What are sauropods?

Sauropods were a group of dinosaurs that were all built to the same general design. They all had a short barrel-shaped body to accommodate the huge gut needed to digest their vegetable diet, a very long neck and tail, a comparatively tiny head and peg-like teeth for grazing. The other important feature of the sauropods is that they were all enormous. They were extremely heavy, and because they lived in large herds they churned up the ground as they move about. It is still possible to see the damage caused by their movements in the ancient rock layers were fossils of the sauropods were found.

The long neck of the sauropods is thought to be an adaptation to help animals feed on tall trees, like the modern giraffe. The whole structure of the dinosaurs is a very clever piece of engineering, because their long neck, which was usually held out horizontally, was balanced by the weight of the tail. The vertebrae were shaped to allow the attachment of powerful muscles and rope-like tendons and ligaments, which held the whole structure together like a suspension bridge. Despite the great length of the neck and tail, they were not a flexible as we might think. They were usually stretched out almost in a straight line.

Is sex necessary?

Is sex really necessary in our everyday life? What are the health benefits of sex?


Improved sense of smell

After sex, production of the hormone prolactin surges. This in turn causes stem cells in the brain to develop new neurons in the brain's olfactory bulb, its smell center.

Reduced risk of heart disease

In a 2001 follow-up to the Queens University study mentioned above, researchers focused on cardiovascular health. Their finding? That by having sex three or more times a week, men reduced their risk of heart attack or stroke by half. In reporting these results, the co-author of the study, Shah Ebrahim, Ph.D., displayed the well-loved British gift for understatement: "The relationship found between frequency of sexual intercourse and mortality is of considerable public interest."

Weight loss, overall fitness

Sex, if nothing else, is exercise. A vigorous bout burns some 200 calories--about the same as running 15 minutes on a treadmill or playing a spirited game of squash. The pulse rate, in a person aroused, rises from about 70 beats per minute to 150, the same as that of an athlete putting forth maximum effort. British researchers have determined that the equivalent of six Big Macs can be worked off by having sex three times a week for a year. Muscular contractions during intercourse work the pelvis, thighs, buttocks, arms, neck and thorax. Sex also boosts production of testosterone, which leads to stronger bones and muscles. Men's Health magazine has gone so far as to call the bed the single greatest piece of exercise equipment ever invented.

Reduced depression

Such was the implication of a 2002 study of 293 women. American psychologist Gordon Gallup reported that sexually active participants whose male partners did not use condoms were less subject to depression than those whose partners did. One theory of causality: Prostoglandin, a hormone found only in semen, may be absorbed in the female genital tract, thus modulating female hormones.

Pain relief

Immediately before orgasm, levels of the hormone oxytocin surge to five times their normal level. This in turn releases endorphins, which alleviate the pain of everything from headache to arthritis to even migraines. In women, sex also prompts production of estrogen, which can reduce the pain of PMS.

Less-frequent colds and flu

Wilkes University in Pennsylvania says individuals who have sex once or twice a week show 30% higher levels of an antibody called immunoglobulin A, which is known to boost the immune system.

Better bladder control

Ever hear of Kegel exercises? You do them, whether you know it or not, every time you stem your flow of urine. The same set of muscles is worked during sex.

Better teeth

Seminal plasma contains zinc, calcium and other minerals shown to retard tooth decay. Since this is a family Web site, we will omit discussion of the mineral delivery system. Suffice it to say that it could be a far richer, more complex and more satisfying experience than squeezing a tube of Crest--even Tartar Control Crest. Researchers have noted, parenthetically, that sexual etiquette usually demands the brushing of one's teeth before and/or after intimacy, which, by itself, would help promote better oral hygiene.

A happier prostate?

Some urologists believe they see a relationship between infrequency of ejaculation and cancer of the prostate. The causal argument goes like this: To produce seminal fluid, the prostate and the seminal vesicles take such substances from the blood as zinc, citric acid and potassium, then concentrate them up to 600 times. Any carcinogens present in the blood likewise would be concentrated. Rather than have concentrated carcinogens hanging around causing trouble, it's better to evict them. Regular old sex could do the job. But if the flushing of the prostate were your only objective, masturbation might be a better way to go, especially for the nonmonogamous male. Having sex with multiple partners can, all by itself, raise a man's risk of cancer by up to 40%. That's because he runs an increased risk of contracting sexual infections. So, if you want all the purported benefits of flushing with none of the attendant risk, go digital. A study recently published by the British Journal of Urology International asserts that men in their 20s can reduce by a third their chance of getting prostate cancer by ejaculating more than five times a week.

What are tectonic plates?

The Earth's crust is made up of about 30 huge plates that float on the semi-liquid mantle surrounding the earth's core. There are currents and movements in the mantle, so these plates move very slowly in relation to each other - about 10 cm per year on average. The floor of the Pacific Ocean is one enormous plate. Some of the plates carrying continents also carry parts of the ocean floor. The thickness of the plates varies from 8 km to 200 km.

Earthquakes are evidence of movement of the tectonic plates that carry the continents. Most of the areas where earthquakes take place are along the edges of the plates. Friction holds the plate edges together for a while, but continuing movement means that huge stresses built up. The tension is suddenly released when the plates shift sharply and this causes earthquakes. There are other causes of earthquakes, but they all involve sudden movement of the crust along a fault or crack. The energy released in an earthquake is enormous - as much as 10,000 times the power released by the world's first atomic bomb.

What are explosives?

Explosives are substances that release a very large amount of energy in a short time when they burn. They all contain a fuel plus an oxidizer, which is a substance containing sufficient oxygen to burn the fuel. Explosives do not need air to explode, because they contain their own oxygen, and so they can burn in confined spaces or even underwater. Some explosives, such as those in a cartridge detonator, explode violently when hit or heated. Others only cause a violent explosion when confined in a gun barrel or a hole drilled in rock for blasting.

Gunpowder, the first ever explosive, was invented in China over 1,000 years ago. Large amounts of modern explosives are commonly used in quarrying and mining, as well as for munitions.

What is health?

Being healthy involves far more than simply not being ill. If you feel you're in good health, your organs will be working properly and you will have the energy to live life to the full. This feeling of wellbeing affects your mind and your body.

The environment you live in, your diet and your lifestyles affect your health. Physical fitness is an important part of health, and this means that your heart, lungs, skeleton and muscles all work together smoothly to carry out your daily activities. Fitness involves strength, stamina and suppleness, and you need regular exercise to maintain all these conditions. Careful exercise develops a healthy heart and lungs, and gives you the strength and stamina that allow you to run, cycle and swim. A sensible diet and sufficient sleep also help you to keep healthy.

Air pollution is an environmental factor that can damage health. Exhaust fumes from motor vehicles contain substances that can cause asthma and other breathing problems. In hot climates, smog can also develop, trapping these air pollutants and making the health risk greater.

Many diseases are infections that are caused by bacteria or virus. Other illnesses are caused by failure of some of the body's organs or tissues. Sometimes part of the body wear out or are not replaced properly, but most health problems are caused when the body simply fails to maintain itself. Joints can wear out, causing arthritis, or the digestive system may not work as efficiently, causing various types of stomach upsets. Other diseases may be caused by a person's own lifestyle, for example lack of exercise or poor eating habits. Smoking is now known to be a contributory factor in many diseases.

What are Hormones?

Hormones are chemical messengers that are produced in one part of the body and have an effect on another part.

Hormones switch body processes on and off, and they regulate most of the body's activity. The nervous system also helps in these processes, giving pared instructions along the nerves. The body's endocrine system uses hormones which work much more slowly. The majority of hormones are carried around the body in the bloodstream, reaching all the major organs and tissues.

The body has more than 30 different hormones. They are mostly produced in organs called endocrine glands.

These glands discharge the hormones directly into the bloodstream. Other types of glands pass their secretions through ducts to the point where they are needed. Endocrine glands are found in the head, neck and torso. The amount of hormones in the body is regulated by a feedback system. This means that once hormones are produced, the body measures them and once they have reached the required level, their production is switched off again. Sometimes this mechanism does not work properly and over or underactive glands such as the thyroid can produce illness.

What is electricity?

Electricity powers our lights, heating, electronic appliances such as computers and television, and a host of other essential services that we take for granted. However, electricity has much more important aspects because it is the force that holds together the molecules and atoms of all substances.

The type of electricity that is most familiar to us is electrical current. This is the flow of electrical charges through a substance called a conductor, such as a metal wire. This flow happens because some of the negatively charged electrons circling the nuclei of the conductor's atoms are held loosely. The electrons can move from one atom to the next, producing an electrical current.

Energy can no be created. An electrical generator is simply a means of converting mechanical energy into electrical energy. In its simplest form, a generator spins coils of wire in a magnetic field, causing the flow of electrical current in the conducting wire. The power to spin the generator comes from other forms of energy. This energy might be stored energy in fossil fuels such as coal or oil, hydroelectric power from dams, wind power from turning huge windmills, or nuclear power produced by the radioactive decay of elements. In all these cases, one form of energy is simply converted into electrical energy.

What is a comet?

Comets are often described as "dirty snowballs". The solid center, or nucleus, of a comet consists mostly of ice mixed with sooty material. The nucleus is quite small and is usually only a few kilometers across

Comets travel around the Sun in an elongated orbit. They plunged out into deep space beyond the farthest planet before diving back into the solar system and passing close to the Sun. As the comet's nucleus comes closer to the Sun, it becomes smaller and may eventually break up into small fragments. Comets are thought to be as old as the solar system itself.

You can not see the nucleus of a comet with the naked eye, but you can sometimes see its tail. It appears as a smear of light that moves very gradually across the sky. As a comet moves closer to the Sun, the ice and other frozen gases in its nucleus begin to boil off, producing a long tail of gas and dust. The tail always point away from the Sun because light and other forms of radiation from the Sun push against the minute particles that are present within the tail.

What is the appendix for?

The appendix is probably a leftover from our very ancient ancestors, and in humans it has very little use. In animals that eat a lot of plant material, such as rabbits, the appendix is large and contains bacteria that helps digestion. The human appendix is a tiny finger-like projection from the lower part of the gut. It sometimes become inflamed and has to be remove surgically.

Who were our first ancestors?

Humans belong to a group of mammals called primates. It includes apes, monkeys and several much smaller animals such as lemurs and bush babies. As much as 50 million years ago, back in the Eocene Period, there were traces of primate-like animals. They were small and looked rather like squirrels, but their eyes faced forwards like modern monkeys and they had grasping hands and feet.

These animals evolved into monkey-like animals, but remains of primates are scarce and the fossil record contains many gaps. Those few remains that have been found are of tree-living monkeys that are very similar to monkeys living today.

The early ancestors of humans were called hominids, and they appear to have evolved in Africa where many of their remains have been discovered.

The earliest remains that were probably our ancestors are those of human-like apes called Australopithecus, which date back more than three million years. These creatures walked erect and looked similar to us, but their brain capacity was small. Several forms of Australopithecus heve been found. All of them were much shorter than modern humans, and their teeth show that they have a vegetarian diet.

The first true humans appeared around two million years ago in Africa. It has been named Homo habilis (handy man) because it used primitive stone tools. It was still rather ape-like, however, and was soon replaced by Homo erectus, which looked very much like us. It had a much heavier jaw, bony ridges over the eyes and a sloped-back forehead. Homo erectus appeared about 1.6 million years ago. Only a few incomplete fossils of these early humans have been found, but their tools have been discovered in large numbers.

Earth's Map

The earliest known maps were made in Babylon on clay tablets, as long ago as 2300 BC. Some Egyptian drawings and paintings found in tombs are almost as old. The Greek mathematician Ptolemy (AD 90-168) produced an enormous eight-volume guide to geography and map-making called The Guide to Geography. It was followed carefully by map-makers for almost 1,000 years.

It is not possible to draw the curved surface of the globe accurately on a flat sheet of paper. This problem puzzled mapmakers for many years. In 1569, Gerardus Mercator showed how to convert the rounded shape of the world into a cylindrical shape, which could be unrolled to make a flat map. However, this can distort the size of countries in the far north and south. Dividing the earth into "orange peel" segments gives a truer image of the size of countries.

What are perestroika and glasnost?

In the Soviet Union, the Communist Party controlled almost every aspect of people's lives. However, in the 1980's Soviet people were aware that their standard of living was slipping far behind that of the West. When Mikhail Gorbachev become party leader in 1985, he begun a process called perestroika, or restructuring. Some political activities were allowed, and economical reforms enabled people to run their own businesses. Gorbachev's policy of glasnost, or openness, allowed people to express themselves freely.

Gorbachev became Soviet president in 1990, but was thrown out in a coup the following year. He returns to power to ban the activities of the Communist Party. The Soviet Union swiftly fell apart, breaking up into its original 11 republics in 1991.

Who was Napoleon Bonaparte?

Napoleon Bonaparte was born on the French island of Corsica. He became a great general in the French army and achieved several military successes. After an unsuccessful campaign against the British in Egypt, Napoleon returned to France in 1799 and took complete control of the country with the backing of the Army.

Napoleon ruled France for 15 years, and in 1804 he crowned himself emperor. He governed effectively, and increased the power of the French army enormously by setting up a system of conscription. It meant that every adult Frenchman had to do military service for a time.

Napoleon had created a massive army, which he used to try and conquer Europe. The French armies conquered huge land territories including Austria and part of Russia, and proposed to invade Britain. Napoleon’s navy was finally defeated by Admiral Nelson at the Battle of Trafalgar, however, and the invasion never took place. Instead Napoleon turned his attention to Spain and Portugal, which were given the support of Britain in their wars against the French.

What led to the Great War?

Continual trouble in the Balkans led to the formation of several complicated military alliances throughout Europe. The continent was eventually split into two groups. Britain, France, and later Russia joined to form the Entente Cordiale; Germany, Austri-Hungary and Italy formed the Triple Alliance. In 1914 Archduke Franz Ferdinand of Austria-Hungary was assassinated in Serbia, activating the alliance agreements. First Austria declared war on Serbia, Russia sided with Serbia, and then Germany declared war on Russia. Germany invaded Belgium, bringing the British and French into the conflict. The British, French and Russians became known as the Allies, while their opponents were the Central Powers.

World War I, or the Great War, was the first mechanized war in history. In the beginning, the fighting was similar to wars fought during the previous century. Mounted cavalry charged enemy lines but were cut down by fire from the recently developed machine guns. No modern tactics had been developed to handle the battles between armies spread across whole countries.

The battlefields became deadlocked, with few advances. The troops dug deep trenches. About 10 million men died in battles, which usually gained an advance of about one kilometer. Another 20 million men were wounded.

What are the Dead Sea Scrolls?

The Dead Sea Scrolls are religious writings that were first discovered in 1947, hidden in caves near the Dead Sea. The dry atmosphere of the caves had the effect of preserving the scrolls. About 800 scrolls have been found, mostly in a place called Qumbran in Israel. They date from between 150 BC and AD 68. They include all of the books of the Old Testament oe Hebrew Bible except for Esther.

Scholars believed that the scrolls were concealed by members of a religious sect called the Essenes, who lived in isolated community. They hid the scrolls to keep them safe during political unrest in the area, where they remained hidden for hundreds of years.

What is evolution?

Evolution is the name given to the gradual adaptation of living things to take advantage of the environment they live in.

This process, which takes place over millions of years, can mean that both animals and plants can change their appearance, size and habits, and eventually become new species.

We can see how evolution has changed living things by examining fossils. Fossils preserve the body parts of living creatures from long ago so that we can see how they have changed over millions of years. Sometimes the changes are very gradual, while others seem to have taken place quite rapidly. It is often possible to find a series of fossils, with each one showing a gradual change. This can tell us how a creature has altered due to the process of evolution. For example, scientists have traced the evolution of the horse from a tiny ancestor with normal toes to the large-hoofed animal we see today.

Eating Ice Cream and Other High-fat Dairy Foods Can Help Women get Pregnant?

A study shows that women who ate at least one fatty dairy food a day were 27 % less likely to have a trouble conceiving than women who ate two or more low-fat dairy products a day. Eating ice cream and other high-fat dairy foods may lower the risk of one type of infertility, the study suggests. Eating ice cream may help women get pregnant.

This was the findings of well-known Nurses Health Study at the Harvard School of Public Health.

But some doctors say that this study sounds too good to be true and probably is. Even the researchers said that women should not conclude to this results because this study are only based to the reports of what women said they ate over many years.

The study doesn't apply to most cases of female infertility - not ovulating is to blame only one-third of the time.

The Harvard study, funded by the university and a long-running federal study, involved 18,555 women, ages 24 to 42, who became pregnant or tried to from 1991-99. Among them, 3,430 reported infertility, including 2,165 who saw a doctor for it. Of those, 438 said an ovulation problem was to blame.

If women do eat more high-fat dairy foods to try to boost their odds of conceiving, it would be important to cut calories elsewhere to avoid gaining weight, doctors said. They also should switch back to low-fat dairy foods once the baby is born, to limit saturated fats.

What happens after fertilization?

The fertilized egg begins to divide as it travels down the fallopian tube towards the womb. By the time it enters the womb, it has divided into a ball of about 100 cells. It settles on the wall of the womb and sinks into the surface, becoming firmly fixed. At this point, the female is pregnant.

For the first eight weeks of pregnancy, the developing egg is called an embryo. A liquid-filled bag develops around the embryo to protect it. By the fourth week of pregnancy, the embryo is the size of a grain of rice. It has a head and a tail and the beginning of limbs, and its tiny heart begins to beat. The placenta is the embryo's life-support system. It is a red, flattened organ that becomes deeply embedded in the wall of the womb. The placenta extracts food substances from the mother's blood and passes waste material from the embryo back to the mother for disposal. The placenta is connected to the developing baby by a thick umbilical cord, which contains large blood vessels.

After the first eight weeks of pregnancy, the developing baby is called a fetus. by now, all of its major organs have formed and it is growing at a very fast rate. By the 16th week, the fetus starts to move about and by the 20th week it may already have eyebrows and fingernails. It weighs approximately 350 grams.

At the 26th week, the baby is big enough to survive if it is born prematurely. It weighs about 1.5 kg and from now on it increases in weight ready to be born. Soon the bay turns over into a head-down position ready for the birth, which usually takes place at around the 38th week.

Can fish make electricity?

Electric ells are well known, and they can stun their prey with a powerful shock. Other fish can also produce electricity to kill their prey or to defend themselves. They include electric rays, which are common in many warm seas and also electric catfish living in African rivers. fish called mormyrids, which live in very muddy waters in Africa, use electrical fields as a form of radar. This allows them to move about safely and to find food. They can also communicate by means of these electrical signals.

Sharks do not produce electricity, but they possess organs in their skin that can detect tiny electrical currents produced by the muscular movements of other fish. In this way they can hunt without being able to see their prey.

Why did the world's climate change?

The appearance of living things changed the Earth's atmosphere, providing the conditions for climate change. The first living things were plant-like creatures. They used the sun's energy to change carbon dioxide and water into sugars, which they used for food, and oxygen, which they released into the atmosphere. Some of this oxygen turned into ozone, forming the layer that now protects us from the sun's ultraviolet radiation.

In more recent times, geologists and paleontologists have been able to make more accurate measurements of the age of ancient rocks. Trees produce a new 'ring' every year, and these can be measured and counted. The width of the ring shows how well the tree grew in any year, reflecting climatic conditions at that time. The rings of even partly fossilized trees buried in bogs can be measured, and these measurements provide accurate records of climate changes over the past 750,000 years. By measuring the radioactivity of once living material, scientists can make accurate measurements up to 40,000 years ago.

What happens to our waste?

The huge quantities of domestic and industrial waste that we produce cause a major environmental problem. sometimes waste is buried in vast landfill sites, which are often old quarries. Alternatively, waste can be burned or in some cases recycled.

Waste from our toilets, baths and washing machines is collected in sewers and carried to a treatment plant. Bacterial action breaks down solid waste into a harmless form, and the waste is stirred in huge pools while this process takes place. after treatment, purified water is run off and can safely be drained into rivers. The solid material remaining is usually processed into fertilizer, after further treatment to make sure it contains no dangerous microbes.

Eight New Places to Have Great Sex

Chances are, you've had your fair share of out-of-bedroom experiences -- booty in the bathtub, getting it on in
your car. But in the name of erotic exploration, here is the list of lusty locales you may have yet to discover. "Incorporating a new venue into your routine can stimulate your sex life and keep it exciting," says Carole Altman, Ph.D., author of Electrify Your Sex Life. So add these original hot spots to your places "to do it" list.... Just make sure no one's looking.

1. A golf course: When on the green, take a time-out for a, er, hole in one. Explore the outskirts of the course for a thunderstorm shelter. These shedlike structures are usually placed in remote areas and, unless it starts to pour, no one's going near them. You may also want to sport a cute little golf skirt to allow for easy access.

2. In front of the fridge: Kitchen carnal action may be nothing new to you, but the icebox might be uncharted territory. Open the door to the refrigerator and have your man sit on the floor with his back against the cool shelves. Then straddle him. Not only will the cold air give you both a thrill (you'll surely perk up!), but you can also incorporate food into your frisky play.

3. A rowboat: Turn an ordinary day by the lake into an erotic excursion. Rent a boat and row it out to a remote area free of people. Once there, get into missionary position -- which allows you both to stay low and out of view -- and try to make some waves.

4. The hood of your car: You can put a new spin on this classic hookup spot by getting out of the backseat. Spread a blanket on the hood and have an old-school romp under the stars.

5. A farmer's field: Take a little inspiration from the movie Match Point and have sex in the tall grass you see by the side of the road when you're taking a spin in the country. You'll be hidden while you enjoy a roll in the hay.

6. A sleeping compartment on a train: If you've ever wanted to make out in a moving vehicle, a train is the way to go. You'll have to pay a little extra to get your own berth, but you can use the private area as your exclusive passion playground. All aboard!

7. On a hike: To get it on in the great outdoors without having to lie down in the dirt, search for a big boulder you can hide behind so you're not visible from the trail. With your back against the rock and your legs wrapped around your man's waist, you can enjoy standup nooky as well as the scenery.

8. An exercise bench: If your guy has a home gym, use it to work up a sweat. The bench is the right balance of firm and soft, plus it puts you in perfect alignment for girl-on-top sex. Have him lie down, then lower yourself on top of him, using your legs to move up and down.

What is a human egg cell?

The ovaries of a newborn baby girl contain about 250,000 egg cells. By the time she reaches maturity, there will be about 10,000 remaining, However, only a few of these eggs will be used - one each month throughout the years when she can have a baby. Every 28 days, a swelling appears on an ovary. This releases the egg cell then enters the fallopian tube. The swelling it emerged from produces hormones to prepare the womb to receive the egg.

Each month, an egg cell is released from the ovary. When this happens, the lining of the womb changes so that it is ready to receive the egg if it is fertilized.

If the egg is not fertilized, the womb lining brakes down, and blood and tissue pass out through the vagina. this process is called menstruation and it happens about every 28 days. The time from one period to the next is known as the menstrual cycle.

Hormones from the pituitary gland and the ovaries control the menstrual cycle, which maybe irregular. However, it usually settles into a regular cycle.

What do we know about dinosaur breeding habits?

As far as we know, all dinosaurs lay eggs rather than giving birth to live young. Many of these eggs have been fossilized, but it is sometime difficult to find out which animal produced them. Sometimes the eggs contain the remains of an unhatched baby dinosaur. Occasionally, the fossil of a newly hatched baby is found near the eggs, showing which species they belong to. Dinosaur eggs were laid in clutches, like those of today’s birds. We think that dinosaurs, like birds, would have had courtship behavior, built nests and cared for their young until they were old enough to look after themselves.

Originally, it was thought that dinosaurs laid their eggs in isolated places, but in 1978 a remarkable find was made in Montana, USA. Fifteen Maiasaurus babies were found scattered around a large mound-shaped structure, together with many broken eggshells. The babies were not newly hatched because their teeth were partly worn. The nest was about 2m across, and covered with vegetation. in the Gobi desert, the pig-sized dinosaur Protoceratops dug holes in the sand and buried her eggs. She left them to hatch in the heat of the sand while she guarded them from predators.

Dinosaur eggs looked very much like bird's eggs and were surprisingly small. Most were about the size and shape of a large potato. Their small size means that the hatchling would also have been small, and would have needed plenty of care from its parent.

There is good evidence to show that dinosaurs such as the Maiasaurus migrated back to its traditional nest site every year, where it laid up to 20 eggs. Scientists have found nest sites containing masses of eggshells, together with the remains of babies of various ages, showing that the dinosaurs re-used the sites over the years.

What are the rings of Saturn?

Shinning rings of billions of tiny chips of ice, rock and dust surround Saturn. The rings reflect light strongly and can be clearly seen through a telescope from the Earth. It was first thought that Saturn had three wide rings, but it is now known that the rings are actually made of thousands of narrow ringlets. The rings are only 100 meters thick, but they extended into space for 76,000 km. The material in the rings was probably capture3d by Saturn's gravity when the solar system was forming, or it might be the remains of a moon that has broken up. Recently, space probes discovered that some rings are braided, or twisted, but so far there is no explanation for this strange effect.

Are all drugs dangerous?

People take so-called recreational drugs, such as cannabis and heroin, because of the effect they have on the brain. These drugs are different from medical drugs that people take when they have an illness disease. Recreational drugs can be a danger to health. Some of them make people feel excited and full of energy. Others make them feel sleepy and some drugs can make people experience imaginary situations. All these drugs cause the brain to malfunction, and if taken regularly they can cause permanent damage to health.

Some of these drugs are addictive. This means that they cause changes in the brain that make people crave them, even though the pleasant effects may wear off.

Medical drugs work by correcting the chemical reactions within the body that are responsible for disease. For example, insulin injections replace insulin that is not being produced by the pancreas, so sugar can be used properly by the body. In depression and mental illness, drugs can restore the balance of chemicals in the brain. Aspirin is often given to cure a headache, but it can also neutralize the inflammation that causes the pain in the joints of people suffering from arthritis.

Modern drug research studies the cause of diseases, and then designs molecules that interrupt or reverse the disease process. All drugs cause some unwanted effects, and scientists try to find new drugs that relieve the disease without causing further problems.

Which is the most successful mammal on Earth?

We like to think that humans are the most successful animals, but it could be argued that rats are even more successful. Rats are found wherever people live, and they can adopt to live in most environment. The two common types are the brown rat and the black rat. rats produce up to seven litters per year, each one containing between six and 22 young.

Rats are a source of disease, and their droppings frequently contaminate stored food. Black rats were responsible for the spread of the Black Death in the Middle Ages, which killed millions of people in Europe. Rats are very difficult to control because they quickly adapt to the effect of poisons and learn to avoid traps.

Rats are also highly intelegent and are able to exploit new food sources. They climb walls to enter food stores, or tunnel beneath walls, and can even bite through palstic or water pipes in order to drink. They are omnivorous, which means that they can live on almost any edible substance.

How did Mao Zedong gain power in China?

When the Japanese occupied much of China during World Warr II, the Nationalist allied themselves with the newly emerging Communists and fought back.

However, after the defeat of the Japanese, the alliance between these natural enemies broke down. The Communists were able to drive the nationalists out of most of the country because they were supported by the peasants.By 1949, the Nationalists forces had been forced to leave the mainland and established themselves on the island of Taiwan, where they still remain. The Communist Chinese leader, mao zedong, formed the People's Republic of China in October 1949. Mao Zedong first became interested in politics while fighting in the revolution in 1911. he became a member of the Chinese Communist Party in 1923.

Which is the largest invertebrate?

The giant squid is by far the largest invertebrate known. This monstrous creature lives in the ocean depths, and is only occasionally washed ashore. The specimens found so far have been 20 meters in length and their eyes are 40 cm across (these are the largest eyes known).

Squids have tentacles like an octopus that surround a powerful beak. Two of these tentacles are enormously long, with gripping suckers at the end. The giant squid's suckers have a ring of sharp teeth around them to help grip their prey. These suckers leave scars on the sperm whales that feed on them, and some of these scars are from suckers nearly three times bigger than those on the largest squid found so far. So there are much larger giant squids still to be discovered.

How are sperms made?

Sperms, the male sex cells, develop in the testes. They are stored for several days until needed. The testes contain long tubes called seminiferous tubules, which are tightly coiled. sperms are produced continuosly in these tubes and then passed to tyhe epididymis and are stored in a large duct called vas deferens. Here liquid is added to the sperm to make a milky fluid called semen. It is stored in pouches called semenal vesicles. during sexual intercourse, the seminal vesicles contract and force out the sperm. It passes out of the penis and into the female sezual organs.

Up to 100 million sperms are produced everyday by the male. If they are not released, they are soon destroyed and replaced. sperms look like tiny tadpoles, with rounded heads and long lashing tails. They use their tails to swim at a speed of about one cm per minute. The head of the sperm contains the nucleus, which will join with the egg cell during fertilization.

How can forecasters predict the weather?

Meteorologists use a wide range of instruments and techniques to help them track changes in the weather and to predict future weather conditions. Weather forecasters have used simple instruments such as thermometers, rain gauges, barometers and wind gauges for many years, but the advent of satelite photography has transformed weather forecasting. Weather satelites can track the movements of clouds, and show the positions of high and low pressure areas and weather fronts. Radar measures the size, speed and direction of storms, so accurate warnings of severe weather can be given. With the use of computers, increasingly accurate forecasting is now possible.

Why does the brain have two sides?

The cerebrum is divided lenghtways into two halves, called cerebral hemispheres. Each side of the brain controls the opposite side of the body.For example, if you move your right leg, the instructions for nthat movement come from the left side of the brain. The nerve cells that carry messages from the brain cross over at the base of the brain. In most people, the left side controls speaking, writing and logical thought, while the right side controls artistic abilities and creative thinking. Most people seem to use one side more trhan the other. This is why some people seem to be more artistic than others, or are better at scientific and mathematical thinking. Usually, the left side of the brain is more dominant as far as movement is concerned, which is why most people are right-handed. About 10 % of people are left-handed.

What job do the kidneys do?

Kidneys are very effective at removing most of the waste from our blood.

Blood is pumped through groups of tiny tubes inside the kidneys and harmful waste material passes out through the walls of these vessels and down a long tube called the ureter, into the bladder. Here it is stored until ready to be discharged from the body as urine. The kidneys have a very important function in controlling the amount of water in the body. water balance needs to be kept at exactly the right level if the body cells are to remain healthy.

If the kidneys become diseased and stop working, it is necessary to use a kidney machine to remove waste from the blood. This machine process is called dialysis. It involves pumping blood from a tube in a person's arm into thin tubing that runs through a tank of sterile liquid. Waste passes from the blood through the walls of the tubing and the cleaned blood is returned to the body. This has to be done throughout the person's life, unless the new kidney can be provided in a transplant operation. Dialysis needs to be carried out frequently-several times a week- to stop waste from building up to dangerous levels.

How is gold mined?

Gold is unsuall because it is found in its metallic form, rather than as a chemical compound. Metallic gold, which is easy to identify and shape, has been mined for thousands of years. Most gold is found in what are called alluvial deposits. They consist of river mud containing tiny particles of gold washed out of rock over thousands of years. Water currents are used to wash away the mud and gravel, leaving the heavy gold particles. Gold is mined in many parts of the world, but most modern gold suppllies have come from countries such as South Africa and Russia.

Gold does not tarnish, and this makes it very valuable. It is used mainly for the manufacture of jewellery and for coating electrical contacts. It is also a very good conductor of electricity.

What are tornadoes and hurricanes?

Tornadoes are violent destructive whirlwinds whose force is concentrated into a much smaller area than that of a hurricanes. They are very common in the central United States, were they cause emourmous damage. Tornadoes travel across the land at high speed, and the roaring noise they make can be heard 40 km away. A tornado happens when huge masses of clouds moving in different directions meet. The air begins to spin ina spiral, and a funnel of twisting air reaches out towards the ground. The low pressure in the funnel sucks up soil, dust and anything else it touches, even cattle!

Hurricanes are powerful tropical storms that can cause serious damage. They from near the Equator, where warm,moist air rises, drawing in coller air below. The air moves in a spiral, eventually forming a whirling mass. Rising warm air continous to cool and drop down in the center of the spiral to repeat the process. The winds inside the hurricane travel at speeds up to 200km/h. Hurricanes form in the Atlantic Ocean, passing over the West Indies and the southern United States. Similar storms in the Pacific ocean are called typhoons, whereas in the Indian Ocean they are called cyclones.

What is Greenwich Mean Time?

In 1884 an international conference decided that the 0 degree line of longitude, or meridian, would run through the Royal Observatory in Greenwich, England. As you move to the east from the Greenwich meridian, the time is one hour ahead of Greenwich Mean Time for each degree you move. If you move to the west, time is one hour behind for each degree. Midday is the point where the sun is highest in the sky, whichever time zone you are in.

The amount of daylight varies with the seasons, so daylight-saving time, or summer time, was introduced to make maximum use of daylight hours. In the northern hemisphere, clocks are reset one hour ahead in spring and one hour back in autumn. In the southern hemisphere the seasons are reversed.

Did the ancient life forms turn into the animals we see today?

Evolution seems to have carried out some very strange experiments. Some of the earliest forms of animal life did not lead to further evolution, so they died out quickly. A few creatures have survived almost entirely unchanged, such as brachiopods. These looks like small clams although they are unrelated. They appear in the oldest fossil beds and survive in exactly the same form to this day, living in ocean depths.

Some of the oldest failures in evolution were found in a layer of rock called the Burgess Shale in Canada. This rock preserved the tiny remains of soft-bodied animals, which is an extremely rare occurence. The animals amazed scientists because most of them had no relationship to any other known life form.

Why is the body complicated?

If we were simple single-celled animal, we would not need a complicated body system to stay alive. Single-celled animals absorb oxygen directly from the water around them, and they get rid of waste in the same way. Many feed by simply crawling over food material and absorbing it, or by letting food pass through the flexible membrane around it.

Human cells operate in a similar way. Our organ systems simply provide the basic conditions that the billions of individual cells in our bodies need to survive. In general, the bigger an animal is, the more complicated its body needs to be in order to survive and reproduce.

Who was Alexander the Great?

Alexander was a king of Macedonia, a poor country that needed to expand in order to survive. Although he was only 20 when he became king, Alexander rapidly conquered Greece. He then led his armies against the mighty persian Empire, and within three years he had conquered it too. He now ruled an empire extending from Egypt and the Mediterranean coast all the way into India.

Alexander developed various methods of warfare, such as siege engines, that were to be used for hundreds of years. He introduced Greek methods of thinking and religion into his empire, and divided it into a series of small kingdoms under his own authority. He was only 32 when he died at Alexandria, in Egypt.

What causes muscle cramps?

Cramp is caused by a build-up of a waste substance called lactic acid. When a muscle works harder than usual, it starts to break down stored food without using oxygen. This process is called anaerobic respiration. it produces lactic acid as a waste product. As the lactic acid builds upit interferes with muscle action, making the muscle feel tired, until the acid is flushed away by the blood. If too much lactic acid builds up, it makes the muscle contract very sharply and painfully, causing a cramp.

Why is there so much argument about the origin of birds?

The difficulty in explaining the evolution of birds is that there are so few fossils. Bird bones are very fragile and honeycombed, with small air spaces. They crumbled away very easily after death, and consequently bird are extremely rare.

The only fossils of ancient birds are those where the animals fell into shallow freshwater lagoons and were covered very quickly with mud, which prevented decay or scattering of the remains by predators or scavengers. These special conditions appeared only occasionally, however. Until more types of bird fossil are found it will be difficult for scientists to fill in the evolutionary gaps and fin out more about the origin of birds.

Why can a body reject a transplant organ?

All your body cells carry a "label" or marker substance on the outside of the cell. This marker is recognized by the immune system, which will not attack it. In some very serious illnesses, when a person's organ has failed completely, an organ from another individual may be transplanted. The donated organ carry different marker substances, so the immune system treats them as invaders and will mount an attack on them called rejection. These attacks from the immune sysyem can be reduced or prevented by the use of powerful drugs.

Why is deforestation damaging the world's ecology?

The world's tropical rainforests are being lost at an alarming rate, and already the effects of the loss can be seen. Rainforest trees are cut down to provide timber as well as land for grazing and raising crops. The remaining scrub and branches are usually burned, providing a rich source of fertilizer for one or two years. Then the land becomes barren. Rainfall washes away the topsoil, leaving bare rock in which very little grows.

The results of deforestation are seen in countries such as Bangladesh, where heavy rains are no longer soaked up by forests in the foothills of the Himalayas. Instead the rainwater sweeps down the valleys, causing enormous flooding and loss of life.

What type of materials are plastics?

Plastics are synthetic materials that consist of long chains of molecules called polymers. Whe nthe chains a positioned in a long the plastic is rigid. When the polymer molecules are tangled tpgether, the plastic is soft and flexible. All plastic can be moulded under pressure into complicated shapes. Thermoplastics melt when they are heated, and this means that they can be remelted at any time. There are other forms of plastic, known as thermosetting plastics, which cannot be remelted.

The majority of plastics are made from synthetic resins, which are usually derived from oil. Other types come sources such as coal or wood. As they do not conduct electricity, most plastics are excellent insulators, so are widely used in electrical wiring.

The main disadvantage of plastics is that they are very slow to break down,causing serious environmental problems when discarded.

Why can too much cholesterol be bad for you?

Cholesterol is a natural fatty subtance that is found in many foods such as dairy produce, eggs and meat. it is also produced naturally in the body. High levels of cholesterol in the blood can sometimes collect on the inside the arteries, like the fur inside a kettle. This gradually reduces the blood flow and can lead to the formation of a clot that may break off and block smaller arteries. Sometimes an artery becomes almost completely blocked by these cholesterol deposits. It becomes so narrow and rigid that it can not expand to let enough blood to pass through. This kind of blockage usually happens in the legs, and is a common result of cigarette smoking.

Why did the Egyptian civilization develop?

The Egyptian civilization grew up as the annual flooding of the River Nile. This provided a green and fertile strip of land that could be cultivated, even in an area that is mostly desert. Every year, when the Nile flooded, it deposited rich, fertile slit along its banks. The ancient Egyptians grew crops of barley, wheat and flax in the fertile soils. They used the flax to make linen for their clothes.

The river provided the Egyptians with papyrus reed. They harvested the reed and used it to make a form of paper known as papyrus. It was easy to keep detailed written records on papyrus.

What are silicon chips?

A silicon chip is a tiny wafer of silicon (a semiconductor) on which a complete electronic device can be produced. An image is produced photographically and etched into the chip, but it differs from a printed circuit in some important ways. The chip is often microscopically small and contains huge amounts of "wiring". More importantly, part of the process allows other devices to be produced in the manufacturing process, such as tiny resistors and capacitors. So a silicon chip, or integrated circuit, which measures just a few millimeters across, is a complete electronic device.

What is the San Andreas Fault?

The San Andreas Fault is a long crack in the earth's crust that extends 970 kilometers through California, in the USA. It runs along the edges of the tectonic plates cerrying the Pacific Ocean and North America. These plates have shifted about 300 kilometers over the past 15 million years. They continue to move about 6 cm each year, building up emormous stresses in the crust. Along the fault line, the ground bulges, cracks open up and roads and railways develop a noticeable kink. The San Andreas Fault is carefully monitored because it is ewxpected to slip at any time.

Which are the most poisonous snakes?

Every year about one milliom people are bitten by piosonous snakes, mostly in tropical regions of the world. Between 30,000 and 40,000 of these people die.

There are several groups of poisonous snakes, and their venom can attack the body in many different ways. venom can attack the blood, the nervous system or in the case of the rattlesnake, most of the body organs. The danger depends on how much venom is injected into the body through the snake's hollow fangs when it bites.

Rattlesnakes and copperheads are common hazards in North America, while vipers and their relatives, together with cobras and mambas, are common dangers in Africa and Asia. The spitting cobra is most unusual because it sprays venom into the eyes of its victim to blind it, rather than biting. Snake bites on humans sre nearly always acts of defence. This is because the snake thinks that it is being attacked.

Why was the Roman army so successful?

The Roman army invented a method of warfare that persisited for 2,000 years. Its troops were rigorously trained and exercised, and divided into small detachments under the control of officers. Roman soldiers wore effective armour, and developed tactica that allowed them to fight sucessfully against almost any enemy. In particular, the Roman soldiers were very effective at defence. They closed ranks and protected themselves with large shields, which deflected arrows and spears, until they reached closed quarters and could use their own weapons.

Paved roads were constructed to allow the Roman armies to move very quickly to any region were trouble flared up. A network of local forts and garrisons made sure that soldiers were always available.

Which was the biggest mammal of all?

The first mammal was small and inconspicuous, and they were vulnerable to all the fierce dinosaur predators. Once the dinosaurs died out, the mammals were able to develop and evolve. Eventually the mammals grew into forms that were almost as gigantic as their dinosaur predecessors. Indricotherium, which was a member of the rhinoceros family, developed into something resembling the giant sauropods but with a shorter neck and tail. It grew to a height of 5 meters at the shoulder and weighed 15 tonnes. it probably grazed on trees, like the modern giraffe. Indricotherium had four large teeth, two in the upper and two in the lower jaw. It also had three toes on each foot. In many ways, it resembled a gigantic tapir.

What is a tsunami?

Tsunamis are tidal waves that are often caused by an undersea earthquake.Usually, there is some warning of a tsunami because scientists can detect the seismic waves caused by the earthquake. The tsunami rushes along at up to 970 km/h, building into a wall of water up to 30 meters high as it approaches land. Tsunamis are most common in earthquake zones, particularly around Japan.

Another form of tsunami is called storm surge, in which giant wave are whipped up by a storm. In 1970, a storm surge and cyclone hit Bangladesh, killing 266,000 people. It returned again in 1985, killing another 10,000 people.

Can our bodies attack themselves?

Sometimes the immune system mistakes some harmless material for an invader and this can cause illness.

Grass pollen and dust are harmless materials are often ihaled. In some people the body mounts a fierce attack on them. The immune system releases the substances normally designed to fight infection, and their effects can cause illnesses such as hay fever and asthma. Sometimes the immune system attacks normal tissue or organs, causing a condition called auto-immune disease. This can produce serious illness, but fortunately it is quite rare.

Who made the terracotta warriors?

In China, the powerful Quin dynasty came to power in the 3rd century BC. They swiftly conquered their neighbors to make a large empire covering most of modern China. The Quin emperor Shi Huangdi standardized weights and measures and introduced a single form of currency. He is best remembered for his construction of the Great Wall of China. It was built to prevent raids from nomadic people in the north. When the emperor died, a huge tomb was built to hold his body. It was filled with a guardian army of thousands of life-sized terracotta (pottery) warriors. After the emperor's death the Qin empire broke up into a series of smaller states.

Fossil Hunter

Fossil hunting can be facinating. It can also be very frustrating when you can not find anything. You can look for fossils near any cliff or area where sedementary rock is exposed, searching among the debris where rock has been broken away. But you must be very carefull. You don't want to get burried under a rock fall while you are poking around.

Here are some simple rules to help you find fossils:

- Look for irregularities in the rock. a color change or an unusually regular pattern may indicate a fossil.

- Do not expect to see a dinusaur sticking out of the rock! You are far more likely to find shells that look much the same like modern seashells.

- Soft shale is a likely place to look for fossils. This is gray flaky material that can be easily be split into sheets, and often contains fossils such as leaves and twigs.

- If you find something that looks unusual and you think it might be an exceptional find, make sure that you can remember exactly where you found it. report your find to a local museum, which may want to excavate to see if there are any more remains.

- Don't try and chip the rock away from any fossil you find. This is a very skilled job that requires specialist tools and knowledge.

- When you do find a fossil, just reflect on its age. Remember that its survival and discovery are a huge coincidence, because millions and millions of its fellow organisms disappeared without trace. Every fossil is an irreplaceable piece of ancient history.

Darwin's Islands

The Galapagos Islands have a unique range of animal life, due to their isolation from the South American mainland. Few new animals have been able to colonize the islands, and the original inhabitants have evolved in isolation. In addition to Darwins' finches, the Galapagos Islands now have a population of penquins ang fur seals that live together with tropical animals. The marine iguanas (large lizards that swim underwater to graze on seaweed) are unique. A different type of the famous giant tortoises has evolved to live on each island inthe group (some are recently extinct). The only natural inhabitant that is not unique to the Galapagos, apart from some bird species, is a small lizard.

How does smoking harm the lungs?

Smoking damages the natural cleaning mechanism of the lungs and also poisons the cells that line the lungs. Tobacco smoke paralyzes the tiny beating hairs inside the air passages of the lungs. These hairs normally clean out any material that is inhaled. Tar from the smoke accumulates inside the lungs, together with small grains of soot and chemicals that can somtimes cuse cancer. These substances are absorbed into the blood and can cause damage to the heart and circulation.

Regular smoker often suffer from lung diseases such as bronchitis, which are caused by tobacco smoke.

What is smog?

Smog is a serious form of air pollution that can cause breathing problems. The tem smog was frist used to describe a type of air pollution in London, when smoke from coal fires combined with fog to produce dense yellow clouds that sometimes persisted for days. The term now describes the hazy fog that is caused mainly by vehicle exhausts and smoke from factories. It builds up when there is little air movement, and can happen when a layer of warm air traps cooler air from the ground, preventing the smog from being blown away. Cities in bowls or sheltered valleys are particularly liable to this condition.

How is natural gas obtained?

Natural gas is widely used to supply energy for domestic use and for industrial processes. It was formesd millions of years ago by the same process that produced oil. Gas flows or is pumped by boreholes, often mixed with air and water. Then gas is separated and passes through a refinery. Some of its constituents, such as propane and butane, are removed and liquified so bthatn they can be pumped into cylinders and used as fuel. Liquified gases held under presure can be carried all around the world in specially constructed ships.

The remaining gas, which consist mainly of methane, is pumped along pipelines for domestic use. Methane has no smell, so a strong-smelling additive is used to make people aware of gas leaks.

What was the Big Bang?

The Big Bang is the most popular theory about the creation of the Universe. According to it, the whole Universe was created in a split second in one huge explosion. All matter was squeezed together into a tiny, super-hot, dense ball that was smaller than an atom. The ball gradually expanded as it cooled, then exploded, releasing energy and matter in all directions. We cannot see the Big Bang because it would have happened billions of years ago. But we can see that the Universe is growing steadily bigger. All the galaxies are speeding away from each other as the Universe expands.

Who invented the first steam engine?

During the first century AD, a Greek inventor and mathematician called Hero of Alexandria produced a device that later led to the development of modern turbines and jet engines. Hero's device was a hollow water-filled ball mounted on a swivel. Two nozzles stuck out of opposite sides, pointing in different directions. When the ball was heated, steam shot out of the nozzles, causing the ball to spin rapidly.

Hero failed to see the practical use of this device and regarded it as an interesting toy. He went to invent several mathematical formulae, one of which is still used for calculating the area of the triangle.

How can fish breathe underwater?

Fish are able to breathe underwater because they have special organs called gills. Gills are bars of tissue at the side of the fish's head. They carry masses of finger-like projections that contain tiny blood vessels. Water enters the fish's mouth and flows over the gills. The gill filaments take in dissolved oxygen from the water and pass it into the fish's blood. In this way the gills have the same function as the lungs of air-breathing animals.

Many fish that live in the water containing little oxygen are ble to breathe air. They usually have to do this in foul water, when bacterial decay reduces oxygen levels. Some fish have a special breathing organ called a labyrinth, and they rise to the surface every few minutes to breathe air into this organ. Many catfish breathe air in similar way -- they swallow it and it passes into their gut where oxygen is absorbed through the thin lining of the gut wall.

What is a Renaissance?

The 1500s was a period when Europe changed rapidly, marking the start of modern history. Before this period most learning was controlled by the Church, and people were mot permitted to question established Church teaching. Art was based on religious subjects, and most scholars trained to become either monks or priests.

During the Renaissance, many highly educated people escaped to Europe from the collapsing Byzantine Empire. They brought with them knowledge and documents that aroused great interests in the Ancient Greeks and Romans, whose contributions to civilization had been largely forgotten. Lost arts such as casting statues in bronze were revived. This whole flowering of knowledge and art is now known as Renaissance.