Why are drugs considered dangerous?

Earlier, the term 'drugs' referred to dried parts of plants that had an intoxicant effect and were used for medicinal purposes. Today, the term also includes those substances which induce a stage of dreamy forgetfulness and are thus often used by people who want to temporarily escape from reality. 'Soft drugs', such as alcohol or tobacco, which are found in cigarettes or cigars, can be purchased anywhere; however, they too can be injurious to health if taken in excess. In contrast, 'hard drugs', such as heroin or cocaine, are prohibited. But they are still smuggled across borders from the countries where they are produced.

Why do smokers find it difficult to quit smoking?

Like every drug, smoking too is addictive. The body gets used to it and needs it constantly. Smokers get addicted to the ingredient nicotine that has a stimulating as well as a calming effect on the brain. Therefore, it is not so easy for habitual smokers to give up the habit. This is the reason why people should avoid smoking. Tobacco advertising is now prohibited in many countries, so that people do not get misled. In addition, smoking in public places is also banned.

Why should we avoid taking alcohol in excess?

Everyone knows that drinking alcohol in excess is unhealthy. But only a few know that an excess of alcohol can damage the nerve and brain cells and disturb the person's sense of balance and perception. Long-term drinking can lead to permanent damage of internal organs. Slowly the entire body is poisoned and the organs stop working normally. Alcohol has the most damaging effect on the liver, whose task is to remove the toxins from our blood. Alcoholics are considered serious patients needing medical help.

Is our brain bigger than that of dinosaurs?

Dinosaurs had small brains, much smaller than the human brain. The dinosaur brain often weighed only a thousandth of their huge body mass. An adult human brain is about one-fifth of its body mass, on an average around 1400 g. Since the early hominid creatures, whose skeletons were found in Africa, the brain mass of humans has increased threefold. In comparison, the size of the brains of other mammals has hardly changed in the course of millions of years.

Who were the Neanderthals?

The Neanderthals were people who lived 130,000 – 30,000 years ago, but then died out due to unknown reasons, One theory is that other lines of humans were stronger and eliminated them. The Neanderthals were about 1.70 m tall, had a heavily build body and were very powerful. They needed this power and strength to hunt woolly mammoths and rhinoceros with their home-mad spears and knives. They made clothes of animals skins, lived in caves, and used fire. Their name is derived from the place where their remains were found, the Neander valley near Dusseldorf.

What is so special about our thumb?

Unlike other animals, our thumb is opposable, which means that it has free movement and can be placed opposite the fingers of the same hand. This helps us to grip things securely and lets us do delicate jobs like threading a needle. Our grooved fingertips prevent smooth things from slipping away. This movement of the hand, combined with the freely moving shoulder joint and the upright posture, gave our ancestors a development advantage: tools or weapons could be used for a specific purpose with great power.

What differentiates humans from animals?

Biologists classify humans as animals and part of the animal kingdom, like our nearest relatives, the apes, humans are also mammals. Humans have evolved from apes, but there are features that differentiate us from other animals - including apes. These include the upright walk, our opposable thumb, our special ability to communicate by a language, and our highly developed brain. Our brain allowed our ancestors, like the Neanderthals, to invent tools.

Did humans evolve from the apes?

Today, one can think of the apes and humans as cousins. They have common ancestors, but have not descended directly from each other. About 5 - 7  million years ago, a line of man - like apes grew apart, and evolved independently of the other apes. The oldest, almost completely intact skeleton of an upright ancestor of human - the Australopithecus - was found in 1974 in Ethiopia (Africa). The scientists named it 'Lucy'.

Do animals used tools?

Animals do make use of tools for getting food or for protecting themselves. Apes reach for sticks or stones when threatened, seal otters break their favorite food, the shells, with the help of stones, and a species of finches picks our insects from tree trunks, with a long cactus quill. For generations the young ones of animals have watched the traits of the adults and imitated them exactly. Humans, on the other hand, may change the traits according to personal requirements. Humans advance and discover new things by adapting and learning. It is hard to believe that the hand axe made by prehistoric man out of stone has today given rise to sharp knives, chainsaws, and many other things.

What is a chain reaction?

Chain reactions are modifications in the composition of the atomic nucleus. The nucleus of a uranium atom, for instance, can be split by bombarding with neutrons. A lot of energy is released in the process. The fragments that arise as a result of the initial reaction fly off at a high speed and collide with the neighboring nuclei, which get split in turn. The whole process takes place as long as the present mass of uranium is split. An enormous amount of heat is released when several nuclei are split at once. This can lead to explosions. For this reason, this chain reaction is initiated in a controlled way in nuclear power plants.

How do atomic power plants works?

In atomic power plants - APP in short the chain reaction of the uranium decay is allowed to run in a controlled way. The uranium rods in the reactor, which are bombarded with neutrons, are dipped in water, which slows down the neutrons and helps achieve a controlled nuclear fission.  In addition, the fuel rods heat up the water to about 330 dC. This heat is transferred in a heat ex-changer to a second, non-radioactive water circulation, where the hot water evaporates and drives stream turbines. the energy is converted into electricity by means of the connected generators similar to other power plants.

Why are atomic power plants considered dangerous?

Nuclear energy is a clean energy source as it does not produce any waste gases that pollute the environment. It is available in abundance on the Earth, but is still considered dangerous. People are afraid of an MCA ('maximum credible accident' or worst-case scenario), something like Fukushima nuclear accident in Japan in March 2011 and Chernobyl in Ukraine in 1986. In both cases, the chain reaction went out of control and resulted in explosion. As a result, hazardous fission products were released in the air exposing people to harmful radiations. Problems are also faced in the normal operation, but precautions are taken to avoid any mishap. the used up fuel rods must be treated or stored at a secure place.

(All image in my blogs taken from google image so credit goes go google)

How is energy obtained from atoms?

There are a lot of strong forces in the nuclei of atoms, which keep the particles together, There are two ways to release the energy hidden in the atomic nuclei. We can fuse them with one another, as occurs in the core of the stars, or we can split them, which is done in at nuclear power plants. To split an atom to release energy, a chain reaction is required in a reactor. Many people consider the atomic power plants also called nuclear power plants dangerous because radioactive material is released in this process.

What force keep the atomic nuclei together?

Atoms are made up of  nucleus and a shell of electrons. The nucleus contains protons and neutrons. The protons are positively charged and repel each other like magnetic poles. At the same time, there is also a strong force of attraction, the nuclear force. This force prevents the  nuclei from flying apart. The origin of this force is complicated and nuclear physicists have been studying this phenomenon.

What is radioactivity?

Radioactivity is a property of the atomic nuclei to decay and thereby release radiation. Many atoms split when they are bombarded with neutrons, and others decay spontaneously. In both the cases, the radiation of radioactive material takes place. This radiation occurs in three forms. The alpha rays can reach only up to a few centimeters. The beta rays are made of electrons resulting from the splitting of atomic nuclei. They can go up to 1 m and are stopped by metallic foils. The gamma rays are bundled energy released in the decay and are very dangerous. Even thick lead plates can only partly stop them. They can penetrate the cells of our body and can modify or destroy them.

 

Why are some countries richer than the other?

In early times, countries became rich because climate was good, water was plenty, and their land was fertile and could be cultivated. When the Europeans discovered other continents and established colonies there, then natural resources of a country became very important. The colonial rulers mined gold, diamonds, and ores. The money they earned went into their pockets and made their countries rich. The colonies lost their natural resources and became poor. Today, it is not much different. Foreign companies frequently manufacture their goods in poor countries, where the wages are low, and then sell them in other countries at high profits. The money thus does not remain in the country which worked to manufacture the goods.

How can poor countries be helped?

Many rich countries help the poor ones through developmental aid by supporting projects in developing countries. An example of such a project would be to provide water pumps for the people in the dry Sahelian zone. However, this project may be harmful in the long run because water pumps would lower the level of ground water and soon no water would be available for the pumps. It is more important to offer sustainable options-like erect small walls around the field, so the the wind does not erode the soil. The soil would then retain its moisture and less irrigation will be required. Thus, 'help for self-help' is important. Donations can also help poor countries, especially after catastrophes like earthquake, floods, or famine.

What is globalization ?

Globalization means that the countries of the world are brought closer to one another due to faster communication and access. Flowers, which were grown in Japan, can now be bought the next day in India. Globalization makes the countries dependent on one another. It also increases competition between them, for better or cheaper products. The opponents of globalization worry that the race for cheaper products may lead to production madness in poor countries.

What has changed the world since 1900?

The technological advancement in the past hundred years has led to radical changes in the lives of people. We talk about 'global village' and 'globalization' because faster communications and transportation have 'shrunk' the world. The death rate has come down considerably due to medical advancement and the population of the Earth has been increasing. The difference between the very poor and very rich countries is more pronounced.

How many people live in the world?

It is not easy to determine the exact number of people who live on the Earth since the number increases every second. Currently, there are more than six billion people on this planet. This is the number six followed by nine zeroes! Population grows in different countries at different rates. It is growing very rapidly in the third-world countries. The increase in population is putting considerable strain on the Earth's resources because more people always need more food and energy.

What is the 'global village'?

The term 'global village' is used to express the fact that distances between people have shortened and their ways of life are now more similar, just like in a village. Today, the same beverages are consumed on all the continents, the same cars are driven, and the same films are seen. However, many things are still unevenly distributed. In Europe there are many doctors, but there are only a few in Africa. Even clean drinking water and schools are taken for granted in some countries while others have to do without them.

How do oases occur?

Oases are fertile areas in the deserts where the water is stored underneath the surface. Sand is very porous, so when it rains most of the water runs right through the sand and goes down to the bedrock, usually several hundred feet below the surface. There are also river-water oases, for example, the one along the river Nile in Egypt. Earlier the oases were important trading places for passing caravans. The conventional oasis economy provided cereals, pomegranates, and figs as well as dates that grew on the high palm trees. But now the oasis products are no longer in demand because of the globalization. The oases are now being abandoned, and are gradually drying up.

What do the antelopes living in the desert drink?

Many antelopes, such as the White Oryx found in the Arabian peninsula, have adapted themselves to a life in the desert. They do not drink water, but eat when it is cooler and when the plants are wet with dewdrops. They pass very little moisture out of their bodies because their bodies have a  system of cooling the blood before it reaches the brain. Their fur is generally paler on their underside to reflect ground heat away from the stomach. Even humans such as the San people living in the Kalahari in South Africa have adapted themselves to the desert life. They are experts at finding juicy melons and water-storing roots. They also bury sealed ostrich eggs filled with water for use during the dry season.

Why are sandstorms dangerous?

Dry, hot winds that whirl up and carry the desert sand are called sandstorms. They can rage for days and can carry so much of dust that nothing is visible. The sandstorm appears as a solid wall of sand that could be as high as 1.6 km. Animals and people caught in it can lose their orientation and die.

Desert nomads stack sandbags around their tents and protect themselves with the help of veils over their heads and faces. Camels can close their nostrils and they have extra-long eyelashes that cover their eyes.

How do animals and plants survive in the desert?

There are many kinds of deserts such as snow deserts, and dry deserts. But when we speak of deserts, we mostly mean the dry deserts. These are stone, debris, or sand deserts that have impressive dunes. These types of deserts are characterized by high temperature differences between day and night. There are sandstorms that threaten humans and animals. Animals and plants must adapt themselves to be able to survive in the this harsh environment. Some insects, like beetles, and some animals, like antelopes, have developed special tricks so that they are able to withstand thirst.

How can cacti live with very little water?

cacti have an outer waxy layer and their leaves have evolved into thorns to prevent evaporation of water. In the morning, their thorns and the outer waxy layer are also able to absorb dewdrops. They store water in their bodies and roots and consume it slowly. The Saguaro cactus, a ribbed column cactus in the Mexico desert, fills itself up completely when it rains heavily and expands like and accordion.

Can the desert really bloom?

Yes, when it rains after years in the desert, the seeds lying dormant in the ground germinate immediately, and the desert becomes a bed of flowers. The splendor, however, is short-lived. After a few days the plants wither again-but not before creating new seeds, which wait for the next time it rains. Rainfall in the desert often lead to devastating floods because the barren land can barely absorb any water. The water flows off the surface and the small rivulets grow very rapidly to become wide, torrential rivers.

What is alternative energy?

Energy resource are of two types. Those resources that are formed over millions of years and cannot be replenished are known as non-renewable millions of years and cannot be replenished are known as non-renewable energy resources, such as coal, natural gas, and crude oil. Those resources that can be replenished are known as alternative energy. Although nuclear energy too is inexhaustible, it is not considered an alternative energy resource because of the risks associated with it.

What does the term 'ecological agriculture' mean?

A lot of things that are commonly used in commercial farming are prohibited in ecological agriculture. In ecological agriculture, fields are not sprayed with chemical pesticides, and artificial fertilizers are not added to the soil. Animals are raised in ways appropriate for maintaining the health of the species. For example, hens and not crammed inside cages for their entire lives. The mostly feed on grains grown organically. Moreover, all animals are fed with 'organic food'. All these measures require a lot of space and time to be completely successful. Hence, organic products are mostly expensive.

Apart from petrol, what other products are made from crude oil?

Apart from petrol, diesel and crude oil serve as raw materials for the manufacture of many types of plastics. Therefore, waste plastic products are separated from garbage and 'recycled' to produce new plastic objects. However, this process consumes a lot of energy. In fact, we can better protect the environment by not buying things made of plastic. We should go for shopping taking our own bags, and should buy unpacked things; in this way, less garbage will be generated.

How can we protect the rain forests?

It is not easy to protect rain forests. However, the choices we make when buying various things of daily use can indirectly protect and conserve the rain forests. For example, we should buy only those wooden products that carry seals or labels mentioning that the material used for manufacture is not hazardous to rain forests. Another important consumer choice is meat. We should check labels to buy only that meat which is not obtained from cattle raised on pastures formed by clearing rain forests.

(all image taken from google image so credit goes to google for educational purpose)

How can we protect nature?

We need to live close to nature; animals, plants, soil, and water are all important for our well-being. Despite this, we keep destroying the gifts of nature with pesticides, garbage, and even through tourism. We must seek ways to protect nature. For example, we should adopt 'ecological agriculture' to produce grains and vegetables and should use alternative Eco-friendly forms of energy. Each one of us can contribute towards saving the environment by avoiding food grown with the help of pesticides and choosing a fuel-efficient means of transport. All countries must come together to save the climate of the world. The Kyoto Protocol is a major step in this direction.

What is the Kyoto Protocol?

The Kyoto Protocol is an international agreement aimed at fighting global warming. The countries that have signed the protocol have committed themselves to reduce the emission of greenhouse gases step by step, and thus prevent air pollution and global warming. The name of the contract comes from the Japaneses city of Kyoto, where this agreement was signed in 1997. Most of the countries of the world have signed the protocol, but many of them have not yet implemented it wholeheartedly as they fear that it would adversely affect their economy.

How does tourism destroy the environment?

Everyone wants to go on a holiday to scenic places. As a result, more and more hotels, roads, and airfields are build in and around tourist spots. A huge amount of water is required in the hotels to provide hygiene and catering services to tourists. A lot of waste water and garbage are also produced in the process. Tourists often litter the places they visit with polythene and leftover food without thinking about the damage they are causing to the environment.

What is Universe?

Universe, cosmos, and space mean the same-the space all around us and what is contains as far as we can see and think. We do not know whether the space is endless or is finite. If there were a border, what would be behind it? The astronomers are still dealing with the question of the origin of the universe and its end. An important factor to support the Big Bang theory of the origin of the universe is the 'cosmic background radiation', which was discovered in 1964. We still wonder whether there are intelligent civilizations somewhere in space and are looking for them.

How did space originate?

The starting point of the universe was a tiny, very compact core, with an unimaginably high temperature. About 14 billion years ago, this core exploded in the event called Big Bang. Space and time were created only after this, so one cannot say what was present before the Big Bang. After the Big Bang, the space expanded within a few seconds. This is known as 'cosmic inflation'. Electromagnetic radiation arose, and after 15 minutes there were the first atomic nuclei. About 300,000 years later, atoms were formed and the universe had cooled down to a temperature of 3000 c . After around 5000 million years the first stars originated.

How far can we see in the Universe?

With the naked eyes, we can see the stars and the planets within the Milky Way. With a telescope we can see the Andromeda galaxy, which is 3 million light years away. With a strong magnifying telescope, a lot of galaxies and stars can be viewed. Telescopes are of different kinds. Earlier, telescopes were built using lenses- the largest measured 1 m in diameter, but the later telescopes worked mainly with mirrors. The Hubble space telescope can see the farthest in the space. In 2004, it took a picture of a region of the sky that is 13-7 billion light years away. One can see the galaxies, the way they looked like just after the Big Bang.

Why does Uranus lie 'on its side'

The impression that Uranus is lying 'on its side' arises from the fact that its axis of rotation is not vertical to its orbit around the sun, as in the other planets of the solar system. It is so strongly tripped that it lies almost parallel to its orbit. The probable reason for this is a collision with another heavenly body. This also probably gave rise to the narrow rings. Uranus goes around the sun once in 84 years. Since its axis of rotation is lying on one side, the poles point alternately in the direction of the sun every 21 years. There is then summer for 21 years and on the opposite side is winter.'

Why is it very cold on Neptune?

It is extremely cold on Neptune:  the ground temperature is around -220 C. The reason for this is that it is far away from the sun, almost double the distance than its neighbor Uranus. As a result, it hardly gets any heat from the sun. Because of its blue color, the eighth planet of the solar system was named after the Roman god of sea, Neptune. The blue color does not indicate liquid water, but instead its atmosphere is made of hydrogen and helium.

How do we know the 'outer planets' so well?

Much of what we know about the gas giants comes from the observations made with telescopes-with the ones that are present on the Earth as well as with the Hubble space telescope. They provide very clear pictures of the outer planets. Many pictures are transmitted to the Earth by the space probes. The most well known of these probes are Voyager 1 and Voyager 2, which started in 1977. They flew in the direction of Jupiter and Saturn, where they took the first exact pictures of the Saturn rings. Voyager 2 then flew past Uranus and Neptune for a 'big tour' of the space taking advantage of the 'slingshot' effect of the gravitational force of Saturn. As of today, both the probes have left our solar system.

Why are some planets so big?

The largest planets of the solar system are the planets Jupiter and Saturn. Both planets have distinct bands around them with stripes. Saturn can be recognized easily by its rings. Uranus, uniquely tilted sideways, and the blue Neptune, the coldest of the outer planets, are also much larger then the inner planets. The outer planets are so big because they are comprised mainly of gases such as helium and hydrogen. These planets have a solid core, which is surrounded by liquid or frozen gas. This reason why they are also known as 'gas giants'

Why does Saturn have so many rings?

Although the rings of Saturn can be seen clearly with a normal telescope and have been known for 350 years, nobody knows exactly how they were formed. Scientists are still trying to learn more about them. The ring system has a diameter of 278,000 km, but is only a few kilometers thick. The rings are not solid 'bands', but are believed to be made of varying sizes of comets, asteroids, and shattered moons that broke up before reaching the planet. They revolve around Saturn at different speeds.

Why does Jupiter have so many stripes?

Jupiter rotates very fast on its axis, once every 10 hours. This has formed a pattern of stripes in its atmosphere, which runs parallel to the equator. The lighter zones are warm, rising masses of clouds, and the dark ones are cold, descending clouds. This pattern is disturbed by storms. One of these, the 'large red spot', is huge and can be seen from the Earth. Jupiter is not only the biggest but also the heaviest planet. It has more than 60 moons. Four of them were detected by the Italian astronomer Galileo Galilei with a telescope as early as 400 years ago

What does 'severely ill' mean?

People suffering from a terminal or incurable disease, such as cancer, are often described as being 'severely ill'. Those who carry a chronic disease such as asthma, rheumatism, or diabetes which influences or grossly hampers their normal routine in some way or other are also considered to be severely ill. Many such patients become dependent on others for help or change their lifestyle to meet the requirements of the treatment.

What is Cancer?

Cancer is a condition in which the body cells of the affected area keep multiplying at an abnormal rate, instead of growing normally; cancerous cells destroy other normal cells and create new tissues called tumours. The tumour subsequently affects the surrounding healthy tissues and damages them. Unlike benign tumours, the malignant ones always try to spread throughout the body by forming secondary growths known as 'metastases'. For instance, in the malignant stage, skin cancer can reach the bones and vital organs and wrack havoc on the patient's health. How and why cancer occurs is not clear yet. But research has confirmed that environmental pollution, smoking, and hereditary traits can favor its occurrence.

How can cancer be cured?

The earlier the cancer is detected, the better are the chances of recovery. There are different methods for treating this disease, some of which are applied in combination with other methods. In one method, the tumour is surgically removed, and subsequently the patient undergoes oral or intravenous medication treatment (chemotherapy). In another method, the tumour is irradiated with strong rays and gradually rendered non-functional. The aim of both the methods is to destroy the cancerous cells in the body, but both have drastic side-effects such as loss of hair and nausea. After the therapy is over, the side-effects vanish and the lost hair grow back.

 

Who invented the postage stamp?

Until the 17th century, the person who received the letter paid the postal charges. This was supposed to motivate the messengers to deliver the mail in a reliable and timely fashion. Later, the sender started paying the charges and got a receipt for that. But managing so many receipts became impractical. Lord Rowland Hill made a proposal to the British government to paste the receipt on the letter in the form of a stamp. This was approved by queen Victoria, who was the queen at that time. Therefore, her picture is there on the first postage stamps -- the Penny-Black stamps -- which were sold starting from 1840.

Since when were messages sent by airmail?

In 2500 B.C., pigeons were used to send messages in Egypt. This was probably the first 'airmail'! In the German-Franch was of 1870-71, a combination of flying machines and pigeons was used. When the Germans occupied Paris, the French smuggled not only mail, but also carrier pigeons from the occupied city in hot-air balloons. Pigeons could then return with new messages - unnoticed by the Germans. Today, airmail is normal and essential for the world, especially in areas that are difficult to reach by road, such as places in Alaska.

Why is post horn a symbol of the post?

The Incas in America had already established a postal system with fixed post offices since the 13th Century. If one wanted to send a message, it was conveyed to the post messengers at the stations by blowing a trumpet. In Germany, the butchers were the first ones to announce their arrival in the market by signalling with their horns. These instruments were made from the horns of the butchered animals. When the Family of Thurn and Taxis established a closely networked postal system in Europe around 1500, they took over the tradition of announcing themselves with a horn. Moreover, the coachmen of postal carriages could ensure that the other travellers would give way by sounding the horn.

Where was the first post established?

Soon after the invention of script, whenever the commanders of armies wanted to convey written messages, messengers and riders were sent with the messages. This was the beginning of the postal system. Every 5-10 km, station were built for spending the night, so that the messengers and the horses could take rest. Such a messenger system was also used by the ancient Egyptians around 5000 years ago. After the downfall of the Roman empire, the messenger system was forgotten. It was developed again only after the medieval ages. Today, postage stamps, air mail. and a mail horn are clear to almost every one as symbols of the post.

What does 'post' mean?

The word 'post' comes from the Latin word 'posita' which means 'defined'. During the time of the Roman ruler Julius Caesar, tired horses could be exchanged for fresh ones at defined places, called post stations. Afew years after Caesar's death, the emperor Augustus introduced a widespread forwarding system, which could be used only by the nobles and the Officials. The goods that were forwarded were also interesting: money, construction materials like marble, and wild animals from Africa for the gladiator games.

How did 'marathon race' in the Olympic games get its name?

There is a Greek legend regarding a messenger and the way he ran a long distance. When the Persians landed with their ships in the Greek coastal city of Marathon in 490 B.C., an army of Athenians defeated them. According to the legend, the messenger Pheidippides was dispatched to Athens to give them this good news. He could not ride his horse on the 40 km stretch between Marathon and Athens because it was very mountainious. So, he ran all the way. It is said that he reached Athens with the victory message and then fell down dead. In 1896, a race with a similar distance was included in the Olympic games as the 'marathon race'

Why is it important to go to school?

People who are educated have a better chance of doing well in life. An educated person also has better understanding of what is going on in the world and why. Education and knowledge are imparted primarily in school- often practical training at a workplace also contributes to your knowledge. After graduating from school you can go for a professional programme, or you can study further at a university. Unfortunately, many children are unable to go to  school because their parents cannot afford it.

What is the difference between a professional training programme and a university course?

Professional training is given at a vocational school, and prepares you for a job. In a university, you can study academic courses which may not necessarily have practical value. In some countries, you can do a professional training programme, such as car mechanics, baking, or cabinet making after nine years of schooling. In some countries training can be done after passing middle school. For studying at a university, however, you will need to complete all years of schooling.

How can you find the correct profession for yourself?

Many of us know as children what we want to become. Earlier, children wanted to be engineers, pilots, nurses, and fashion designers-- but now the choices may be different. Before choosing a profession, you should always ask yourself a few questions: What do I enjoy doing? Can I earn a living through this? What can I do really well? Your answers could be mathematics or dealing with people, wood carving, or a PC game. Almost all inclinations and capabilities can lead to  a profession, but often this may not be apparent. You can then go to an expert for advice.

What are the other changes during puberty?

Puberty is often a time of rebellion, in which familiar things, such as rules in the family, are questioned. Due to hormonal changes in the body, young people undergo emotional instability. Friends and people of the same age become very important. They are torn between being the glamour of being independent and the risk of leaving a secure life. Unfortunately, at this time peer pressure poses a grave danger of getting into conflicts and addictions – such as alcohol or drugs.

At what age does one becomes and adult?

In most countries, a person is legally treated as an adult after his/her 18^th birthday and is, considered responsible by the law for all his actions. For example, in most countries, a person is considered responsible enough to vote at the age of 18. Some cultures consider reaching physical maturity as the sign of growing-up and girls are often married at this time. In some religions, there are some ceremonies open only to boys and girls over a certain age. For instance, in Judaism, a person is allowed to read the Torah, their sacred writing, for the first time only after he/she attains a certain age.

What is the difference between sex and love?

Sex is a purely physical act, while love is also about emotions. There is trust, acceptance, security, and much more, in love. Love is a feeling that can change, and is tested at times, such as between the parents and the children during puberty and between friends. Love may include sex, but there are lifelong friendships that have nothing to do with sexuality. Sex between two people can take place without any feeling of love.

What happens at puberty ?

Puberty starts at about 11 or 12 years of age for girls and around 13 years of boys. This is a phase of development, in which the body and the mind undergo a change. Growth spurts, the production of sex hormones start, girls experience their first menstruation, and boys experience the breaking of their voices. Boys and girls start discovering their own sexuality and emotions run high. The transition from childhood to the adult phase is a special time and has different meanings in different cultures.

How does the body change?

The production of sex hormones results in the growth of breasts in girls, a broadening of the hips, and the start menstruation. In case of boys, the body becomes more muscular, testes and penis increase in size, the production of semen starts, and the night ejaculations begin. This is the time for first loves and understanding sexual orientation. A lot of activity goes on in the brain too. New nerve paths arise, and old ones disappear.

Do only boys undergo a voice change?

Girls also undergo a voice change, but it is not as pronounced as in boys. The larynx in the throat is responsible for the voice and the vocal cord are present inside it. In children, the vocal are short, so that the voice is rather shrill. During puberty, the larynx grows rapidly in boys and one can clearly see it, the 'Adam's Apple', in the centre of the throat. The vocal cords enlarge and become thicker, and the voice becomes deeper. The muscles of the vocal cords take time to adjust to the changes. Till then, the voice 'jump' between high and low tones and is either shrill or deep.

(all picture in my blogs from google image for education purpose, credit goes to google image) 

Where do the oxygen in the blood come from?

When we breathe, the oxygen reaches our lungs via the mouth, nose, and trachea. The lungs have a member of very tiny cavities known as air sacs which are covered by a network of very fine blood vessels. An exchange of gases takes place here, Impure blood reaches these capillaries and releases the waste gas carbon dioxide in the air sacs. This is exhaled out of the body, and freshly inhaled oxygen is absorbed into the air sacs. This oxygen is released into the blood via the capillaries.

What are cells made of?

The different cells of our body have very different tasks, but they are all similar in their structure. They have a cell wall or a cell remembrance, which protects the inner matter of the cell and controls what goes in the cell and what comes out of it. The nucleus inside the cell controls all the processes int he cell. The energy for these processes comes from mitochondria, the power house of the cell. They are responsible for cell respiration. The endoplasmic reticulum takes care of the conversion of substances and for detoxifying the cells. Al these organelles are embedded in the liquid cytoplasm inside the cell. If we drink less fluids, the cytoplasm will dry out and the cell may die.

What are organs ?

Organs are parts of the body having specific tasks. An example is the intestine, in which food is broken down and the nutrients are absorbed in the blood. Another important organ is the liver, which utilizes the components of food. Other organs are the kidneys, the spleen, the heart, and our biggest organ, the skin. They are all made up fo different kinds of tissues, such as muscular tissue, fatty or supportive tissue, and blood vessels. The tissue in each organ is specifically designed to perform the task assigned to that organ. Thus, the muscular tissue of the heart is different and performs different functions as compared to that in the upper thigh. Each organ interacts with other organs ot keep the body healthy

Why is drinking water important for humans?

The human body is made up of 80% water, which is present in blood and other cells. Since we lose a lot of fluid through sweat, urine, and breath, we need to replenish it constantly. Drinking less water can cause immediate problems. The body cells become dry, and the skin wrinkles. Blood becomes thicker, and the heart has to make more effort to pump it through the body. Since the blood is responsible for transporting oxygen around the body, oxygen is not supplied adequately to the organs. The heart and the brain react immediately to a lack of oxygen-they get damaged in just a few minutes.

Why do we need blood?

Our body consists or millions of cells, which must be supplied with water properly. This supply is the responsibility of the blood. The red blood cells transport vital oxygen around the body. The blood also absorbs nutrients from the digestive tract, distributes them to the organs, and in return, takes away the waste products from the organs. Blood contains platelets that seal the wounds and white blood cells that help us fight disease-causing germs.

How does the heart work?

The heart, a hollow organ with four chambers. can be imagined as an unbelievably strong pump. It is about the same size as a fist. Electrical signals coming from the brain cause the heart muscle to contract about 70 times in a minute in an adult. The contraction are more frequent in children and while we are playing sports. These contractions pump the blood through the whole body through the circulatory system. This system consist of two types of vessels: arteries with blood rich in oxygen and veins with blood poor in oxygen. While the arterial blood supplies oxygen to every cell in the body, the venous blood is sent to the lungs where the it is purified by removing the waste product carbon dioxide and absorbing new oxygen

What are ultrasonic waves?

Ultrasonic waves are those sound waves that are inaudible to our ears because they have a very high frequency. These high frequency. These energy-rich waves are used in many ways such as cleaning dental braces or spectacle glasses. Ultrasonic waves excite the liquid to vibrate so fast that it removes the dirt. Ultrasonic waves are also reflected from the inner organs of our body; thus, an echo is  produced. This echo can be recorded and displayed by medical devices.  In this way, doctors can safely monitor the development of a foetus inside the mother's womb.

How do bats orient themselves with ultrasound?

Bats cannot see very well. To orient themselves during their night flights, they emit ultrasounds. We cannot hear these sounds. The ultrasonic waves falling on obstacles or preys get 'reflected' back and reach the sensitive ears of bats. Thus, they come to know what all is present around them and where their prey is. This concept is also used in shipping to determine the depth of the seal using a device called sonar. It comprises a sound transmitter,  a receiver, and a clock. The time difference e between sending and receiving sound waves is measured, which is used to calculate the depth of the sea.

What is an echo?

If you call out your name in the direction of a vertical bare rocky wall, you will hear it again after some time. An echo comes because the sound waves are reflected back from the wall. When sound is produced in enclosed space, such as churches any gymnasiums, multiple reflections build up and blen together.

This phenomenon is known as reverberation.

What happens when an aircraft breaks the sound barrier?

Jets that fly faster than sound compress the air at  the front. This forms a head wave. After a certain point of time, the pressure of the air gets discharged like an explosion. As a result, a loud bang takes place and we hear a loud sound. However, ultrasonic sounds are not audible to us. Bats and other animals use ultrasonic waves for orientation. Sound always propagates in the form of waves. Because of this reason we notice a change in the pitch of the siren of the vehicle passing us.

How do we perceive sound?

Sound is produced when the chords of a guitar are set in vibration. This vibratory movement then propagates in the form of waves, like the waves that arise when a stone falls in water. Waves can travel only in a medium such as water or air, but the vacuum is completely silent. Sound waves compress the air. Sometimes sound compresses the air so strongly that it causes pain in the eardrum because of the high pressure of the waves. Very deep sounds propagate into the ground, and our body feels vibrations. This is why, the deaf can also perceive sound and dance to it.

Why does a police car siren change pitch when it passes us?

As the police car approaches us, the pitch increases, and when it moves away from us, the pitch decreases. When the car approaches us, the sound waves of the siren are 'compressed' more towards us, resulting in higher pitch. When the car is moving away, the sound waves get stretched; as a result sound fades away. This effect can be noticed only try an outside observer; the driver hears the same pitch of sound at all times. This phenomenon is called the Doppler effect, which is name after its discoverer,

Who invented the script?

It is not know exactly who invented the first script. After oral communication for thousands of years, there came the need to have something in writing because trade started at many place on Earth. For instance, written records were required to keep a note of payments made or the name of the vessel in which the cereals were kept. At first, small pictures were painted as written records. The first scripts such as those of the Sumerians or the hieroglyphs of the Egyptians developed from these pictures - to be followed later by the first alphabets. Today, we are going back to pictures. New cipher languages and special scripts for the blind have been developed in the last century. 

What is an alphabet?

Alphabets are a standardized set of letter, each of which represents a sound that is spoken out loud. The alphabets, unlike the hieroglyphs of the ancient Egyptians or the picture symbol of the Mayans, are not based on a picture system. The English alphabet has 26 letters: out of which six are vowels. The Arabic alphabet has more letters and is also read in a different way: from right to left. In the earliest alphabet that we know, there were letters only for consonants. Starting from 1000 B.C., the Greeks introduced letters for vowels. The word 'alphabet' is derived from the first two letters of the Greek alphabet: alpha and beta.

How did the Sumerians write?

Many of the early script languages did not use any letters, but used small pictures instead. Around 3500 B.C., the Sumerians in Mesopotamia invented the cuneiform script: Notches ere made in wet clay tablets with a wooden handle. The clay tablets then dried and became hard. Initially, there were about 1500 picture-like symbols, from which 800 simplified symbols developed gradually. Many of these small notches put together resulted in a word - just like a picture puzzle of today or the script of the Chinese.