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)

Thanksgiving Day

A legal holiday observed annually in the United States on the fourth Thursday of November. In Canada, Thanksgiving falls on the second Monday in October. Most people celebrate Thanksgiving by gathering with family or friends for a holiday feast. Thanksgiving was first celebrated by Pilgrim [English settlers] and Native Americans in colonial New England in the early 17th century. Its actual origin, however, probably traces to harvest festivals that have been traditional in many parts of the world since ancient times. Today Thanksgiving is mainly a celebration of domestic life, centered on the home and family.

The early English settlers who founded Plymouth Colony, the first permanent settlement in New England, were originally known as the Forefathers or Founders. The term Pilgrim was later first used in the writings of colonist William Bradford.

The Pilgrims, shown here celebrating their first Thanksgiving, were a group of Puritans who landed at Plymouth Rock, in what is now Massachusetts, United States, in 1620. In 1621 Governor William Bradford of New England proclaimed a day of “thanksgiving” and prayer to celebrate the Pilgrims’ first harvest in America. United States president Abraham Lincoln, following the precedent of a number of states, designated a national Thanksgiving Day in 1863. Now Thanksgiving Day falls annually on the fourth Thursday of November. (Encarta Encyclopedia)

Tallest mountain in the solar system

The tallest known mountain in the solar system is Olympus Mons (Latin for Mount Olympus), located on Mars. It is a large volcano built almost entirely of lava flows. Its height is nearly 22 km (14 miles), almost 2.5 times the height of Everest. (National Geographic)

Fever

Fever, also known as pyrexia, is the rise in the body’s temperature, as measured in the mouth, above 37° C (98.6° F). Fever is a symptom of many disorders, such as infection by a virus or a bacterium, and it is not itself a disease. The term fever is also used to name certain diseases, such as relapsing fever, rheumatic fever, scarlet fever, undulant fever, and yellow fever, in which high fever is a major symptom. The first signs of fever may be chilly sensations, with associated periods of flushed or warm feelings. The temperature may rise slowly or rapidly and may fluctuate. A rise in temperature may be accompanied by shaking chills. A falling temperature may bring on heavy sweating.

Although people have survived temperatures over 43° C (110° F), a fever higher than 41° C (106° F) typically results in convulsions, particularly in babies or the elderly.

Human embryo at 6 weeks – only a half inch long!

At six weeks a translucent form reveals the dark mass of heart and liver at its center.

Now a half inch long, the embryo floats in the cushioning waters of a sac known as the amnion. Still tethered like a balloon to the embryo, the yolk sac is a measure of the embryo's progress: The sac manufactured blood for the embryo until its own liver assumed the task during the fifth week; the bone marrow will ultimately take over this function. The yolk sac, now useless, will soon detach and begin to shrink and harden. (National Geographic)

Is glass a solid or a liquid?

Even at room temperature, glass appears to be a solid in the ordinary sense of the word. However, it actually is a fluid with an extremely high viscosity. It has been documented that century-old windows show signs of flow. The internal friction of fluids is called viscosity. It is a property of fluids by which the flow motion is gradually damped (slowed) and dissipated by heat. Viscosity is a familiar phenomenon in daily life. An opened bottle of wine can be poured: the wine flows easily under the influence of gravity. Maple syrup, on the other hand, cannot be poured so easily; under the action of gravity, it flows sluggishly. The syrup has a higher viscosity than the wine.

Kites for scientific investigations and special occasions

Kites have been valuable scientific tools. The most famous experiment involving a kite was conducted by Benjamin Franklin during a thunderstorm in 1752. Flying a kite made of a silk handkerchief stretched on two cedar sticks, Franklin proved that lightning was the same as the electric current that flows through wires. (This was a very dangerous experiment; it could easily have killed Franklin!)

From the 1700's until the early 1900’s, kites were used to collect weather data. Thermometers, anemometers, and other instruments used to measure weather factors were attached to kites and launched into sky. Kites have also been used to tow boats and sleds and carry cameras into the atmosphere to take pictures of the Earth.

And kites are used to celebrate special occasions. In Japan, for example, people fly kites to welcome in the new Year and to celebrate Children's Day on May 5. In China, the Festival of Ascending on High is actually a celebration of the practice of kite flying. (The New Book of Knowledge by Grolier)

The amazing hummingbirds

In a burst of brilliant color, a tiny bird appears. It hovers for a second in front of a flower, its wings beating so fast that they are nothing but a blur. Then it zips away, vanishing as quickly as it appeared.

The bird could only be a hummingbird, one of nature's smallest and most charming creatures. Hummingbirds invite superlatives. Besides including the world's smallest birds, they are among the most colorful, with iridescent feathers in a range of jewel-like tones. They are easily the most acrobatic birds, performing astounding feats in flight. And without doubt, hummingbirds are among the most fascinating of all birds.

Variety

There are more than 300 different kinds, or species, of hummingbirds. All of them live only in the Western Hemisphere, but they are found in almost all parts of it.

The smallest hummingbird - and the smallest bird - is the rare and tiny bee hummingbird of Cuba. This bird really could be mistaken for a bee. It weighs about as much as a penny and is just 2.5 inches (6.4 centimeters) long. And half that length is made up of its beak and its tail!

The largest hummingbird is the giant hummingbird, which lives in western South America from Ecuador to Chile. It weighs ten times as much as the bee hummingbird and is over 8 inches (21 centimeters) long, about the length of a common starling.

The primary colors in light

Color is determined by the wavelength of its light (the distance between one crest of the light wave and the next). Those colors that blend to form "white light" are from shortest wave length to longest: red, orange, yellow, green, blue, indigo, and violet. All these monochromatic colors, except indigo, occupy large areas of the spectrum (entire range of wavelengths produced when a beam of electromagnetic radiation is broken up). These colors can be seen when a light beam is refracted through a prism. Some consider the primary colors to be six monochromatic colors that occupy large areas of the spectrum: red, orange, yellow, green, blue, and violet. Many physicists recognize three primary colors: red, yellow, and blue; or red, green, and blue; or red, green, and violet. All other colors can be made from these by adding two primary colors in various proportions. Within the spectrum, scientists have discovered 55 distinct hues. Infrared and infra-violet rays at each end of the spectrum are invisible to the human eye. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)

The Ideal Intellectual?

Several years ago, a quartet of scientists studying IQ did a survey among average folks on what they believed were the characteristics of an intelligent person.

They found that almost everyone has a preconceived ideal of how an intelligent person acts and interacts with others. They also found that most people had a relatively similar notion of what these behavioral characteristics should be.

Below is a partial list of some of the traits that came out of the survey. These are not necessarily true traits of the intelligent personality, note the scientists, but only what others think it should be. They say an intelligent person:

* Accepts others for who they are; * Admits his own mistakes; * Displays an interest in the world at large; * Is on time for appointments; * Has a social conscience; * Thinks before speaking or acting; * Displays curiosity.;* Does not make snap judgments; * Is sensitive to other people's needs; * Is frank and honest with both himself and others; (Boost Your Brain Power, by Ellen Michaud, Russell Wild and the editors of Prevention Magazine)

The Densest Planet

Earth is the densest of the terrestrial planets. It is made up of a crust, mantle and core. The Earth's crust is the thinnest of these layers while the mantle comprises 84% of Earth's volume and extends 1,800 miles (2,900 km) below the surface. The average thickness of the Earth’s crust, however, is between 9 to 47 miles (below dry land) and 3 to 6 miles under oceans. What makes Earth the densest of these planets however is its core. It is the only terrestrial planet with a liquid outer core that is surrounded with a solid, dense inner core. (Internet Sources)

Halloween

The Halloween customs that we observe on October 31 had their beginnings long, long ago. They came from the beliefs of the druids -priests of ancient Gaul and Britain. The druids believed that witches, demons, and spirits of the dead roamed the earth on the eve of November 1. Bonfires were lit to drive the bad spirits away. To protect themselves further from the mean tricks of the bad spirits, the druids offered them good things to eat. They also disguised themselves so that the spirits would think the druids belonged to their own evil company. Surely the spirits would not harm members of their own group! Or so the druids thought. And thus we celebrate Halloween by playing "trick or treat," dressing up in costumes, and wearing masks.

The autumn leaves, cornstalks, apples, and nuts that are so much a part of the Halloween season are reminders of the druids' autumn festival in honor of the harvest.

Much later the Roman Catholic Church set aside the first day of November to honor all the saints who had no special days of their own. Saints were known as the hallowed, or holy, ones. Their special day was known as All Saints', or All Hallows', Day. The night before was called All Hallows' Even. All Hallows' Even was shortened to Halloween. (Grolier Book of Knowledge Encyclopedia)

Earth Day

On April 22, 1990, some 200 million people in 140 countries joined in a common cause: to save the Earth. It was Earth Day 1990- an event that was a call for action to protect the fragile environment we live in. There were street festivals, concerts, fairs, marches, and rallies. In France, people linked hands in a human chain that stretched 500 miles (805 kilometers). In Italy, 5,000 people lay down on a roadway to protest car exhaust. In Nepal, people climbed Mount Everest, picking up trash as they went. In Halifax, Nova Scotia, people gathered at sunrise and again at sunset to hear the singing of children's choirs and the chanting of a Micmac Indian medicine man. (Grolier Book of Knowledge Encyclopedia)

The name and concept of Earth Day was pioneered by John McConnell in 1969 at a UNESCO Conference in San Francisco. He proposed March 21, 1970, the first day of spring in the northern hemisphere. This day of nature's equipoise was later sanctioned in a Proclamation signed by Secretary General U Thant at the United Nations. A month later a separate Earth Day was founded by United States Senator Gaylord Nelson as an environmental teach-in first held on April 22, 1970. While this April 22 Earth Day was focused on the United States, an organization launched by Denis Hayes, who was the original national coordinator in 1970, took it international in 1990 and organized events in 141 nations. Numerous communities celebrate Earth Week, an entire week of activities focused on environmental issues. (Wikipedia online Encyclopedia)

Everybody Dreams!

Dreams, most experts believe, are messages from our subconscious. Buried feelings and fears are called up and interwoven with events that take place during the day. But in sleep, these messages are often disguised-and that's what makes dreams so fascinating. Scientists say there's no chance about it: everybody dreams! Even people who say they never dream actually do-they just don't remember their dreams. How do scientists know? They have watched people dream in sleep laboratories. At a sleep laboratory, volunteers are hooked up to electronic monitoring equipment. An electroencephalograph, or EEG, records brain waves-the electrical impulses that are constantly given off by the brain. Other machines monitor eye movements and heart and breathing rates. The volunteers' job is easy-they simply go to sleep. But all night long, scientists keep watch on the monitoring equipment. Brain waves vary with the brain's activity, so watching the EEG tells scientists what's going on while the volunteer is sleeping. Heart rate and other physical signs also vary through the night. (Grolier Book of Knowledge Encyclopedia)

Nursing

In earlier centuries, nursing care was usually provided by volunteers who had little or no training—most commonly men and women of various religious orders. During the Crusades, for example, some military orders of knights also provided nursing care, most notably the Knights Hospitalers. Toward the end of the 18th century nursing was considered an unsuitable occupation for “proper” young women, undoubtedly due to the fact that hospitals in those days were dirty and pestilent places where patients usually died. As a result, those who provided nursing care were commonly persons who had been imprisoned for drunkenness or who could not find work elsewhere.

Modern nursing began in the mid-19th century with the advent of the Nightingale training schools for nurses. Florence Nightingale established the foundations of modern nursing with her treatment of the sick and injured during the Crimean War of 1853 to 1856. Once back in London after the war, she founded the Nightingale School and Home for Nurses using money donated in tribute to her services. The school marked the beginning of professional education in the nursing field. Her book Notes on Nursing became the first definitive textbook for the field.

A comparison of some common sources of refined and natural sugar

As you look at the pictures below, please keep in mind the following two points:

1. One sugar cube = 1 teaspoon of sugar, which weighs 4.2 grams.

2.  Per the latest recommendations from the American Heart Association, the daily recommended limit of refined sugar intake for a healthy person is:

Men: 36 grams or 9 teaspoons = 150 calories

Women: 20 grams or 5 teaspoons =100 calories

Children: 12 grams or 3 teaspoons = 60 calories