How does a ferry work without an engine ?

Ferries without engines are driven by the flow of water. They are attached to a wire cable, which is spanned across the river by means of two short ropes. When the ferryman shortens one of the two short ropes with the help of a device called 'winch', the ferry is tilted at an angle to the current, and the force of  the current propels the ferry across the river

How is energy obtained from high and low tides ?

High and low tides come alternately, that is, one after the other. In high tides, the level of water rises and covers a part of the coast, and in low tides it flows away again. This energy of the tides is sued to run turbines. Special water turbines are used in tidal power plants. Water - rising in case of high tides and receding in case of low tides - can flow through these turbines in both the directions. electricity is generated in tidal power plants due to the rotary movement of the turbines. These power plants need a tidal hub - the difference in the height of water between high and low tides - of more than 5 m to be able to work economically. Such a power plant is int he French Bretagne, in St. Malo.Here, the tidal hub is at 12-15

What is hydro power ?

Water has huge power. We can feel this one our bodies when we cross a sea or river. The power we get from water is called hydro-power. Hydro-power has been one of the first force used by human beings to simplify their work. For example, tasks such as turning wheat into flour, processing wood to make paper, making textile, and turning hard metals into various interesting shapes, which were difficult to do earlier, have been made easy by using hydro-power. Dams are made by erecting huge walls in water to generate electricity. Even today there are ferries and boats without engines that use the force of flowing water. Even tides in the oceans can be used to produce energy.

How does a watermill work ?

A watermill uses a large wooden or metal wheel to generate power. It consists of many small blades, over which the flowing water of a stream run; this wheel is called the 'water wheel'. The flowing water rotates the wheel. This rotational movement produces electricity when connected to a generator. Although mills were used to generate hydro power in earlier times in all countries, people in the underdeveloped countries uses them even today. Electricity produced in such a manner is pollution free and does not harm our environment.

How is electricity generated by using a dam ?

Dam walls are mostly made of a material called concrete. These dams retain a large amount of water. The retained water puts very high pressure on the lowermost layers of water. If the water in these lowermost layers is diverted, it flows at a very high speed, and hence a high energy is produced with the hep of a device called turbine. In the turbine, the energy is sued to generate  electricity. The type of energy we can reuse since it is unlimited in nature is called renewable energy, such as the energy from the sun, wind, and water. Hydro-power is currently the only renewable energy that is used to a large extent. In Austria, approximately half of the electricity is generated by hydro-power, while in Norway all the electricity is generated by hydro-power

(all the image from google image credit goes to google)

How is urine formed?

Urine is a waste product, which is formed in the kidneys after the purification of blood. Kidneys contain millions of very tiny canals, called nephrons, which filter out harmful substances as well as excess water from the blood to form primary urine. This liquid still contains some useful components that are reabsorbed into the body in the kidneys. The remaining fluid that can no longer be used flows through the ureters into the bladder. Once the bladder is full, we need to go the the toilet and relieve ourselves.

What happens when we don not eat?

If we do not eat for some time, we lose weight and feel tired and weak. In the absence of food. the body start using its fat reserves. Once these are used up and if there is still nor or very little food supply from outside, the result is malnutrition. Life-saving processes in the body slow down because there is no fuel/energy to maintain them. We become susceptible to disease-causing germs. We have all seen pictures of children with bloated stomach and very thing legs. The  bloated stomach filled with water is a result of server malnutrition.

What causes diarrhoea ? 

Stress, an unhealthy way of life, bacteria, and viruses are the most important causes of intestinal problems. Bacteria and viruses reach the body via food or water and cause sickness, vomitting, and diarrhoea. Diarrhoea is caused because the body fights against these invaders and wants to get rid of them as quickly as possible. Sometimes, with diarrhoea, we have fever too, since an increase in the body temperature accelerates the healing processes of the body.

What happens to the food after it is swallowed?

After the food has been chewed and mixed with saliva, it reaches the stomach through the esophagus. The food is prepared for actual digestion in the small intestine, which is connected to the large intestine, and ends in the rectum. The undigested remains of the food and urine are excreted from the body. We can survive without water  only for a few days, but the body can manage without food for quite some time. If the starvation goes on  for a very long time, the body becomes weak and prone to diseases.

Why is the small intestine so long?

The function of the small intestine is to digest the food into simpler nutrients, and to absorb these nutrients. If food stays longer in the small intestine, it will have more time to get digested completely and will also enable the body to absorb all the nutrients. The very long length (more then 6 m) of the small intestine enables the food to stay there longer. The finger-line 'intestinal villi' on the inner wall of the small intestine help in absorbing the nutrients in the bloodstream. The liver and pancreas produce enzymes that travel to the small intestine to help break down proteins, fats, and carbohydrates into sugar. This process is knows as metabolism.

What does the large intestine do?

After the absorption of the nutrients the small intestine, the 1.5 m long large intestine absorbs water from the remaining undigested food and converts in into a solid mass. The solid mass of waste matter is stored in the lowermost part of the large intestine, the rectum, and is then excreted as 'stools' through the anus.

HOW DO WE JUDGE THE DIRECTION OF SOUND?

We can judge the direction of sound only because we have two ears. The sound  waves reach the right and the left ear with a small time difference because the ears are at slightly different distances from the source of the sound. The eardrums vibrate, and the ear ossicle transmits the impulse to the inner ear. The inner ear sends it further to the brain where the signals from both ears reach at marginally different times. The brain calculates the direction of the sound from the tiny difference in these times.

WHY IS THE SENSE OF TOUCH IMPORTANT?

Without the sense of touch we would be quite helpless. We would not be able to feel oneself, we would not feel our feet hitting the floor while walking and injuries would go unnoticed because no pain would be felt. We would also be deprived of many pleasant experiences important for social interaction. For blind people the sense of touch is very important. They move around safely be feeling and touching objects in their surroundings. Blind people compensate for their lack of sight by highly developed sense of touch.

What is hallucinations?

Whatever we perceive is not always real. For actually it is an illusion. Evan our sense of balance can be deceived. Hallucinations often occur because things do not happen the way we expect them to, and the brain gets 'confused'.

How does the eye work?

We can think of the eye as a kind of camera. The iris behind the cornea is light sensitive and corresponds to the aperture of the camera. This can be set near or far, depending on the amount of light falling on it. The light rays penetrate the lens of the eye, and fall on the retina. Millions of light-sensitive cells convert the light into signals sent to the brain via the optic nerve. These are put together to make images,and are interpreted by the brain. There are two types of cells in the retina: the light-sensitive rods that help us see in the dark and the less sensitive cones that help us see colours.

Why is the sense of touch important?

Without the sense of touch we would be quite helpless. We would not be able to feel oneself, we would not feel our feet hitting the floor while walking and injuries would go unnoticed because no pain would be felt. We would also be deprived of many pleasant experience important for social interaction. For blind people the sense of touch is very important. They move around safely by feeling and touching objects in their surroundings. Blind people compensate for their lack of sight by highly development sense of touch.

Where does the oxygen we breath comes from?

Gaseous oxygen was created on the Earth about 3.5 billion years ago. At that time the UV light of the sun decomposed the water vapour molecules present in the atmosphere, and released oxygen and hydrogen. But a major part of the oxygen immediately reacted with other substances, so that it was no longer available in the atmosphere as gas. Oxygen was also produced by the seas, where the 'blue algae' carried out photosynthesis. These bacteria converted sunlight and carbon dioxide into energy. In the process, gaseous oxygen was released as a 'waste product', which accumulated in the atmosphere. About one billion years ago, about one - twentieth (4%) of the atmosphere consisted of oxygen.

What would happen if there was no water on the Earth?

Without water, there would be no animals or plant, which carry out photosynthesis and release oxygen, and consequently the oxygen content in the atmosphere would go down. Moreover, the absence of oceans would have serious consequences as they help to keep the Earth's climate moderate by storing heat inside them. Without large water bodies, the temperatures of the sunlit areas and those away from the sunlight would change drastically. The temperature difference between day and night and between summer and winter would by very large. As a result, hurricanes would be a constant occurrence on the Earth.

Is there life on any planet other than the Earth?

There is no life on the other planets in our solar system because their environments are not favourable for life. They are either too hot, too cold, or too stormy. The only place that can be assumed capable of sustaining life is Europa, the moon of Jupiter. Scientists say that an ocean of liquid water could be present on this celestial body under a 10 km thick layer of ice. They also say the civilizations like our could be present - if at all - only outside of our solar system.

What makes the Earth Unique ?

Unlike the other planets of our solar system, life developed into many forms on the Earth after its emergence. Liquid water and oxygen for breathing made this possible. Millions of species of plants and animals thrive today on land and in water. Water covers more than two-thirds of the Earth's surface. Therefore, the Earth appears blue from the moon or from the international Space Station. For this reason, it is also called the 'blue plant'. Till now, scientists have not discovered life in any other place in the universe, but they believe that one day they will do so.

How was the Earth formed?

The Earth along with the sun and the remaining planets of our solar system, originated around 4-8 billion years ago from dust particles, which agglomerated gradually. At that time, the young Earth was bombarded by countless meteorites from space. The Earth's interior was molten and volcanoes erupted  constantly. But over millions of years, the Earth's surface cooled down. Around 3-8 billion years ago, the temperature decreased to about 100 dC and the Earth's crust slowly becoming solid. At this time the gaseous cover on the Earth was mostly made up of water vapour.

Why did life develop on the Earth?

The origin of life on the Earth is a fortunate series of events. The Earth's distance from the sun was such that its atmosphere and surface cooled down to a moderate level. Liquid water - and not just water vapour- also formed, and it did not freeze as the sun was not too far away. The cooling of the Earth gave rise to a kind of 'primordial ocean'. The Action of the UV rays of the sun, the lightning flashes produced by storms, and the countless volcanic eruptions gave rise to new complex chemical compounds. About 4 billion years ago, the first molecules appeared, from which the firs unicellular organisms were formed.

This image taken from google image for educational purpose.

HOW DOES OIL REACH US?

At places where crude oil is found, huge, hollow chisels drill several hundred meters deep in the Earth to reach the rocky layers containing oil. In some cases, the oil shoots out because of the pressure of the natural gas, which is found frequently with crude oil. Pumps are used to bring the oil to the surface if the pressure is not adequate. The oil is then transported to the big harbours with ships or through pipelines- hundreds of kilometers long. Sometimes it is also transported directly to refinery, which it is processed further.

How is oil discovered ?

By using acoustic or sound signals, the geologists identify the place where oil can occur on the Earth. They study these regions by looking in the rocky layers and taking samples at different depths. if  the studies point to a deposit of oil, a hole is drilled in the ground in the hope of finding oil. Scientists believe that crude oil arose from the smallest sea organisms, the planktons. After dying, the planktons sank to the seabed and were covered with sand and sludge over a long period of time. Because of the high pressure exerted by this layer, the dead mass got converted into digested sludge, which gradually got converted into crude oil. Since oil is lighter than rock, it rose up and was held in pores of the rock , like water in a sponge.

How is petrol obtained from crude oil?

Crude oil is a mixture of different substance and must first be 'refined in a refinery- it must be broken down to its components. For this, it is heated at about 300 dC in a distillation set - up. The individual substance evaporate at different temperatures. Petrol, used as  fuel in many cars, becomes gaseous at temperatures between 35 dC and 140 dC, whereas diesel oil becomes gaseous at about 300 d C. The different vapours are collected and cooled or liquefied in this way, the individual components of crude oil are separated from one another and stored as diesel oil, kerosene, or petrol.

What are fossil fuels?

The Latin word fossils means 'unearthed' or 'excavated' because we need to excavate these fuels. In other words, they are buried deep inside the Earth and we need to dig them out. Fossil fuels are made of plants and animals that died millions of years ago and were converted - by the processes inside the Earth - into coal, crude oil, or natural gas. The energy stored in these fossils can be released and used by burning them.
Searching for coal or crude oil, pumping out these fuels from the depths, and transporting them require a lot of effort and time. The crude oil must then be converted into petrol for cars.

How is coal formed?

Coal is essentially made from dead plant material. Around 300 million years ago, in the Carboniferous period, huge ferns grew in the tropical climate and dead plants sank in the swamp. The dead plant layers forced oxygen out and left rich carbon deposits.
The pressure of this layer pressed the water out of the remains of the plants slowly. This first gave rise to brown coal. Hard coal was formed when the pressure increased further. It is found in deeper layers and is a high-quality fuel. It is dug out in mines. Brown coal, on the other hand, is mined by using excavators.

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

What does air carry?

Even though we cannot see air, it is not just empty space, Air that surrounds us all the time is mainly a mixture of many gases. Air exerts pressure on us, but still does not crush us. In principle, we are living on the floor of a kilometer- thick ocean of air knows as the air cover or the atmosphere of  the Earth. Since, air is matter, it can also carry things: leaves in autumn, birds, aircrafts, hot-air balloons, and many more things. However, all objects need propulsion to lift from the ground - birds beat their wings, aircraft depends on propellers or jet engines.

How do aircrafts fly?

Aircrafts need a combination of procedure to fly in the air. They need a propulsion system- a propeller or a jet engine. They also need a lift, which comes from their wings. While flying, the forward thrust causes the air to flow at great speeds along the wings. The curved shape of the wings and their slightly tilted position give rise to a low pressure above the aircraft and high pressure below it. This is how the aircraft is pushed upwards. This is how the aircraft is pushed upwards. The pressure difference thus generates a buoyancy  which is greater then the weight of the aircraft, which of the aircraft, which pulls it down. The aircraft will fall if the buoyancy is less

How does a hot-air balloon float in air?

Air at a temperature of around 90 C is filled into the hot-air balloon. The hot air keeps the balloon in the air because its density is lower than that of the surrounding cold air. Before starting the balloon, a gas burner is ignited below  the opening of the huge balloon cover and the flame heats up the air in the balloon. When the balloon rises to the desired height, the burner is switched off; if one wants to rise further, it is started again. The balloon must have a minimum size so that it can overcome the force of gravitational attraction of  the Earth. Thus, hot air balloons are able to float in air and look so beautiful in the sky.

HOW IS ELECTRICITY GENERATED FROM SOLAR ENERGY?

The sun is the source of all energy either in the form of fossil fuels or wood. After all, these substance have been made from the energy of  the sun and have stored its energy. However, the heat of the sun can be used directly in the form of solar energy. Solar cells and giant solar plants are used for generating electricity. It has been estimated that the solar energy reaching the Earth's surface in one year is double than we will ever receive from all the Earth's resources of coal, oil, natural gas, and uranium together.


HOW CAN WE CAPTURE THE HEAT ENERGY OF THE SUN?

The easiest way to capture the heat energy of the sun is to use it to heat water. In countries with regular supply of abundant sunlight, the roofs of the houses have tanks with water that gets heated by the sunlight. 'Solar houses' can now be seen in various countries across the world. Solar collectors are placed on the roofs of these houses which collect heat from the sunlight. This energy is used to heat water, which in turn produces steam which drives a turbine connected to an electrical generator produce electricity.

Why is it important to know about the past?

Past helps us in understanding our present world in a much better way and to better future. If we known how our ancestors lived or why the wars were waged, we can understand the today's world better and get idea for a fairer future
What appears to us as wrong today could have been right earlier. It is also interesting to know how inventions in the past improved the life of humans. Some major inventions that changed the way we live are: metal processing that was invented around 5000 bc and the invention of the calendar, without which we cannot determine when the important events happened in past. So how much i can know about past i will built a better present and future.