Chinese Characters

Chinese alphabet is represented by "characters", a set of symbols each of which represents a word or idea. Tsang Kie, the hero with two pairs of eyes, is said to have created Chinese characters after studying traces left by birds’ feet in the sand. (Adapted from ‘Inventions and Discoveries’, by Vale-Anne Giscard d’Estaing and Mark Young)

Tomato

Of South American origin, the tomato was brought to Europe in 1596. At first cultivated as a curiosity, it was considered to be a violent poison. This vegetable-fruit had to wait more than two centuries before its nutritional qualities were recognized. President Thomas Jefferson cultivated the tomato in his garden but didn’t eat the fruit. (‘Inventions and Discoveries’, by Vale-Anne Giscard d’Estaing and Mark Young)

Our brains are as individual as our fingerprints

How well and how fast your brain works, says Leif Finkel, M.D., Ph.D., a neuroscientist at the University of Pennsylvania, depends on the genetic structure of your brain and the experiences you've exposed it to over your own 40, 50, or 60 years.

"Everybody's brain starts off just a little bit differently," explains Dr. Finkel, "because genetic programming influences how your nervous system gets set up in the first place. If you have a hundred antelopes, for example, they're not all equally fast at running and they don't have the same visual capability. So when the lion comes to chase them, certain ones are going to get away and certain ones aren't."

The same difference in ability is true in people, he adds. All of us have billions of densely interconnected brain cells that continually fire electrochemical messages back and forth. But the difference in the way these cells connect is the reason that some of us can do complicated math in our head, others can write novels, and some can ace a tennis serve.

Largest and longest kites

The largest kite ever built had an area of 6,000 square feet (557 square meters). When it was sent aloft, seventy people held onto it. But it was so powerful that it almost pulled those seventy people into the sky. What is believed to have been the longest kite was called the Thai Snake. When fully stretched out across the sky, it had a length of almost half a mile (0.8 kilometer). (Grolier Book of Knowledge Encyclopedia)

The language of stocks

People who invest in stocks or follow the progress of the stock market encounter a wide variety of terms unique to these investments. These terms include price-to-earnings ratio, earnings per share, market capitalization, mutual fund, bull market, bear market, and day trading, among others. Understanding this vocabulary helps explain many of the workings of the market in stocks.

1.  Price-to-Earnings Ratio and Earnings Per Share

Investors use several techniques to determine whether a particular stock should be purchased. Some investors examine a stock’s fundamentals such as its earnings per share or its price-to-earnings ratio. Earnings per share is calculated by dividing the corporation’s total earnings or income by the number of shares the corporation has outstanding. A corporation’s price-earnings ratio is calculated by dividing the current price of a share of the company’s stock by its earnings per share. These calculations represent fundamentals in the sense that they reflect the effectiveness of a company’s business operation (earnings per share) and the market’s current assessment of the company’s worth in relation to its earnings (price-earnings ratio).

Brain's intricate network of blood vessels

The brain abides in a world of liquid that both cushions and nourishes it. Nearly a fifth of the blood pumped by the heart surges through the brain's intricate network of blood vessels to meet its unflagging demand for oxygen and glucose.

Specialized blood vessels within the brain called choroid plexuses produce protective cerebrospinal fluid. Each of the brain's four cavities, the ventricles, contains a choroid plexus. The cerebrospinal fluid continuously washes over the brain and spinal cord, suspending these organs in a liquid cushion that protects them from injury.

The blood-brain barrier, another protective feature, consists of a network of uniquely structured blood vessels. These capillaries are nearly impermeable to many harmful chemicals carried by the blood, but do allow oxygen, water, and glucose to enter the brain. The cells of these capillaries are more tightly joined than cells of other blood vessels. The vessels themselves are wrapped twice - first by a layer called a basement membrane, then by the fatty extensions, or end feet, of special glial cells. (National Geographic)

Walking vs. Other Activities: calories expended by a 150-pound person per hour

Race walking: 600
Uphill walking, 10% incline (3 mph): 500
Walking, 15-lb. backpack (4 mph): 410
Brisk walking (4mph): 350
Slow running (5 mph): 550
Recreational tennis, singles: 430
Swimming, slow crawl: 400
(The Wellness Guide to Lifelong Fitness, by Timothy White, PhD., and the editors of the University of California at Berkeley Wellness Letter)

Laser: a device that produces a beam of high-energy light

Laser stands for "light amplification by stimulated emission of radiation." Inside a laser is a material called a lasing medium. Passing an electric current or light into the medium gives energy to, or excites, its atoms. The excited atoms suddenly give up their extra energy and emit light. One atom emits a light ray, which strikes another atom and causes it to emit another ray, and so on in a rapid cascade of emissions. The rays are all in phase. This means that the waves of energy in the rays are exactly in step, making the light very concentrated. This kind of light is coherent radiation. Mirrors reflect the rays, so that the cascade builds up. The light leaves through one of the mirrors, which is partly transparent. Lasers can also emit invisible infrared rays. A maser is like a laser, but emits microwaves. (Dictionary of Science, by Neil Ardley)

The origin of Earth’s oceans

Little is known about the origin of Earth's oceans, but there are currently two main hypotheses: One is that the water was always here; the other is that it came from somewhere else. The first of these hypotheses stems from the simple observation that, among all the gases released by the Hawaiian volcanoes, steam (water vapor) is the most prevalent. Thus it could be that simple volcanic outgassing of water trapped within Earth's rocky mantle produced the planet's oceans.

The premise of the second hypothesis, that the source of Earth's water is extraterrestrial, seems unlikely at first glance because, at least in our solar system, liquid water is quite rare. In the solid form of ice, however, water in actually quite abundant. Comets, for instance, are made of ice mixed with other debris. Specialists believe that large comets may contain fifty or more cubic kilometers of water in the form of ice. Although 10 of these comets, if they collided with Earth and melted, would provide enough water to fill Lake Erie, another 240 would be needed to fill Lake Superior, and about 7 million would be necessary to fill the Atlantic Ocean. That so many millions of large comets would have impacted Earth seems not very likely, but comets may well have been the source of a great deal of the water on Earth.

The most severe earthquake in recorded American history

The New Madrid earthquakes (a series of quakes starting on December 16, 1811, and lasting until March 1812) are considered to be the most severe earthquake event in United States history. It shook more than two-thirds of the United States and was felt in Canada. It changed the level of land by as much as 20 feet, altered the course of the Mississippi River, and created new lakes, such as Lake St. Francis west of the Mississippi and Reelfoot Lake in Tennessee. Because the area was so sparsely populated, no known loss of life occurred. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Endangered Species Worldwide

In 2010, the International Union for Conservation of Nature (I.U.C.N.) issued its updated list of threatened species of animals and plants worldwide, the "Red List" (www.iucnredlist.org). Species judged as "critically endangered," (with population declines of at least 80 percent),"endangered," or "vulnerable," are regarded as threatened with extinction. The Red List contained 9,618 species of animals and 12,914 species of plants in 2010. These include 21 percent (more than one in five) of mammalian species described and 12.4 percent (one in eight) of bird species. The list includes 8,724 threatened plants, but because only about 4 percent of plant species have been evaluated for threat, the number actually endangered is believed to be much larger. Although the endangered species include plants and animals of every type, the growing list of endangered mammals (for example, the great panda, the Siberian tiger, and orangutans), has caught the attention of the general public. Overall 1,131 mammalian species, large and small, were considered threatened in 2010.

Oil Deposits in North America

Some of North America’s richest known offshore oil deposits are in the Gulf of Mexico. (National Geographic)

Cleaner Wrasse

Most animals in water can't groom themselves the way cats, monkeys, and many other land animals do. They depend on other creatures to do it for them. The cleaner wrasse is a specialist in this job. These small fish are brightly colored, which makes them easy to spot. They set up cleaning stations in the ocean and attract clients with a sort of dance, swimming head down and waving their bodies from side to side. Larger fish line up at the cleaner wrasse station, each waiting for its turn to be cleaned. The cleaners ' clients include many fish that are predators-but the cleaners themselves are rarely eaten. As the larger fish wait calmly, the little cleaners swim right into their mouths and gill cavities to clear away parasites, fungi, and debris, getting a free meal in the process. (Grolier Book of Knowledge Encyclopedia)

Human heartbeat rate compared with that of other mammals

Mammal	Heartbeats per minute
Human	70
Elephant	25
Mouse	600-700
Large dog	80
Small dog	120

(The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Viruses

Viruses are infectious agents found in virtually all life forms, including humans, animals, plants, fungi, and bacteria. Viruses consist of genetic material—either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)—surrounded by a protective coating of protein, called a capsid, with or without an outer lipid envelope. Viruses are between 20 and 100 times smaller than bacteria and hence are too small to be seen by light microscopy. Viruses vary in size from the largest poxviruses of about 450 nanometers (about 0.000014 in) in length to the smallest polioviruses of about 30 nanometers (about 0.000001 in). Viruses are not considered free-living, since they cannot reproduce outside of a living cell; they have evolved to transmit their genetic information from one cell to another for the purpose of replication.

The intricate structure of the Helix Nebula – seen in January 2012

A new infrared picture reveals the intricate structure of the Helix Nebula, the rust-colored remains of a star like our sun that puffed up as it died and shed its shells of gas and dust into space. These thin clouds of molecular gas are difficult to see in visible light, but infrared detectors can pick them out, and they show up in the new image as a dark red haze. The Helix Nebula is a complex object composed of dust, ionized material and molecular gas, arrayed in an intricate, flower-like pattern.

The dying star at the heart of the Helix Nebula is evolving to become a white dwarf, a shrunken, super-dense object that can pack a sun's worth of material into a sphere the size of Earth. The star is visible as a tiny blue dot at the center of the picture.

The main ring of the Helix is about 2 light-years across, roughly equivalent to half the distance between our sun and its closest star. However, wispy material from the nebula spreads out at least 4 light-years into space from the central star.

In visible light, fine details in the Helix are largely obscured by dust. But the infrared view—snapped by the European Southern Observatory's VISTA telescope—can pierce this veil to see radiating filaments of cooler gas in the rings as well as a faint halo of thinly spread gas that extends to at least four light-years from the dead star's core.

Our Immune System

The immune system protects the body from invaders, such as viruses and bacteria. The system includes the lymphatic system and various white blood cells (WBCs).

Lymphatic system

The lymphatic system has a network of vessels that drain intracellular fluid from the intracellular space and return it to the blood. The lymph vessels are not connected to the heart and do not benefit from its contraction. They, like many veins, are embedded in skeletal muscle and rely on muscle contractions to move the lymphatic fluid (intracellular fluid inside lymph vessels). Also like veins, lymph vessels contain valves that prevent backflow. The lymph vessels deliver the fluid into large veins inthe chest, where the fluid again becomes part of the blood.

Connected to lymph vessels are small masses of spongy tissue called lymph nodes, which remove contaminants such as bacteria and dead cells from lymphatic fluid. In addition, the nodes are homes for certain types of white blood cells (WBCs).

White blood cells

A healthy human typically has 5,000 to 9,000 WBCs per milliliter of blood. When bacteria or other foreign particles are present, however, WBCs rapidly proliferate. Unlike RBCs (red blood cells), WBCs can move on their own; they frequently pass through the walls of blood vessels and go into intercellular space and the lymphatic system in search of invaders.

The father of medicine

Hippocrates (ca.460-ca.377 B.C.E.), a Greek physician, is generally regarded as the father of medicine. Greek medicine, previous to Hippocrates, was a mixture of religion, mysticism, and necromancy. Hippocrates established the rational system of medicine as a science, separating it from religion and philosophy. Diseases developed from natural causes and natural laws; they were not the "wrath of the gods." Hippocrates believed that the four elements (earth, air, fire, and water) were represented in the body by four body fluids (blood, phlegm, black bile, and yellow bile), or "humors." When they existed in harmony within the body, the body was in good health. The duty of the physician was to help nature to restore the body's harmony. Diet, exercise, and moderation in all things kept the body well, and psychological healing (good attitude toward recovery), bed rest, and quiet were part of his therapy. Hippocrates was the first to recognize that different diseases produced different symptoms; and he described them in such detail that the descriptions generally would hold today. His descriptions not only included diagnosis but prognosis. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Kites used for military purposes

From early times kites have been more than toys. They have had many practical uses. Some uses were military. About 500 A.D. one Chinese emperor used kites to signal his soldiers. The soldiers would work on nearby farms until they saw the kites flying above the emperor's palace. This was a signal that they should rush to the palace to help defend it against enemies seen approaching on the horizon.
During the American Civil War in the 1860's, the Union used kites to scatter leaflets over Confederate troops. The leaflets urged the Confederates to surrender, promising them amnesty if they would lay down their arms. During the Boer War in South Africa in the late 1890's, large kites were used to carry British soldiers over the fighting front to observe the enemy. During World Wars I and II, kites were used to disable enemy aircraft. (Grolier Book of Knowledge Encyclopedia)

Spider Webs: Strong as Steel

Covered with dew, a spider's web hangs from a branch like a jeweled necklace. The silk that forms the web is feather-light and looks fragile and delicate in the early morning rays of the sun. Yet this amazing material is actually stronger than steel and, at the same time, as elastic as a rubber band.

People have never been able to make a material with all the wonderful properties of natural spider silk. But now, using new techniques, researchers are trying to produce the silk commercially. If they succeed, spider silk may one day be used in everything from bullet-proof vests to stockings.

Silken Nets

Spiders are hunters that catch and eat insects. (Spiders themselves aren't insects. They belong to a group called the arachnids, which also includes scorpions and ticks.) All spiders have special glands that produce spider silk, which is a protein. The silk is spun by being forced out as a liquid through tiny fingerlike organs called spinnerets. The liquid hardens into fine, tough threads after hitting the air.

Most spiders use their silk to build webs that will capture their prey. And there are almost as many different kinds of webs as there are different kinds of spiders. Some webs consist of just a strand or two of silk; others are a jumbled tangle of threads. Some spiders spin broad sheets that hang horizontally in bushes and trees. Still others construct tunnel-like traps of silk.

The first leap year

The first leap year was 46 B.C. It was then that the Julian calendar of 36S.2S days was adopted. The calendar required that an extra day be added every fourth year. (The Book of Answers, by Barbara Berliner)

Einstein's Early Years

Albert Einstein was born in Ulm, Germany, on March 14, 1879. His parents were Jewish but not observant. Initially, they were concerned about his intelligence because he was slow to speak, but these worries passed quickly.

Because his father was an electrical engineer with a manufacturing business in Munich, Einstein was exposed to science at an early age. The needle of his father's compass held particular interest for him. He understood intuitively that if two objects were in contact, one could exert a force upon the other. But the idea that the earth could exert a force upon the compass needle without touching it amazed him.

When Einstein was ten years old, a family friend introduced him to some important texts on math and science, and Einstein began studying them, teaching himself geometry and calculus. Particularly important was his study of logic, especially the deductive reasoning associated with Euclidean geometry. Deductive reasoning is the process by which one moves from general premises to specific conclusions. To create his system of geometry, Euclid began with a set of statements, called postulates, that he asserted as true, even though they were unprovable. From these, Euclid made a series of deductions to arrive at his theorems. If one accepts the truth of the postulates that form the basis of the system, then the theorems must also be true because they follow logically from the postulates. Einstein used a similar method when developing his own work on relativity.

Characteristics of the Sun

Position in solar system: Center

Mean distance from Earth: 92,960,000 mi. (149,600,000 km)
Distance from center of Milky Way galaxy: 27,710 light-years
Period of rotation: 25.45 days at 16' longitude
Inclination (relative to Earth's orbit): 7.25°
Equatorial diameter: 865,000 mi. (1,392,000 km)
Diameter relative to Earth: 109.2 times

Mass: 2.192XI0(to the power 27) tons, (1.9891XI0 [to the power 30] kg)
Mass converted to energy each second: 9,500 million pounds (4,300 million kg)
Surface gravity relative to Earth's: 28 times
Temperature at core: 28,280,000°F (15,710,000°C)
Temperature at bottom of photosphere: 12,4oo°F (6,900'C)
Main components: Hydrogen and helium
Present age: 4.6 billion years
Expected future life of hydrogen fuel supply: 6.4 billion years (New York Times ‘Guide to Essential Knowledge’)

How long have humans been on Earth?

We’ve evolved through a very lengthy process of evolution -- during certain phases we may have looked like apes. Scientific evidence shows that the physical and behavioral traits shared by all people evolved over a period of at least 6 million years.

One of the earliest defining human traits, bipedalism—walking on two legs, as the primary form of locomotion—evolved more than 4 million years ago. Other important human characteristics—such as a large and complex brain, the ability to make and use tools, and the capacity for language—developed more recently. Many advanced traits—including complex symbolic expression, such as art, and elaborate cultural diversity—emerged mainly during the last 100,000 years. It is estimated that our ancestors lived between 8 million and 5 million years ago.

Fire Ants creating survival rafts

When floodwaters strike, the fire ant species Solenopsis invicta reacts with a clever escape plan: Within minutes colony members link their bodies together to form a water-repellent raft that can stay afloat for weeks. Intrigued, Georgia Tech researchers studied in the lab how the insects, native to South America and now roaming the southern United States, interlock claws, mandibles, and sticky pads on their legs to construct the roughly circular rafts. Air bubbles trapped among the ants' bodies and hairs create buoyancy for the two-tiered structure and enable members on its underside to breathe.

Colonies of as many as 200,000 ants can form rafts measuring up to two feet wide. And in a remarkable feat of swarm intelligence that helps maintain the raft's integrity, ants on the bottom quickly move on top when others succumb to encounters with debris, predators, or swift currents. Scientists believe that studying this superorganism could provide new insights into micro-robotics and improved water repellency. (Adapted from National Geographic)

The largest nerve in the body

The Sciatic nerve is the largest nerve in the human body – about as thick as a lead pencil – 0.78 inches (1.98 centimeters). It is a broad, flat nerve composed of nerve fibers, and it runs from the spinal cord down the back of each leg. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Some insights gained from life …

Q: It is known as "the most destructive habit." … A: Worry
Q: This action provides the "the greatest Joy." … A: Giving
Q: What is the "the greatest loss?" … A: Loss of self-respect 
Q: This type of work is known as "the most satisfying work.” …A: Helping others
Q: What is the “ugliest personality trait?" …A: Selfishness
Q: This species is known as "the most endangered species." …A: Dedicated leaders
Q: What is "our greatest natural resource?" …A: Our youth
Q: This activity is known as "the greatest "shot in the arm." …A: Encouragement
Q: This obstacle is known as "The greatest problem to overcome." …A: Fear 
Q: What is the “most effective sleeping pill?" …A: Peace of mind
Q: What is the "most crippling failure disease?" …A: Excuses
Q: This force is known as "The most powerful force in life." …A: Love
Q: This person is known as "the one who is cast out or refused acceptance as a member of the society." …A: Gossiper 
Q: It is known as "The world's most incredible computer." …A: Human brain
Q: It is known to be "The worst thing to be without." …A: Hope
Q: It is known as the "The deadliest weapon." …A: The tongue
Q: What are the "two most power-filled words?" …A: "I Can"
Q: What is the “greatest asset" that a person can have? …A: Faith
Q: What is the "most worthless emotion?" …A: Self-pity
Q: What is the "most beautiful attire?" …A: Smile!
Q: What is a person's "most prized possession?" …A: Integrity
Q:  This method of communication is known as "The most powerful channel of communication." …A: Prayer
Q: What is the "most contagious spirit" that a person can have? …A: Enthusiasm (Internet Sources)

Before Earth

Once upon time, there was a universe but no Earth. We know this from geology, which tells us that Earth is made up of "heavy" elements - that is, elements with relatively high atomic masses. Only a supernova, or exploding star, could have produced these elements. Therefore, such a star must have existed before Earth did.

The core of this argument, the heavy-element evidence, requires a little chemistry and some astrophysics to understand. We'll begin with the basic unit of matter, the atom, and its component parts: protons, electrons, and neutrons. Electrons, which have a negative charge, orbit the nucleus of the atom, where the protons and neutrons reside. Because protons have a positive charge, they would repel one another when grouped together unless buffered by neutrons, which have no charge and act as glue.

The simplest atom, consisting of a single electron orbiting a single proton, is elemental hydrogen. The next step up, elemental helium, consists of two electrons orbiting a nucleus with two protons and two neutrons. Elemental carbon has six electrons, six protons, and six neutrons.

In the early universe, the first and most abundant element was hydrogen. Initially, the hydrogen was probably evenly distributed, but over time it began to clump, the result of random motion and the attractive force of gravity. Eventually, some of these clumps became dense enough for nuclear fusion to begin. (This is the process by which stars "burn" matter to produce energy.)

Myth and Folklore: Do any animals besides black cats supposedly bring bad fortune?

Yes- hares. Legend has it that witches transform themselves into hares, so crossing a hare’s path may mean meeting up with a witch. Further, hares have been believed by some to be melancholy creatures; thus, eating a hare can ruin your day. (The Book of Answers, by Barbara Berliner) 

Fight between a dominant stallion and a male rival

The dominant stallion fights off one of the frequent and aggressive thrusts of a colt which irrevocably tries to take over stallion's natural position in their herd. This depicts internal conflict between stallions and colts where the latter tries to win the primacy in the herd of all the mares. In a word, this gives us an impression of the survival of species and their internal conflicts which result in a perfect harmony of natural hierarchy. Those horses allow us to see their strength which is necessary for survival in a dangerous coexistence with wild animals and their frequent attacks. (National Geographic)

What kind of calendar do we use - the Julian or the Gregorian?

Most of the world's non-Muslim countries use the Gregorian calendar, introduced by Pope Gregory XIII in 1582 as a reform of the Julian calendar. (The latter, instituted by Julius Caesar, had been in use since 46 B.C.) Americans have used the Gregorian calendar since 1752.

What is the difference?

The principal difference between the two calendars is that in the Gregorian system a century year must be divisible by 400 in order to qualify as a leap year (e.g., A.D. 2000 is a leap year but not A.D. 1900). For each century that is not divisible by 400, the Julian calendar falls one day behind the Gregorian calendar. Thus, by 1542, October 4 on the Julian calendar was equivalent to October 15 on the Gregorian calendar. (The Book of Answers, by Barbara Berliner)

Electromagnetic radiation -- electromagnetic spectrum

We are bombarded by rays of energy all the time. This is electromagnetic radiation. Your eyes can detect some of these rays, but most of the radiation is invisible. Although some are harmful, all of the rays can be useful to us. They are waves of energy that can travel through space and matter. Electromagnetic radiation comes from the Sun, stars and galaxies, traveling through space to reach us. It can also be made artificially. It consists of electromagnetic waves with a wide range of frequencies and wavelengths.In order of increasing frequency (or decreasing wavelength), some of these are: radio waves, microwaves, infrared rays, light rays, ultraviolet rays, X-rays, and gamma rays. All electromagnetic radiation travels at the speed of light, and the waves or rays can penetrate materials. The complete range of frequencies of electromagnetic radiation is the electromagnetic spectrum. (Dictionary of Science, by Neil Ardley

A bird is known by his feathers – a Yiddish proverb

How does the breath-holding capability of a human compare with other mammals?

Mammal	Average time in minutes
Human	1
Polar bear	1.5
Pearl diver (human)	2.5
Sea otter	5
Platypus	10
Muskrat	12
Hippopotamus	15
Sea cow	16
Beaver	20
Porpoise	15
Seal	15 to 28
Greenland whale	60
Sperm whale	90
Bottlenose whale	120

(The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Inflation in Germany after First World War

After World War I (1914-1918), inflation in Germany was so high that millions of marks were required to buy even the most basic item. As a result, German money frequently had more value as kindling than as legal tender. (Encarta Encyclopedia)

Lava

Lava is magma that breaks the surface and erupts from a volcano. If the magma is very fluid, it flows rapidly down the volcano’s slopes. Lava that is more sticky and less fluid moves slower. Lava flows that have a continuous, smooth, ropy, or billowy surface are called pahoehoe (pronounced pah HOH ee hoh ee) flows, while aa (pronounced ah ah) flows have a jagged surface composed of loose, irregularly shaped lava chunks. Once cooled, pahoehoe forms smooth rocks, while aa forms jagged rocks. The words pahoehoe and aa are Hawaiian terms that describe the texture of the lava. Lava may also be described in terms of its composition and the type of rock it forms. Basalt, andesite, dacite, and rhyolite are all different kinds of rock that form from lava. Each type of rock, and the lava from which it forms, contains a different amount of the compound silicon dioxide. Basaltic lava has the least amount of silicon dioxide, andesitic and dacitic lava have medium levels of silicon dioxide, while rhyolitic lava has the most. (Encarta Encyclopedia)

Immigrants

Between 1820 and 1970, 36 million people left Europe to come to the United States. (National Geographic)

Sea Anemones

Sea anemones are animals that look like flowers, with dozens of brightly colored tentacles that wave about in the water. The tentacles deliver a deadly poisonous sting-and when an unfortunate fish blunders into them, it’s usually killed and eaten by the anemone. Sea anemones secret a poison that kills fish if they come near them. Clownfish is the only fish not eaten by sea anemones. They live right among the tentacles without being harmed. Sea anemones and clownfish are partners in a relationship that benefits both animals. The clownfish cleans away debris from among the anemone's tentacles. And this debris is often food for the clownfish. In addition, the relationship gives the fish protection: Few predators will risk the anemone's sting to pursue them.

How does the clownfish avoid being stung? Before it tries to swim among anemone's tentacles, the clownfish will brush lightly against the anemone. It does this repeatedly, quickly swimming away ach time. Scientists think that by doing this, the fish builds up an immunity to the anemone's poison. But the fish must remember which anemone to go back to --if it swims into the wrong one, it won't be immune. (Grolier Book of Knowledge Encyclopedia)

The Ozone Layer

High in the atmosphere is a layer of ozone that performs an important job: It screens out much of the sun's harmful ultraviolet radiation. Without protection from the radiation, life on Earth couldn't survive. And the ozone layer is being destroyed by chemicals that people put in the air.

The ozone layer is thought to have formed billions of years ago, through the interaction of sunlight and oxygen. Because this interaction is still going on, the layer is constantly renewed. But since the 1970’s, scientists have observed a thinning in the layer. The thinning is most serious over the Earth's poles -- over Antarctica, the ozone level has dropped so much that scientists talk about a "hole" in the layer. But it's occurring worldwide.

Several pollutants are thought to be destroying the ozone. The most important are chlorofluorocarbons, or CFC's. CFC's are used as solvents, refrigerants, foaming agents in styrofoam and similar products, and propellants in aerosol sprays. When they are released into the air, they rise into the upper atmosphere and destroy the ozone.

Why is the sky blue?

The sunlight interacting with the Earth's atmosphere makes the sky blue. In outer space the astronauts see blackness because outer space has no atmosphere. Sunlight consists of light waves of varying wavelengths, each of which is seen as a different color. The minute particles of matter and molecules of air in the atmosphere intercept and scatter the white light of the sun. A larger portion of the blue color in white light is scattered, more so than any other color because the blue wavelengths are the shortest. When the size of atmospheric particles are smaller than the wavelengths of the colors, selective scattering occurs - the particles only scatter one color and the atmosphere will appear to be that color. Blue wavelengths especially are affected, bouncing off the air particles to become visible. This is why the sun looks yellow (yellow equals white minus blue). At sunset, the sky changes color because as the sun drops to the horizon, sunlight has more atmosphere to pass through and loses more of its blue wavelengths (the shortest of all the colors). The orange and red, having the longer wavelengths and making up more of sunlight at this distance, are most likely to be scattered by the air particles. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

Light

Light is a form of energy visible to the human eye that is radiated by moving charged particles. Light from the Sun provides the energy needed for plant growth. Plants convert the energy in sunlight into storable chemical form through a process called photosynthesis. Petroleum, coal, and natural gas are the remains of plants that lived millions of years ago, and the energy these fuels release when they burn is the chemical energy converted from sunlight. When animals digest the plants and animals they eat, they also release energy stored by photosynthesis.

Scientists have learned through experimentation that light behaves like a particle at times and like a wave at other times. The particle-like features are called photons. Photons are different from particles of matter in that they have no mass and always move at the constant speed of about 300,000 km/sec (186,000 mi/sec) when they are in a vacuum. When light diffracts, or bends slightly as it passes around a corner, it shows wavelike behavior. The waves associated with light are called electromagnetic waves because they consist of changing electric and magnetic fields.

Galileo (1564-1642)

He was an Italian philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.

The heliocentric system is a cosmological model in which the Sun is assumed to lie at or near a central point (e.g., of the solar system or of the universe) while the Earth and other bodies revolve around it. In the 5th century BC the Greek philosophers Philolaus and Hicetas speculated separately that the Earth was a sphere revolving daily around some mystical “central fire” that regulated the universe. Two centuries later, Aristarchus of Samos extended this idea by proposing that the Earth and other planets moved around a definite central object, which he believed to be the Sun.

Creative young photographers

Three of the winning photographs in 1990 Scholastic Art Awards competition, which includes divisions in drawing, and many other forms of arts as well as photographs. The contest is open to US and Canadian students in grades 7 through 12. (Adapted from Grolier Book of Knowledge Encyclopedia)

Fire Ant

A name given to any of a number of species of ants in recognition of their painful, burning stings. They are a variety of stinging ants with over 285 species worldwide with several common names, including ginger ants, tropical fire ants, and red ants. Fire ants use their venom for defense, to kill prey, and as an aerosol disinfectant against bacteria and fungi in the nest. When stung, mammals develop blisters, which may become secondarily infected. Some people are dangerously allergic to the ant’s venom.

Colonies of fire ants can cause significant economic and ecological losses. Although individual ants are small, 3 to 6 mm (0.1 to 0.25 in) in length, mature colonies may have more than 200,000 workers, and they build sizable mounds. In clay soils, fire ant mounds may be more than 60 cm (24 in) high and very hard, impeding agricultural operations and creating a hazard for farming machinery. Fire ants can also undermine roadbeds and damage electrical equipment — they are attracted by electrical fields. They also destroy native fauna, especially other ants, egg-laying reptiles, and birds.

Source of our fresh water

About 80 per cent of our planet's fresh water originates in the mountains. In some mountainous areas the rivers are permanently frozen. These are called glaciers. (Internet sources)

How much skin does an average person have?

The average human body is covered with about 20 square feet or 2 square meters of skin. Weighing almost 6 pounds (2.7 kilograms), the skin is composed of two main layers: the epidermis (outer layer) and the dermis (inner layer). The epidermis layer is replaced continually as new cells, produced in the stratum basale, mature and are pushed to the surface by the newer cells beneath; the entire epidermis is replaced in about 27 days. The dermis, the lower layer, contains nerve endings, sweat glands, hair follicles, and blood vessels. The upper portion of the dermis has small fingerlike projections, called "papillae," which extend into the upper layer. The capillaries in these papillae deliver oxygen and nutrients to the epidermis cells and also function in temperature regulation. The patterns of ridges and grooves visible on the skin of the soles, palms, and fingertips are formed from the tops of the dermal papillae. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh; Encarta Encyclopedia)