips or hollows on mountainsides. Every year more snow falls into these hollows than melts. The weight of the snow eventually squeezes the air out of the bottom layers of the snow to form ice. Where this ice meets the rock below, pressure generates energy to melt the ice. The melted water on the rock surface seeps into tiny cracks in the rock. The water then freezes and expands, forcing the cracks open, allowing more water to seep in and freeze. Finally, a piece of rock breaks off. This process is called freeze-thaw. In the hollow, the freeze-thaw causes more pieces of rock to break away, making the hollow bigger. The hollow is now called a cirque. When the layer of ice becomes very heavy, it starts to flow out of the h...

What is an ice age? Have you ever tried to make a snowball? Snow is soft and fluffy when it falls from the sky, but when you press it into a ball, it can become quite hard. If you press it very tightly, it turns into a lump of ice. It is so cold at the North and South poles, that the snow there never has a chance to melt. As more snow falls, it presses down into tightly packed layers which then turn to ice. Some areas of the earth are covered by huge sheets of ice and snow all year round. Around the North Pole there is no land, but an ice sheet, also known as a continental glacier, covers the Arctic Ocean. An ice sheet also covers most of Greenland and some northern parts of Canada and Europe. The largest ice sheet in the world lies around the South Pole. It covers about 5.1 million square miles (13.2 million square kilometers) of the huge continent called Antarctica. This ice sheet has an average thickness of 6,600 feet (2,000 meters). The Antarctic ice contains about three...

A transformer can make an electric current smaller or larger. As an electric current flows along the wires from a power station, it loses energy. A large current loses much more energy than a small current. So power stations use transformers to reduce the current. Transformers do this by increasing the voltage. When the voltage is increased, the current becomes smaller. A transformer that increases the voltage is called a step-up transformer. Many household appliances, such as radios and battery chargers, also use transformers. The voltage these appliances need is lower than the voltage of the electricity in your home. A transformer that reduces the voltage is called a step-down transformer. Alternating current passes through the first coil in this step-up transformer. This makes an electric current flow in the second coil, which has more turns of wire. The voltage of the second coil is higher than the voltage of the first coil. How do transformers work? A transformer con...

You can make a bulb light up by using two wires to join it to a battery.  The bulb lights up because an electric current is flowing through it.  The battery produces the current by pushing electrons along the wires.  The stronger the push, the more electrons flow along the wire each second.  The current heats the thin wire inside the bulb and makes it glow brightly. The force of this push is measured in volts.  The word volts comes from the name of the Italian who invented the first battery—Alessandro Volta.  The more volts a battery has, the stronger its push. In a copper wire (A), some electrons move freely in all directions. When a battery is connected to the wire (B), the battery pushes the electrons in the same direction. An electric current can now flow along the wire. When we do experiments with electricity, we use small batteries. These batteries give a push of 1.5, 6.0, or 9.0 volts. We describe this as the voltage of the batte...

Do you know how water gets to the faucets on your kitchen sink? It comes through pipes. Pipes let water flow in the direction we want it to go. How do we make electricity flow in the direction we want it to go?  The electrical energy we call "electricity" is made in huge power stations. What connects the electric sockets in your home with the power station? The answer is wires.  Wires are the "pipes" of the electricity system. A wire is a long, thin piece of metal. It may be a single strand of metal, or it may be two or more strands twisted together. Some wires are thick and stiff, and others are thin and bend easily. Why are electric wires covered? A material that allows electricity to flow through it is called a conductor. Metals are good conductors. Some metals are better conductors than others. Silver is the best conductor of all, but it is too expensive to use to make wires. Copper is also a very good conductor and much cheaper to use than silver. ...

Did you know that light rays can cut through a steel plate?  What sort of light can do this? The answer is laser light. A laser can produce a thin but very powerful beam of light. Ordinary white light is made up of many different colors. Its photons have many different wavelengths. They are out of step with each other. In a beam of laser light, all the photons have the same wavelength and move in step, traveling along like a well-drilled army. A laser beam doesn't spread out like a beam of ordinary light. Scientists have shone laser beams onto the moon, around 238,857 miles (384,403 kilometers) away.  Over this huge distance, the beam spreads out by only 80 inches (2 meters) or less. The laser beam's energy is concentrated into a narrow width and is very powerful. Laser light can also be focused very accurately. This is why lasers can cut steel and why surgeons can use laser light to perform very delicate operations. Laser light, which can pass through skin tis...

What color is the sky?  On a sunny day, the sky looks blue. Sometimes, early in the morning and just before sunset, it may look greenish-yellow, or even orange-red. The sky actually has no color at all. It is a great ocean of air, called the atmosphere, which is made up of colorless gases. The sky looks colored to us because of what happens to the sunlight which passes through the atmosphere. All kinds of particles, such as dust, smoke, and ash, float in the air. Many of these particles come from human activities, such as burning fuels to provide energy. Other particles are the result of natural happenings. Sometimes, strong winds whip up particles of desert sand. When volcanoes erupt, they send clouds of smoke and ash into the air. When light strikes the tiny particles that are found in air and water, the light is scattered in all directions. When the sun is overhead and high in the sky, its light is scattered by the particles in the atmosphere. The light photons with the h...

The first moon landing The most exciting thing astronauts have done so far is to travel to the moon. They went in Apollo spacecraft, three astronauts at a time. Each Apollo spacecraft was made in three parts. The first part, the command module, carried the crew. The second, the service module, carried equipment and a rocket motor. The third, the lunar module, carried the astronauts down to the moon's surface. The spacecraft was launched by the mighty Saturn V rocket, the tallest rocket there has ever been. The journey to the moon took about three days. The first astronauts landed on the moon on July 20,1969,  They were Neil Armstrong and Edwin Aldrin, from Apollo 11.  Armstrong was the first person to set foot on the moon. As he stepped onto the moon, he said, "That's one small step for man, one giant leap for mankind." Altogether, twelve astronauts from six Apollo spacecraft landed on the moon. They collected rocks, took photographs, and carried out ...

Our eyes are good enough for simple stargazing. But they tell us very little about what the stars are really like. To see the stars more clearly and find out about them, we need to look through a telescope. The word telescope means "see far," and that is just what a telescope enables us to do. The Italian scientist, Galileo Galilee, was the first person to study the heavens through a telescope, in 1609. Galileo made his telescope using glass lenses. Some astronomers still use this type of telescope today. It is called a refractor, because the lenses refract, or bend, light into the telescope. But the biggest and most powerful telescopes use mirrors to gather the starlight. They are called reflectors, because the mirrors reflect light into the telescope. Up in the mountains The places where astronomers work are called observatories. You find most observatories high up in the mountains. Here, the air is thin and clear, so the light can reach the telescope more easily....

From the earth, we can see six of the other planets in our solar system without a telescope. They look like bright stars, but they change their position from night to night. This is why they are called planets. Planet means "wanderer." The six planets are Mercury, Venus, Mars, Jupiter, Saturn, and Uranus. We can see them because they reflect the light of the sun—just as our moon does. The planet closest to us, Venus, is also the brightest. We see Venus sometimes at dawn as the "morning star" and sometimes at sunset as the "evening star." When they are closest to Earth, Mars and Jupiter shine nearly as brightly as Venus. Mars is easy to spot because it has a reddish-orange color. It is often called the Red Planet. Mars and Venus appear so bright because they are our nearest neighbors among the planets. Jupiter lies very far away. It seems bright because it is so gigantic. It is more than a thousand times bigger than Earth! In fact, it is the biggest plan...

Space Information for Kids - What is a Supernova? Throughout the universe, there are great clouds of gas and dust. These clouds are called nebulae.  In larger nebulae, stars may form. The process begins when gravity pulls the gas and dust particles together. As the mass of particles becomes tightly packed, or compressed, it heats up. In time, the temperature inside rises to about 2,000,000 °F (1,100,000 °C). At such temperatures, atoms of hydrogen gas begin to combine, or fuse, together to form helium gas. As they do so, they release an enormous amount of energy as light and heat. The mass of gas and dust begins to shine—as a star. ...and dies. A star the size of the sun has a long life.  The sun is now about 4.6 billion years old and will probably stay as it is for another 5 billion years. Then, scientists believe, it will run out of hydrogen "fuel" and begin to die. First, it will swell in size and become a type of star we call a red giant. Then it will slo...

Interesting Facts About the Sun Every morning the sun rises, bringing light and warmth to our world. It is daytime. The sun rises in the east, and during the day it appears to travel in an arc across the sky. In the evening, it sets in the west. As it disappears below the horizon, the earth becomes dark. It is night. However, this is not really what happens. The sun only seems to move across the sky. It is the earth, not the sun,  that is moving. The earth is spinning in space. The sun moves into our view and out of sight again as the earth whirls around. It takes the earth 24 hours to turn around an imaginary line that runs from the North Pole to the South Pole. We call this line the earth's axis. Without the sun's light and heat, the earth would be a dark, cold world.  Plants need sunlight to make their food. Animals cannot make their own food. They must eat plants or other animals in order to live. So without sunlight, there would be no living things. Wh...

Atomic Mass Number - What is Atomic Mass Number? The total number of neutrons and protons in the nucleus (core) of an atom, makes the mass number of the atom (abbreviated A). This number is an approximation of the mass of the atom. Electrons contribute very little to the mass of the atom, so that they are not included in the mass number. A stable helium atom may have a number of mass equal to three (two protons + one neutron) or equal to four (two protons and two neutrons). The element Bismuth, which has 83 protons, requires 126 neutrons in order to be stable, so that its mass number is 209 (83 + 126 = 209).

Why do we Need Salt - Importance of Salt in Human Body The human body contains about 60 percent water. Many of our organs have an incredibly high percentage of water. For example, the muscles are about 70 percent water, the same percentage of the liver, the brain  -  79%, and 83 percent the kidneys. But the body fluid is not pure water. This is actually a salt solution. For what? According to one scientific theory, all land animals, including man, descended from organisms that lived in the sea. Bodily fluid of living creatures was seawater. When these creatures moved to the mainland, in their bodies remained sea water, but the land was not able to provide enough salt naturally. Plants growing on the land does not contain enough salt. Therefore, animals that feed on plants - herbivores - are in need of salt. Why do we need salt? The body of every-day loses a certain amount of liquid containing salt and plant foods do not compensate this. However, animals that feed ...

Why do people sweat? Let us imagine that our body is one perpetually lit stove. The food that we take is the fuel that burns in our body. During this process, the body takes about 2,500 calories. This amount of heat is sufficient for 28.5 liters (7.5 gallons) of water to be heated to the boiling point. What's going on with so much heat in our body? If there was no temperature control, we'd probably be "hot." But we know that our body temperature is 37 ° C (98.6F), except when we are sick. Sweating is one way of ensuring the maintenance of normal body temperature. If the temperature of the blood is increased, the center of the cooling comes into action. The process of oxidation or burning substance slows down and something else that is important happens. Blood vessels in the skin expand, and excess heat goes away trough the evaporation of perspiration. Therefore, for example, we feel cold after swimming, because the water that remains in contact with our war...

Did you know that in ancient Rome ordinary man was expected to live up to 23 years? About a hundred years ago the average life span was 40 years. Most people would like to live a very long time, no one wants to get old. But aging is a process that starts from birth and continues throughout the entire life. What causes aging? When someone enters a deepening age, all actions and processes of living organisms are slowed. Man loses part of his strength and his senses lose sharpness. It usually comes in the reduction of body weight and height. Along with this, it may impair vision, partial deafness, white hair and relaxation and less supple skin. Not all people are aging at the same speed, but some of the changes that come with age can not be avoided, because they occur in the tissues of the body and all its organs. For example, cells in the kidney, liver, pancreas and spleen begin to gradually decline, because the blood vessels are old and not strong enough to supply blood a...

What is a Hormone? Hormones are secreted by the glands of internal secretion, which means that they are excreted in the body. They are also called glands without drainage, because they do not send their products in the channels, but directly into the bloodstream. Hormones also create some organs such as the liver and kidneys, but most of the hormones are product of the glands. What do hormones do? Each hormone has its own special function in the body. In general, the task of hormones is to regulate internal body functions such as growth, nutrition esc., stockpiling of nutrients and their use, as well as the processes of reproduction. If glands produce too much or insufficient hormones, it can lead to abnormal physical appearance of the human. Here's what some of the major glands and hormones work in our bodies. Pituitary Gland Function The pituitary gland is the most important of all, because it manages the work of all other glands of internal secretion. Its size is re...

What Causes Aging? When do People Stop Growing? The newborn is on average 48-50 cm long. Over the next twenty years, the body length is increased over three times and in a woman is about 160 cm and at males about 175 cm. But the human then does not ceases to grow. It actually continues to grow, even after twenty-five years, and its highest altitude is reached in about 35 or 40 year. What happens after these years?  The man stops growing and starts to decrease.  Everyone decreases after the age of forty, about 1 cm every ten years. Explanation for this decrease is the gradual loss of water from the cartilage in the joints of the spinal column. Did you know that we are every morning higher than the previous night, and during the day we shorten? The growth rate is also changed during the different seasons. Young children grow faster in summer than in winter. Better food, better quality of life and a variety of other circumstances, make the today's generation, on ...

How do we Grow? One feature of the living things is growth. By growth the living being improves its composition and functions. The most important factors that cause growth are hereditary and can be found in embryo of the human being. Different stages of human development Human beings and animals go through several stages of development. These are: embryonic stage (in the womb),  period of the infant,  childhood,  adolescence,  adulthood an old age. Some creatures barely have early childhood. Some birds, for example, can fly as soon as they hatch. Guinea pig is able to take care of itself, on the third day after the arrival in the world. A human being is fully grown until approximately twenty years! From the first moment the newborn has all those nerve cells that will have in a lifetime: the brain and the peripheral. Development of connections between these neurons allows the child to control his movements, to enter and act as a social being. ...

The Giraffe is one of the rarest of animals, and very few are to be found in captivity. So if you make a giraffe, which is not difficult to do, you will have a feature in your show that none but the very largest combines can afford. The animal's head should be drawn the shape of Fig. 272 on a board, and then cut out with the aid of a saw and draw-knife. The jaw, ears, and horns should be cut out separately, the shape of Figs. 273, 274, and 275. Bore two holes in the head at A, slanting them toward one another, and fit in them the pegs cut for the horns. The jaw should be pivoted with a small nail at B on one side of the head, and an ear should be likewise fastened at C on each side of the head. When these portions of the giraffe's anatomy have been put in place, stretch a rubber band from a tack driven in the top of the jaw to another tack driven into the neck (see Fig. 272), and attach another rubber band similarly to each of the ears. These rubber bands will act as springs, c...

The Elephant is one of the oldest forms of animated animals, and is at the same time one of the most popular. Four or five yards of gray cambric should be purchased for its covering. Excerpt from the book - THE BOY CRAFTSMAN Practical and Profitable Ideas for a Boy's Leisure Hours BY A. Neely Hall / Published, August, 1905. With more than four hundred illustrations by the author and Norman P. Hall BOSTON LOTHROP, LEE & SHEPARD CO. The cloth should be cut out like the pattern shown in Fig. 270, the correct measurements being secured from two boys who have taken the position shown in Fig. 271. Fold the cloth along the centre and then sew the dotted lines AA and BB together. Paper cornucopiæ form the tusks, and the ears are made of gray cambric cut the shape shown in Fig. 271, and lined with heavy wrapping-paper to make them stiff. Two boys are required for the elephant. These must bend forward, as shown in Fig. 271. The rear boy places one hand upon the front boy's back and w...

Authorities claim that the best materials from which to make bows are mulberry, sassafras, Southern cedar, black locust, black walnut, apple, and slippery elm, in the order named; but if a boy selects what appears to be a good sound piece of wood, with straight grain, he has something which will suit the purpose. Excerpt from the book - THE BOY CRAFTSMAN Practical and Profitable Ideas for a Boy's Leisure Hours BY A. Neely Hall (Published, August, 1905.) Fig. 241.—A Boy's Bow. The Length of the Bow should be about the height of the person using it. Figure 241 shows a five-foot bow, with the other proportions such as are on makes to be found in the stores. Cut your piece of wood five feet long, and, after placing it in the bench-vise, shape it down with a draw-knife or plane until it is one inch wide by one-half inch thick at the handle and three-quarters of an inch wide by one-quarter inch thick at the ends. The bow can be made round on the inside or face toward the archer, ...