Planets 2

Earth
     Earth, the largest and densest rocky planet among the inner planets, was formed about 4,5 billion years ago. The earth’s interior is divided into four layers, which is typical of rocky planets. Each layer has different characteristics and is made of different elements and minerals.

1. Name the densest major body of the solar system.
     The Earth is the densest major body in the Solar System. The other terrestrial planets probably have similar structures and compositions with some differences.

2. What fraction of earth is covered with water?
     About 71% of the Earth’s surface is covered with water. Earth can exist in liquid form on the surface.

3. How is the oxygen in earth’s atmosphere produced and maintained?
     The atmosphere in Earth’s atmosphere is produced and maintained by the biological processes. Without life, there would be no free Oxygen.

4. What is magnetosphere?
     The magnetic field of the Earth is surrounded in a region called the magnetosphere. The magnetosphere prevents most of the particles from the sun, carried in solar wind, from hitting the Earth.
Nasa: The magnetosphere is that area of space, around the Earth, that is controlled by the Earth's magnetic field.
Did you know that the Earth's environment extends all the way from the sun to the Earth and beyond? It is not an empty wasteland of space. Instead, near-Earth space is full of streaming particles, electromagnetic radiation, and constantly changing electric and magnetic fields. All of these things make up our magnetosphere.

5. Describe the structure and interior of Earth.
     The Earth’s interior consists of rocks and metals. It is made up of four main layers.
(a) The inner core: A solid metal core made up of nickel and iron.
(b) The outer core: A liquid molten core of nickel and iron.
(c) The mantle: Dense and mostly solid silicate rock.
(d) The crust: Thin silicate rock material.

6. Briefly describe the earth’s atmosphere.
     The atmosphere surrounds earth and protects us by blocking out dangerous rays from the sun. The atmosphere is a mixture of gases that becomes thinner until it gradually reaches space. It is composed of 78% nitrogen, 21% oxygen, 1% argon and other gases.

Evolution of plants. 4

Reproductive part of plants
     It is the flowers which carry out the function of reproduction in plants. The female part of a flower is known as carpel and the male part is known as stamen. A yellow colored dust known as pollen is produced by the stamen, while female cells (ovules) are produced by the carpel. The pollen grains get carried to the female part by the wind, birds, animals and insects. The entire process is referred to as pollination. The pollen grain in the ovules fertilizes and it develops into seeds. A seed is a reproductive part which has the embryo plant and the stored food for the plant. Not all seeds grow into new plants; only when the conditions are suitable and they are not destroyed by animals, insects or birds do they sprout into new plants. Some of the plants grow through vegetative propagation like radish, carrot, onion, potato etc. The vegetative propagation is a way by which some plants can survive the winters. The part of the plant above the ground dies but it remains alive in the form of a corn bulb, tuber or rhizome.

     Another important contribution of plants is that they shape the environment. They are found everywhere from the tundra to the rainforests, to the deserts and everywhere except the arctic wastelands. It is the plant which maintains the terrestrial environment.

     Scientists have divided plants into
     •Algae
     •Mosses and liverworts
     •Ferns
     •Bryophytes
     •Pteridophytes
     •Angiosperms
     •Gymnosperms

     Gradually botanists came to know about more and more plants and they grouped these plants into various groups. Carolus Linnaeus (1707-78) a Swedish naturalist was the first scientist to group plants according to the number and type of stamens and pistils on their flowers. Linnaeus system gave each plant two names, the first one indicated the genus or the family while the second one indicated the species or a particular member of the family. After some years this classification was replaced by a more accurate one.

Aztec Civilization 1

1. How far had education developed?
     The Mexicans were especially interested in education. During the first years of life, fathers educated boys, while mothers took care of girls. Once family education was over, the children of the nobles and priests went to the Calmecac, and all others went to the Tepochcalli. The Aztecs believed that education was extremely valuable and insisted that boys, girls and young people attend school. The Tepochcalli was for the children of common families and there was one in each neighborhood. Here, children learned history, myths, religion and Aztec ceremonial songs. Boys received intensive military training and also learned about agriculture and the trades. Girls were educated to form a family, and were trained in the arts and trades that would ensure the welfare of their future homes.

2. Describe briefly the Aztec calendar?
     Aztec Calendar is perhaps the most famous symbol of Mexico. It is a twelve feet, massive stone slab, carved in the middle of the 15th century. Many renditions of it still exist and have existed throughout the years and throughout Mexico.

     Historically, the Aztec name for the huge basaltic monolith is Cuauhxicalli, the Eagle Bowl, but it is universally known as the Aztec Calendar or Sun Stone. It was during the reign of the 6th Aztec monarch in 1479 that this stone was carved and dedicated to the principal Aztec deity, the sun. The stone has both mythological and astronomical significance. It weighs almost 25 tons, has a diameter of just under twelve feet, and a thickness of three feet.

     The Aztec calendar kept two different aspects of time; tonalpohualli and xiuhpohualli. Each for these systems had a different purpose. The tonalpohualli was the ‘counting of days’. The xiuhpohualli was the ‘counting of the years’. This calendar was kept on a 365 day solar count. It was divided into 18 periods, with each period containing 20 days, called “veintenas”. This left five that were not represented. These were called “nemontemi”. These are the five transition days between the old and the new year, and were considered days of nothing.

Water and Clouds 2

1. Briefly describe the water cycle.
     Due to the Sun’s heat, the water evaporates from the rivers, lakes and seas. Plants suck up water from the ground and it escapes from their leaves as tiny droplets. People and animals breathe out water droplets in their breath. As the water droplets rise, they get cooler, because the air is cooler higher up. This makes the water to condense, or turn into liquid again, to form bigger droplets, which can be seen as clouds. As the clouds get cooler, the water droplets join together and grow bigger. When they are heavy enough, they fall as rain and flow back into the rivers, lakes and seas. This process is called the water cycle.

2. On what does the look of the cloud depend?
     The cloud’s look depends upon how fast they have been formed and how much water do they contain. When the clouds are formed slowly and steadily, they spread out across the sky in sheets. On hot days, clouds grow faster and puff up into heaps. The clouds, which are full of big droplets, look darker.

3. Briefly describe how are the hail storms formed.
     The Hail begins as ice crystals in giant cumulonimbus clouds. Air currents push the crystals bump into water droplets, which freeze around them in layers. The layers of ice build up until they form heavy hailstorms, which fall in the Earth.

4. What is precipitation?
     The water, which falls onto the Earth’s surface, is called precipitation. Rain is the most important form of precipitation. There are many types of rain, from light drizzle to heavy downpours and monsoon rains.

Heart and Lungs

1. How does your heart work?
     Your heart acts as a pump. The heart is like a tubular bag of thick muscular tissues having four chambers: two auricles and two ventricles which are connected to different arteries and veins.
Arteries carry pure blood from the heart to all parts of the body and veins carry impure blood from various parts of the body to the heart.

     The right auricle receives blood from the body. As it contracts, blood flows into the right ventricle. When this contracts, it pumps the blood to the lungs. The left auricle receives blood from the lungs and passes it to the left ventricle. This pumps blood to the rest of the body.

2. How do your lungs work?
     The contraction and relaxation of your diaphragm controls the movement of your lungs. When the diaphragm contracts, it becomes flatter, the pressure in the chest cavity is reduced and the lungs expand resulting in rushing of air into them. At the same time, the rib muscles contract lifting the ribs upwards and outwards.

     When the diaphragm and the ribs relax, the lungs shrink and force the air out (breathing out). Air is breathed in through the mouth and nose.

     It passes through the windpipe or trachea. The trachea is divided into two bronchial tubes that are further divided into a number of smaller tubes called bronchioles. These finally end into air sacs called alveoli, which are surrounded by a network of blood capillaries.

     When air reaches these alveoli, the oxygen of the air is absorbed by the blood. Waste carbon dioxide passes from the blood into the alveoli and is breathed out.

When did stained glass windows become popular?

     There are ample historical documents that prove that stained glass windows were introduced in the 12th century. They were first introduced in Western Europe. The churches during those days had stained glass windows. They are part of the Gothic architecture. References of such windows have been made in the religious writings dating back to 240 AD.

     One such reference is, “Gothic interiors with their full complement of stained glass were as dark as those of Romanesque Churches”. During the medieval period, such windows were much in use. The openings of the windows were covered with thin sheets of marble or wood. Holes were made in the marble or wood. Stained glasses were placed in these holes. This type of window was called a mosaic window. Attractive designs were also made by joining the glasses, leading was used. Some of the windows had religious stories painted on them

Fact
     The Royal Abbey at St. Denis, Salisbury Cathedral, Cathedral of Notre-Dame in Paris, Reims Cathedral in France, etc. are some of the churches where stained glass windows can still be seen. They are perfect examples of Gothic architecture.

Mercury and Venus

Mercury
     Mercury, the planet nearest to the Sun, is the second largest planet among the inner planets, only slightly smaller than the earth.

1. Briefly describe the surface features of Mercury.
     The surface of the Mercury is covered with craters, like the Moon, but it’s temperature can reach over 800oF because Mercury is very close to the Sun and rotates slowly.

2. How is Mercury similar and dissimilar to the moon?
     Mercury is, in many ways, similar to the Moon. It’s surface is heavily cratered and very old.
On the other hand, Mercury is much denser than the moon. Mercury is the second densest, major body in the Solar System, after Earth.

3. Dose Mercury have a magnetic field?
     Mercury has a small magnetic field whose strength is about 1% of that of the earth.

4. What do you known about Mercury’s atmosphere?
     Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the Solar wind. As Mercury is so hot, these atoms quickly escape into space.

Venus
     Venus is the second planet from the sun and is Earth’s closest neighbor in the Solar System. It is the brightest object in the sky just like the sun and the moon and sometimes looks like a bright star in the morning or evening sky.

1. Briefly describe Venus’s surface?
     Venus’s surface is covered with craters, over 1600 major volcanoes, mountains, lava highland terrains, and vast lava plains.

2. Name the two large high land areas on Venus.
     The two large highland areas on Venus are Isatar Terra in the Northern Hemisphere and Aphrodite Terra along the Southern Hemisphere.

3. Why is Venus regarded as Earth’s sister planet?
     Venus is regarded as Earth’s sister planet, as in some ways, they are very similar. Venus is only slightly smaller than Earth and Mercury. Both have few craters indicating relatively young surfaces. Because of these similarities, it was thought that below its dense clouds, Venus might be very Earth like, and might even have life.

4. How is the atmosphere of Venus?
     Its atmosphere is 90 times heavier than earth, and clouds of sulphuric acid bloat around to top it. The atmosphere of Venus is so hot and thick that we can not breathe in the air. We would be crushed by the enormous pressure of the atmosphere.

5. How is the Venus rotation unusual?
     Venus rotation is somewhat unusual as, it is both very slow and retrograde. In addition, the periods of Venus’s rotation and its orbit are synchronized in such a way that it always presents the same face towards earth when the two planets are at their closest approach.

6. Why is it tricky to spot Venus?
     It is tricky to spot Venus because it is always near the Sun. Because of this, it rises and sets with the Sun each day. Ancient people believed that, the morning and the evening stars were actually two different objects.

Evolution of plants. 3

Root
    Roots provide support to the plant and enable it to hold onto the soil firmly. They help the plants to absorb water and nutrients from the soil. The tips of the roots are protected by the root cap and they are deeply rooted in the soil.

Stem
    Some stems are tender while some are tough. The stem supports the branches and leaves, and it provides all the ingredients to the plants to manufacture their food. Stems have a vascular system which consists of two kinds of tissues-xylem and phloem which carry the necessary roots food and water prepared by the leaves to other parts of the plant. Xylem is made from dead woody material and it carries plant water from the roots to the rest of the plant. Carbon dioxide enters the plant through the stomata where photosynthesis takes place and oxygen is released. The water evaporates through the individual cells below each stoma. Xylem helps in transporting water and nutrients from the soil to the various parts of a plant. Phloem is more complex than xylem as it consists of sieve tubes joined together from one end to another end. It transports the carbohydrates made in leaves to every living cell in the plant through a process known as translocation. Phloem cells are able to survive as they are sustained by companion cells which lie between sieve tube elements. It has a nuclei and a number of mitochondrias which produce cells energy. The outer wall of the plant cell consists of a membrane which is selectively permeable. Substance leave and enter through active transport system.

Leaves
    Leaves are the green parts of a plant. They are made up of numerous tiny packets known as cells. The leaf is attached to the plant by a stalk or a petiole, and through the mid part of a leaf run veins which not only support the leaf but also carry water and nutrients to all the cells of the leaf. A leaf is made up to two part- an epidermis and a mesophyll. The epidermis is the outer layer found on the upper and lower surfaces of a leaf while the mesophyll and parenchyma lie between these surfaces. The leaves help the plant to make its food through the process of photosynthesis. The leaves absorb carbon dioxide from the atmosphere and roots absorb water and nutrients from the soil; the stem carries the water and nutrients to the leaves, here with the help of sunlight chlorophyll (a green pigment in the cells of leaves) converts carbon dioxide and water to produce glucose and release oxygen as a waste product.

Inca Civilization

    As ancient civilizations sprang up across the planet thousands of years ago, the Inca civilization also evolved.
As with all ancient civilizations, its exact origins are unknown. The Inca of Peru have long held a mystical fascination for people of the western world. The Inca Empire was quite short-lived. It lasted for just short of 100 years, from 1438 AD.

1. Describe briefly the religious life of Incas.
    The Incan religion was based on nature. All of the elements on which they depended, and even some on which they didn’t, were given a divine character. They believed that all deities were created by an everlasting, invisible, and all powerful god named Wiraqocha, or Sun god. The King Incan was seen as Sapan Intiq Churin, or the Only Son of the Sun. The Inca were a deeply religious people. They feared that evil would befall at any time.

2. Describe the social structure of Incas.
    Inca society was made up of ‘tribes’, which were clans of families who lived and worked together. Each tribe was supervised by a “curaca” or chief. Families lived in thatched-roof houses, built of stone and mud. Furnishings were unknown, with the families sitting and sleeping on the floor. Potatoes were the basic Inca food. The Imperial Incas clothed themselves in garments made from Alpaca and many of their religious ceremonies involved animals.
In Inca social structure, the ruler, Sapa Inca and his wives, the Coyas, had supreme control over the empire. The High Priest and the Army Commander in Chief were next. Then came the Four Apus, the regional army commanders. Next were temple priests, architects, administrators and army generals. Next were artisans, musicians, army captains and the Inca accountants. At the bottom were sorcerers, farmers, herding families and conscripts.

3. Describe briefly agriculture and economic condition of Inca.
    Everyone worked except for the very young and the very old. About 2/3rd of a farmer’s goods were shared by a tax system, and the rest were for keeps. Some of the goods were distributed to others, while goods were received in return, and the rest was stored in government storehouses or sacrificed to the gods. The Incas adopted and improved upon the terracing method of farming invented by pre-Inca civilizations. They built stone walls to create raised, level fields. Camels, such as llamas, alpacas, and vicuas, were very important to the economy. In addition to carrying burdens, llamas and alpacas were raised as a source of coarse wool and of dung, which was used as a fuel.

Water And Clouds - 1

    The amount of water on earth always remains constant, it never changes. The only thing, which changes, is the form of water. Water exists in liquid from in seas and rivers, freezes into a solid to make snow and hail and it floats in the air in the form of clouds.

1. What is evaporation?
    When the water is heated up, it changes from liquid into tiny invisible water droplets, which float in the air. This process is called evaporation.

2. How do the snowflakes form?
    Snowflakes form when water droplets freeze into ice crystals. These snowflakes have been tinted so that you can see their six-sided shapes more clearly.

3. Briefly describe the three clouds.
    The cumulus clouds look like white, puffy heaps. They often form high in the sky in warm, sunny weather. Stratus clouds form low, flat layers and often block out the sunshine. Cirrus clouds are high and wispy.

What does Our Brain do?

Brain is a very important organ of our body. It is placed securely in the skull, also known as brain box. The brain controls our body.

It contains more than 10 billion neurons with complex pathways linking our senses, our movements and memory.

It uses information from our sensory organs like the eyes and ears and decides the action to be taken and sends messages through the nerves to the muscles or gland concerned.

We learn things and can remember them later because the brain can store the information.

The three main parts of the brain are:
(i) Cerebrum – The largest part which controls conscious feelings and voluntary movements.
(ii) Cerebellum – It controls the muscles and body balance.
(iii) Medulla – This controls involuntary actions like breathing.

when did man begin to mine gold?

It is not known for sure when gold mining began. But, it is believed to have started around 5,000 years back. Some pictures dating back to five thousand years have been found. These pictures depict gold being mined. It was in Egypt that gold was first mined. In the beginning, it was panned from river water.

Gold was sorted out carefully from the river water by separating it from the sand. For panning gold, a round dish was used. It had a pouch at its bottom. The miner filled the dish with the mixture of sand and gold. Then, holding the dish under flowing water, he moved it in a circular motion. The lighter part of the sand got separated and the gold settled down in the pouch of the dish. This was how gold was mined around 5,000 years back. At around 3,000 BC, gold rings were used as a mode of disbursement. It was also used for ornamental purposes. It was around 2,000 BC that Greeks and Romans made shafts to extract ores of gold from deep inside the ground.

Fact:
In 1849, gold mines were discovered at California by W Marshall, a carpenter. The year is marked by the great gold rush. A great number of people moved to California to extract as much gold as possible.

Evolution of plants. 2

Lycopodiale remains from most of the great coal beds of the earth Lycopodia and other species thrived for a short period and then their trunks were blown down by storms and gradually piled up and were changed to coal. The Equiset or horse tails can be seen even today in sandy areas and barren lands. The horsetails are the last descendants of the calamites which covered the entire forest in prehistoric times. Nearly twenty five species of horsetails are found at present in every part of the earth except Southern Asia. These horsetails were like gigantic trees which in the process of degeneration became smaller till it reached the dwarf size that we see today.

The climate during that period, when the algae transformed into land plants, was favourable; it was quite pleasant climate for the growth of plants. The little plants gave rise to complex vegetation like the Giant Sigillaria which were 23 metres high. The Gingko tree is the only survivor of the ancient group of tree plants.

Flowers marked the last stage of evolution in the plant kingdom. They appeared nearly 100 million years ago. This was an important landmark in the evolution of plants. Thus the swarms of pollinating insects soon invaded the land and gave the forests a new look where mammals had remained hidden behind these plants for million of year.

Plants are the only living things on the earth that can make their own food. Animals are directly or indirectly dependent upon plants. A typical plant is made up of roots and shoots which include stem, leaves and branches. The branches bear flower and fruits.

Egyptian Civilization. 2

1. Give a vivid description of the famous Karnak Temple.
It is located at the northern end of the town of Luxor. It has three main sacred areas that honour three gods, Montu, an ancient local warrior, God Ameen, the chief god of Thebes and the goddess Mut, wife of Ameen and Khonsu. The son of the Ameen and Mut were members of the sacred family known as the Theban Triad.
The temple was constructed in the middle kingdom and completed in New Kingdom. The temple covers two hectares of land, as every successive king of this era added to the temple. It had four courtyards, ten pylons, a sacred lake and many buildings.

2. Who was Osiris?
Osiris was one of the principal Egyptian gods who appeared in funerary texts during pyramid age. According to the Egyptian mythology, he was murdered by his brother Seth, then brought back to life by the Love of his sister and wife Isis. Osiris and Isis had a son named Horus. Together, they represent a holy family of god, goddess and divine child.

3. Who was Horus?
Horus was the falcon headed god of Egypt. He was the son of Osiris and Isis, the divine child. His name means “he who is above” and “he who is distant”.
Horus is depicted as a falcon wearing a crown with a cobra or the double crown of Egypt.
He has become one of the most commonly used symbol of Egypt seen on the Egyptian airplanes, hotels and restaurants throughout the land.

4. Describe the Egyptian calendar.
The Egyptian calendar was based on a year of 365 days with twelve months and three seasons. Each month had three ten day weeks for a total of 30 days, while the last five days corresponded to the birthdays of five deities, Osiris, Isis, Horus, Seth and Nepthys. As the Egyptians did not take leap year into account, their calendar got further and further away from the seasons.
Besides the civic calendar, there was a religious calendar that displayed the festivals and ceremonies associated with particular deities and temples. This was based on 29.5 days per month.

5. Who was Galen?
He was an anatomist, physiologist and theoretical physician of all time during 129- c 199. He was born in Perganum and studied in Smyrna and Alexandria and was appointed surgeon of gladiators in Perganun, He discovered that arteries contain blood and not air as had been taught upto his time. He wrote more than 400 books throughout the middle ages on medical theory.

6. What do you known about mummification?
The ancient Egyptians buried their dead in small pits in the desert. Later they started burying their dead in coffins to protect them from wild animals in the desert, which decayed when they were not exposed to the hot, dry sand of the desert.
Later on, they developed a method of preserving bodies, so that they would remain life like. The process included embalming, as the body was wrapped in trips of linen. This process is called mummification.

7. What where the sources of their recreation?
Hunting and Fishing – Pharaohs and nobles participated in hunting, fishing and fowling expeditions, a means of recreation that had ritualistic and religious significance.
Hunting scenes often depicted on temple walls and tombs reinforce the powers of kings and nobles, deer, rabbit, gazelles, oryx, antelopes, lions were hunted for their meat and skins.

Solar System

Solar system is the name given to a group of nine planets; Mercury, Venus, Earth, Jupiter, Mars, Neptune, Uranus, Saturn, and Pluto that orbit around the Sun, and these planets satellites, asteroids, etc.

1. How was the solar system created?
The Solar System was created when a rotating cloud of gas and dust in space started to coalesce. They were pulled together and towards the center of the gas/dust cloud by their gravitational attraction. The gas and dust at the center collapsed to form the central star of the Solar System.

2. Where is our solar system placed in the Milky way?
The Solar system is placed away in a corner of the Milky way at a distance of about 33,000 light years from the center of the Galaxy.

3. How did the solar system originate?
The Solar System originated in a primitive Solar nebula, a rotating disc of gas and dust. It is from this rotating disc that the planets and the rest of the Solar System evolved.

4. Name the nine planets according to their distance from to sun.
The nine planets according to their distance from the sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

5. Name the inner planets of the solar system.
The inner planets of the solar system are Mercury, Venus, Earth and Mars. The Earth is the largest of the inner planets.

6. Name the outer planets of the solar system.
The outer planets of the solar system are Saturn, Uranus, Neptune and Pluto.

7. How are the planets kept in position in the solar system?
The planets are kept in their position in solar system due to their gravitational pull.

8. Name the planets, which can be seen from earth without a telescope?
The five planets, which are the nearest to the sun, can be seen without telescope. They are Mercury, Venus, Mars, Jupiter and Saturn.

Egyptian Civilization. 1

     Ancient Egypt is a land of mysteries. Mystery surrounds its origins its religion and its monumental architecture: colossal temples, pyramids and the enormous Sphinx. The Egyptian pyramids are the most famous of all the ancient monuments.

1. What is Hieroglyphics?
     Hieroglyphics are original form of writing from which other forms evolved like hieratic and demotic.
Hieratic was a simplified form of hieroglyphics used for administrative, business purposes and for literary scientific and religious texts. The last hieroglyphic text was written at the temple of Philae in A.D. 450.

2. Who were the scribes?
     Scribes were the men who, at a young age, mastered the skill of writing and wrote the ancient language. A scribe’s equipment containing two cakes of ink, usually red and black, a leather bag or pot filled with water and a set of reed bushes.

3. Give a brief description of the Mastaba tombs.
     Mastaba Tombs were built on the western side of the Nile River (a symbol of death, where sun falls into the underworld). They surround the pyramids of the old kingdoms. Statuettes known as Shabti was placed in the tombs to perform work on behalf of the deceased. A false door was carved on the interior tomb wall near the entrance to the shaft. For the comfort of the deceased, the burial chamber was filled with food offerings and material goods and the walls were decorated with the scenes of daily activities.

4. Give a brief description of the pyramids at Giza.
     The most famous pyramids are found at Giza. They were built by three pharaohs during second half of the third millennium B.C. The largest of the three pyramids is the Great pyramid of Cheops at Giza. It comprised of 2.5 million limestone blocks weighing 2.5 tonnes. It was 146.6 metres (481 feet) tall and 230.3 metres (756 feet) square. The capstones of all the pyramids were made of solid polished granite. The great pyramid is open to the public. Its entrance is through a narrow passage on the north side, thus leading to a sloping corridor with a low ceiling where one has to bend over while climbing a ramp. The ramp leads to a passage with a high ceiling called the Grand Gallery, from where it leads to the king’s burial chamber.

5. Give a brief description of the Sphinx at Giza.
     The Great Sphinx at Giza near Cairo is the most famous sculpture in the world. It has the body of a lion and the head of a human and represents Ra Horakty , a form of Sun God and the incarnation of royal powers and the protector of the temple doors. During the eighteenth dynasty, it was popularly known as the ‘Horus of the Horizon’ and ‘Horus of the Necropolic’. The Sphinx is located at a short distance from the Great Pyramid. It is carved out of a natural limestone outcrop and is 19.8 metres (65 feet) high and 73.2 metres (240 feet) long.

6. Why is the Valley of the Kings so famous?
     The Valley of the Kings is well known for its tombs. For many years, the kings, queens and nobles of the New Kingdom were buried in this valley. The tombs were cut into the limestone rock near a dried up river valley on the western side of Nile river. The walls displayed the magnificent murals, which depicted the scenes of daily life and the land of gods.

7. Describe briefly the famous Tutankhamun’s Tomb.
     Tutankhamun’s Tomb is located in the Valley of the Kings. At the entrance of the tomb, there is a flight of stairs leading to a short corridor. The first room is the antechamber where household items for Tutankhamun’s voyage to eternity were found. The walls of burial chamber were painted with scenes of Tutankhamun in the afterworld.

8. Give a vivid description of the famous Luxor temple.
     The temple is located a mile South of Karnak Temple. Luxor temples were once joined by an avenue lined with two rows of human headed stone Sphinxes; guardians of the temple gate and the underworld. The temple stands on the site of a New Kingdom building commissioned by Amenhotop III in 1380 B.C. Unlike Karnak, it was not enhanced by late Pharaohs.

Evolution of plants. 1

     There are more than 250,000 species of plants which include mosses, ferns, conifers, flowering plants etc. Plants have been there for a very long time. They first appeared in the Ordovician period and didn’t resemble modem plants till late in the Silurian period. By the Devonian period nearly 360 million years ago, a large variety of plants with different shapes and sizes appeared which included tiny creepers and tall trees.

     The first plants didn’t grow on land but in water. They were like microscopic living begins which reproduced by splitting up and gradually became more complex. Flagellates were so tiny that they left no trace of their existence. It took many years for the flagellates to develop into half plant and half animal, then separately into plants and animal cells. According to the scientists plant life originated in the sea more than two thousand million years ago.

     During that period, the land was bare and without any sign of life. The first living beings took nearly two and half thousand million years to develop into a plant form. Algae were the first plants which spread all over the earth wherever it found water. It was during the Silurian period that a great upheaval took place when the crust of the earth lifted the seabed out of water. Thus the sea plants had to adapt themselves to survive. For million of years they vegetated in water but slowly and gradually when the water basins dried up they found themselves in contact with air so their surroundings. Late , the evolution of plants progressed rapidly and within a span of 150 million years the algae transformed into gigantic trees which formed the immense forest of the Carboniferous period.

     The first plants that emerged from marine algae were incapable of making seeds to reproduce. So, spores were carried along by the wind and when they fell on the ground they produced gametophytes which got rooted in the soil and gave rise to egg cells and male cells, which when united a new plant was born. The spores needed damp ground and this type of plant could spread only in marshy regions and lowlands filled with water while the drier places remained bare. Another type complex plants from another variety of plants, were Equiseta, ferns and Lycopodiales which soon covered the earth in a dense forest.

What is the structure of the skeleton?

The skeleton of the average adult is made up of about 206 bones. Each of the different parts of the skeleton is designed to do a particular job. The skull has 29 bones. It protects the brain and also the eyes and ears. The central supporting part of the skeleton is the spine or vertebral column.

The spine or backbone is made up of a chain of small bones called vertebrae. It has enormous strength. Instead of being one solid piece of bone, the backbone is made up of large number of small bones to make the body flexible and thus enable us to bend down.

The vertebrae protect the delicate spinal cord which passes through the middle. The bottom end of the tip of the spinal column is cared the coccyx.

The rib cage is made up of the ribs. The arms are joined on to the central axis of the spinal column by the shoulder girdle and the legs by the pelvis. The bones of the legs are the longest and biggest in the body.

What is plastic made of?

Plastic is a light, man-made material made from chemicals. It can be heated up and moulded into different shapes and products. The chemical process by which plastic is mage is known as polymerization. The 19th century chemists were the first ones to make plastic. Vinyl chloride was the first plastic. It was made in 1838. In 1839, another plastic called styrene was made. It was followed by acrylics in 1843 and polyester in 1847. These plastic were quite expensive. Moreover, people at that time did not realize their possible uses. The chemists continued to find cheaper chemicals to manufacture plastic. It was in 1869 that celluloid was discovered by John Hyatt. It was the plastic made from camphor and cellulose nitrate. It was a substitute for ivory and was much cheaper than it. Its discovery brought a revolution and chemists began to make synthetic materials. In the year 1909, phenolformaldehyde was discovered by Leo Baekeland. It was the cheapest of all chemicals used so far. Also, it was found that this could be moulded into any shape. It was called Bakelite. Henceforth, plastic began to be produced in bulk. People throughout the world began to use it.

Fact:
Plastic is water impervious, air permeable, and shrink resistant. Therefore, rainwears are generally made of plastic. These days, light-weight kitchen wares made of plastic are much in use. These can be easily used in Microwave ovens.

What is weather?

The way in which the Earth’s atmosphere be behaves is known as weather. It may be hot or cold, windy or sill, raining, snowing or hailing. The overall temperature and patterns of weather in a particular place is known as climate. As the weather changes from day to day, therefore, it is very much difficult to predict.

1. What is the importance of weather in everybody’s life?
The weather plays dominant role in everybody’s life. Crops depend on the right weather condition for their proper growth and development. Summer vacations and trips to the resort can be ruined if the weather behaves unexpectedly. It also plays a major role in causing natural disasters, such as floods, landslides, ice, storms, droughts and famines.

2. How is the hot weather caused?
Hot weather is caused by the sun’s heating up the land and the atmosphere. If the sun is hidden by clouds or if a cold wind is blowing, the atmosphere becomes cooler.

3. What is weather made up of?
Weather is made up of three main ingredients, which are temperature, the movement of the wind and the amount of water in the air.

4. How does the Sun’s heat help in forming clouds?
The Sun’s heat makes water from the soil, rivers, seas evaporate into the air. This evaporated water forms clouds and they may fall as rain, snow or hail on the earth.

5. How do the scientists predict the weather?
Today, the scientists predict the weather by using satellites, computers, etc. There was a time when people predicted the weather by observing signs, such as how the clouds worked and the way in which animals behaved.

6. Name the wettest and driest places of the world.
The wettest place of the world is Tutunendo, Columbia. It gets 12m of rain in a year.
The driest place in the world is Calama, Chile. The most amazing fact about Calama is that until 1971, there had been no rain for 400 years.

7. How is the wind caused by the Sun?
Wind is also caused by the Sun. As the air gets hotter, it expands, gets less dense and rises. A mass of colder, heavier air called a cold front rushes in to replace it, making the wind to blow.

Space

The term space defines the region, which is beyond the planet Earth. In other words, we can say that space means the whole universe including the Earth.

1. Who gave the Big Bang theory and what does the Big Bang theory explain?
The Big Bang theory was given by a Belgian astronomer named Abbe Georges Lemaitre. Thus theory explains the process of expansion of the Universe.

2. What was the theory given by the Polish astronomer Copernicus?
Polish astronomer Copernicus stated that the Sun was the centre of the Universe, not the Earth.

3. What do the modern theories of universe state gout the size of the diverse?
Modern theories assume that the Universe is in a state of rapid expansion.

4. What does universe contain?
The Universe contains everything from minute supersonic particles to galactic super clusters.

5. What is a light year? For what purpose is it used?
A light year is the distance covered by light in one year in vacuum, traveling at a speed of three lakh kms per second. Scientists measure huge distances in light years, such as the distance between stars and planets.

6. Describe briefly the Earth.
The Earth’s crust is comparatively very thin an average thickness of 40 km. This layer is mainly made up of elements like Oxygen, Silicon, Calcium, Aluminum, and Sodium. It is thinnest under the oceans, i.e., about eight km and thickest under continents, i.e., about 70 km.
Earth’s outer surface is divided into four spheres. These are Lithosphere, Hydrosphere, Atmosphere and Biosphere.
The only layer that is completely liquid in form and lies between the mantle and the inner core, is known as the outer core. It is made up of molten metal mainly iron and a little amount of nickel and has a temperature ranging between 4,000 5,500oC.
The upper portion of the Mantle, about 250 km thick, is called Asthenosphere. It is fairly soft and is considered to be the lubricating layer on which the plates of the earth move during plate tectonics.