Dragon fruit, also known as pitahaya or strawberry pear, is a tropical fruit known for its vibrant red skin and sweet, seed-speckled pulp.

Its unique look and acclaimed superfood powers have made it popular among foodies and the health-conscious.

Luckily, you don’t have to live in the tropics to enjoy the many benefits of dragon fruit. In fact, you can find it fresh or frozen in supermarkets worldwide.

1. High in Nutrients

Dragon fruit is low in calories but packed with essential vitamins and minerals. It also contains a substantial amount of dietary fiber.

Here’s a rundown of the main nutrients in a one-cup serving (227 grams)

* Calories: 136
* Protein: 3 grams
* Fat: 0 grams
* Carbohydrates: 29 grams
* Fiber: 7 grams
* Iron: 8% of the RDI
* Magnesium: 18% of the RDI
* Vitamin C: 9% of the RDI
* Vitamin E: 4% of the RDI

Beyond essential nutrients, dragon fruit supplies beneficial plant compounds like polyphenols, carotenoids and betacyanins


* Dragon fruit is low in calories but rich in vitamins, minerals and beneficial plant compounds such as polyphenols, carotenoids and betacyanins.

2. May Help Fight Chronic Disease

Free radicals are unstable molecules that cause cell damage, which may lead to inflammation and disease.

One way to combat this is by eating antioxidant-rich foods like dragon fruit.

Antioxidants work by neutralizing free radicals, thus preventing cell damage and inflammation.

Studies suggest that diets high in antioxidants may help prevent chronic diseases such as heart disease, cancer, diabetes and arthritis.

Dragon fruit contains several types of potent antioxidants, including

* Vitamin C: Observational studies have found correlations between vitamin C intake and cancer risk. For example, a study in 120,852 people associated higher intakes of vitamin C with lower rates of head and neck cancer

* Betalains: Test-tube studies indicate betalains can combat oxidative stress and may have the ability to suppress cancer cells

* Carotenoids: Beta-carotene and lycopene are the plant pigments that give dragon fruit its vibrant color. Diets rich in carotenoids have been linked to a reduced risk of cancer and heart disease

Importantly, antioxidants work best when eaten naturally in food, rather than in pill form or as a supplement. In fact, antioxidant supplements may have harmful effects, and taking them without medical supervision is not recommended

On the other hand, dragon fruit is highly recommended.


* Dragon fruit contains the antioxidants vitamin C, beta-carotene, lycopene and betalain. Studies have linked diets high in antioxidants to a reduced risk of chronic disease.

3. Loaded With Fiber

Dietary fibers are nondigestible carbohydrates that boast an extensive list of potential health benefits.

Health authorities recommend 25 grams of fiber per day for women and 38 grams for men. Like antioxidants, fiber supplements do not have the same health benefits as fiber from foods

With 7 grams per one-cup serving, dragon fruit is an excellent whole-food source.

Although fiber is probably most well known for its role in digestion, research has suggested it may also play a role in protecting against heart disease, managing type 2 diabetes and maintaining a healthy body weight.

Although more research is needed, some observational studies suggest that diets high in fiber may protect against colon cancer.

While no studies have linked dragon fruit to any of these conditions, its high-fiber content can help you meet your recommended daily values.

However, it’s important to note that high-fiber diets can have drawbacks, especially if you’re accustomed to a low-fiber diet. To avoid stomach discomfort, increase your intake of dietary fiber gradually and drink plenty of fluids.


* Dragon fruit offers 7 grams of fiber per serving, making it an excellent choice for meeting your daily fiber needs.

4. Promotes a Healthy Gut

Your gut is home to some 100 trillion diverse microorganisms, including more than 400 species of bacteria.

Many researchers believe this community of microorganisms may impact your health. Both human and animal studies have associated imbalances in your gut to conditions like asthma and heart disease.

Given that dragon fruit contains prebiotics, it can potentially improve the balance of good bacteria in your gut.

Prebiotics are a specific type of fiber that promotes the growth of healthy bacteria in your gut.

Like all fibers, your gut cannot break them down. However, the bacteria in your gut can digest them. They use the fiber as fuel for growth, and you reap the benefits.

In particular, dragon fruit mainly promotes the growth of two families of healthy bacteria: lactic acid bacteria and bifidobacteria.

Regularly consuming prebiotics may reduce the risk of infection in your digestive tract and diarrhea. This is because prebiotics promote the growth of good bacteria, which researchers believe may outcompete the bad.

For example, a study in travelers showed that those who consumed prebiotics before and during travel experienced fewer and less severe episodes of traveler’s diarrhea.

Some studies also suggest prebiotics may ease symptoms of inflammatory bowel disease and colon cancer. Unfortunately, these findings are inconsistent.

While much of the research on prebiotics is favorable, the research on the prebiotic activity of dragon fruit is limited to test-tube studies. More studies are needed to determine its true effect on the human gut.


* Dragon fruit may promote the growth of healthy bacteria in the gut, which is associated with a healthy gastrointestinal tract.

5. Strengthens Your Immune System

Your body’s ability to fight infection is determined by several different factors, including the quality of your diet.

The vitamin C and carotenoids in dragon fruit may boost your immune system and prevent infection by protecting your white blood cells from damage.

The white blood cells in your immune system attack and destroy harmful substances. However, they are extremely sensitive to damage by free radicals.

As potent antioxidants, vitamin C and carotenoids can neutralize free radicals and defend your white blood cells against harm.


* Dragon fruit’s high supply of vitamin C and carotenoids may offer immune-boosting properties.

6. May Boost Low Iron Levels

Dragon fruit is one of the few fresh fruits that contain iron.

Iron plays a crucial role in transporting oxygen throughout your body. It also plays an important role in breaking down food into energy.

Unfortunately, many people do not get enough iron. In fact, it has been estimated that 30% of the world’s population is deficient in iron, making it the most common nutrient deficiency worldwide.

To combat low iron levels, it’s important to consume a variety of iron-rich foods. Rich sources of iron include meats, fish, legumes, nuts and cereals.

Dragon fruit may be another great option, as one serving contains 8% of your recommended daily intake (RDI). It also contains vitamin C, which helps your body absorb iron


* Dragon fruit supplies iron along with vitamin C, a combination that may improve your body’s absorption of this important mineral.

7. Good Source of Magnesium

Dragon fruit offers more magnesium than most fruits, with 18% of your RDI in just one cup.

On average, your body contains 24g of magnesium, or roughly one ounce.

Despite this seemingly small amount, the mineral is present in every one of your cells and takes part in over 600 important chemical reactions within your body.

For example, it takes part in reactions needed for the breakdown of food into energy, muscle contraction, bone formation and even the creation of DNA.

More studies are needed, but some indicate that higher intakes of magnesium may reduce the risk of heart disease and stroke.

Studies also show that diets adequate in magnesium support bone health


* Dragon fruit is a great source of magnesium, a nutrient needed for over 600 biochemical reactions in your body.


Camel, (genus Camelus), any of three species of large ruminating hoofed mammals of arid Africa and Asia known for their ability to go for long periods without drinking. The Arabian camel, or dromedary (Camelus dromedarius), has one back hump, while the domesticated Bactrian camel (C. bactrianus) and the wild Bactrian camel (C. ferus) have two.

These “ships of the desert” have long been valued as pack or saddle animals, and they are also exploited for milk, meat, wool, and hides. The dromedary was domesticated about 3000–2000 BCE in Arabia, the Bactrian camel by 4000 BCE in the steppes of Central Asia. Most of today’s 13 million domesticated dromedaries and roughly 97 domesticated breeds are in India and in the Horn of Africa. Wild dromedaries are extinct, although there is a large feral population in interior Australia descended from pack animals imported in the 19th century. About one million domesticated Bactrian camels range from the Middle East to China and Mongolia. The International Union for Conservation of Nature (IUCN) has classified the wild Bactrian camel as a critically endangered species since 2002. The largest population—numbering approximately 650 adult animals—lives in the Gobi Desert.

Natural history

Camels have an unmistakable silhouette, with their humped back, short tail, long slim legs, and long neck that dips downward and rises to a small narrow head. The upper lip is split into two sections that move independently. All three species are about 3 metres (10 feet) long and 2 metres (6.6 feet) high at the hump (itself 20 cm [8 inches]). Males weigh 400 to 650 kg (900 to 1,400 pounds), and females are about 10 percent smaller. Colour is usually light brown but can be grayish. Domesticated Bactrian camels are darker, stockier, and woollier than the wild form. Heavy eyelashes protect the eyes from blowing sand, and the nostrils can be squeezed shut. The dromedary has horny pads on the chest and knees that protect it from searing desert sand when it lies down, but the Bactrian camel lacks these callosities. Camels are generally docile, but they will bite or kick when annoyed. When excited, camels huff so sharply that spit is incidentally expelled.

Camels do not walk on their hooves. On each leg, weight is borne on two large toes that spread apart to keep the animal from sinking into the sand. Dromedaries have a soft wide-spreading pad for walking on sand; Bactrian camels have a firmer foot. Like the giraffe’s, the camel’s gait is a pace, with both legs on a side moving together. Short bursts of 65 km (40 miles) per hour are possible, but camels are excellent plodders. Bactrian camels can carry more than 200 kg (about 440 pounds) for 50 km (31 miles) in a day, while the more lightly built dromedaries can carry up to 100 kg (about 220 pounds) for 60 km (about 37 miles) if they are worked in the coolness of night.

During catastrophic droughts, herdsmen may lose all of their cattle, sheep, and goats while 80 percent of the camels will survive, owing to the camel’s ability to conserve water and tolerate dehydration. In severe heat a camel survives four to seven days without drinking, but it can go 10 months without drinking at all if it is not working and the forage contains enough moisture. Even salty water can be tolerated, and between drinks it forages far from oases to find food unavailable to other livestock. The body rehydrates within minutes of a long drink, absorbing over 100 litres (25 gallons) in 5–10 minutes. Cattle could not tolerate such a sudden dilution of the blood, because their red blood cells would burst under the osmotic stress; camel erythrocyte membranes are viscous (that is, sticky and flow-resistant), which permits swelling. A thirsty camel can reduce its urine output to one-fifth of its normal volume and produce feces dry enough for herders to use as fuel for fires.

Another adaptation is minimization of sweating. The fine woolly coat insulates the body, reducing heat gain. The camel also can allow its body temperature to rise to 41 °C (106 °F) before sweating at all. This reduces the temperature difference between the camel and its environment and thereby reduces heat gain and water loss by as much as two-thirds. Only in the hottest weather must the camel sweat. It tolerates extreme dehydration and can lose up to 25–30 percent of its body weight—twice what would be fatal for most mammals.

Camels have also adapted to desert conditions by being able to endure protein deficiency and eat items other livestock avoid, such as thorns, dry leaves, and saltbush. When food is plentiful, camels “overeat,” storing fat in one area on the back and forming a hump. When the fat is depleted, the hump sags to the side or disappears. Storing fat in one place also increases the body’s ability to dissipate heat everywhere else.

When not corralled, camels form stable groups of females accompanied by one mature male. Females breed by three to four years of age. Males begin to manufacture sperm at age three but do not compete for females until they are six to eight years old. Males compete for dominance by circling each other with the head held low and biting the feet or head of the opponent and attempting to topple it. After one camel withdraws from the bout, the winner may roll and rub secretions onto the ground from a gland on the back of its head. The dominant male breeds with all the females in each stable group. After a gestation of 13 or 14 months, one calf weighing up to 37 kg (81 pounds) is born, usually during the rainy season. Milk yields of 35 kg (about 77 pounds) per day are achieved in some breeds (e.g., the “milch dromedary” of Pakistan), though normal yield is about 4 kg (9 pounds) per day. Herders typically divert most milk to their own use during the calf’s first 9 to 11 months, then force weaning and take the rest. The calf is otherwise suckled 12 to 18 months. Females and males reproduce until about 20 years old. Longevity is 40 years.

Camels are classified in the family Camelidae, which first appeared in North America 40 million years ago. North American camelid stock became extinct 10,000 years ago. Living South American camelids are represented by the llama (Lama glama), guanaco (L. guanicoe), vicuña (Vicugna vicugna), and alpaca (V. pacos). The lineage that produced modern dromedary and Bactrian camels diverged from the South American camelid lineage between 11 million and 25 million years ago. Dromedary and Bactrian camel lineages split from one another between 4 million and 5 million years ago, with wild and domestic Bactrian camels separating from one another between 1.5 million and 700,000 years ago. Bactrian camel domestication by human beings came much later, however, occurring between 6,000 and 4,000 years ago. By 2 million years ago (the early Pleistocene Epoch) Camelus representatives had crossed back to Asia and were present in Africa (Tanzania). During the Pleistocene Epoch (2.5 million to 11,700 years ago) camelids reached South America. The family Camelidae belongs to the order Artiodactyla, a large group of hoofed mammals.

Cultural significance

Camels are among those few creatures with which humans have forged a special bond of dependence and affinity. Traditional lifestyles in many regions of the Middle East, North Africa, and Central Asia would never have developed without the camel, around which entire cultures have come into being. This camel-based culture is best exemplified by the Bedouin of the Arabian Peninsula—the native habitat of the dromedary—whose entire traditional economy depended on the produce of the camel. Camel’s milk and flesh were staples of the Bedouin diet, and its hair yielded cloth for shelter and clothing; its endurance as a beast of burden and as a mount enabled the Bedouin to range far into the desert. The mobility and freedom that the camel afforded to desert Arabs helped forge their independent culture and their strong sense of self-reliance, and they celebrated the camel in their native poetic verse, the qaṣīdah, in which the nāqah (female camel) was a faithful, unwavering mount. Among these nomadic people, a man’s wealth was measured not only by the number of camels he possessed but also by their speed, stamina, and endurance.

Until modern times, the camel was the backbone of the caravan trade, a central pillar of the economy in large parts of Asia and Africa. In settled regions, the caravansary, located on the outskirts of most urban centres, served as a hub for business and as a source of information about the outside world for the city’s residents. In the central Islamic lands, it likewise set the scene for many tales in the rich Arab-Persian oral tradition of storytelling, such as those found in The Thousand and One Nights. In Central Asia, vast and numerous camel caravans ensured the wealth and growth of the great trading cities of the Silk Road, upon which goods moved between Asia and Europe.

Today the camel remains an important part of some local economies, although it has been surpassed by automated forms of transportation for most tasks. Camels are still bred for their meat, milk, and hair, and, beginning in the late 20th century, the age-old sport of camel racing was revived, particularly in the countries of the Arabian Peninsula but also as far afield as Australia and the United States.


Jupiter was appropriately named after the king of the gods. It’s massive, has a powerful magnetic field, and more moons that any planet in the Solar System. Though it has been known to astronomers since ancient times, the invention of the telescope and the advent of modern astronomy has taught us so much about this gas giant.

In short, there are countless interesting facts about this gas giant that many people just don’t know about. And we here at Universe Today have taken the liberty of compiling a list of ten particularly interesting ones that we think will fascinate and surprise you. Think you know everything about Jupiter? Think again!

Facts about jupiter

1. Jupiter Is Massive:

It’s no secret that Jupiter is the largest planet in the Solar System. But this description really doesn’t do it justice. For one, the mass of Jupiter is 318 times as massive as the Earth. In fact, Jupiter is 2.5 times more massive than all of the other planets in the Solar System combined. But here’s the really interesting thing.

2. Jupiter Cannot Become A Star:

Astronomers call Jupiter a failed star, but that’s not really an appropriate description. While it is true that, like a star, Jupiter is rich in hydrogen and helium, Jupiter does not have nearly enough mass to trigger a fusion reaction in its core. This is how stars generate energy, by fusing hydrogen atoms together under extreme heat and pressure to create helium, releasing light and heat in the process.

This is made possible by their enormous gravity. For Jupiter to ignite a nuclear fusion process and become a star, it would need more than 70 times its current mass. If you could crash dozens of Jupiters together, you might have a chance to make a new star. But in the meantime, Jupiter shall remain a large gas giant with no hopes of becoming a star. Sorry, Jupiter!

3. Jupiter Is The Fastest Spinning Planet In The Solar System:

For all its size and mass, Jupiter sure moves quickly. In fact, with an rotational velocity of 12.6 km/s (~7.45 m/s) or 45,300 km/h (28,148 mph), the planet only takes about 10 hours to complete a full rotation on its axis. And because it’s spinning so rapidly, the planet has flattened out at the poles a little and is bulging at its equator.

In fact, points on Jupiter’s equator are more than 4,600 km further from the center than the poles. Or to put it another way, the planet’s polar radius measures to 66,854 ± 10 km (or 10.517 that of Earth’s), while its diameter at the equator is 71,492 ± 4 km (or 11.209 that of Earth’s). This rapid rotation also helps generate Jupiter’s powerful magnetic fields, and contribute to the dangerous radiation surrounding it.

4. The Clouds On Jupiter Are Only 50 km Thick:

That’s right, all those beautiful whirling clouds and storms you see on Jupiter are only about 50 km thick. They’re made of ammonia crystals broken up into two different cloud decks. The darker material is thought to be compounds brought up from deeper inside Jupiter, and then change color when they reacted with sunlight. But below those clouds, it’s just hydrogen and helium, all the way down.

5. The Great Red Spot Has Been Around For A Long Time:

The Great Red Spot on Jupiter is one of its most familiar features. This persistent anticyclonic storm, which is located south of its equator, measures between 24,000 km in diameter and 12–14,000 km in height. As such, it is large enough to contain two or three planets the size of Earth’s diameter. And the spot has been around for at least 350 years, since it was spotted as far back as the 17th century.

The Great Red Spot was first identified in 1665 by Italian astronomer Giovanni Cassini. By the 20th century, astronomers began to theorize that it was a storm, one which was created by Jupiter’s turbulent and fast-moving atmosphere. These theories were confirmed by the Voyager 1 mission, which observed the Giant Red Spot up close in March of 1979 during its flyby of the planet.

However, it appears to have been shrinking since that time. Based on Cassini’s observations, the size was estimated to be 40,000 km in the 17th century, which was almost twice as large as it is now. Astronomers do not know if or when it will ever disappear entirely, but they are relatively sure that another one will emerge somewhere else on the planet.

6. Jupiter Has Rings:

When people think of ring systems, Saturn naturally comes to mind. But in truth, both Uranus and Jupiter have ring systems of their own. Jupiter’s were the third set to be discovered (after the other two), due to the fact that they are particularly faint. Jupiter’s rings consist of three main segments – an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring.

These rings are widely believed to have come from material ejected by its moons when they’re struck by meteorite impacts. In particular, the main ring is thought to be composed of material from the moons of Adrastea and Metis, while the moons of Thebe and Amalthea are believed to produce the two distinct components of the dusty gossamer ring.

This material fell into orbit around Jupiter (instead of falling back to their respective moons) because if Jupiter’s strong gravitational influence. The ring is also depleted and replenished regularly as some material veers towards Jupiter while new material is added by additional impacts.

7. Jupiter’s Magnetic Field Is 14 Times Stronger Than Earth’s:

Compasses would really work on Jupiter. That’s because it has the strongest magnetic field in the Solar System. Astronomers think the magnetic field is generated by the eddy currents – i.e. swirling movements of conducting materials – within the liquid metallic hydrogen core. This magnetic field traps particles of sulfur dioxide from Io’s volcanic eruptions, which producing sulfur and oxygen ions. Together with hydrogen ions originating from the atmosphere of Jupiter, these form a plasma sheet in Jupiter’s equatorial plane.

Farther out, the interaction of the magnetosphere with the solar wind generates a bow shock, a dangerous belt of radiation that can cause damage tos spacecraft. Jupiter’s four largest moons all orbit within the magnetosphere, which protects them from the solar wind, but also make the likelihood of establishing outposts on their surface problematic. The magnetosphere of Jupiter is also responsible for intense episodes of radio emission from the planet’s polar regions.

8. Jupiter Has 67 Moons:

As of the penning of this article, Jupiter has a 67 confirmed and named satellites. However, it is estimated that the planet has over 200 natural satellites orbiting it. Almost all of them are less than 10 kilometers in diameter, and were only discovered after 1975, when the first spacecraft (Pioneer 10) arrived at Jupiter.

However, it also has four major moons, which are collectively known as the Galilean Moons (after their discovered Galileo Galilei). These are, in order of distance from Jupiter, Io, Europa, Ganymede, and Callisto. These moons are some of the largest in the Solar System, with Ganymede being the largest, measuring 5262 km in diameter.

9. Jupiter Has Been Visited 7 Times By Spacecraft:

Jupiter was first visited by NASA’s Pioneer 10 spacecraft in December 1973, and then Pioneer 11 in December 1974. Then came the Voyager 1 and 2 flybys, both of which happened in 1979. This was followed by a long break until Ulysses arrived in February 1992, followed by the Galileo space probe in 1995. Then Cassini made a flyby in 2000, on its way to Saturn. And finally, NASA’s New Horizons spacecraft made its flyby in 2007. This was the last mission to fly past Jupiter, but it surely won’t be the last.

10. You Can See Jupiter With Your Own Eyes:

Jupiter is the third brightest object in the Solar System, after Venus and the Moon. Chances are, you saw Jupiter in the sky, and had no idea that’s what you were seeing. And here at Universe Today, we are in the habit of letting readers know when the best opportunities for spotting Jupiter in the night sky are.

Chances are, if you see a really bright star high in the sky, then you’re looking at Jupiter. Get your hands on a pair of binoculars, and if you know someone with a telescope, that’s even better. Using even modest magnification, you might even spot small specks of light orbiting it, which are its Galilean Moons. Just think, you’ll be seeing precisely what Galileo did when he gazed at the planet in 1610.


Human body, the physical substance of the human organism, composed of living cells and extracellular materials and organized into tissues, organs, and systems.

Human anatomy and physiology are treated in many different articles. For detailed discussions of specific tissues, organs, and systems, see human blood; cardiovascular system; digestive system, human; endocrine system, human; renal system; skin; human muscle system; nervous system; reproductive system, human; respiration, human; sensory reception, human; skeletal system, human. For a description of how the body develops, from conception through old age, see aging; growth; prenatal development; human development.

For detailed coverage of the body’s biochemical constituents, see protein; carbohydrate; lipid; nucleic acid; vitamin; and hormone. For information on the structure and function of the cells that constitute the body, see cell.

Many entries describe the body’s major structures. For example, see abdominal cavity; adrenal gland; aorta; bone; brain; ear; eye; heart; kidney; large intestine; lung; nose; ovary; pancreas; pituitary gland; small intestine; spinal cord; spleen; stomach; testis; thymus; thyroid gland; tooth; uterus; vertebral column.

Humans are, of course, animals—more particularly, members of the order Primates in the subphylum Vertebrata of the phylum Chordata. Like all chordates, the human animal has a bilaterally symmetrical body that is characterized at some point during its development by a dorsal supporting rod (the notochord), gill slits in the region of the pharynx, and a hollow dorsal nerve cord. Of these features, the first two are present only during the embryonic stage in the human; the notochord is replaced by the vertebral column, and the pharyngeal gill slits are lost completely. The dorsal nerve cord is the spinal cord in humans; it remains throughout life.

Characteristic of the vertebrate form, the human body has an internal skeleton that includes a backbone of vertebrae. Typical of mammalian structure, the human body shows such characteristics as hair, mammary glands, and highly developed sense organs.

Beyond these similarities, however, lie some profound differences. Among the mammals, only humans have a predominantly two-legged (bipedal) posture, a fact that has greatly modified the general mammalian body plan. (Even the kangaroo, which hops on two legs when moving rapidly, walks on four legs and uses its tail as a “third leg” when standing.) Moreover, the human brain, particularly the neocortex, is far and away the most highly developed in the animal kingdom. As intelligent as are many other mammals—such as chimpanzees and dolphins—none have achieved the intellectual status of the human species.

Chemical composition of the body

Chemically, the human body consists mainly of water and of organic compounds—i.e., lipids, proteins, carbohydrates, and nucleic acids. Water is found in the extracellular fluids of the body (the blood plasma, the lymph, and the interstitial fluid) and within the cells themselves. It serves as a solvent without which the chemistry of life could not take place. The human body is about 60 percent water by weight.

Lipids—chiefly fats, phospholipids, and steroids—are major structural components of the human body. Fats provide an energy reserve for the body, and fat pads also serve as insulation and shock absorbers. Phospholipids and the steroid compound cholesterol are major components of the membrane that surrounds each cell.

Proteins also serve as a major structural component of the body. Like lipids, proteins are an important constituent of the cell membrane. In addition, such extracellular materials as hair and nails are composed of protein. So also is collagen, the fibrous, elastic material that makes up much of the body’s skin, bones, tendons, and ligaments. Proteins also perform numerous functional roles in the body. Particularly important are cellular proteins called enzymes, which catalyze the chemical reactions necessary for life.

Carbohydrates are present in the human body largely as fuels, either as simple sugars circulating through the bloodstream or as glycogen, a storage compound found in the liver and the muscles. Small amounts of carbohydrates also occur in cell membranes, but, in contrast to plants and many invertebrate animals, humans have little structural carbohydrate in their bodies.

Nucleic acids make up the genetic materials of the body. Deoxyribonucleic acid (DNA) carries the body’s hereditary master code, the instructions according to which each cell operates. It is DNA, passed from parents to offspring, that dictates the inherited characteristics of each individual human. Ribonucleic acid (RNA), of which there are several types, helps carry out the instructions encoded in the DNA.

Along with water and organic compounds, the body’s constituents include various inorganic minerals. Chief among these are calcium, phosphorus, sodium, magnesium, and iron. Calcium and phosphorus, combined as calcium-phosphate crystals, form a large part of the body’s bones. Calcium is also present as ions in the blood and interstitial fluid, as is sodium. Ions of phosphorus, potassium, and magnesium, on the other hand, are abundant within the intercellular fluid. All of these ions play vital roles in the body’s metabolic processes. Iron is present mainly as part of hemoglobin, the oxygen-carrying pigment of the red blood cells. Other mineral constituents of the body, found in minute but necessary concentrations, include cobalt, copper, iodine, manganese, and zinc.

Organization of the body

The cell is the basic living unit of the human body—indeed, of all organisms. The human body consists of trillions of cells, each capable of growth, metabolism, response to stimuli, and, with some exceptions, reproduction. Although there are some 200 different types of cells in the body, these can be grouped into four basic classes. These four basic cell types, together with their extracellular materials, form the fundamental tissues of the human body: (1) epithelial tissues, which cover the body’s surface and line the internal organs, body cavities, and passageways; (2) muscle tissues, which are capable of contraction and form the body’s musculature; (3) nerve tissues, which conduct electrical impulses and make up the nervous system; and (4) connective tissues, which are composed of widely spaced cells and large amounts of intercellular matrix and which bind together various body structures. (Bone and blood are considered specialized connective tissues, in which the intercellular matrix is, respectively, hard and liquid.)

The next level of organization in the body is that of the organ. An organ is a group of tissues that constitutes a distinct structural and functional unit. Thus, the heart is an organ composed of all four tissues, whose function is to pump blood throughout the body. Of course, the heart does not function in isolation; it is part of a system composed of blood and blood vessels as well. The highest level of body organization, then, is that of the organ system.

The body includes nine major organ systems, each composed of various organs and tissues that work together as a functional unit. The chief constituents and prime functions of each system are summarized below. (1) The integumentary system, composed of the skin and associated structures, protects the body from invasion by harmful microorganisms and chemicals; it also prevents water loss from the body. (2) The musculoskeletal system (also referred to separately as the muscle system and the skeletal system), composed of the skeletal muscles and bones (with about 206 of the latter in adults), moves the body and protectively houses its internal organs. (3) The respiratory system, composed of the breathing passages, lungs, and muscles of respiration, obtains from the air the oxygen necessary for cellular metabolism; it also returns to the air the carbon dioxide that forms as a waste product of such metabolism. (4) The circulatory system, composed of the heart, blood, and blood vessels, circulates a transport fluid throughout the body, providing the cells with a steady supply of oxygen and nutrients and carrying away waste products such as carbon dioxide and toxic nitrogen compounds. (5) The digestive system, composed of the mouth, esophagus, stomach, and intestines, breaks down food into usable substances (nutrients), which are then absorbed from the blood or lymph; this system also eliminates the unusable or excess portion of the food as fecal matter. (6) The excretory system, composed of the kidneys, ureters, urinary bladder, and urethra, removes toxic nitrogen compounds and other wastes from the blood. (7) The nervous system, composed of the sensory organs, brain, spinal cord, and nerves, transmits, integrates, and analyzes sensory information and carries impulses to effect the appropriate muscular or glandular responses. (8) The endocrine system, composed of the hormone-secreting glands and tissues, provides a chemical communications network for coordinating various body processes. (9) The reproductive system, composed of the male or female sex organs, enables reproduction and thereby ensures the continuation of the species.

Basic form and development

In general structure, the human body follows a plan that can be described as a cylinder enclosing two tubes and a rod. This body plan is most clearly evident in the embryo; by birth, the plan is apparent only in the trunk region—i.e., in the thorax and abdomen.

The body wall forms the cylinder. The two tubes are the ventrally located alimentary canal (i.e., the digestive tract) and the dorsally located neural tube (i.e., the spinal cord). Between the tubes lies the rod—the notochord in the embryo, which becomes the vertebral column prior to birth. (The terms dorsal and ventral refer respectively to the back and the front, or belly, of an animal.)

Within the embryo, the essential body parts are:

(1) the outer enclosing epidermal membrane (in the embryo called ectoderm).

(2) the dorsal neural tube.

(3) the supporting notochord.

(4) the ventral alimentary tube, which becomes the lining of the stomach and intestine (in the embryo called endoderm).

(5) the intermediate mass (in the embryo called mesoderm).

(6) a rather fluid tissue that fills the interspaces, derived from the mesoderm and in the embryo called mesenchyme. Everything in the body derives from one of these six embryonic parts.

The mesoderm constitutes a considerable pad of tissue on each side of the embryo, extending all the way from the back to the front sides of the body wall. It is hollow, for a cleftlike space appears in it on each side. These are the right and left body cavities. In the dorsal part of the body they are temporary; in the ventral part they become permanent, forming the two pleural cavities, which house the lungs; the peritoneal cavity, which contains the abdominal organs; and the pericardial cavity, which encloses the heart. The dorsal part of the mesoderm becomes separated from the ventral mesoderm and divides itself into serial parts like a row of blocks, 31 on each side. These mesodermal segments grow in all directions toward the epidermal membrane. They form bones, muscles, and the deeper, leathery part of the skin. Dorsally they form bony arches protecting the spinal cord, and ventrally the ribs protecting the alimentary canal and heart. Thus they form the body wall and the limbs—much the weightier part of the body. They give the segmental character to the body wall in neck and trunk, and, following their lead, the spinal cord becomes correspondingly segmented. The ventral mesoderm is not so extensive; it remains near the alimentary tube and becomes the continuous muscle layer of the stomach and intestine. It also forms the lining of the body cavities, the smooth, shining, slippery pleura and peritoneum. The mesenchyme forms blood and lymph vessels, the heart, and the loose cells of connective tissues.

The neural tube itself is formed from the ectoderm at a very early stage. Anteriorly (i.e., toward the head) it extends above the open end of the cylinder and is enlarged to form the brain. It is not in immediate contact with the epidermis, for the dorsal mesoderm grows up around it and around the roots of the cranial nerves as a covering, separating the brain from the epidermis. Posteriorly the neural tube terminates in the adult opposite the first lumbar vertebra.

If the cylindrical body wall is followed headward, it is found to terminate ventrally as the tongue, dorsally in the skull around the brain, ears, and eyes. There is a considerable interval between eyes and tongue. This is occupied partly by a deep depression of the epidermis between them, which dips in to join the alimentary tube (lining of the mouth). Posteriorly the ventral body wall joins the dorsal at the tailbone (coccyx), thus terminating the body cavities.

Headward, the alimentary tube extends up in front of the notochord and projects above the upper part of the body wall (tongue) and in front of and below the brain to join the epidermal depression. From the epidermal depression are formed the teeth and most of the mouth lining; from the upper end of the alimentary canal are formed the pharynx, larynx, trachea, and lungs. The alimentary canal at its tail end splits longitudinally into two tubes—an anterior and a posterior. The anterior tube becomes the bladder, urethra, and, in the female, the lining of the vagina, where it joins a depression of the ectoderm. The posterior (dorsal) tube becomes the rectum and ends just in front of the coccyx by joining another ectodermal depression (the anus).


Starfish (or sea stars) are beautiful marine animals found in a variety of colors, shapes, and sizes. All starfish resemble stars, and though the most common have only five arms, some of these animals can grow up to 40 arms. The amazing sea creatures—part of a group of animals known as echinoderms—travel using their tube feet. They can regenerate lost limbs and swallow large prey using their unusual stomachs.

Sea Stars Are Not Fish

Although sea stars live underwater and are commonly called “starfish,” they are not true fish. They do not have gills, scales, or fins like fish do.

Sea stars also move quite differently from fish. While fish propel themselves with their tails, sea stars have tiny tube feet to help them move along.

Because they are not classified as fish, scientists prefer to call starfish “sea stars.”

Sea Stars Are Echinoderms

Sea stars belong to the phylum Echinodermata. That means they are related to sand dollars, sea urchins, sea cucumbers, and sea lilies. Overall, this phylum contains approximately 7,000 species.

Many echinoderms exhibit radial symmetry, meaning their body parts are arranged around a central axis. Many sea stars have five-point radial symmetry because their body has five sections. This means that they do not have an obvious left and right half, only a top side and a bottom side. Echinoderms also usually have spines, which are less pronounced in sea stars than they are in other organisms such as sea urchins.

There Are Thousands of Sea Star Species

There are about 2,000 species of sea stars.2 Some live in the intertidal zone, while others live in the deep water of the ocean. While many species live in tropical areas, sea stars can also be found in cold areas—even the polar regions.

Not All Sea Stars Have Five Arms

While many people are most familiar with the five-armed species of sea stars, not all sea stars have just five arms. Some species have many more, such as the sun star, which can have up to 40 arms.

Sea Stars Can Regenerate Arms

Amazingly, sea stars can regenerate lost arms, which is useful if a sea star is injured by a predator. It can lose an arm, escape, and grow a new arm later.

Sea stars house most of their vital organs in their arms. This means that some species can even regenerate an entirely new sea star from just one arm and a portion of the star’s central disc. This won’t happen too quickly, though; it takes about a year for an arm to grow back.

Sea Stars Are Protected by Armor

Depending on the species, a sea star’s skin may feel leathery or slightly prickly. Sea stars have a tough covering on their upper side, which is made up of plates of calcium carbonate with tiny spines on their surface.

A sea star’s spines are used for protection from predators, which include birds, fish, and sea otters. One very spiny sea star is the aptly named crown-of-thorns starfish.

Sea Stars Do Not Have Blood

Instead of blood, sea stars have a circulatory system made up primarily of seawater.

Seawater is pumped into the animal’s water vascular system through its sieve plate. This is a sort of trap door called a madreporite, often visible as a light-colored spot on the top of the starfish.

From the madreporite, seawater moves into the sea star’s tube feet, causing the arm to extend. Muscles within the tube feet are used to retract the limb.

Sea Stars Eat With Their Stomachs Inside-Out

Sea stars prey on bivalves like mussels and clams as well as small fish, snails, and barnacles. If you’ve ever tried to pry the shell of a clam or mussel open, you know how difficult it is. However, sea stars have a unique way of eating these creatures.

A sea star’s mouth is on its underside. When it catches its food, the sea star will wrap its arms around the animal’s shell and pull it open just slightly. Then it does something amazing: the sea star pushes its stomach through its mouth and into the bivalve’s shell. It then digests the animal and slides its stomach back into its own body.

This unique feeding mechanism allows the sea star to eat larger prey than it would otherwise be able to fit into its tiny mouth.

Sea Stars Have Eyes

Many people are surprised to learn that starfish have eyes. It’s true. The eyes are there—just not in the place you would expect.

Sea stars have an eye spot at the end of each arm. This means that a five-armed sea star has five eyes, while the 40-armed sun star has 40 eyes.

Each sea star eye is very simple and looks like a red spot. It doesn’t see much detail but it can sense light and dark, which is just enough for the environments the animals live in.

All True Starfish Are in the Class Asteroidea

Starfish belong to the animal class Asteroidea. These echinoderms all have several arms arranged around a central disk.

Asteroidea is the classification for “true stars.” These animals are in a separate class from brittle stars and basket stars, which have a more defined separation between their arms and their central disk.


Types of Materials For Dresses– There is an assortment of textiles fabrics which are available in the market nowadays. If you are having an issue with the laundries, or get caught in other dilemmas. Then might be you apparently don’t know the characteristics of different types of fabrics and it’s properties.

The content of fiber and how the material is produced makes a tremendous variation in spot removal and it also defines how a garment should be washed. For genuine fine results, it is suitable to have a twitching knowledge of different types of fabric materials of dresses. The Dictionary of textile will help you interpret apparel caring labels. Each one of us carries clothes made up of different fabrics.

Different Types of Fabrics – Types of Materials For Dresses

If you are having an issue with the laundries, or get caught in other dilemmas. Then might be you apparently don’t know the characteristics of different types of fabrics and it’s properties. The content of fiber and how the material is produced makes a tremendous variation in spot removal and it also defines how a garment should be washed.

For genuine fine results, it is suitable to have a twitching knowledge of different types of dress materials. The Dictionary of textile will help you interpret apparel caring labels. Each one of us carries clothes made up of different fabrics material types.

Here are the most popular fabrics used for clothing attire are:

1. Cotton Fabric

Cotton is a natural fabric, most soothing and skin friendly, light thin and soft. Hence, cotton is available in all colors. It really breathes well but does not dry quickly. It is one of the most popular and used fabrics in the world. It is most used type of fabric for kurtis. Mostly used in kurti, saree, suit set, jump suits, pants.

2. Silk Fabric

Silk is well known for its luxurious, smooth, soft touch and glistening looks. It is the most durable and strongest natural fabric. Mostly used in Sarees, wedding gowns, evening gowns, and scarves.

3. Linen Fabric

Linen is very strong and durable material. It is smooth and very cool to touch. It needs regular ironing as it absorbs water very fast. Linen fabric has been practiced for table coverings, bed coverings, and apparel for eras.

4. Wool Fabric

Wool is soft to touch, durable and long-lasting which keeps the body warm in winters. It is wrinkle free and resistant to dust, fade and tear. Mostly used in sweaters woolen socks, woolen gloves, and other warm clothes.

5. Leather Material

The leather is also used to keep a body warm in winter. It is both strong and stylish It gives a very classy look. Frequently used in jackets, shoes, belts and other fashion accessories.

6. Georgette Fabric

Georgette is a lightweight, dull appearance and creped surface fabric. It is opaque and slightly heavier than chiffon. It is available in grams in weight like 20 grams, 40 grams, 60 grams depends upon the purpose of use. Georgette is much in demand in the fashion industry. Most of the designer clothes are made from Georgette.

7. Chiffon Fabric

Chiffon is very insubstantial fabric originally manufactured from silk. Though it is smoother than Georgette. It can be easily dyed to any color and used for evening wear, gowns, sarees.

8. Nylon Fabric

Nylon is a synthetic fabric made up of polymers. It is a strong fabric with stretchable and high elasticity properties. It is very long lasting and unaffected by wear and tear. This fabric is extremely immune to attack from such typical repellent as rusts, fungi, and insects.

9. Polyester Fabric

Polyester is also a synthetic fabric made up of the polymer. It is strong, soft and wrinkles free textile and hence used in clothing. This textile is an artificially made fiber. It’s much rebounding and can resist a good chance of wear and tear outfit.

10. Velvet Fabric

Velvet is very soft and smooth material, very luxurious and shiny, it comes in different qualities and textures, ranging from low to very high prices. Coarse to the very thin fiber material. Chiefly used in blouses, shawls, lenghas and Indian wedding dress in winters.

11. Denim Fabric

Denim is sturdy rugged cotton twill, colored with indigo dye to create blue jeans mostly. It has a vivid texture, cozy to feel, and very long durability. Denim is the most widely available fabric for jeans.

12. Rayon Fabric

Rayon is created from cellulose fiber. It’s is famous for its smooth texture and look which closely resembles the feel and appearance of silk and wool. It is highly absorbent and does not insulate the body heat due to this property it is very useful for summer and humid conditions.

13. Viscose Fabric

Viscose is also manufactured from cellulose. It feels soft and smooth as similar to Rayon on the skin. This fabric is mostly used in gowns lining, shirts and jackets.

14. Satin Fabric

Satin FabricSatin is originally made from silk. Satin is famous for its evening gowns, skirts, corsets, inner lining, wedding dresses, loungewear, hats, and ties. In particular, this is the softer and brighter the further clean and easier to keep clean.

15. Crepe Fabric

Crepe is twisted weave fabric does not wrinkle or crease easily. It is rich in texture and style and is fairly easy to work with. It varies in weight and capacity. It is a feather soft material which has excellent draping qualities. Crepe is soft, very comfy to wear and easy to care.


1.Air pollution is one of the UK’s (and the world’s) biggest killers

Breathing in air pollution can increase the risk of heart disease and stroke. It worsens asthma symptoms and can even cause lung cancer.

To address this, as a first step we are calling on the government to phase-out of diesel vehicles by 2025.

Worldwide, the human costs of indoor and outdoor air pollution are terrible – millions of premature deaths each year  are linked to air pollution.

2.Children are most vulnerable to air pollution – but we are all affected

The impacts of toxic air are worse for the most vulnerable people. Air pollution damages children’s lung development. It also makes existing respiratory and cardiovascular conditions worse, particularly in older people. The poorest people in our society tend to suffer more as they tend to live near main roads where air pollution is worst.

All road users are affected by air pollution. However, pedestrians and cyclists are often exposed to less air pollution than people in vehicles, especially if using backstreets.

3.A child born today might not breathe clean air until they are 8

Long-term childhood exposure to air pollution can lead to permanently reduced lung function. Dirty air has been shown to affect the development of foetuses as well.  

Most areas of the UK are breaking EU limits on air pollution. Yet the government’s current plans won’t reduce pollution to legal levels until at least 2020 – and in London, 2025.

4.Air pollution causes up to 36,000 early deaths a year in the UK

Outdoor air pollution is responsible for the equivalent of up to 36,000 premature deaths a year in the UK, says the government’s Committee on the Medical Effects of Air Pollutants (COMEAP ).

Fine particle air pollution is responsible for 29,000 early deaths a year. The effect of the toxic gas nitrogen dioxide (NO2) brings the figure up to 36,000 a year.

5. Air pollution was bad then…

In the 1970s the UK was known as the Dirty Man of Europe.

Pollution from the UK’s coal-fired power stations caused acid rain. Forests across Europe withered. EU action thankfully put an end to this.

As a result, sulphur dioxide emissions dropped by 94% by 2011 . This prevented an estimated 46,000 premature deaths between 1990 and 2001.

6. And air quality is still bad now

Invisible pollution claims more than 9,000 early deaths each year in London.

London’s air is some of the dirtiest in Europe. In 2016 the government was ordered by the High Court to come up with a plan to clean up air across the UK in the shortest possible time.

7. Five days into 2017 annual air pollution limits in London were breached

Just 5 days into the new year Brixton Road in London breached air pollution limits for the whole of 2017.

EU air pollution rules say monitoring stations must not record particularly high levels of nitrogen dioxide more than 18 times a year at any given location. But Brixton Road, in London, exceeded this limit for the 19th time on 5 January 2017.

A number of other London locations, including Putney High Street and Brompton Road in Knightsbridge, followed shortly.

8. Sitting inside a car can be more dangerous for your health

Being shut inside a car may not protect you from pollution. In fact, you can be exposed to almost 8 times as much as a cyclist .

When driving in heavy traffic, use the recycled-air setting on your fan so your car doesn’t suck in harmful fumes.

9. Two thirds of all UK car journeys are under 5 miles

By leaving your car at home, you are helping reduce air pollution for everyone. You can make it safer for yourself by avoiding busy main roads when walking.

But if you can’t avoid a main road, walk as far away from the kerb as you can – even a few metres can make a difference to your level of pollution exposure.

10. About 11 million cars were designed to cheat air pollution tests

It has long been known that diesel cars pollute far more in the real world than in laboratory tests. A 2016 study by the Department for Transport confirmed this, finding that all diesel cars tested produced more pollution on the road than in the laboratory  – some emitted up to 12 times the EU maximum.

Worse still, in 2015 car manufacturer Volkswagen was caught using software programmes to cheat emissions tests.

Volkswagen eventually admitted to fitting this software to millions of its diesel vehicles. Basically they were programmed to spew out less filth in the lab than on the road.

The ramifications of this shocking deception continue to rumble on, with record fines imposed on Volkswagen in the US and legal action mooted in Europe.

11. There’s been a 26-fold increase in electric cars in the UK in the past 4 years

Tax incentives for low- and zero-emission cars are an essential part of the solution to air pollution. But so is massive investment in clean public transport and better integrated walking and cycling routes, to help people get out of their cars altogether.

Fact: In the past 4 years, the number of registered electric cars in the UK has increased by around 2,600%.

New registrations of electric cars rose from 3,500 in 2013 to almost 95,000  by the end of March 2017. Data from the Society of Motor Manufacturers and Traders show that around 500 electric cars were registered per month during the first half of 2014. By the end of 2016, more than 35,000 plug-in cars had been registered over the course of the year – the highest number ever – and an average of over 3,000 per month.

There are plans in the Netherlands and Norway to halt the sale of diesel and petrol cars entirely from 2025. Friends of the Earth is calling for similarly radical action in the UK.

12. There are around 12 million diesel cars on UK roads

Diesel vehicles now represent more than 40% of new car sales in the UK , up from around 13% little more than a decade ago. There are approximately 12 million diesel cars on the road in the UK at the moment.

This is largely the result of government incentives based on the carbon savings and greater fuel efficiency of diesel compared to petrol. Diesel cars produce high levels of deadly NOx, more than their petrol equivalents.

13. Air pollution costs the UK £20 billion a year

The health problems resulting fromexposure to air pollution have a high cost to people  who suffer from illness, to our health services and to businesses. In the UK these costs add up to more than £20 billion every year.

Not only does air pollution cost our health service and result in worse productivity due to ill-health, but measures to cut air pollution are beneficial to business. Strong action on air pollution can drive green innovation, and if traffic levels are cut so should congestion. Less congestion and air pollution would make our cities and towns more attractive places to live and work and visit.

14. The global cost of air pollution is staggering

The global cost of air pollution is US$225 billion annually, according to the World Bank.

A study by the World Bank and the Institute for Health Metrics and Evaluation (IHME) highlights the eye-watering economic and social impacts of dirty air. It makes clear what’s fairly obvious: polluted places are less productive, see fewer tourists, and put off potential workers.

In asurvey of the world’s liveable cities  – London came 38th due to traffic and air pollution.

15. Air pollution makes climate change worse

As well as fine particle air pollution directly affecting the climate , many of the causes of air pollution – such as traffic emissions – are also contributors to climate change.

There are strong benefits  from tackling these issues together.

16. The smallest particles are the most dangerous

The most dangerous tiny particles of air pollution are smaller than the width of a human hair. This means they are largely invisible. And they can penetrate deep into our lungs.

Particle air pollution  worsens heart and lung disease.

17. That orange haze is nitrogen dioxide… and it’s toxic

Nitrogen dioxide – also known as NO2 – gets worse the closer you go to road traffic.

It is a toxic gas which is often colourless. This means you often won’t be able to see it, although sometimes an orange haze can be seen hanging over a city from a distance.

NO2 inflames the lining of the lung  and reduces immunity to lung infections such as bronchitis.

18. Diesel exhaust causes cancer

The World Health Organisation (WHO) has declared outdoor air pollution, including particulate matter (PM) and also diesel exhaust, carcinogenic to humans, in the strongest class (Group 1). That’s the same class as tobacco.

19. Time of day matters

The best time to run or jog is generally first thing in the morning, before the day’s traffic affects air quality.

If you can, try to exercise in green leafy spaces like parks. It will make a big difference – joggers inhale more pollution than those walking the same distance.

20. Plants can filter pollution

Our homes are vulnerable to noxious gases which can build up over time.

Readily-available houseplants can help filter some harmful compounds out. Helpful plants include: peace lilies, English ivy, cornstalk dracaena and broadleaf lady palm.


The brain is one of the largest and most complex organs in the human body.
It is made up of more than 100 billion nerves that communicate in trillions of connections called synapses.

The brain is made up of many specialized areas that work together:
• The cortex is the outermost layer of brain cells. Thinking and voluntary movements begin in the cortex.
• The brain stem is between the spinal cord and the rest of the brain. Basic functions like breathing and sleep are controlled here.
• The basal ganglia are a cluster of structures in the center of the brain. The basal ganglia coordinate messages between multiple other brain areas.
• The cerebellum is at the base and the back of the brain. The cerebellum is responsible for coordination and balance.

The brain is also divided into several lobes:
• The frontal lobes are responsible for problem solving and judgment and motor function.
• The parietal lobes manage sensation, handwriting, and body position.
• The temporal lobes are involved with memory and hearing.
• The occipital lobes contain the brain’s visual processing system.

The brain is surrounded by a layer of tissue called the meninges. The skull (cranium) helps protect the brain from injury

Brain Conditions

* Headache: There are many types of headaches; some can be serious but most are not and are generally treated with analgesics/painkillers.
* Stroke (brain infarction): Blood flow and oxygen are suddenly interrupted to an area of brain tissue, which then dies. A blood clot, or bleeding in the brain, are the cause of most strokes.
* Brain aneurysm: An artery in the brain develops a weak area that swells, balloon-like. A brain aneurysm rupture can causes a stroke.
* Subdural hematoma: Bleeding within or under the dura, the lining inside of the skull. A subdural hematoma may exert pressure on the brain, causing neurological problems.
* Epidural hematoma: Bleeding between the tough tissue (dura) lining the inside of the skull and the skull itself, usually shortly after a head injury. Initial mild symptoms can progress rapidly to unconsciousness and death, if untreated.
* Intracerebral hemorrhage: Any bleeding inside the brain.

* Concussion: A brain injury that causes a temporary disturbance in brain function. Traumatic head injuries cause most concussions.
* Cerebral edema: Swelling of the brain tissue in response to injury or electrolyte imbalances.
* Brain tumor: Any abnormal tissue growth inside the brain. Whether malignant (cancer) or benign, brain tumors usually cause problems by the pressure they exert on the normal brain.
* Glioblastoma: An aggressive, malignant brain tumor (cancer). Brain glioblastomas progress rapidly and are very difficult to cure.
* Hydrocephalus: An abnormally increased amount of cerebrospinal (brain) fluid inside the skull. Usually this is because the fluid is not circulating properly.
* Normal pressure hydrocephalus: A form of hydrocephalus that often causes problems walking, along with dementia and urinary incontinence. Pressures inside the brain remain normal, despite the increased fluid.

* Encephalitis: Inflammation of the brain tissue, usually from infection with a virus. Fever, headache, and confusion are common symptoms.
* Traumatic brain injury: Permanent brain damage from a traumatic head injury. Obvious mental impairment, or more subtle personality and mood changes can occur.
* Parkinson’s disease: Nerves in a central area of the brain degenerate slowly, causing problems with movement and coordination. A tremor of the hands is a common early sign.
* Huntington’s disease: An inherited nerve disorder that affects the brain. Dementia and difficulty controlling movements (chorea) are its symptoms.
* Epilepsy: The tendency to have seizures. Head injuries and strokes may cause epilepsy, but usually no cause is identified.
* Dementia: A decline in cognitive function resulting from death or malfunction of nerve cells in the brain. Conditions in which nerves in the brain degenerate, as well as alcohol abuse and strokes, can cause dementia.

* Alzheimer’s disease: For unclear reasons, nerves in certain brain areas degenerate, causing progressive dementia. Alzheimer’s disease is the most common form of dementia.
* Brain abscess: A pocket of infection in the brain, usually by bacteria. Antibiotics and surgical drainage of the area are often necessary.

Brain Tests

• Computed tomography (CT scan): A scanner takes multiple X-rays, which a computer converts into detailed images of the brain and skull.
• Magnetic resonance imaging (MRI scan): Using radio waves in a magnetic field, an MRI scanner creates highly detailed images of the brain and other parts of the head.
• Angiography (brain angiogram): A special substance doctors call “a contrast agent” is injected into the veins, and travels into the brain. X-ray videos of the brain are taken, which can show problems in the brain’s arteries.
• Magnetic resonance angiography (MRA): A special MRI scan of the brain’s arteries. An MRA scan may show a blood clot or another cause for stroke.
•Lumbar puncture (spinal tap): A needle is inserted into the space around the spinal nerves, and fluid is removed for analysis. Lumbar puncture is often done if meningitis is suspected.

• Electroencephalogram (EEG): Brain activity is monitored through electrodes placed on the skin on the head. EEG can help diagnose seizures, or other brain problems.
• Neurocognitive testing: Tests of problem-solving ability, short-term memory, and other complex brain functions. Usually, neurocognitive testing is done through questionnaires.
• Brain biopsy: In rare situations, a very small piece of the brain is needed to make the diagnosis of a brain condition. Brain biopsies are generally done only when the information is needed to provide proper treatment

Brain Treatments

* Thrombolytics: Clot-busting medicines injected into the veins can improve or cure some strokes if given within a few hours after symptoms start.
* Antiplatelet agents: Medicines like aspirin and clopidogrel (Plavix) help prevent blood clots. This can reduce the chance of a stroke.
* Cholinesterase inhibitors: These medicines can improve brain function slightly in mild or moderate Alzheimer’s disease. They do not slow or prevent Alzheimer’s disease.
* Antibiotics: When a brain infection is caused by bacteria, antibiotics can kill the organisms and make a cure more likely.
* Levodopa: A medicine that increases brain levels of dopamine, which is helpful in controlling symptoms of Parkinson’s disease.
* Brain surgery: An operation on the brain can cure some brain tumors. Brain surgery may be performed any time increased pressure in the brain threatens brain tissue.

* Ventriculostomy: A drain is placed into the natural spaces inside the brain (ventricles). Ventriculostomy is usually performed to relieve high brain pressures.
* Craniotomy: A surgeon drills a hole into the side of the skull to relieve high pressures.
* Lumbar drain: A drain is placed into the fluid around the spinal cord. This can relieve pressure on the brain and spinal cord.
* Radiation therapy: If cancer affects the brain, radiation can reduce symptoms and slow the cancer’s growth.


Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth’s hydrosphere and the fluids of all known living organisms (in which it acts as a solvent[1]). It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°.[2] “Water” is the name of the liquid state of H2O at standard conditions for temperature and pressure.

A globule of liquid water, and the concave depression and rebound in water caused by something dropping through the water surface

A block of solid water (ice)

Clouds in Earth’s atmosphere condense from gaseous water vapor.

A number of natural states of water exist. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor.

Water covers approximately 70.9% of the Earth’s surface, mostly in seas and oceans.Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland (1.7%), and in the air as vapor, clouds (consisting of ice and liquid water suspended in air), and precipitation (0.001%).Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea.

Water plays an important role in the world economy. Approximately 70% of the freshwater used by humans goes to agriculture.[6] Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of the long-distance trade of commodities (such as oil, natural gas, and manufactured products) is transported by boats through seas, rivers, lakes, and canals. Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of substances both mineral and organic; as such it is widely used in industrial processes, and in cooking and washing. Water, ice and snow are also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, diving, ice skating and skiing.

Chemical and physical properties

Water (H2O) is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the “universal solvent” for its ability to dissolve many substances.[8][9] This allows it to be the “solvent of life”:[10] indeed, water as found in nature almost always includes various dissolved substances, and special steps are required to obtain chemically pure water. Water is the only common substance to exist as a solid, liquid, and gas in normal terrestrial conditions


Along with oxidane, water is one of the two official names for the chemical compound H
2O;it is also the liquid phase of H
2O.The other two common states of matter of water are the solid phase, ice, and the gaseous phase, water vapor or steam. The addition or removal of heat can cause phase transitions: freezing (water to ice), melting (ice to water), vaporization (water to vapor), condensation (vapor to water), sublimation (ice to vapor) and deposition (vapor to ice)


Water differs from most liquids in that it becomes less dense as it freezes.In 1 atm pressure, it reaches its maximum density of 1,000 kg/m3 (62.43 lb/cu ft) at 3.98 °C (39.16 °F).The density of ice is 917 kg/m3 (57.25 lb/cu ft), an expansion of 9%.This expansion can exert enormous pressure, bursting pipes and cracking rocks (see Frost weathering).

In a lake or ocean, water at 4 °C (39.2 °F) sinks to the bottom, and ice forms on the surface, floating on the liquid water. This ice insulates the water below, preventing it from freezing solid. Without this protection, most aquatic organisms would perish during the winter.

Phase transitions

At a pressure of one atmosphere (atm), ice melts or water freezes at 0 °C (32 °F) and water boils or vapor condenses at 100 °C (212 °F). However, even below the boiling point, water can change to vapor at its surface by evaporation (vaporization throughout the liquid is known as boiling). Sublimation and deposition also occur on surfaces.For example, frost is deposited on cold surfaces while snowflakes form by deposition on an aerosol particle or ice nucleus.In the process of freeze-drying, a food is frozen and then stored at low pressure so the ice on its surface sublimates.

The melting and boiling points depend on pressure. A good approximation for the rate of change of the melting temperature with pressure is given by the Clausius–Clapeyron relation:

where {\displaystyle v_{\text{L}}}{\displaystyle v_{\text{L}}} and {\displaystyle v_{\text{S}}}{\displaystyle v_{\text{S}}} are the molar volumes of the liquid and solid phases, and {\displaystyle L_{\text{f}}}{\displaystyle L_{\text{f}}} is the molar latent heat of melting. In most substances, the volume increases when melting occurs, so the melting temperature increases with pressure. However, because ice is less dense than water, the melting temperature decreases.In glaciers, pressure melting can occur under sufficiently thick volumes of ice, resulting in subglacial lakes.

The Clausius-Clapeyron relation also applies to the boiling point, but with the liquid/gas transition the vapor phase has a much lower density than the liquid phase, so the boiling point increases with pressure. Water can remain in a liquid state at high temperatures in the deep ocean or underground. For example, temperatures exceed 205 °C (401 °F) in Old Faithful, a geyser in Yellowstone National Park.In hydrothermal vents, the temperature can exceed 400 °C (752 °F).

At sea level, the boiling point of water is 100 °C (212 °F). As atmospheric pressure decreases with altitude, the boiling point decreases by 1 °C every 274 meters. High-altitude cooking takes longer than sea-level cooking. For example, at 1,524 metres (5,000 ft), cooking time must be increased by a fourth to achieve the desired result. (Conversely, a pressure cooker can be used to decrease cooking times by raising the boiling temperature.) In a vacuum, water will boil at room temperature.

Triple and critical points

On a pressure/temperature phase diagram (see figure), there are curves separating solid from vapor, vapor from liquid, and liquid from solid. These meet at a single point called the triple point, where all three phases can coexist. The triple point is at a temperature of 273.16 K (0.01 °C) and a pressure of 611.657 pascals (0.00604 atm); it is the lowest pressure at which liquid water can exist. Until 2019, the triple point was used to define the Kelvin temperature scale.

The water/vapor phase curve terminates at 647.096 K (373.946 °C; 705.103 °F) and 22.064 megapascals (3,200.1 psi; 217.75 atm).This is known as the critical point. At higher temperatures and pressures the liquid and vapor phases form a continuous phase called a supercritical fluid. It can be gradually compressed or expanded between gas-like and liquid-like densities, its properties (which are quite different from those of ambient water) are sensitive to density. For example, for suitable pressures and temperatures it can mix freely with nonpolar compounds, including most organic compounds. This makes it useful in a variety of applications including high-temperature electrochemistry and as an ecologically benign solvent or catalyst in chemical reactions involving organic compounds. In Earth’s mantle, it acts as a solvent during mineral formation, dissolution and deposition.

Phases of ice and water

The normal form of ice on the surface of Earth is Ice Ih, a phase that forms crystals with hexagonal symmetry. Another with cubic crystalline symmetry, Ice Ic, can occur in the upper atmosphere.As the pressure increases, ice forms other crystal structures. As of 2019, 17 have been experimentally confirmed and several more are predicted theoretically.The 18th form of ice, ice XVIII, a face-centred-cubic, superionic ice phase, was discovered when a droplet of water was subject to a shock wave that raised the water’s pressure to millions of atmospheres and its temperature to thousands of degrees, resulting in a structure of rigid oxygen toms in which hydrogen atoms flowed freely.When sandwiched between layers of graphene, ice forms a square lattice.

The details of the chemical nature of liquid water are not well understood; some theories suggest that its unusual behaviour is due to the existence of 2 liquid states.

Taste and odor

Pure water is usually described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths,and frogs are known to be able to smell it.However, water from ordinary sources (including bottled mineral water) usually has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water by avoiding water that is too salty or putrid.

Color and appearance

Pure water is visibly blue due to absorption of light in the region ca. 600 nm – 800 nm. The color can be easily observed in a glass of tap-water placed against a pure white background, in daylight. The principal absorption bands responsible for the color are overtones of the O–H stretching vibrations. The apparent intensity of the color increases with the depth of the water column, following Beer’s law. This also applies, for example, with a swimming pool when the light source is sunlight reflected from the pool’s white tiles.

In nature, the color may also be modified from blue to green due to the presence of suspended solids or algae.

In industry, near-infrared spectroscopy is used with aqueous solutions as the greater intensity of the lower overtones of water means that glass cuvettes with short path-length may be employed. To observe the fundamental stretching absorption spectrum of water or of an aqueous solution in the region around 3500 cm−1 (2.85 μm) a path length of about 25 μm is needed. Also, the cuvette must be both transparent around 3500 cm−1 and insoluble in water; calcium fluoride is one material that is in common use for the cuvette windows with aqueous solutions.

The Raman-active fundamental vibrations may be observed with, for example, a 1 cm sample cell.

Aquatic plants, algae, and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. Practically no sunlight reaches the parts of the oceans below 1,000 meters (3,300 ft) of depth.

The refractive index of liquid water (1.333 at 20 °C (68 °F)) is much higher than that of air (1.0), similar to those of alkanes and ethanol, but lower than those of glycerol (1.473), benzene (1.501), carbon disulfide (1.627), and common types of glass (1.4 to 1.6). The refraction index of ice (1.31) is lower than that of liquid water.

Polar molecule

In a water molecule, the hydrogen atoms form a 104.5° angle with the oxygen atom. The hydrogen atoms are close to two corners of a tetrahedron centered on the oxygen. At the other two corners are lone pairs of valence electrons that do not participate in the bonding. In a perfect tetrahedron, the atoms would form a 109.5° angle, but the repulsion between the lone pairs is greater than the repulsion between the hydrogen atoms.The O–H bond length is about 0.096 nm.

Other substances have a tetrahedral molecular structure, for example, methane (CH
and hydrogen sulfide (H2S). However, oxygen is more electronegative (holds on to its electrons more tightly) than most other elements, so the oxygen atom retains a negative charge while the hydrogen atoms are positively charged. Along with the bent structure, this gives the molecule an electrical dipole moment and it is classified as a polar molecule.

Water is a good polar solvent, that dissolves many salts and hydrophilic organic molecules such as sugars and simple alcohols such as ethanol. Water also dissolves many gases, such as oxygen and carbon dioxide—the latter giving the fizz of carbonated beverages, sparkling wines and beers. In addition, many substances in living organisms, such as proteins, DNA and polysaccharides, are dissolved in water. The interactions between water and the subunits of these biomacromolecules shape protein folding, DNA base pairing, and other phenomena crucial to life (hydrophobic effect).

Many organic substances (such as fats and oils and alkanes) are hydrophobic, that is, insoluble in water. Many inorganic substances are insoluble too, including most metal oxides, sulfides, and silicates.

Hydrogen bonding

Because of its polarity, a molecule of water in the liquid or solid state can form up to four hydrogen bonds with neighboring molecules. Hydrogen bonds are about ten times as strong as the Van der Waals force that attracts molecules to each other in most liquids. This is the reason why the melting and boiling points of water are much higher than those of other analogous compounds like hydrogen sulfide. They also explain its exceptionally high specific heat capacity (about 4.2 J/g/K), heat of fusion (about 333 J/g), heat of vaporization (2257 J/g), and thermal conductivity (between 0.561 and 0.679 W/m/K). These properties make water more effective at moderating Earth’s climate, by storing heat and transporting it between the oceans and the atmosphere. The hydrogen bonds of water are around 23 kJ/mol (compared to a covalent O-H bond at 492 kJ/mol). Of this, it is estimated that 90% is attributable to electrostatics, while the remaining 10% is partially covalent.

These bonds are the cause of water’s high surface tension and capillary forces. The capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.


Water is a weak solution of hydronium hydroxide – there is an equilibrium 2H
2O ⇔ H
+ OH−
, in combination with solvation of the resulting hydronium ions.

Electrical conductivity and electrolysis

Pure water has a low electrical conductivity, which increases with the dissolution of a small amount of ionic material such as common salt.

Liquid water can be split into the elements hydrogen and oxygen by passing an electric current through it—a process called electrolysis. The decomposition requires more energy input than the heat released by the inverse process (285.8 kJ/mol, or 15.9 MJ/kg)

Mechanical properties

Liquid water can be assumed to be incompressible for most purposes: its compressibility ranges from 4.4 to 5.1×10−10 Pa−1 in ordinary conditions.Even in oceans at 4 km depth, where the pressure is 400 atm, water suffers only a 1.8% decrease in volume.

The viscosity of water is about 10−3 Pa·s or 0.01 poise at 20 °C (68 °F), and the speed of sound in liquid water ranges between 1,400 and 1,540 meters per second (4,600 and 5,100 ft/s) depending on temperature. Sound travels long distances in water with little attenuation, especially at low frequencies (roughly 0.03 dB/km for 1 kHz), a property that is exploited by cetaceans and humans for communication and environment sensing (sonar).


Metallic elements which are more electropositive than hydrogen, particularly the alkali metals and alkaline earth metals such as lithium, sodium, calcium, potassium and cesium displace hydrogen from water, forming hydroxides and releasing hydrogen. At high temperatures, carbon reacts with steam to form carbon monoxide and hydrogen.


Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is collected from roofs, rather than creeks, drains, roads, or any other land surfaces. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.

Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, and residential and household-scale projects, usually financed by the user. However, larger systems for schools, hospitals, and other facilities can run up costs only able to be financed by owners, organizations, and governmental units.


Rainwater harvesting provides the independent water supply during regional water restrictions, and in developed countries, it is often used to supplement the main supply. It provides water when a drought occurs, can help mitigate flooding of low-lying areas, and reduces demand on wells which may enable groundwater levels to be sustained. It also helps in the availability of potable water, as rainwater is substantially free of salinity and other salts. Applications of rainwater harvesting in urban water system provides a substantial benefit for both water supply and wastewater subsystems by reducing the need for clean water in water distribution systems, less generated stormwater in sewer systems,and a reduction in stormwater runoff polluting freshwater bodies.

A rainwater harvesting system that could be easily installed and maintained by local people

A large body of work has focused on the development of life cycle assessment and its costing methodologies to assess the level of environmental impacts and money that can be saved by implementing rainwater harvesting systems.

Independent water supply

Rainwater harvesting provides an independent water supply during water restrictions. In areas where clean water is costly, or difficult to come by, rainwater harvesting is a critical source of clean water. In developed countries, rainwater is often harvested to be used as a supplemental source of water rather than the main source, but the harvesting of rainwater can also decrease a household’s water costs or overall usage levels. Rainwater is safe to drink if the consumers do additional treatments before drinking. Boiling water helps to kill germs. Adding another supplement to the system such as a first flush diverter is also a common procedure to avoid contaminants of the water.

Supplemental in drought

When drought occurs, rainwater harvested in past months can be used. If rain is scarce but also unpredictable, the use of a rainwater harvesting system can be critical to capturing the rain when it does fall. Many countries with arid environments, use rainwater harvesting as a cheap and reliable source of clean water. To enhance irrigation in arid environments, ridges of soil are constructed to trap and prevent rainwater from running downhills. Even in periods of low rainfall, enough water is collected for crops to grow. Water can be collected from roofs and tanks can be constructed to hold large quantities of rainwater.

In addition, rainwater harvesting decreases the demand for water from wells, enabling groundwater levels to be further sustained rather than depleted.

Life-cycle assessment

Life-cycle assessment is a methodology used to evaluate the environmental impacts of a system from cradle-to-grave of its lifetime. Devkota et al,developed such a methodology for rainwater harvesting, and found that the building design (e.g., dimensions) and function (e.g., educational, residential, etc.) play critical roles in the environmental performance of the system.

To address the functional parameters of rainwater harvesting systems, a new metric was developed – the demand to supply ratio (D/S) – identifying the ideal building design (supply) and function (demand) in regard to the environmental performance of rainwater harvesting for toilet flushing. With the idea that supply of rainwater not only saves the potable water but also saves the stormwater entering the combined sewer network (thereby requiring treatment), the savings in environmental emissions were higher if the buildings are connected to a combined sewer network compared to separate one.


Although standard RWH systems can provide a water source to developing regions facing poverty, the average cost for an RWH setup can be costly depending on the type of technology used. Governmental aid and NGOs can assist communities facing poverty by providing the materials and education necessary to develop and maintain RWH setups.

Some studies show that rainwater harvesting is a widely applicable solution for water scarcity and other multiple usages, owing to its cost-effectiveness and eco-friendliness. Constructing new substantial, centralized water supply systems, such as dams, is prone to damage local ecosystems, generates external social costs, and has limited usages, especially in developing countries or impoverished communities. On the other hand, installing rainwater harvesting systems is verified by a number of studies to provide local communities a sustainable water source, accompanied by other various benefits, including protection from flood and control of water runoff, even in poor regions. Rainwater harvesting systems that do not require major construction or periodic maintenance by a professional from outside the community are more friendly to the environment and more likely to benefit the local people for a longer period of time.Thus, rainwater harvesting systems that could be installed and maintained by local people have bigger chances to be accepted and used by more people.

The usage of in-situ technologies can reduce investment costs in rainwater harvesting. In-situ technologies for rainwater harvesting could be a feasible option for rural areas since less material is required to construct them. They can provide a reliable water source that can be utilized to expand agricultural outputs. Above-ground tanks can collect water for domestic use; however, such units can be unaffordable to people in poverty.


Rainwater harvesting is a widely used method of storing rainwater in the countries presenting with drought characteristics. Several pieces of research have derived and developed different criteria and techniques to select suitable sites for harvesting rainwater. Some research was identified and selected suitable sites for the potential erection of dams, as well as derived a model builder in ArcMap 10.4.1. The model combined several parameters, such as slope, runoff potential, land cover/use, stream order, soil quality, and hydrology to determine the suitability of the site for harvesting rainwater.

Harvested water from RWH systems can be minimal during below-average precipitation in arid urban regions such as the Mideast. RWH is useful for developing areas as it collects water for irrigation and domestic purposes. However, the gathered water should be adequately filtered to ensure safe drinking.

Quality of water harvesting

Rainwater may need to be analyzed properly, and used in a way appropriate to its safety. In the Gansu province, for example, solar water disinfection is used by boiling harvested rainwater in parabolic solar cookers before being used for drinking.These so-called “appropriate technology” methods provide low-cost disinfection options for treatment of stored rainwater for drinking.

While rainwater itself is a clean source of water, often better than groundwater or water from rivers or lakes,the process of collection and storage often leaves the water polluted and non-potable. Rainwater harvested from roofs can contain human, animal and bird feces, mosses and lichens, windblown dust, particulates from urban pollution, pesticides, and inorganic ions from the sea (Ca, Mg, Na, K, Cl, SO4), and dissolved gases (CO2, NOx, SOx). High levels of pesticide have been found in rainwater in Europe with the highest concentrations occurring in the first rain immediately after a dry spell; the concentration of these and other contaminants are reduced significantly by diverting the initial flow of run-off water to waste. Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, withdraw from the last in series. Prefiltration is a common practice used in the industry to keep the system healthy and ensure that the water entering the tank is free of large sediments.

A very interesting concept of rainwater harvesting and cleaning it with solar energy for rural household drinking purposes has been developed by Nimbkar Agricultural Research Institute.

Conceptually, a water supply system should match the quality of water with the end-user. However, in most of the developed world, high-quality potable water is used for all end uses. This approach wastes money and energy and imposes unnecessary impacts on the environment. Supplying rainwater that has gone through preliminary filtration measures for non-potable water uses, such as toilet flushing, irrigation, and laundry, maybe a significant part of a sustainable water management strategy.


The Shrimad Bhagavad Gita (/ˌbʌɡəvəd ˈɡiːtɑː, -tə/; Sanskrit: श्रीमद्भगवद्गीता, lit. ’The Song by God’;[a] IAST: bhagavadgītā),[1] often referred to as the Gita (IAST: gītā), is a 700-verse Hindu scripture that is part of the epic Mahabharata (chapters 23–40 of Bhishma Parva), dated to the second half of the first millennium BCE and exemplary for the emerging Hindu synthesis. It is considered to be one of the holy scriptures for Hinduism.


Religion Hinduism

Author Traditionally attributed to Vyasa

Language Sanskrit

Period 1st-millennium BCE

Chapters 18

Sutras Yoga Sutras

Verses 700 (approx.)

The Gita is set in a narrative framework of a dialogue between Pandava prince Arjuna and his guide and charioteer Krishna, an avatar of Lord Vishnu. At the start of the Dharma Yuddha (righteous war) between Pandavas and Kauravas, Arjuna is filled with moral dilemma and despair about the violence and death the war will cause in the battle against his own kin.He wonders if he should renounce and seeks Krishna’s counsel, whose answers and discourse constitute the Bhagavad Gita. Krishna counsels Arjuna to “fulfill his Kshatriya (warrior) duty to uphold the Dharma” through “selfless action”.The Krishna–Arjuna dialogues cover a broad range of spiritual topics, touching upon ethical dilemmas and philosophical issues that go far beyond the war Arjuna faces.



The Bhagavad Gita is a poem written in the Sanskrit language.Its 700 verses are structured into several ancient Indian poetic meters, with the principal being the shloka (Anushtubh chanda). It has 18 chapters in total. Each shloka consists of a couplet, thus the entire text consists of 1,400 lines. Each shloka line has two quarter verses with exactly eight syllables. Each of these quarters is further arranged into “two metrical feet of four syllables each”, state Flood and Martin.The metered verse does not rhyme.While the shloka is the principal meter in the Gita, it does deploy other elements of Sanskrit prosody.At dramatic moments, it uses the tristubh meter found in the Vedas, where each line of the couplet has two quarter verses with exactly eleven syllables.


The Gita is a dialogue between Krishna and Arjuna right before the start of the climactic Kurukshetra War in the Hindu epic Mahabharata.Two massive armies have gathered to destroy the other. The Pandava prince Arjuna asks his charioteer Krishna to drive to the center of the battlefield so that he can get a good look at both the armies and all those “so eager for war”.He sees that some among his enemies are his own relatives, beloved friends, and revered teachers. He does not want to fight to kill them and is thus filled with doubt and despair on the battlefield.He drops his bow, wonders if he should renounce and just leave the battlefield.He turns to his charioteer and guide Krishna, for advice on the rationale for war, his choices and the right thing to do. The Bhagavad Gita is the compilation of Arjuna’s questions and moral dilemma, Krishna’s answers and insights that elaborate on a variety of philosophical concepts. The compiled dialogue goes far beyond the “a rationale for war”; it touches on many human ethical dilemmas, philosophical issues and life’s choices.According to Flood and Martin, although the Gita is set in the context of a war epic, the narrative is structured to apply to all situations; it wrestles with questions about “who we are, how we should live our lives, and how should we act in the world”.According to Sargeant, it delves into questions about the “purpose of life, crisis of self-identity, human Self, human temperaments, and ways for spiritual quest”.


The thematic story of Arjuna and Krishna at the Kurukshetra War became popular in southeast Asia as Hinduism spread there in the 1st-millennium CE.Above, an Arjuna-Krishna chariot scene in Jakarta center, Indonesia.

* Arjuna, one of the five Pandavas
* Krishna, Arjuna’s charioteer and guru who was actually an incarnation of Vishnu
* Sanjaya, counselor of the Kuru king Dhritarashtra (secondary narrator)
* Dhritarashtra, Kuru king (Sanjaya’s audience) and father of the Kauravas


Bhagavad Gita comprises 18 chapters (section 23 to 40)in the Bhishma Parva of the epic Mahabharata. Because of differences in recensions, the verses of the Gita may be numbered in the full text of the Mahabharata as chapters 6.25–42 or as chapters 6.23–40. The number of verses in each chapter vary in some manuscripts of the Gita discovered on the Indian subcontinent. However, variant readings are relatively few in contrast to the numerous versions of the Mahabharata it is found embedded in, and the meaning is the same.

The original Bhagavad Gita has no chapter titles. Some Sanskrit editions that separate the Gita from the epic as an independent text, as well as translators, however, add chapter titles such as each chapter being a particular form of yoga.For example, Swami Chidbhavananda describes each of the eighteen chapters as a separate yoga because each chapter, like yoga, “trains the body and the mind”. He labels the first chapter “Arjuna Vishada Yogam” or the “Yoga of Arjuna’s Dejection”. Sir Edwin Arnold titled this chapter in his 1885 translation as “The Distress of Arjuna”.

Chapter 1 (46 verses)

Some translators have variously titled the first chapter as Arjuna vishada yoga, Prathama Adhyaya, The Distress of Arjuna, The War Within, or Arjuna’s Sorrow.The Bhagavad Gita is opened by setting the stage of the Kurukshetra battlefield. Two massive armies representing different loyalties and ideologies face a catastrophic war. With Arjuna is Krishna, not as a participant in the war, but only as his charioteer and counsel. Arjuna requests Krishna to move the chariot between the two armies so he can see those “eager for this war”. He sees family and friends on the enemy side. Arjuna is distressed and in sorrow.The issue is, states Arvind Sharma, “is it morally proper to kill?” This and other moral dilemmas in the first chapter are set in a context where the Hindu epic and Krishna have already extolled ahimsa (non-violence) to be the highest and divine virtue of a human being.The war feels evil to Arjuna and he questions the morality of war. He wonders if it is noble to renounce and leave before the violence starts, or should he fight, and why.

Chapter 2 (72 verses)

Some translators title the chapter as Sankhya Yoga, The Book of Doctrines, Self-Realization, or The Yoga of Knowledge (and Philosophy).[The second chapter begins the philosophical discussions and teachings found in Gita. The warrior Arjuna whose past had focused on learning the skills of his profession now faces a war he has doubts about. Filled with introspection and questions about the meaning and purpose of life, he asks Krishna about the nature of life, Self, death, afterlife and whether there is a deeper meaning and reality. Krishna answers. The chapter summarizes the Hindu idea of rebirth, samsara, eternal Self in each person (Self), universal Self present in everyone, various types of yoga, divinity within, the nature of Self-knowledge and other concepts.The ideas and concepts in the second chapter reflect the framework of the Samkhya and Yoga schools of Hindu philosophy. This chapter is an overview for the remaining sixteen chapters of the Bhagavad Gita. Mahatma Gandhi memorized the last 19 verses of the second chapter, considering them as his companion in his non-violent movement for social justice during the colonial rule.

Chapter 3 (43 verses)

Some translators title the chapter as Karma yoga, Virtue in Work, Selfless Service, or The Yoga of Action.Arjuna, after listening to Krishna’s spiritual teachings in Chapter 2, gets more confounded and returns to the predicament he faces. He wonders if fighting the war is “not so important after all” given Krishna’s overview on the pursuit of spiritual wisdom. Krishna replies that there is no way to avoid action (karma), since abstention from work is also an action. Krishna states that Arjuna has an obligation to understand and perform his duty (dharma), because everything is connected by the law of cause and effect. Every man or woman is bound by activity. Those who act selfishly create the karmic cause and are thereby bound to the effect which may be good or bad.Those who act selflessly for the right cause and strive to do their dharmic duty do God’s work.Those who act without craving for fruits are free from the karmic effects, because the results never motivated them. Whatever the result, it does not affect them. Their happiness comes from within, and the external world does not bother them. According to Flood and Martin, chapter 3 and onwards develops “a theological response to Arjuna’s dilemma”.

Chapter 4 (42 verses)

Some translators title the fourth chapter as Jñāna–Karma-Sanyasa yoga, The Religion of Knowledge, Wisdom in Action, or The Yoga of Renunciation of Action through Knowledge.Krishna reveals that he has taught this yoga to the Vedic sages. Arjuna questions how Krishna could do this, when those sages lived so long ago, and Krishna was born more recently. Krishna reminds him that everyone is in the cycle of rebirths, and while Arjuna does not remember his previous births, he does. Whenever dharma declines and the purpose of life is forgotten by men, says Krishna, he returns to re-establish dharma.Every time he returns, he teaches about inner Self in all beings. The later verses of the chapter return to the discussion of motiveless action and the need to determine the right action, performing it as one’s dharma (duty) while renouncing the results, rewards, fruits. The simultaneous outer action with inner renunciation, states Krishna, is the secret to the life of freedom. Action leads to knowledge, while selfless action leads to spiritual awareness, state the last verses of this chapter.The 4th chapter is the first time where Krishna begins to reveal his divine nature to Arjuna.

Chapter 5 (29 verses)

Some translators title this chapter as Karma–Sanyasa yoga, Religion by Renouncing Fruits of Works, Renounce and Rejoice, or The Yoga of Renunciation. The chapter starts by presenting the tension in the Indian tradition between the life of sannyasa (monks who have renounced their household and worldly attachments) and the life of grihastha (householder). Arjuna asks Krishna which path is better. Krishna answers that both are paths to the same goal, but the path of “selfless action and service” with inner renunciation is better. The different paths, says Krishna, aim for—and if properly pursued, lead to—Self-knowledge. This knowledge leads to the universal, transcendent Godhead, the divine essence in all beings, to Brahman – the Krishna himself. The final verses of the chapter state that the self-aware who have reached self-realization live without fear, anger, or desire. They are free within, always. Chapter 5 shows signs of interpolations and internal contradictions. For example, states Arthur Basham, verses 5.23–28 state that a sage’s spiritual goal is to realize the impersonal Brahman, yet the next verse 5.29 states that the goal is to realize the personal God who is Krishna.

Chapter 6 (47 verses)

Some translators title the sixth chapter as Dhyana yoga, Religion by Self-Restraint, The Practice of Meditation, or The Yoga of Meditation.The chapter opens as a continuation of Krishna’s teachings about selfless work and the personality of someone who has renounced the fruits that are found in chapter 5. Krishna says that such self-realized people are impartial to friends and enemies, are beyond good and evil, equally disposed to those who support them or oppose them because they have reached the summit of consciousness. The verses 6.10 and after proceed to summarize the principles of Yoga and meditation in the format similar to but simpler than Patanjali’s Yogasutra. It discusses who is a true yogi, and what it takes to reach the state where one harbors no malice towards anyone.

Chapter 7 (30 verses)

Some translators title this chapter as Jnana–Vijnana yoga, Religion by Discernment, Wisdom from Realization, or The Yoga of Knowledge and Judgment. The chapter 7 once again opens with Krishna continuing his discourse. He discusses jnana (knowledge) and vijnana (realization, understanding) using the Prakriti-Purusha (matter-Self) framework of the Samkhya school of Hindu philosophy, and the Maya-Brahman framework of its Vedanta school. The chapter states that evil is the consequence of ignorance and the attachment to the impermanent, delusive Maya. It equates self-knowledge and the union with Purusha (Krishna) as the Self to be the highest goal of any spiritual pursuit.

Chapter 8 (28 verses)

Some translators title the chapter as Aksara–Brahma yoga, Religion by Devotion to the One Supreme God, The Eternal Godhead, or The Yoga of the Imperishable Brahman. The chapter opens with Arjuna asking questions such as what is Brahman and what is the nature of karma. Krishna states that his own highest nature is the imperishable Brahman, and that he lives in every creature as the adhyatman. Every being has an impermanent body and an eternal Self, and that “Krishna as Lord” lives within every creature. The chapter discusses cosmology, the nature of death and rebirth.This chapter contains eschatology of the Bhagavad Gita. Importance of the last thought before death, differences between material and spiritual worlds, and light and dark paths that a Self takes after death are described

Chapter 9 (34 verses)

Some translators title the ninth chapter as Raja–Vidya–Raja–Guhya yoga, Religion by the Kingly Knowledge and the Kingly Mystery, The Royal Path, or The Yoga of Sovereign Science and Sovereign Secret. Chapter 9 opens with Krishna continuing his discourse as Arjuna listens. Krishna states that he is everywhere and in everything in an unmanifested form, yet he is not in any way limited by them. Eons end, everything dissolves and then he recreates another eon subjecting them to the laws of Prakriti (nature).He equates himself to being the father and the mother of the universe, to being the Om, to the three Vedas, to the seed, the goal of life, the refuge and abode of all. The chapter recommends devotional worship of Krishna.According to theologian Christopher Southgate, verses of this chapter of the Gita are panentheistic,while German physicist and philos opher Max Bernhard Weinstein deems the work pandeistic. It may, in fact, be neither of them, and its contents may have no definition with previously-developed Western terms.

Chapter 10 (42 verses)

Some translators title the chapter as Vibhuti–Vistara–yoga, Religion by the Heavenly Perfections, Divine Splendor, or The Yoga of Divine Manifestations. Krishna reveals his divine being in greater detail, as the ultimate cause of all material and spiritual existence, one who transcends all opposites and who is beyond any duality. Krishna says he is the atman in all beings, Arjuna’s innermost Self, also compassionate Vishnu, the Surya (sun god), Indra, Shiva-Rudra, Ananta, Yama, as well as the Om, Vedic sages, time, Gayatri mantra, and the science of Self-knowledge. Arjuna accepts Krishna as the purushottama (Supreme Being).

Chapter 11 (55 verses)

Main article: Vishvarupa
Some translators title the chapter as Vishvarupa–Darshana yoga, The Manifesting of the One and Manifold, The Cosmic Vision, or The Yoga of the Vision of the Cosmic Form. On Arjuna’s request, Krishna displays his “universal form” (Viśvarūpa).This is an idea found in the Rigveda and many later Hindu texts, where it is a symbolism for atman (Self) and Brahman (Absolute Reality) eternally pervading all beings and all existence. Chapter 11, states Eknath Eswaran, describes Arjuna entering first into savikalpa samadhi (a particular), and then nirvikalpa samadhi (a universal) as he gets an understanding of Krishna. A part of the verse from this chapter was recited by Robert Oppenheimer as he witnessed the first atomic bomb explosion.

Chapter 12 (20 verses)

Some translators title the chapter as Bhakti yoga, The Religion of Faith, The Way of Love, or The Yoga of Devotion.In this chapter, Krishna glorifies the path of love and devotion to God. Krishna describes the process of devotional service (Bhakti yoga). This chapter of the Gita, states Easwaran, offers a “vastly easier” path to most human beings to identify and love God in an anthropomorphic representation, in any form. He can be projected as “a merciful father, a divine mother, a wise friend, a passionate beloved, or even a mischievous child”, according to Easwaran. The text states that combining “action with inner renunciation” with the love of Krishna as a personal God leads to peace. In the last eight verses of this chapter, Krishna states that he loves those who have compassion for all living beings, are content with whatever comes their way, who live a detached life that is impartial and selfless, unaffected by fleeting pleasure or pain, neither craving for praise nor depressed by criticism.

Chapter 13 (34 verses)

Sanskrit, Kannada script (Karnataka)
Bhagavad Gita and related commentary literature exists in numerous Indian languages.

Some translators title this chapter as Ksetra–Ksetrajna Vibhaga yoga, Religion by Separation of Matter and Spirit, The Field and the Knower, or The Yoga of Difference between the Field and Field-Knower.The chapter opens with Krishna continuing his discourse from the previous chapter. He describes the difference between transient perishable physical body (kshetra) and the immutable eternal Self (kshetrajna). The presentation explains the difference between ahamkara (ego) and atman (Self), from there between individual consciousness and universal consciousness. The knowledge of one’s true self is linked to the realization of the Self. The 13th chapter of the Gita offers the clearest enunciation of the Samkhya philosophy, states Basham, by explaining the difference between field (material world) and the knower (Self), prakriti and purusha.According to Miller, this is the chapter which “redefines the battlefield as the human body, the material realm in which one struggles to know oneself” where human dilemmas are presented as a “symbolic field of interior warfare”.

Chapter 14 (27 verses)

Some translators title the fourteenth chapter as Gunatraya–Vibhaga yoga, Religion by Separation from the Qualities, The Forces of Evolution, or The Yoga of the Division of Three Gunas.The chapter once again opens with Krishna continuing his discourse from the previous chapter. Krishna explains the difference between purusha and prakriti, by mapping human experiences to three Guṇas (tendencies, qualities).These are listed as sattva, rajas and tamas. All phenomena and individual personalities are a combination of all three gunas in varying and ever-changing proportions. The gunas affect the ego, but not the Self, according to the text.This chapter also relies on the Samkhya theories.

Chapter 15 (20 verses)

Some translators title the chapter as Purushottama yoga, Religion by Attaining the Supreme Krishna, The Supreme Self, or The Yoga of the Supreme Purusha.The fifteenth chapter expounds on Krishna theology, in the Vaishnava Bhakti tradition of Hinduism. Krishna discusses the nature of God, according to Easwaran, wherein Krishna not only transcends impermanent body (matter), he also transcends the atman (Self) in every being.According to Franklin Edgerton, the verses in this chapter in association with select verses in other chapters make the metaphysics of the Gita to be dualistic. Its overall thesis is, states Edgerton, more complex however, because other verses teach the Upanishadic doctrines and “through its God the Gita seems after all to arrive at an ultimate monism; the essential part, the fundamental element, in every thing, is after all One — is God.”

Chapter 16 (24 verses)

Some translators title the chapter as Daivasura–Sampad–Vibhaga yoga, The Separateness of the Divine and Undivine, Two Paths, or The Yoga of the Division between the Divine and the Demonic.According to Easwaran, this is an unusual chapter where two types of human nature are expounded, one leading to happiness and the other to suffering. Krishna identifies these human traits to be divine and demonic respectively. He states that truthfulness, self-restraint, sincerity, love for others, desire to serve others, being detached, avoiding anger, avoiding harm to all living creatures, fairness, compassion and patience are marks of the divine nature. The opposite of these are demonic, such as cruelty, conceit, hypocrisy and being inhumane, states Krishna.Some of the verses in Chapter 16 may be polemics directed against competing Indian religions, according to Basham The competing tradition may be the materialists (Charvaka), states Fowler.

Chapter 17 (28 verses)

Some translators title the chapter as Shraddhatraya-Vibhaga yoga, Religion by the Threefold Kinds of Faith, The Power of Faith, or The Yoga of the Threefold Faith. Krishna qualifies the three divisions of faith, thoughts, deeds, and even eating habits corresponding to the three modes (gunas)

Chapter 18 (78 verses)

Some translators title the chapter as Moksha–Sanyasa yoga, Religion by Deliverance and Renunciation, Freedom and Renunciation, or The Yoga of Liberation and Renunciation.In the final and long chapter, the Gita offers a final summary of its teachings in the previous chapters.It covers many topics, states Easwaran.It begins with discussion of spiritual pursuits through sannyasa (renunciation, monastic life) and spiritual pursuits while living in the world as a householder. It re-emphasizes the karma-phala-tyaga teaching, or “act while renouncing the fruits of your action”


What Are Rainbows?

A rainbow is a multicolored arc in the sky which appears when sunlight hits water droplets. How does it get its colors? Why is it curved? And what is at the end of the rainbow?

Low Sun and Water Droplets

A rainbow can only form under the following conditions:

1. The Sun must be above the horizon and not be obscured by clouds, mountains, or other obstacles.
2.The Sun has to be quite low in the sky. If you are at the same elevation as your horizon, the Sun’s altitude must be below 42° to create a rainbow that can be seen from your perspective. Solar altitude table
3.The air opposite the Sun, as seen from your position, must be filled with a large number of water droplets.

Rainbows always appear in the sky opposite to the Sun. So, if you have your back to the Sun, the rainbow will arch across the sky in front of you.

How Do Rainbows Form?

A rainbow is an optical phenomenon which involves three processes: reflection, dispersion, and refraction.


Water droplets can act like little mirrors. When a ray of sunlight strikes one of these tiny spheres of water, most of the light bounces off its rear wall and is reflected back. During a rain shower, the air is full of water droplets acting together like a reflective curtain made of millions of minuscule mirrors casting the sunlight back at you.


But sunlight is white—so, if the water droplets reflect the sunlight, how does the rainbow gets its colors? This is where the second process comes into play: dispersion of light.

Pure sunlight may appear white to us, but it consists of all visible colors. As soon as a ray of sunlight enters a water droplet, it is split up into its components, causing its colors to fan out and become visible as a spectrum of colors. This happens both when the ray enters the droplet and when it leaves the droplet again.


As the ray of light enters and leaves the water droplet, its direction is also changed slightly in a process called refraction. Each color is refracted in a marginally different direction, creating the impression of a fan of colors. For example, in relation to the direction of the incoming ray of light, the red light component leaves the droplet at a slightly larger angle than the orange component.

The Colors of the Rainbow

This means each water droplet reflects all of the colors of the sunlight back to you. However, because it reflects and refracts each color at a slightly different angle, only one color from each droplet reaches your eyes. For example, you can only see the red light from droplets that are higher in the sky, and only the orange light from the droplets that are a little lower.

This is how the top two stripes of the rainbow—red and orange—form. Further below, the droplets form an even sharper angle between you and the Sun, so they throw the yellow, green, blue, indigo, and violet components of the sunlight back at you, creating the remaining stripes of the rainbow.

Memorize the Color Sequence

If you are having trouble remembering the order of the rainbow colors, simply memorize the name Roy G. Biv. This imaginary first, middle, and last name is an acronym made up of the initial letter of each color, in the order they appear in a rainbow. From top to bottom, they are: red, orange, yellow, green, blue, indigo, and violet.

Why Is a Rainbow Curved?

Technically, a rainbow is the upper half of a circle of light, which centers on the antisolar point, the point directly opposite the Sun, as seen from your perspective. The lower half of the circle, however, is usually not visible since the water droplets hit the ground before it can form. You may be able to see a circular rainbow if you have a high vantage point and the terrain sharply drops off in the direction of the rainbow, allowing the rain to fall down farther and reflect the sunlight from a lower angle. It is also possible to see a circular rainbow from an airplane.

The shape of a rainbow is a result of the refractive index of water. This causes the sunlight to be reflected off rain droplets within a limited range of angles that lie between 0° and 42°. Most of the light is cast back at you in an angular range from 40° for violet light to 42° for red light. This is why the circle of light always has an angular distance of 40-42° from the antisolar point, meaning a rainbow always appears 40-42° away from the point opposite the Sun, as seen from your perspective.

What Is a Double Rainbow?

Sometimes you can see a fainter, second rainbow appear above a rainbow. This happens when sunlight is reflected twice inside each water droplet and directed back to you.

The second rainbow is not as bright as the primary rainbow, because some of the sunlight passes through the droplet, while most of it is reflected. This means more light goes astray when a ray of sunlight is reflected twice, leaving less light to be reflected back to you. The double reflection process also results in an inversion of the colors of the secondary rainbow. Here, the violet stripe is at the top while the red stripe appears at the bottom (click on the image to see this detail).

The angular distance between the second rainbow and the antisolar point is 50-53°, so the two rainbows are always about 10° apart.

Why Is the Area Below the Rainbow Brighter?

While most of the sunlight is concentrated at an angle of 40-42°, some of it is also reflected in the range of 0-39°. Crucially, the angle also determines the extent to which the sunlight is dispersed and refracted. For example, a ray of light that is reflected at 0°—right back where it came from—is not dispersed or refracted at all.

For this reason, we experience it as white light. The same is the case for light that is reflected at higher angles, although to a slightly lesser extent. This is why the area below the main rainbow looks comparatively bright, as shown in the images.

Alexander’s Band

The physical properties of the water droplet prevent the sunlight from being reflected at angles above 42°. For example, it is impossible for a horizontal beam of light to be reflected at an angle of 90° and sent straight down toward the ground. While this maximum reflective angle is a little different for each wavelength (color), ranging from 40° for violet light to 42° for red light, none of the sunlight can be redirected at angles exceeding 42°.

Because of this, water droplets that are more than 42° away from the antisolar point, as seen from your perspective, will not reflect any sunlight back at you. This is why the sky above the primary rainbow looks a great deal darker than the sky below it (see image).

About 10° above the main rainbow, the doubly reflected sunlight of the second rainbow reaches your eyes, so the sky above that is a little brighter again, creating the impression of a dark band of sky sandwiched between the two rainbows. This phenomenon is called Alexander’s band

Is There a Pot of Gold at the End of the Rainbow?

According to an Irish legend, a pot of gold can be found at a rainbow’s end. We probably all agree this is highly unlikely, but did you know it is possible to actually disprove that claim? In fact, you have probably been at the end of the rainbow many times without noticing!

To check the veracity of the pot-of-gold-legend, you need to go to the location where a rainbow touches the ground. This may seem like an impossible feat, given that a rainbow is, in a way, an optical illusion. As tangible and real a bright rainbow may appear, it is formed by countless small reflections of sunlight that are only visible from a certain perspective. This makes it impossible to actually approach a rainbow. If you move toward it, the rainbow will recede at an equal pace; a person who stands at the end of the rainbow you see will see a different, equally unapproachable rainbow farther back, if the weather conditions permit.

But in this realization also lies a chance to empirically disprove the Irish legend. If you can see another person at the end of your rainbow, you can stand at the end of another person’s rainbow, or at least of a rainbow that is visible from a different perspective. So, you have probably been there, at the end of the rainbow, even if that particular rainbow was invisible to you at the time.

Facts About Turtles and Tortoises

One of the four main families of reptiles, turtles and tortoises have been objects of human fascination for thousands of years. But how much do you really know about these vaguely comical reptiles? Here are 10 facts about turtles and tortoises, ranging from how these vertebrates evolved to why it’s unwise to keep them as pets.

1.Turtle vs Tortoise Linguistics

* Few things in the animal kingdom are more confusing than the difference between turtles and tortoises, for linguistic (rather than anatomical) reasons.

Terrestrial (non-swimming) species should technically be referred to as tortoises, but residents of North America are just as likely to use the word “turtle” across the board.

* Further complicating matters, in Great Britain “turtle” refers exclusively to marine species, and never to land-based tortoises.

* To avoid misunderstandings, most scientists and conservationists refer to turtles, tortoises, and terrapins under the blanket name “chelonians” or “Testudines.” Naturalists and biologists specializing in the study of these reptiles are known as “Testudinologists.”

2.They Are Divided Into Two Major Families

* The vast majority of the 350 or so species of turtles and tortoises are “cryptodires,” meaning these reptiles retract their heads straight back into their shells when threatened.

* The rest are “pleurodires,” or side-necked turtles, which fold their necks to one side when retracting their heads. There are other, more subtle anatomical differences between these two Testudine suborders. For example, the shells of cryptodires are composed of 12 bony plates, while pleurodires have 13, and also have narrower vertebrae in their necks.

* Pleurodire turtles are restricted to the southern hemisphere, including Africa, South America, and Australia. Cryptodires have a worldwide distribution and account for most familiar turtle and tortoise species.

3.The Shells Are Securely Attached to Their Bodies

* You can forget all those cartoons you saw as a kid where a turtle jumps naked out of its shell, then dives back in when threatened.

* The fact is that the shell, or carapace, is securely attached to its body. The inner layer of the shell is connected to the rest of the turtle’s skeleton by various ribs and vertebrae.

* The shells of most turtles and tortoises are composed of “scutes,” or hard layers of keratin. The same protein as in human fingernails.

* The exceptions are soft-shelled turtles and leatherbacks, the carapaces of which are covered with thick skin. Why did turtles and tortoises evolve shells in the first place? Clearly, shells developed as a means of defense against predators.

* Even a starving shark would think twice about breaking its teeth on the carapace of a Galapagos tortoise!

4.They Have Bird-Like Beaks, No Teeth

* You might think turtles and birds are as different as any two animals can be, but in fact, these two vertebrate families share an important common trait: they’re equipped with beaks, and they completely lack teeth.

* The beaks of meat-eating turtles are sharp and ridged. They can do serious damage to the hand of an unwary human, while the beaks of herbivorous turtles and tortoises have serrated edges ideal for cutting fibrous plants.

* Compared to other reptiles, the bites of turtles and tortoises are relatively weak. Still, the alligator snapping turtle can chomp down on its prey with a force of over 300 pounds per square inch, about the same as an adult human male.

* Let’s keep things in perspective, however: the bite force of a saltwater crocodile measures over 4,000 pounds per square inch!

5.Some Live for Over 100 Years

* As a rule, slow-moving reptiles with cold-blooded metabolisms have longer life spans than comparably-sized mammals or birds.

* Even a relatively small box turtle can live for 30 or 40 years, and a Galapagos tortoise can easily hit the 200-year mark.

* If it manages to survive into adulthood (and most turtle babies never get the chance, since they’re gobbled up by predators immediately after hatching), a turtle will be invulnerable to most predators thanks to its shell.

* There are hints that the DNA of these reptiles undergoes more frequent repair and that their stem cells are more easily regenerated.

* It should come as no surprise that turtles and tortoises are avidly studied by gerontologists, who hope to isolate “miracle proteins” that can help extend the human life span.

6.Most Don’t Have Very Good Hearing

* Because their shells provide such a high degree of protection, turtles and tortoises haven’t evolved the advanced auditory capabilities of, for example, herd animals like wildebeest and antelopes.

* Most Testudines, while on land, can only hear sounds above 60 decibels. For perspective, a human whisper registers at 20 decibels.

* This figure is much better in the water, where sound conducts differently. The vision of turtles isn’t much to brag about, either, but it gets the job done, allowing carnivorous Testudines to track prey.

* Also, some turtles are especially well-adapted to seeing at night. Overall, the general intelligence level of Testudines is low, though some species can be taught to navigate simple mazes and others have been shown to possess long-term memories.

7.They Lay Their Eggs in the Sand

* Depending on species, turtles and tortoises lay anywhere from 20 to 200 eggs at a time. One outlier is the eastern box tortoise, which lays only three to eight eggs at once.

* The female digs a hole in a patch of sand and soil deposits her clutch of soft, leathery eggs, and then promptly ambles away.

* What happens next is the kind of thing producers tend to leave out of TV nature documentaries: nearby carnivores raid the turtle nests and devour most of the eggs before they’ve had a chance to hatch.

* For example, crows and raccoons eat about 90 percent of the eggs laid by snapping turtles. Once the eggs have hatched, the odds aren’t much better, as immature turtles unprotected by hard shells are gobbled up like scaly hors-d’oeuvres.

* It only takes one or two hatchlings per clutch to survive in order to propagate the species; the others wind up being part of the food chain.

8.Their Ultimate Ancestor Lived During the Permian Period

* Turtles have a deep evolutionary history that extends to a few million years before the Mesozoic Era, better known as the Age of Dinosaurs.

* The earliest identified Testudine ancestor is a foot-long lizard called Eunotosaurus, which lived in the swamps of Africa 260 million years ago. It had wide, elongated ribs curving along its back, an early version of the shells of later turtles and tortoises.

* Other important links in Testudine evolution include the late Triassic Pappochelys and the early Jurassic Odontochelys, a soft-shelled marine turtle that sported a full set of teeth.

* Over the ensuing tens of millions of years, Earth was home to a series of truly monstrous prehistoric turtles, including Archelon and Protostega, each of which weighed almost two tons.

9.They Don’t Make Ideal Pets

* Turtles and tortoises may seem like the ideal “training pets” for kids (or for adults who don’t have a lot of energy), but there are some very strong arguments against their adoption. First, given their unusually long lifespans, Testudines can be a long-term commitment.

* Second, turtles need very specialized (and sometimes very expensive) care, especially in regard to their cages and food and water supplies.

* Third, turtles are carriers of salmonella, serious cases of which can land you in the hospital and even endanger your life. You don’t necessarily have to handle a turtle to contract salmonella, as these bacteria can thrive on the surfaces of your home.

* The general view of conservation organizations is that turtles and tortoises belong in the wild, not in your kid’s bedroom.

10.The Soviet Union Once Shot Two Tortoises Into Space

* It sounds like a science-fiction TV series, but Zond 5 was actually a spacecraft launched by the Soviet Union in 1968. It was carrying a payload of flies, worms, plants, and two presumably very disoriented tortoises.

* Zond 5 circled the moon once and returned to Earth, where it was discovered that the tortoises had lost 10 percent of their body weight, but were otherwise healthy and active.

* What happened to the tortoises after their triumphant return isn’t known and given the long life spans of their breed, it’s possible that they’re still alive today.

* One likes to imagine them mutated by gamma rays, blown up to monster sizes, and spending their dotage in a post-Soviet research facility on the fringes of Vladivostok.


Instagram (commonly abbreviated to IG, Insta or the gram)[9] is an American photo and video sharing social networking service created by Kevin Systrom and Mike Krieger. In April 2012, Facebook acquired the service for approximately US$1 billion in cash and stock. The app allows users to upload media that can be edited with filters and organized by hashtags and geographical tagging. Posts can be shared publicly or with pre-approved followers. Users can browse other users’ content by tags and locations and view trending content. Users can like photos and follow other users to add their content to a personal feed.

Original author(s) Kevin Systrom

Mike Krieger

Developer(s) Facebook, Inc.

Initial release October 6, 2010; 10 years


Stable release(s)[±]

Android / July 26, 2021; 36

days ago

iOS 198.0 / July 26, 2021; 36 days ago

Fire OS / July 26, 2021; 36

days ago

Preview release(s)[±]

Android / July 27, 2021; 35

(Alpha) days ago

Android / July 27, 2021; 35

(Beta) days ago

Operating system iOS, Android, Fire OS,

Microsoft windows

Size 171.7 MB (iOS)
38.49 MB (Android)
42.6 MB (Fire OS)

Available in 32[8] languages

List of languages
Chinese (Simplified and Traditional),Croatian,Czech,Danish,Dutch,English,Finnish,French,German,Greek,Hindi,Hungarian,Indonesian,Italian,Japanese,Korean,Malay,Norwegian,Polish,Portuguese,Romanian,Russian,Slovak,Spanish,Swedish,Tagalog,Thai,Turkish,Ukrainian,Vietnamese,Persian.

License Proprietary software with

Teams of use

Website http://www.instagram.com

Instagram was originally distinguished by only allowing content to be framed in a square (1:1) aspect ratio with 640 pixels to match the display width of the iPhone at the time. In 2015, these restrictions were eased with an increase to 1080 pixels. The service also added messaging features, the ability to include multiple images or videos in a single post, and a ‘stories’ feature—similar to its main opposition Snapchat—which allows users to post photos and videos to a sequential feed, with each post accessible by others for 24 hours each. As of January 2019, the Stories feature is used by 500 million users daily.

Originally launched for iOS in October 2010, Instagram rapidly gained popularity, with one million registered users in two months, 10 million in a year, and 1 billion as of June 2018.The Android version was released in April 2012, followed by a feature-limited desktop interface in November 2012, a Fire OS app in June 2014, and an app for Windows 10 in October 2016. As of October 2015, over 40 billion photos had been uploaded. Although praised for its influence, Instagram has been the subject of criticism, most notably for policy and interface changes, allegations of censorship, and illegal or improper content uploaded by users.

As of June 2021, the most followed person is Portuguese professional footballer Cristiano Ronaldo with over 300 million followers.The most followed woman is American singer Ariana Grande. As of January 14, 2019, the most-liked photo on Instagram is a picture of an egg, posted by the account @world_record_egg, created with the sole purpose of surpassing the previous record of 18 million likes on a Kylie Jenner post. The picture currently has over 55 million likes.The second most-liked photo is a wedding photo of Ariana Grande and her husband Dalton Gomez.Instagram became the 4th most downloaded mobile app of the 2010s.


In 2021, Washington Post reported that it has made an international black market for migrant workers, women in Africa and Asia, sold into servitude as maids in Persian Gulf countries.


Instagram was the runner-up for “Best Mobile App” at the 2010 TechCrunch Crunchies in January 2011. In May 2011, Fast Company listed CEO Kevin Systrom at number 66 in “The 100 Most Creative People in Business in 2011”. In June 2011, Inc. included co-founders Systrom and Krieger in its 2011 “30 Under 30” list.

Instagram won “Best Locally Made App” in the SF Weekly Web Awards in September 2011. 7x7Magazine’s September 2011 issue featured Systrom and Krieger on the cover of their “The Hot 20 2011” issue.In December 2011, Apple Inc. named Instagram the “App of the Year” for 2011.[326] In 2015, Instagram was named No. 1 by Mashable on its list of “The 100 best iPhone apps of all time,” noting Instagram as “one of the most influential social networks in the world.” Instagram was listed among Time’s “50 Best Android Applications for 2013” list

Mental health

In May 2017, a survey conducted by the United Kingdom’s Royal Society for Public Health, featuring 1,479 people aged 14–24, asking them to rate social media platforms depending on anxiety, depression, loneliness, bullying and body image, concluded that Instagram was the “worst for young mental health”. Some have suggested it may contribute to digital dependence, whist this same survey noticed its positive effects, including self-expression, self-identity, and community building. In response to the survey, Instagram stated that “Keeping Instagram a safe and supportive place for young people was a top priority”. The company filters out the reviews and accounts. If some of the accounts violate Instagram’s community guidelines, it will take action, which could include banning them.

In 2017, researchers from Harvard University and University of Vermont demonstrated a machine learning tool that successfully outperformed general practitioners’ diagnostic success rate for depression. The tool used color analysis, metadata components, and face detection of users’ feeds.

Throughout 2019, Instagram began to test the hiding of like counts for posts made by its users.

Correlations have been made between Instagram content and poor body dissatisfaction, as a result of body comparisons. In a recent survey half of the applicants admitted to photo editing behavior which has been linked with concerns over body image.

Negative comments

In response to abusive and negative comments on users’ photos, Instagram has made efforts to give users more control over their posts and accompanying comments field. In July 2016, it announced that users would be able to turn off comments for their posts, as well as control the language used in comments by inputting words they consider offensive, which will ban applicable comments from showing up.[334][335] After the July 2016 announcement, the ability to ban specific words began rolling out early August to celebrities, followed by regular users in September.In December, the company began rolling out the abilities for users to turn off the comments and, for private accounts, remove followers.

In September 2017, the company announced that public users would be able to limit who can comment on their content, such as only their followers or people they follow. At the same time, it updated its automated comment filter to support additional languages.

In June 2017, Instagram announced that it would automatically attempt to filter offensive, harassing, and “spammy” comments by default. The system is built using a Facebook-developed deep learning algorithm known as DeepText (first implemented on the social network to detect spam comments), which utilizes natural-language processing techniques, and can also filter by user-specified keywords.

In July 2019, the service announced that it would introduce a system to proactively detect problematic comments and encourage the user to reconsider their comment, as well as allowing users the ability to “restrict” others’ abilities to communicate with them, citing that younger users felt the existing block system was too much of an escalation.


On August 9, 2012, English musician Ellie Goulding released a new music video for her song “Anything Could Happen.” The video only contained fan-submitted Instagram photographs that used various filters to represent words or lyrics from the song, and over 1,200 different photographs were submitted.


In August 2017, reports surfaced that a bug in Instagram’s developer tools had allowed “one or more individuals” to gain access to the contact information, specifically email addresses and phone numbers, of several high-profile verified accounts, including its most followed user, Selena Gomez. The company said in a statement that it had “fixed the bug swiftly” and was running an investigation.However, the following month, more details emerged, with a group of hackers selling contact information online, with the affected number of accounts in the “millions” rather than the previously-assumed limitation on verified accounts. Hours after the hack, a searchable database was posted online, charging $10 per search.The Daily Beast was provided with a sample of the affected accounts, and could confirm that, while many of the email addresses could be found with a Google search in public sources, some did not return relevant Google search results and thus were from private sources.The Verge wrote that cybersecurity firm RepKnight had found contact information for multiple actors, musicians, and athletes, and singer Selena Gomez’s account was used by the hackers to post naked photos of her ex-boyfriend Justin Bieber. The company admitted that “we cannot determine which specific accounts may have been impacted”, but believed that “it was a low percentage of Instagram accounts”, though TechCrunch stated in its report that six million accounts were affected by the hack, and that “Instagram services more than 700 million accounts; six million is not a small number”.

In 2019, Apple pulled an app that let users stalk people on Instagram by scraping accounts and collecting data.

Iran has DPI blocking for Instagram.

Content ownership

On December 17, 2012, Instagram announced a change to its Terms of Service policy, adding the following sentence:

To help us deliver interesting paid or sponsored content or promotions, you agree that a business or other entity may pay us to display your username, likeness, photos (along with any associated metadata), and/or actions you take, in connection with paid or sponsored content or promotions, without any compensation to you.

There was no option for users to opt out of the changed Terms of Service without deleting their accounts before the new policy went into effect on January 16, 2013.The move garnered severe criticism from users,prompting Instagram CEO Kevin Systrom to write a blog post one day later, announcing that they would “remove” the offending language from the policy. Citing misinterpretations about its intention to “communicate that we’d like to experiment with innovative advertising that feels appropriate on Instagram”, Systrom also stated that it was “our mistake that this language is confusing” and that “it is not our intention to sell your photos”. Furthermore, he wrote that they would work on “updated language in the terms to make sure this is clear”.

The policy change and its backlash caused competing photo services to use the opportunity to “try to lure users away” by promoting their privacy-friendly services,and some services experienced substantial gains in momentum and user growth following the news.On December 20, Instagram announced that the advertising section of the policy would be reverted to its original October 2010 version.The Verge wrote about that policy as well, however, noting that the original policy gives the company right to “place such advertising and promotions on the Instagram Services or on, about, or in conjunction with your Content”, meaning that “Instagram has always had the right to use your photos in ads, almost any way it wants. We could have had the exact same freakout last week, or a year ago, or the day Instagram launched”

The policy update also introduced an arbitration clause, which remained even after the language pertaining to advertising and user content had been modified.


History of Computers

The computer was born not for entertainment or email but out of a need to solve a serious number-crunching crisis. By 1880, the U.S. population had grown so large that it took more than seven years to tabulate the U.S. Census results. The government sought a faster way to get the job done, giving rise to punch-card based computers that took up entire rooms.

Today, we carry more computing power on our smartphones than was available in these early models. The following brief history of computing is a timeline of how computers evolved from their humble beginnings to the machines of today that surf the Internet, play games and stream multimedia in addition to crunching numbers.

Parts of computer

The computer is one of the most versatile and beneficial inventions for mankind. Its enormous capacity to process data makes it a fundamental part of the development of the world. There are some basic parts of computer that make it possible to process and complete the task at extraordinary speed.


The computer monitor is a significant part, without it the user cannot function the computer. The screen of the monitor allows the user to interact with the computer. The monitor screen is for visual display of all types of information provided by the computer.

The main function of the monitor is obviously visual. As it acts as an interface between the CPU and the user. It doesn’t matter how powerful or fast your computer is, without a monitor display, the computer is incomplete or even useless.

The monitor is designed to display all kinds of information like image, video, symbolic, graphical, etc, as Soft Copy on its screen. A cable is connected with a video adapter that is set up with the computer’s motherboard to display the given data.

Through computer monitors, we can carry out, or view all the important content, review stored information, and do a lot of tasks.


The keyboard is one of the most important parts of computer. The keyboard is designed to input the data by typing letters, symbols, numbers (ABC,123,!@#). The keyboard is used for writing work on the computer.

The shape of the keyboard is rectangular and the buttons are arranged horizontal contain about 108 Keys. These keys allowing us to the entry of information encoded into the computer system by pressing the keys.

The main function of the keyboard is to enter data and information into the computer. The keyboard is a means of communicating with the computer system by the user. By using Keyboard, we can make PPT, spreadsheets, use the Internet, calculations, sending mails, etc, on the monitor screen.


The mouse is an input device also known as a pointing device of a computer. Its main function is to facilitate user interaction with the monitor screen of the computer like the keyboard. A mouse is a device connected to a computer for controlling the cursor on the screen.

The control is detected by the mouse when it is moving it along on the flat surface on which it is located, as well as by pressing the buttons that located on the upper surface of the device and scrolling the wheel, which, as a rule, is located between the control buttons.

In this way, it issues various commands and information to the computer to perform certain actions, that it is interpreted by the CPU and, thus, the mouse pointer imitates the movement on the computer screen.

Some mice types have a Laser Light or some have a rubber ball attached below it. When the mouse moves on a surface, the rubber ball rotates or laser light also moves. The speed and direction of the mouse convert into the monitor’s screen cursor, this is how the mouse works.

The mouse is placed on the Mouse Pad, for controlling the cursor. By Right-Clicking, Left-Clicking, Dragging, scrolling, Double Clicking. By using the mouse, we can do basic tasks on the computer like selecting, opening, deleting the files and folders, etc.


A printer is a device whose main function is to print electronic information like text and images onto paper as a hard copy. In this way, the process of transferring data to hard paper is called printing, and the result is a printout.

The printer prints the files like images, and text stored in a computer, by converting the data from soft copy to hard copy. Printers are used to print signs, printing online images, Excel sheets, PPT, and office documents at offices.

Normally the printer is equipped with a computer with a USB port, LAN, Ethernet, or simply a wireless connection. At present, many printed devices are featured with technologies like Wi-Fi, Cloud, and Bluetooth. Due to this, it becomes easier to complete the printing task by computer.

5.computer case

The computer case is a visible and most important part of computers also known as the computer tower and chassis. It is used to store the main components of a computer like a motherboard with a processor, power supply, a video card, and RAM, hard disks, CPU fans, optical disk drive, memory cards, etc.

A computer tower is not only a “packing box”, but also an important function that provides storage and rigid fixation of all its internal devices. As well as providing them with a power supply and a hard protective structure against internal damage from external influences like dust, liquid, etc.

There are a lot of sizes and models of computer cases, and each type of case is designed to occur storage and perform a specific task.


The computer motherboard is to acts as the main circuit that enables the integration of all components of a computer. Its main function is to connect the different devices, components, or peripherals to the systems to transport the information to the corresponding destination, through this, it facilitates communication between devices.

They are designed based on the type of CPU (central processing unit) in which they will be installed. The motherboard houses the connectors necessary for the processor, RAM, ports, and other devices like video cards, network cards, ROM, processors, power supply, etc.

The main function of the motherboard is communication between the devices that include, control and monitoring, administration, or management of electrical energy as well as its distribution throughout the computer.


The processor is the most important component placed on the motherboard, present in the computer case as a CPU (Central Processing Unit). The processor acts as the brain of the entire operation of the computer system and it is the 4th generation of computer.

The processor unit allows the computer to perform different tasks like processing the data, control the operation of all the computer’s devices, and most importantly performing logical and mathematical operations.

And other actions like controlling the flow of information within the PC, managing and controlling the RAM and ROM memory, and performing basic operations on the computer’s data.

In simple words, it is just processes everything that happens on the computer and executes all the actions. The faster the processor a computer has, the faster the computer will be work.


The hard drive or HDD is one of the computer storage devices that can store any kind of digital information based on magnetic technology. As well a Hard drive is a ROM Memory of computers.

They are used to store the information and data like photos, videos, text small or big files, computer programs storing backup copies of data, like file storage, etc. on our computer system.

The storage capacities of the hard drive disk have now reached 6TB. On such a 6TB hard drive computer is able to can store up to 1,600,000 photos or 615 hours of video and up to 2,000,000 songs.

In this way, it is possible to keep the information stored on such a medium permanently (hence it is not volatile memory). And one of the important parts of computer.

However, a computer user can use other latest storage devices like Pen drive, SSD, Memory card, etc.


The RAM’s full form is ‘Random Access Memory’. RAM is a type of operative memory of computer systems. The ROM memory is used to store data but in the case of RAM memory is used to run the whole computer system in real-time.

Like the processor, RAM is inserted into the motherboard for communication with various elements of the system. RAM runs the software like computer programs, games, software applications, and other information in (CPU) the central processing unit for direct and quick access when needed to perform tasks.

RAM is the fastest type of memory, and it has the ability to be read and write the data but temporarily until the Power Supply to the device. Because as the computer is turned off, all the processed data of RAM automatically goes to the trash.

Nowadays the maximum capacity of RAM is up to 32 GB that is specially made for gaming computers.


Computer speakers are a way that computers make sounds by means of digital or analog audio. In other terms, the speaker is also called the ‘dynamic head’. This speaker can now be found on many other devices, like, on a TV, radio, smartphone, telephone, children’s toys, and others.

The main function of speakers is a way for computers to interact with their users. These provide a means for the computer to produce audio. The sound produced by computer speakers is done by a hardware component whose name is a sound card that is pre-installed with the computer.

The speaker is important because for listening to the audios and sounds fo the videos and games which is significant for a computer user to perform all kinds of tasks on the computer.

However, in order to increase the sound of the computer in a louder way one may need external speakers. Alternatives to the speaker for computers are headphones, earphones, earbuds, etc.

Uses of computer


* Playing computer games
* Writing
* Solving math problems
* Watching videos
* Listening to music and audio
* Audio, Video and photo editing
* Creating sound or video
* Communicating with other people
* Using The Internet
* Online shopping
* Drawing
* Online bill payments
* online business


* Word processing
* Spreadsheets
* Presentations
* Photo Editing
* E-mail
* Video editing/rendering/encoding
* Audio recording
* System Management
* Website Development
* Software Development


The modern Olympic Games or Olympics (French: Jeux olympiques)are leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a variety of competitions. The Olympic Games are considered the world’s foremost sports competition with more than 200 nations participating.The Olympic Games are normally held every four years, alternating between the Summer and Winter Olympics every two years in the four-year period.

Their creation was inspired by the ancient Olympic Games (Ancient Greek: Ὀλυμπιακοί Ἀγῶνες), held in Olympia, Greece from the 8th century BC to the 4th century AD. Baron Pierre de Coubertin founded the International Olympic Committee (IOC) in 1894, leading to the first modern Games in Athens in 1896. The IOC is the governing body of the Olympic Movement,[definition needed] with the Olympic Charter defining its structure and authority.

The evolution of the Olympic Movement during the 20th and 21st centuries has resulted in several changes to the Olympic Games. Some of these adjustments include the creation of the Winter Olympic Games for snow and ice sports, the Paralympic Games for athletes with disabilities, the Youth Olympic Games for athletes aged 14 to 18, the five Continental games (Pan American, African, Asian, European, and Pacific), and the World Games for sports that are not contested in the Olympic Games. The IOC also endorses the Deaflympics and the Special Olympics. The IOC has needed to adapt to a variety of economic, political, and technological advancements. The abuse of amateur rules by the Eastern Bloc nations prompted the IOC to shift away from pure amateurism, as envisioned by Coubertin, to the acceptance of professional athletes participating at the Games. The growing importance of mass media has created the issue of corporate sponsorship and general commercialisation of the Games. World wars led to the cancellation of the 1916, 1940, and 1944 Olympics; large-scale boycotts during the Cold War limited participation in the 1980 and 1984 Olympics; and the 2020 Olympics were postponed until 2021 as a result of the COVID-19 pandemic.

The Olympic Movement consists of international sports federations (IFs), National Olympic Committees (NOCs), and organising committees for each specific Olympic Games. As the decision-making body, the IOC is responsible for choosing the host city for each Games, and organises and funds the Games according to the Olympic Charter. The IOC also determines the Olympic programme, consisting of the sports to be contested at the Games. There are several Olympic rituals and symbols, such as the Olympic flag and torch, as well as the opening and closing ceremonies. Over 14,000 athletes competed at the 2016 Summer Olympics and 2018 Winter Olympics combined, in 35 different sports and over 400 events.The first, second, and third-place finishers in each event receive Olympic medals: gold, silver, and bronze, respectively.

The Games have grown so much that nearly every nation is now represented. This growth has created numerous challenges and controversies, including boycotts, doping, bribery, and a terrorist attack in 1972. Every two years the Olympics and its media exposure provide athletes with the chance to attain national and sometimes international fame. The Games also provide an opportunity for the host city and country to showcase themselves to the world


The Olympic Movement uses symbols to represent the ideals embodied in the Olympic Charter. The Olympic symbol, better known as the Olympic rings, consists of five intertwined rings and represents the unity of the five inhabited continents (Africa, The Americas (is considered one continent), Asia, Europe, and Oceania). The coloured version of the rings—blue, yellow, black, green, and red—over a white field forms the Olympic flag. These colours were chosen because every nation had at least one of them on its national flag. The flag was adopted in 1914 but flown for the first time only at the 1920 Summer Olympics in Antwerp, Belgium. It has since been hoisted during each celebration of the Games.

The Olympic motto, Citius, Altius, Fortius, a Latin expression meaning “Faster, Higher, Stronger” was proposed by Pierre de Coubertin in 1894 and has been official since 1924. The motto was coined by Coubertin’s friend, the Dominican priest Henri Didon OP, for a Paris youth gathering of 1891.[143]

Coubertin’s Olympic ideals are expressed in the Olympic creed:

The most important thing in the Olympic Games is not to win but to take part, just as the most important thing in life is not the triumph but the struggle. The essential thing is not to have conquered but to have fought well.

Months before each Games, the Olympic Flame is lit at the Temple of Hera in Olympia in a ceremony that reflects ancient Greek rituals. A female performer, acting as a priestess joined by ten female performers as Vestal Virgins, ignites a torch by placing it inside a parabolic mirror which focuses the sun’s rays; she then lights the torch of the first relay bearer, thus initiating the Olympic torch relay that will carry the flame to the host city’s Olympic stadium, where it plays an important role in the opening ceremony.[144] Though the flame has been an Olympic symbol since 1928, the torch relay was only introduced at the 1936 Summer Games to promote the Third Reich.

The Olympic mascot, an animal or human figure representing the cultural heritage of the host country, was introduced in 1968. It has played an important part of the Games’ identity promotion since the 1980 Summer Olympics, when the Soviet bear cub Misha reached international stardom. The mascot of the Summer Olympics in London was named Wenlock after the town of Much Wenlock in Shropshire. Much Wenlock still hosts the Wenlock Olympian Games, which were an inspiration to Pierre de Coubertin for the Olympic Games.

The Ancient Olympic Games

The history of the Olympics began some 2,300 years ago. Their origin lays in the Olympian Games, which were held in the Olympia area of ancient Greece. Although there are some theories on its initial purposes, the Games have been said to have started as a festival of art and sport, to worship gods. The ancient Olympic Games, however, ended in 393 because of the outbreaks of wars in the region in which they were held.

The Modern Olympic Games

After a 1,500 year absence of the ancient Olympic Games, the event was resumed in the late nineteenth century, thanks to the efforts of Baron Pierre de Coubertin, a French educator. In 1894, his proposal to revive the Olympic Games was unanimously approved at the International Congress in Paris, and the first Olympic Games were held in Athens, Greece, two years later. He also devised the five-ring emblem that is familiar to most people as the Games’ symbol, which represents the unity of the five continents.

The Olympic Games in Japan

The “Father of the Olympic Movement” in Japan is Jigoro Kano – a man who also contributed to the propagation of judo – who was the president of the Tokyo Higher Normal School (the present day University of Tsukuba). In 1909, he was appointed a member of the International Olympic Committee for the first time as an Asian and established the Japan Amateur Athletic Association (today’s Japan Sports Association) to realize the participation of Japanese athletes in the Olympics. The selection of athletes for the Olympics was carried out in 1911, when Yahiko Mishima, a track athlete, and Shiso Kanaguri, a marathon runner, were chosen to represent Japan. Japanese athletes participated in the Olympic Games (the V Olympic Games) for the first time in Stockholm, Sweden in 1912.


Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larva that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.

Scientific classification

Kingdom : Animalia
Phylum : Cnidaria
Subphylum : Medusozoa

Groups included

Cubozoa—box jellyfish
Scyphozoa—true jellyfish
Staurozoa—stalked jellyfish
*some Hydrozoa—small jellyfish

Cladistically included but traditionally excluded taxa

* some Hydrozoa, such as Hydra

Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the “true jellyfish”) are exclusively marine, but some hydrozoans with a similar appearance live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years,and possibly 700 million years or more, making them the oldest multi-organ animal group.

Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomae order are pressed and salted to remove excess water. Australian researchers have described them as a “perfect food”, sustainable, and protein-rich but relatively low in food energy.

They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.

The stinging cells used by jellyfish to subdue their prey can injure humans. Many thousands of swimmers are stung every year, with effects ranging from mild discomfort to serious injury or even death; small box jellyfish are responsible for many of these deaths. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.


The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies (ctenophores, another phylum).The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word “fish” with its modern connotation of an animal with a backbone, though shellfish, cuttlefish and starfish are not vertebrates either. In scientific literature, “jelly” and “jellyfish” have been used interchangeably.Many sources refer to only scyphozoans as “true jellyfish”.

A group of jellyfish is called a “smack”.


* Some jellyfish can glow in the dark.

* Jellyfish are the oldest multi-organ animal.

* Jellyfish don’t have brains.

* Jellyfish are found all over the world.

* Some jellyfish are immortal.

* Not all jellyfish have tentacles.

* There’s a giant jellyfish called the hair jelly.

* Jellyfish stings can be deadly.

* 150 million people are stung by jellyfish each year.

* Jellyfish have many predators.


1.Crystal Jellyfish

Coming in at number one is the Crystal jellyfish. Located in the waters around North America’s coast, this jellyfish species is actually completely colorless, hence its name! This beautiful specimen has around 150 tentacles lining its glass-like bell and in the daylight looks crystal clear. Although, this transparency belies a brighter side.

2.Bloodybelly Comb Jellyfish

Ranking high in the charts for the coolest and beautiful jelly-fish, is our next contender, the Bloodybelly Comb jellies, which, technically speaking are comb jellies and are only very distantly related to the jellyfish. This one doesn’t have the famous jellyfish stinging tentacles that others possess, and it is actually a harmless Comb jelly to humans.

Red looks very much like black in the depths of the ocean and specifically, the red belly of this Bloodybelly comb also helps to mask the bioluminescence glow of its prey and keeps it extra safe from the attention of its predators.

3.Cauliflower Jellyfish

Getting its name from the wart-like projections this type has on its bell resembling that of a vegetable, we give you the Cauliflower jellyfish also referred to as the Crown jellyfish! While this jelly may not sound the prettiest of its species, it is still a truly beautiful species of jellyfish.

Very much like its vegetable nickname, this kind is often also found on dinner plates! Mostly in China and Japan where the species is considered to be a delicacy and is also known to be used for medicinal purposes within these locations.

4. White-spotted Jellyfish

At number four on, we have the White-spotted jellyfish. These jellies have very mild venom and therefore any jellyfish stings from its stinging cells are harmless to us humans. In fact, the white-spotted jelly doesn’t generally even use their venom to catch food at all!

5. Black Sea Nettle Jellyfish

Next, one of the largest jellyfish (the largest jellyfish is the Lion Mane jellyfish) is the Black Sea Nettles jellyfish! This particular species can be found in the deep sea Pacific waters around Southern California.

The bell of the Black Sea Nettles can reach up to three-foot across, its long tentacles reach up to 20 feet in length, and its stinging tentacles 25 feet long. Without saying, it would be pretty damn scary if you caught yourself in the middle of a bloom of these giants while in the water, but don’t worry too much as they are not that common to a lot of ocean waters.


The Moon is Earth’s only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia),[15] it is the largest natural satellite in the Solar System relative to the size of its planet,[f] the fifth largest satellite in the Solar System overall, and is larger than any known dwarf planet. Orbiting Earth at an average distance of 384,400 km (238,900 mi),[16] or about 30 times Earth’s diameter, its gravitational influence slightly lengthens Earth’s day and is the main driver of Earth’s tides. The Moon is classified as a planetary-mass object and a differentiated rocky body, and lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth’s (0.1654 g); Jupiter’s moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.


Designation – Earth I
Alternative names – LunaSelene (poetic)


Adjectives – Lunar

Selenian (poetic)

Cynthian (poetic)

Moonly (poetic)

Orbital characteristics

Perigee 362600 km
(356400–370400 km)

Apogee 405400 km
(404000–406700 km)

Semi-major axis 384399 km (1.28 ls, 0.00257 AU)

Eccentricity 0.059

Orbital period 27.321661 d
(27 d 7 h 43 min 11.5 s[1])

Synodic period 29.530589 d
(29 d 12 h 44 min 2.9 s)

Average orbital speed 1.022 km/s

Longitude of Regressing by one revolution in

ascending node 18.61 years

Satellite of Earth

Physical characteristics

Mean radius 1737.4 km
(0.2727 of Earth’s)

Equatorial radius 1738.1 km
(0.2725 of Earth’s)

Polar radius 1736.0 km
(0.2731 of Earth’s)

Flattening 0.0012

Circumference 10921 km (equatorial)

Surface area 3.793×107 km2
(0.074 of Earth’s)

Volume 2.1958×1010 km3
(0.020 of Earth’s)

Mass 7.342×1022 kg
(0.012300 of Earth’s)

Surface gravity 1.62 m/s2


Surface pressure 10−7 Pa (1 picobar) (day)
10−10 Pa (1 femtobar) (night)

Composition by volume He,Ar,Ne,Na,K,Hi,Rn

The Moon’s orbit around Earth has a sidereal period of 27.3 days. During each synodic period of 29.5 days, the amount of visible surface illuminated by the Sun varies from none up to 100%, resulting in lunar phases that form the basis for the months of a lunar calendar. The Moon is tidally locked to Earth, which means that the length of a full rotation of the Moon on its own axis causes its same side (the near side) to always face Earth, and the somewhat longer lunar day is the same as the synodic period. That said, 59% of the total lunar surface can be seen from Earth through shifts in perspective due to libration

The most widely accepted origin explanation posits that the Moon formed about 4.51 billion years ago, not long after Earth, out of the debris from a giant impact between the planet and a hypothesized Mars-sized body called Theia. It then receded to a wider orbit because of tidal interaction with the Earth. The near side of the Moon is marked by dark volcanic maria (“seas”), which fill the spaces between bright ancient crustal highlands and prominent impact craters. Most of the large impact basins and mare surfaces were in place by the end of the Imbrian period, some three billion years ago. The lunar surface is relatively non-reflective, with a reflectance just slightly brighter than that of worn asphalt. However, because it has a large angular diameter, the full moon is the brightest celestial object in the night sky. The Moon’s apparent size is nearly the same as that of the Sun, allowing it to cover the Sun almost completely during a total solar eclipse.

Both the Moon’s prominence in the earthly sky and its regular cycle of phases have provided cultural references and influences for human societies throughout history. Such influences can be found in language, calendar systems, art, and mythology. The first artificial object to reach the Moon was the Soviet Union’s Luna 2 uncrewed spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States’ Apollo program, which landed twelve men on the surface between 1969 and 1972. These and later uncrewed missions returned lunar rocks that have been used to develop a detailed geological understanding of the Moon’s origins, internal structure, and subsequent history.


1. The Moon is Earth’s only permanent natural satellite

It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits.

2. The Moon is the second-densest satellite

Among those whose densities are known anyway. The first densest is Jupiter’s satellite Io.

3. The Moon always shows Earth the same face

The Moon is in synchronous rotation with Earth. Its near side is marked by large dark plains (volcanic ‘maria’) that fill the spaces between the bright ancient crustal highlands and the prominent impact craters.

4. The Moon’s surface is actually dark

Although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day.

5. The Sun and the Moon are not the same size

From Earth, both the Sun and the Moon look about same size. This is because, the Moon is 400 times smaller than the Sun, but also 400 times closer to Earth.

6. The Moon is drifting away from the Earth

The Moon is moving approximately 3.8 cm away from our planet every year.

7. The Moon was made when a rock smashed into Earth

The most widely-accepted explanation is that the Moon was created when a rock the size of Mars slammed into Earth, shortly after the solar system began forming about 4.5 billion years ago.

8. The Moon makes the Earth move as well as the tides

Everyone knows that the Moon is partly responsible for causing the tides of our oceans and seas on Earth, with the Sun also having an effect. However, as the Moon orbits the Earth it also causes a tide of rock to rise and fall in the same way as it does with the water. The effect is not as dramatic as with the oceans but nevertheless, it is a measurable effect, with the solid surface of the Earth moving by several centimetres with each tide.

9. The Moon has quakes too

They’re not called earthquakes but moonquakes. They are caused by the gravitational influence of the Earth. Unlike quakes on Earth that last only a few minutes at most, moonquakes can last up to half an hour. They are much weaker than earthquakes though.

10. There is water on the Moon!

This is in the form of ice trapped within dust and minerals on and under the surface. It has been detected on areas of the lunar surface that are in permanent shadow and are therefore very cold, enabling the ice to survive. The water on the Moon was likely delivered to the surface by comets.


Human eye, in humans, specialized sense organ capable of receiving visual images, which are then carried to the brain.

Anatomy of the visual apparatus

Structures auxiliary to the eye

The orbit

The eye is protected from mechanical injury by being enclosed in a socket, or orbit, which is made up of portions of several of the bones of the skull to form a four-sided pyramid, the apex of which points back into the head. Thus, the floor of the orbit is made up of parts of the maxilla, zygomatic, and palatine bones, while the roof is made up of the orbital plate of the frontal bone and, behind this, by the lesser wing of the sphenoid. The optic foramen, the opening through which the optic nerve runs back into the brain and the large ophthalmic artery enters the orbit, is at the nasal side of the apex; the superior orbital fissure is a larger hole through which pass large veins and nerves. These nerves may carry nonvisual sensory messages—e.g., pain—or they may be motor nerves controlling the muscles of the eye. There are other fissures and canals transmitting nerves and blood vessels. The eyeball and its functional muscles are surrounded by a layer of orbital fat that acts much like a cushion, permitting a smooth rotation of the eyeball about a virtually fixed point, the centre of rotation. The protrusion of the eyeballs—proptosis—in exophthalmic goitre is caused by the collection of fluid in the orbital fatty tissue.

The eyelids

It is vitally important that the front surface of the eyeball, the cornea, remain moist. This is achieved by the eyelids, which during waking hours sweep the secretions of the lacrimal apparatus and other glands over the surface at regular intervals and which during sleep cover the eyes and prevent evaporation. The lids have the additional function of preventing injuries from foreign bodies, through the operation of the blink reflex. The lids are essentially folds of tissue covering the front of the orbit and, when the eye is open, leaving an almond-shaped aperture. The points of the almond are called canthi; that nearest the nose is the inner canthus, and the other is the outer canthus. The lid may be divided into four layers: (1) the skin, containing glands that open onto the surface of the lid margin, and the eyelashes; (2) a muscular layer containing principally the orbicularis oculi muscle, responsible for lid closure; (3) a fibrous layer that gives the lid its mechanical stability, its principal portions being the tarsal plates, which border directly upon the opening between the lids, called the palpebral aperture; and. (4) the innermost layer of the lid, a portion of the conjunctiva. The conjunctiva is a mucous membrane that serves to attach the eyeball to the orbit and lids but permits a considerable degree of rotation of the eyeball in the orbit.

The conjunctiva

The conjunctiva lines the lids and then bends back over the surface of the eyeball, constituting an outer covering to the forward part of this and terminating at the transparent region of the eye, the cornea. The portion that lines the lids is called the palpebral portion of the conjunctiva; the portion covering the white of the eyeball is called the bulbar conjunctiva. Between the bulbar and the palpebral conjunctiva there are two loose, redundant portions forming recesses that project back toward the equator of the globe. These recesses are called the upper and lower fornices, or conjunctival sacs; it is the looseness of the conjunctiva at these points that makes movements of lids and eyeball possible.

The fibrous layer

The fibrous layer, which gives the lid its mechanical stability, is made up of the thick, and relatively rigid, tarsal plates, bordering directly on the palpebral aperture, and the much thinner palpebral fascia, or sheet of connective tissue; the two together are called the septum orbitale. When the lids are closed, the whole opening of the orbit is covered by this septum. Two ligaments, the medial and lateral palpebral ligaments, attached to the orbit and to the septum orbitale, stabilize the position of the lids in relation to the globe. The medial ligament is by far the stronger.

The skin

The outermost layer of the lid is the skin, with features not greatly different from skin on the rest of the body, with the possible exception of large pigment cells, which, although found elsewhere, are much more numerous in the skin of the lids. The cells may wander, and it is these movements of the pigment cells that determine the changes in coloration seen in some people with alterations in health. The skin has sweat glands and hairs. As the junction between skin and conjunctiva is approached, the hairs change their character to become eyelashes.

The glandular apparatus

The eye is kept moist by secretions of the lacrimal glands (tear glands). These almond-shaped glands under the upper lids extend inward from the outer corner of each eye. Each gland has two portions. One portion is in a shallow depression in the part of the eye socket formed by the frontal bone. The other portion projects into the back part of the upper lid. The ducts from each gland, three to 12 in number, open into the superior conjunctival fornix, or sac. From the fornix, the tears flow down across the eye and into the puncta lacrimalia, small openings at the margin of each eyelid near its inner corner. The puncta are openings into the lacrimal ducts; these carry the tears into the lacrimal sacs, the dilated upper ends of the nasolacrimal ducts, which carry the tears into the nose.

The evaporation of the tears as they flow across the eye is largely prevented by the secretion of oily and mucous material by other glands. Thus, the meibomian, or tarsal glands, consist of a row of elongated glands extending through the tarsal plates; they secrete an oil that emerges onto the surface of the lid margin and acts as a barrier for the tear fluid, which accumulates in the grooves between the eyeball and the lid barriers.


General description

The eyeball is not a simple sphere but can be viewed as the result of fusing a small portion of a small, strongly curved sphere with a large portion of a large, not so strongly curved sphere. The small piece, occupying about one-sixth of the whole, has a radius of 8 mm (0.3 inch); it is transparent and is called the cornea; the remainder, the scleral segment, is opaque and has a radius of 12 mm (0.5 inch). The ring where the two areas join is called the limbus. Thus, on looking directly into the eye from in front one sees the white sclera surrounding the cornea; because the latter is transparent one sees, instead of the cornea, a ring of tissue lying within the eye, the iris. The iris is the structure that determines the colour of the eye. The centre of this ring is called the pupil. It appears dark because the light passing into the eye is not reflected back to any great extent. By use of an ophthalmoscope, an instrument that permits the observer to illuminate the interior of the eyeball while observing through the pupil, the appearance of the interior lining of the globe can be made out. Called the fundus oculi, it is characterized by the large blood vessels that supply blood to the retina; these are especially distinct as they cross over the pallid optic disk, or papilla, the region where the optic nerve fibres leave the globe.

The dimensions of the eye are reasonably constant, varying among normal individuals by only a millimetre or two; the sagittal (vertical) diameter is about 24 mm (about one inch) and is usually less than the transverse diameter. At birth the sagittal diameter is about 16 to 17 mm (about 0.65 inch), it increases rapidly to about 22.5 to 23 mm (about 0.89 inch) by the age of three years, and between age three and 13 the globe attains its full size. The weight is about 7.5 grams (0.25 ounce) and its volume about 6.5 cm3 (0.4 cubic inch).

The retina

The retina is the part of the eye that receives the light and converts it into chemical energy. The chemical energy activates nerves that conduct the messages out of the eye into the higher regions of the brain. The retina is a complex nervous structure, being, in essence, an outgrowth of the forebrain.

Ten layers of cells in the retina can be seen microscopically. In general, there are four main layers: (1) Next to the choroid is the pigment epithelium, already mentioned. (2) Above the epithelium is the layer of rods and cones, the light-sensitive cells. The changes induced in the rods and cones by light are transmitted to (3) a layer of neurons (nerve cells) called the bipolar cells. These bipolar cells connect with (4) the innermost layer of neurons, the ganglion cells; and the transmitted messages are carried out of the eye along their projections, or axons, which constitute the optic nerve fibres. Thus, the optic nerve is really a central tract, rather than a nerve, connecting two regions of the nervous system, namely, the layer of bipolar cells, and the cells of the lateral geniculate body, the latter being a visual relay station in the diencephalon (the rear portion of the forebrain).

Importance of Eye Care

Your eyesight is one of your most important senses: 80% of what we perceive comes through our sense of sight. By protecting your eyes, you will reduce the odds of blindness and vision loss while also staying on top of any developing eye diseases such as cataracts and glaucoma.

Eye Health = Brain Health

Healthy brain function needs healthy eyesight. The brain is our most vital organ, allowing us to live complex lives. Considering that your optic nerve connects your eyes and your brain, a healthy co-dependent relationship is necessary. By keeping your eyes healthy, you keep your brain healthy – improving your overall quality of life!

Good vision contributes to improved athletic ability, better driving skills, improved learning and comprehension and better quality of life.

Your future can be colorful and full of life just by making sure you see your optometrist as recommended. The experienced eye doctors at Medical Eye Associates in Medford are ready to help you preserve and protect your vision. Contact them today at 800-824-2688 or medicaleycenter.com to schedule an eye exam.


A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological function.The Food and Agriculture Organization defines a forest as land spanning more than 0.5 hectares with trees higher than 5 meters and a canopy cover of more than 10 percent, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban land use.Using this definition FRA 2020 found that forests covered 4.06 billion hectares or approximately 31 percent of the global land area in 2020.

Forests are the predominant terrestrial ecosystem of Earth, and are distributed around the globe. More than half of the world’s forests are found in only five countries (Brazil, Canada, China, Russian Federation and United States of America). The largest part of the forest (45 percent) is found in the tropical domain (Tropical forests), followed by the boreal, temperate and subtropical domains.

Forests account for 75% of the gross primary production of the Earth’s biosphere, and contain 80% of the Earth’s plant biomass. Net primary production is estimated at 21.9 gigatonnes carbon per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.


1.Equatorial Moist Evergreen or Rainforest:


This evergreen hardwood forest is the natural vegetation of low-latitude high precipitation zone. This vegetation generally occur in between 10° N. and S. of equator where annual rainfall is very high and distributed equitably throughout the year. The total extent of tropical rainforest was 714 million hectares in 1990, which is half of the world’s forest cover.

Spatially, this forest is distributed in three separate regions:

(a) South American Amazonia basin:

This region is confined between Amazon River in the east to the foothills of the Andes in the west and Orinoco river basin in the north to Mardira River in the south.

(b) Equatorial Africa:

Mostly occur in Equatorial Africa including Zaire and Congo.

(c) Asia:Some parts of Western India and Sri Lanka

(d) South-East Asia:

Found in Indonesia, Malaysia, and Philippines etc.

The uses of forest resources in different economic activities are:

A. Teak and Mahogany are widely used in furniture industry.

B. Wood collected from forest is used as fuel.

C. (a) Brazil nut is rich in protein.

(b) Tagua nut is used for button-making.

(c) Barasu is an important raw material to produce soap and margarin.

(d) The milky juice of zopota tree is chickle which is converted to chewing gum.

(e) Wild rubber can be collected from rubber trees.

(f) Balata gathered from this forest is used for cable-making and other industrial purpose.

(g) Babassu palm nut is used in paint industry.

(h) Cohune nuts for perfume manufacturing,

(i) Toquilla palm for hat making.

2.Tropical Deciduous Forest:


In tropical monsoon region where rainfall is seasonal and a definite dry season exists, this deciduous and semi-evergreen forests are prevalent. Unlike Equatorial region, here variation of trees in different regions are much more.

This type of vegetation occurs in:

(a) India, Myanmar (Burma), Indonesia, Thailand, Laos, Cambodia, South China, Phil­ippines etc.

(b) Northern Australia.

(c) Margins of tropical rainforest in Africa.

(d) Central South America.

Characteristics of Vegetation:

(i) Most of the tress are broadleaved and provide hardwood variety.

(ii) Trees are so heavy that in most cases they do not float in water.

(iii) Several layers are visible in forest, according to height of the trees. Trees with height of 50 meters to 10 meters are common.

(iv) Wide variety of climbers, creepers, parasites, epiphytes and saprophytes are com­mon.

(v) No dominance of single species — as trees are intermingled with one another.

(vi) Thick undergrowth of shrubs, bushes and bamboos are common.

(vii) Swampy, marshy areas exhibit mangrove forests, e.g. Sundarban in West Bengal.

3.Mediterranean Forests:


Primarily found in the Mediterranean climate within 35°-45° North and South of the equator.

It is a peculiar climo-floral development found in several areas:

(a) Adjacent regions of Mediterranean coast, extending east-west over 2,500 kms cov­ering countries like Portugal, Spain, France, Italy, Albania, Greece, Turkey etc.

(b) California in U.S.A. of N. America.

(c) Central Chile of S. America.

(d) S-E and southern parts of Australia.

(e) Cape region of South Africa.

Important among these are:

1. Trees are covered by hairs, e.g. Olive trees.

2. Leaves are very thick and skin-like, e.g. Bolen trees.

3. Some trees may adopt wax layers in the leaves.

4. Barks are very thick, e.g. cork and oak.

5. Roots are very long, e.g. grapes.

Beside these characteristics, some trees like lavender, rose-merry etc.. are orchids and dis­tinctly different from others.

Economic Importance:

1. Large trees are rare. Trees are isolated. So lumbering industry is limited.

2. The barks of cork and oak are used to produce caps of the bottles.

3. Lavender and rose-merry trees produce perfumes.

4. Olive oil is extracted from olive trees.

5. Wine is produced from grapes.

4.Temperate Broad-leaved Deciduous and Mixed Forest:


In the eastern side of the continents, in warm temperate region, this forest is located in:

(i) South China.

(ii) South Japan.

(iii) South Africa.

(iv) South-East Australia.

(v) South Brazil.

Climatic Characteristics:

1. Rainfall all the year, minimum annual temperature over 10°C.

2. Due to heavy rainfall, evenly distributed throughout the year, trees are evergreen, broad-leaved and hard-wood type.

Major Species:

1. Koebrack in South-East Brazil.

2. Deodar.

3. Eucalyptus.

5.Warm Temperate Broad-leaved Deciduous Forest:


In warm temperate region, where temperature remains above 6°C at least 6 months of the year. This forest developed in central and north-west China, Korea, Japan, New Zealand and Tasmania.


1. Trees shed their leaves during spring.

2. No layer in the leaves.

Major Species:

Elm, Beach, Maple, Walnut etc.


1. As same type of trees are concentrated in different regions, wood collection is easier.

2. Wood transportation is also easier.

3. As there is very little undergrowth, collection of forest product is much easier.


1.They let us breathe!

2.They cool the Earth

3.They keep people cool too

4.Forests can make it rain

5.They block wind

6.Forests clean the air

7.They fight erosion

8.They provide medicine

9.They provide food

10.Forests create jobs


The term “air” refers generally to gas, but exactly which gas depends on the context in which the term is used. Let’s learn about the modern definition of air in scientific disciplines and the earlier definition of the term.


Air is the general name for the mixture of gases that makes up the Earth’s atmosphere. This gas is primarily nitrogen (78%), mixed with oxygen (21%), water vapor (variable), argon (0.9%), carbon dioxide (0.04%), and trace gases. Pure air has no discernible scent and no color. Air typically contains dust, pollen, and spores; other contaminants are referred to as “air pollution.” On another planet—Mars, for example—the so-called air would have a different composition since there is technically no air in space.


Air is also an early chemical term for a type of gas. In the older definition, many individual types of so-called air made up the air we breathe: Vital air was later determined to be oxygen; what was called phlogisticated air turned out to be nitrogen. An alchemist might refer to any gas released by a chemical reaction as its “air.”


Air masses are classified into groups depending on their basic temperature and humidity characteristics.

There are six main types of air masses that affect the British Isles. We classify these air masses primarily by the area in which they originate.

They are classified as continental or maritime – dependent on whether they originate over land or sea – and arctic or antarctic, equatorial, tropical, or polar, depending on the particular region in which they form.

There are a total of six air masses that affect the British Isles, they are classified as follows:

Tropical continental

This air mass originates over North Africa and the Sahara (a warm source region). It is most common during the summer months June, July and August, although it can occur at other times of the year.

Our highest temperatures usually occur under the influence of tropical continental air (over 30 °C by day and around 15 to 20 °C at night).

Visibility is usually moderate or poor due to the air picking up pollutants during its passage over Europe and from sand particles blown into the air from Saharan dust storms. Occasionally, the Saharan dust is washed out in showers producing coloured rain and leaving cars covered in a thin layer of orange dust.

Tropical maritime

The source region for this air mass is warm waters of the Atlantic Ocean between the Azores and Bermuda. The predominant wind direction across the British Isles, in a tropical maritime air mass, is south-westerly.

Tropical maritime air is warm and moist in its lowest layers and, although unstable over its source region, during its passage over cooler waters becomes stable and the air becomes saturated. Consequently when a tropical maritime air mass reaches the British Isles it brings with it low cloud and drizzle, perhaps also fog around windward coasts and across hills. To the lee of high ground though, the cloud my break up and here the weather, particularly in the summer months, can be fine and sunny.

This is a mild air stream and during the winter month in particular, can raise the air temperature several degrees above the average.

Polar continental

This air mass has its origins over the snow fields of Eastern Europe and Russia and is only considered a winter (November to April) phenomena.

The weather characteristics of this air mass depend on the length of the sea track during its passage from Europe to the British Isles: this air is inherently very cold and dry and if it reaches southern Britain with a short sea track over the English Channel, the weather is characterised by clear skies and severe frosts. With a longer sea track over the North Sea, the air becomes unstable and moisture is added giving rise to showers of rain or snow, especially near the east coast of Britain.

The lowest temperatures across the British Isles usually occur in this air mass, lower than -10 °C at night, and sometimes remaining below freezing all day.

Polar maritime

This air mass has its origins over northern Canada and Greenland and reaches the British Isles on a north-westerly air stream.

This air mass is characterised by frequent showers at any time of the year. In the winter months when instability (convection) is most vigorous over the sea, hail and thunder are common across much of the western and northern side of the British Isles. However, eastern Britain may see fewer showers as here the surface heating is reduced. During the summer, the reverse is true, land temperatures are higher than sea temperatures and the heaviest showers occur over eastern England.

Arctic maritime

An arctic maritime air mass has similar characteristics to a polar maritime air mass, but because of the shorter sea track the air is colder and less moist.

Arctic air is uncommon during the summer, but when it does occur it may bring heavy showers or thunderstorms and unseasonably low temperature.

An arctic maritime air mass has its origins over the North Pole and the Arctic Ocean.

Polar low-pressure systems forming in this air mass can sometimes lead to widespread and heavy snowfall, but otherwise inland areas remain free of cloud in the winter months. In northern Scotland, arctic maritime is usually the coldest air mass, but over the rest of Britain, this air mass is not as cold as polar continental.

Returning polar maritime

Returning polar maritime is another version of polar maritime, but this time with a longer sea track which takes the air first southwards over the North-Atlantic, the north-eastwards across the British isles.

During its passage south, the air becomes unstable and moist but on moving north-east it passes over cooler water making it stable in its lowest layers.

Although the weather across the British Isles in this air mass is largely dry, there can be extensive cloud cover.


Air is a natural resource and is available abundantly. It is an essential element of nature that support life on earth. Air is equally important for living organisms for their survival just like water. Air is very useful and has many applications. Uses of air are as follows:

* Sustain life and growth
* Combustion
* Maintaining Temperature
* Supplier of Energy
* Photosynthesis

Sustain Life and Growth

Oxygen present in the air is one of the main life-sustaining gas. All living things breathe in and breathe out the air in the form of oxygen and carbon dioxide. Nitrogen and Carbon dioxide are vital for plants and their growth.


Another use of air is that it supports burning or combustion. The oxygen present in air help in the burning of the fuels leads to carry out activities like cooking food, running industries, and vehicles as well as generating heat and electricity.

Temperature Control

Air helps in maintaining the temperature on the earth’s surface by circulating hot and cold air. Air acts as a conductor of heat. The phenomena of the water cycle are also dependent on air.

Supplier of Energy

Air which consists of energy is one of the main suppliers of energy. Living things are made up of cells and these cells extract oxygen within the blood to produce energy in the form of ATP. The generation of ATP which is biochemical in nature is essential to maintain life on the Earth.


Carbon dioxide which is also a component of air is used by plants during the process of photosynthesis and oxygen, water vapor is released by plants as a by-product.

Apart from these gases, other gases are also useful such as nitrogen is used in the production of ammonia.


water, a substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A tasteless and odourless liquid at room temperature, it has the important ability to dissolve many other substances. Indeed, the versatility of water as a solvent is essential to living organisms. Life is believed to have originated in the aqueous solutions of the world’s oceans, and living organisms depend on aqueous solutions, such as blood and digestive juices, for biological processes. Water also exists on other planets and moons both within and beyond the solar system. In small quantities water appears colourless, but water actually has an intrinsic blue colour caused by slight absorption of light at red wavelengths.

Although the molecules of water are simple in structure (H2O), the physical and chemical properties of the compound are extraordinarily complicated, and they are not typical of most substances found on Earth. For example, although the sight of ice cubes floating in a glass of ice water is commonplace, such behaviour is unusual for chemical entities. For almost every other compound, the solid state is denser than the liquid state; thus, the solid would sink to the bottom of the liquid. The fact that ice floats on water is exceedingly important in the natural world, because the ice that forms on ponds and lakes in cold areas of the world acts as an insulating barrier that protects the aquatic life below. If ice were denser than liquid water, ice forming on a pond would sink, thereby exposing more water to the cold temperature. Thus, the pond would eventually freeze throughout, killing all the life-forms present.

Water occurs as a liquid on the surface of Earth under normal conditions, which makes it invaluable for transportation, for recreation, and as a habitat for a myriad of plants and animals. The fact that water is readily changed to a vapour (gas) allows it to be transported through the atmosphere from the oceans to inland areas where it condenses and, as rain, nourishes plant and animal life. (See hydrosphere: The hydrologic cycle for a description of the cycle by which water is transferred over Earth.)

The water on the surface of Earth is found mainly in its oceans (97.25 percent) and polar ice caps and glaciers (2.05 percent), with the balance in freshwater lakes, rivers, and groundwater. As Earth’s population grows and the demand for fresh water increases, water purification and recycling become increasingly important. Interestingly, the purity requirements of water for industrial use often exceed those for human consumption. For example, the water used in high-pressure boilers must be at least 99.999998 percent pure. Because seawater contains large quantities of dissolved salts, it must be desalinated for most uses, including human consumption.

This article describes the molecular structure of water as well as its physical and chemical properties. For other major treatments of water, see climate; environmental works; hydrosphere; ice; and pollution.


The water molecule is composed of two hydrogen atoms, each linked by a single chemical bond to an oxygen atom. Most hydrogen atoms have a nucleus consisting solely of a proton. Two isotopic forms, deuterium and tritium, in which the atomic nuclei also contain one and two neutrons, respectively, are found to a small degree in water. Deuterium oxide (D2O), called heavy water, is important in chemical research and is also used as a neutron moderator in some nuclear reactors.

Although its formula (H2O) seems simple, water exhibits very complex chemical and physical properties. For example, its melting point, 0 °C (32 °F), and boiling point, 100 °C (212 °F), are much higher than would be expected by comparison with analogous compounds, such as hydrogen sulfide and ammonia. In its solid form, ice, water is less dense than when it is liquid, another unusual property. The root of these anomalies lies in the electronic structure of the water molecule.

The water molecule is not linear but bent in a special way. The two hydrogen atoms are bound to the oxygen atom at an angle of 104.5°.
structure of the water molecule showing the two hydrogen atoms bound to the oxygen atom at an angle of 104.5 degrees.

The O―H distance (bond length) is 95.7 picometres (9.57 × 10−11 metres, or 3.77 × 10−9 inches). Because an oxygen atom has a greater electronegativity than a hydrogen atom, the O―H bonds in the water molecule are polar, with the oxygen bearing a partial negative charge (δ−) and the hydrogens having a partial positive charge (δ+).

The electron arrangement in the water molecule can be represented as follows.
structure of the water molecule showing the electron arrangement

Each pair of dots represents a pair of unshared electrons (i.e., the electrons reside on only the oxygen atom). This situation can also be depicted by placing the water molecule in a cube.

Each ↑↓ symbol represents a pair of unshared electrons. This electronic structure leads to hydrogen bonding.


The liquid state of water has a very complex structure, which undoubtedly involves considerable association of the molecules. The extensive hydrogen bonding among the molecules in liquid water produces much larger values for properties such as viscosity, surface tension, and boiling point than are expected for a typical liquid containing small molecules. For example, based on the size of its molecules, water would be expected to have a boiling point nearly 200 °C (360 °F) lower than its observed boiling point. In contrast to the condensed states (solid and liquid) of water, which exhibit extensive association among the water molecules, its gaseous (vapour) phase contains relatively independent water molecules at large distances from each other.

The polarity of the water molecule plays a major part in the dissolution of ionic compounds during the formation of aqueous solutions. Earth’s oceans contain vast amounts of dissolved salts, which provide a great natural resource. In addition, the hundreds of chemical reactions that occur every instant to keep organisms alive all take place in aqueous fluids. Also, the ability of foods to be flavoured as they are cooked is made possible by the solubility in water of such substances as sugar and salt. Although the solubility of substances in water is an extremely complex process, the interaction between the polar water molecules and the solute (i.e., the substance being dissolved) plays a major role. When an ionic solid dissolves in water, the positive ends of the water molecules are attracted to the anions, while their negative ends are attracted to the cations. This process is called hydration. The hydration of its ions tends to cause a salt to break apart (dissolve) in the water. In the dissolving process the strong forces present between the positive and negative ions of the solid are replaced by strong water-ion interactions.

When ionic substances dissolve in water, they break apart into individual cations and anions. For instance, when sodium chloride (NaCl) dissolves in water, the resulting solution contains separated Na+ and Cl− ions.

Generally speaking, the greater the charge density (the ratio of charge to surface area) of an ion, the larger the hydration number will be. As a rule, negative ions have smaller hydration numbers than positive ions because of the greater crowding that occurs when the hydrogen atoms of the water molecules are oriented toward the anion.

Many nonionic compounds are also soluble in water. For example, ethanol (C2H5OH), the alcoholic component of wine, beer, and distilled spirits, is highly soluble in water. These beverages contain varying percentages of ethanol in aqueous solution with other substances. Ethanol is so soluble in water because of the structure of the alcohol molecule. The molecule contains a polar O―H bond like those in water, which allows it to interact effectively with water.


Water has several important physical properties. Although these properties are familiar because of the omnipresence of water, most of the physical properties of water are quite atypical. Given the low molar mass of its constituent molecules, water has unusually large values of viscosity, surface tension, heat of vaporization, and entropy of vaporization, all of which can be ascribed to the extensive hydrogen bonding interactions present in liquid water. The open structure of ice that allows for maximum hydrogen bonding explains why solid water is less dense than liquid water—a highly unusual situation among common substances.


What is Photography?

Answering the question, “What is photography?” is kind of like trying to answer the question, “What’s the meaning of life?”

That’s because photography is incredibly complex. It has many facets and types. There are technical aspects to photography as well as creative ones. The manner in which photography is used is even different, often from one person to the next.

Moreover, there is an unlimited variety in the quality of photos. In that regard, trying to explain the difference between an ordinary snapshot and a work of art is a very difficult job. You can tell by looking at two photographs which one is which, but conveying how to get from being an amateur to a pro is not an easy task.

But, you have to start somewhere, so in this guide, I offer a few foundational ideas that will help you answer the question, “What is photography?”

Photography Defined

When trying to quantify what is photography, it’s important to first start with a photography definition.

In layman’s terms, photography is quite simply the process of capturing light with a camera to create an image.

This was done for the first time in 1826, when Joseph Nicéphore Niépce took a photo out of his window. The image, shown above, was entitled View from the Window at Le Gras.

In terms of subject matter, the photo isn’t all that impressive. However, as the oldest surviving photograph, it is nonetheless an important part of photography.

As simple as this image is, it demonstrates the technical process of photography perfectly.

To process the image captured by his camera, Niépce used a process of his invention called heliography.

A Brief Timeline of Photography

After Joseph Nicéphore Niépce successfully created the first permanent photograph, there were many other turning points in photography that got us to where we are today.

The Basics of Photography

For all you beginner photographers out there, photography is built on light, and as such, you have to learn how to control it.

There are three camera settings that comprise the very basics of photography, and that each independently control light in a different way. Yet, these three settings are used together to create an exposure.

Sure, you can shoot in full auto mode and let the camera determine the exposure. In many cases, it works okay. But we’re here to learn, right? So, here’s a quick overview of the exposure triangle – aperture, shutter speed, and ISO.

Types of Photography

Just like there are all sorts of things to learn when you’re studying photography, there are all sorts of types of photography you can explore.

You can learn about the most popular types of photography in our detailed guide, but for our purposes in this article, here’s a quick run-down of some of the possibilities you can try:

* Landscape photography
* Portrait photography
* Wildlife photography
* Travel photography
* Street photography
* Newborn photography
* Macro photography

Again, this isn’t a complete list of the types of photography, but it’ll get you started. And as you explore and learn more about photography, you’ll likely find that the answer to our original question – What is photography? – is much deeper and broader than we’ve covered here.

More than the technical and artistic elements that comprise it, photography is about feelings, emotions, and making connections with people and places.

So, what is photography? It’s an incredibly personal experience, that’s what!

What photography is to me is probably very similar to what it is for you, but at the end of the day, our own experiences, opinions, biases, beliefs, and so forth influence what photography means. That’s part of what makes photography so great; it can bring us together thanks to the power of the lens, yet at the same time, we can enjoy it as a highly personal experience.



diameter: 1,390,000 km.
mass: 1.989e30 kg
temperature: 5800 K (surface) 15,600,000 K (core)


The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest).

It is often said that the Sun is an “ordinary” star. That’s true in the sense that there are many others similar to it. But there are many more smaller stars than larger ones; the Sun is in the top 10% by mass. The median size of stars in our galaxy is probably less than half the mass of the Sun.

The Sun is personified in many mythologies: the Greeks called it Helios and the Romans called it Sol.

The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else (“metals”) amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core.

The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles it’s as much as 36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun but the core of the Sun rotates as a solid body.

Conditions at the Sun’s core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun’s density is more than 150 times that of water.

The Sun’s power (about 386 billion billion mega Watts) is produced by nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light. For the last 20% of the way to the surface the energy is carried more by convection than by radiation.

The Sun’s output is not entirely constant. Nor is the amount of sunspot activity. There was a period of very low sunspot activity in the latter half of the 17th century called the Maunder Minimum. It coincides with an abnormally cold period in northern Europe sometimes known as the Little Ice Age. Since the formation of the solar system the Sun’s output has increased by about 40%.

The Sun is about 4.5 billion years old. Since its birth it has used up about half of the hydrogen in its core. It will continue to radiate “peacefully” for another 5 billion years or so (although its luminosity will approximately double in that time). But eventually it will run out of hydrogen fuel. It will then be forced into radical changes which, though commonplace by stellar standards, will result in the total destruction of the Earth (and probably the creation of a planetary nebula).


There are eight planets and a large number of smaller objects orbiting the Sun. (Exactly which bodies should be classified as planets and which as “smaller objects” has been the source of some controversy, but in the end it is really only a matter of definition. Pluto is no longer officially a planet but we’ll keep it here for history’s sake.)


*The Sun is one of the millions of stars in the solar system. It is, however, larger than most (although not the biggest) and a very special star to us. Without the Sun there would be absolutely no life on Earth.
*The Sun is 870,000 miles (1.4 million kilometers) across. This is so big it is hard to imagine, but it would take more than one million Earths to fill the size of the Sun!
*The Sun is so big it takes up 99% of the matter in our solar system. The 1% left over is taken up by planets, asteroids, moons and other matter.

*The Sun is about 4.5 billion years old. It is thought to be halfway through its lifetime. Stars get bigger as they get older.
*As the Sun ages, it will get bigger. When this happens, it will consume some of the things close to it, and this includes Mercury, Venus and maybe even Earth and Mars. Luckily this is billions of years in the future.
*The Sun is the centre of the solar system.
*The Sun is 92.96 million miles (149.6 kilometers) away from Earth.
*The Sun is made of a ball of burning gases. These gases are 92.1% hydrogen and 7.8% helium.

*The Sun’s core is extremely hot! An unthinkable 13,600,000 degrees Celcius!
*The Sun has a very big magnetic field. It is the most powerful magnetic field in the whole solar system. This field is regenerating itself, but scientists are unsure how.


The human heart is an organ that pumps blood throughout the body via the circulatory system, supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes.

“The tissues of the body need a constant supply of nutrition in order to be active,” said Dr. Lawrence Phillips, a cardiologist at NYU Langone Medical Center in New York. “If [the heart] is not able to supply blood to the organs and tissues, they’ll die.”


In humans, the heart is roughly the size of a large fist and weighs between about 10 to 12 ounces (280 to 340 grams) in men and 8 to 10 ounces (230 to 280 grams) in women, according to Henry Gray’s “Anatomy of the Human Body.”

The physiology of the heart basically comes down to “structure, electricity and plumbing,” Phillips told Live Science.

The human heart has four chambers: two upper chambers (the atria) and two lower ones (the ventricles), according to the National Institutes of Health. The right atrium and right ventricle together make up the “right heart,” and the left atrium and left ventricle make up the “left heart.” A wall of muscle called the septum separates the two sides of the heart.

A double-walled sac called the pericardium encases the heart, which serves to protect the heart and anchor it inside the chest. Between the outer layer, the parietal pericardium, and the inner layer, the serous pericardium, runs pericardial fluid, which lubricates the heart during contractions and movements of the lungs and diaphragm.

The heart’s outer wall consists of three layers. The outermost wall layer, or epicardium, is the inner wall of the pericardium. The middle layer, or myocardium, contains the muscle that contracts. The inner layer, or endocardium, is the lining that contacts the blood.

The sinoatrial node produces the electrical pulses that drive heart contractions.


The heart circulates blood through two pathways: the pulmonary circuit and the systemic circuit.In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.

In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood returns via veins to the venae cavae, re-entering the heart’s right atrium.

Of course, the heart is also a muscle, so it needs a fresh supply of oxygen and nutrients, too, Phillips said.

“After the blood leaves the heart through the aortic valve, two sets of arteries bring oxygenated blood to feed the heart muscle,” he said. The left main coronary artery, on one side of the aorta, branches into the left anterior descending artery and the left circumflex artery. The right coronary artery branches out on the right side of the aorta.

Blockage of any of these arteries can cause a heart attack, or damage to the muscle of the heart, Phillips said. A heart attack is distinct from cardiac arrest, which is a sudden loss of heart function that usually occurs as a result of electrical disturbances of the heart rhythm. A heart attack can lead to cardiac arrest, but the latter can also be caused by other problems, he said.

“Each cell has the ability to be the ‘band leader’ and [to] have everyone follow,” Phillips said. In people with an irregular heartbeat, or atrial fibrillation, every cell tries to be the band leader, he said, which causes them to beat out of sync with one another.

A healthy heart contraction happens in five stages. In the first stage (early diastole), the heart is relaxed. Then the atrium contracts (atrial systole) to push blood into the ventricle. Next, the ventricles start contracting without changing volume. Then the ventricles continue contracting while empty. Finally, the ventricles stop contracting and relax. Then the cycle repeats.

Valves prevent backflow, keeping the blood flowing in one direction through the heart.



*A human heart is roughly the size of a large fist.
*The heart weighs between about 10 to 12 ounces (280 to 340 grams) in men and 8 to 10 ounces (230 to 280 grams) in women.
*The heart beats about 100,000 times per day (about 3 billion beats in a lifetime).
An adult heart beats about 60 to 80 times per minute.
*Newborns’ hearts beat faster than adult hearts, about 70 to 190 beats per minute.
*The heart pumps about 6 quarts (5.7 liters) of blood throughout the body.
*The heart is located in the center of the chest, usually pointing slightly left.


Global warming is a dangerous effect on our environment that we are facing these days. Rapid industrialization, increase in the population growth and pollution are causing a rise in global warming. Global warming refers to the increase in the average temperature of the earth’s surface during the last century. One of the reasons why global warming is dangerous is because it disturbs the overall ecology of the planet. This results in floods, famine, cyclones and other issues. There are many causes and results of this warming and is a danger for the existence of life on earth.

The sign of global warming is already visible with many natural phenomena happening around globally, affecting each living species.

The most evident causes of global warming are industrialization, urbanization, deforestation, sophisticated human activities. These human activities have led to an increase in the emission of the greenhouse, including CO₂, nitrous oxide, methane, and others.


Global warming is certainly an alarming situation, which is causing a significant impact on life existence. Extreme global warming is resulting in natural calamities, which is quite evident happening around. One of the reasons behind global warming is the extreme release of greenhouse gases stuck on the earth surface, resulting in the temperature increase.

Similarly, volcanoes are also leading global warming because they spew too much CO₂ in the air. One of the significant causes behind global warming is the increase in the population. This increase in the population also results in air pollution. Automobiles release a lot of CO₂, which remains stuck in the earth.

This increase in the population is also leading to deforestation, which further results in global warming. More and more trees are being cut, increasing the concentration of CO₂.

The greenhouse is the natural process where the sunlight passes through the area, thus warming the earth’s surface. The earth surface releases energy in the form of heat in the atmosphere maintaining the balance with the incoming energy. Global warming depletes the ozone layer leading to the doom’s day.

There is a clear indication that the increase in global warming will lead to the complete extinction of life from the earth surface.


Although we are almost late in slowing down the global warming rate, it is crucial to find the right solution. From individuals to governments, everyone has to work upon a solution for global warming. Controlling pollution, population and use of natural resources are some of the factors to consider. Switching over to the electric and hybrid car is the best way to bring down the carbon dioxide.

As a citizen, it is best to switch over to the hybrid car and to use public transport. This will reduce pollution and congestion. Another significant contribution you can do is minimise the use of plastic. Plastic is the primary cause of global warming taking years to recycle.

Deforestation is another thing to consider that will help in controlling global warming. Planting of more trees should be encouraged to make the environment go green.

Industrialization should be under certain norms. The building of industries should be banned in green zones affecting plants and species. Hefty penalties should be levied on such sectors contributing towards global warming.


The effect of global warming is widely seen in this decade. Glacier retreat and arctic shrinkage are the two common phenomena seen. Glaciers are melting in a fast way. These are pure examples of climate change.

Rise in sea level is another significant effect of global warming. This sea-level rise is leading to floods in low-lying areas. Extreme weather conditions are witnessed in many countries. Unseasonal rainfall, extreme heat and cold, wildfires and others are common every year. The number of these cases is increasing. This will indeed imbalance the ecosystem bringing the result of the extinction of species.

Similarly, marine life is also widely getting affected due to the increase in global warming. This is resulting in the death of marine species and other issues. Moreover, the changes are expected in coral reefs, which are going to face the end in coming years.

These effects will take a steep rise in coming years, bringing the expansion of species to a halt. Moreover, humans too will witness the negative impact of global warming in the end.


Vehicles a means of carrying or transporting something


A bicycle, also called a bike or cycle, is a human-powered or motor-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A bicycle rider is called a cyclist, or bicyclist.

Bicycles were introduced in the 19th century in Europe, and by the early 21st century, more than 1 billion were in existence. These numbers far exceed the number of cars, both in total and ranked by the number of individual models produced. They are the principal means of transportation in many regions. They also provide a popular form of recreation, and have been adapted for use as children’s toys, general fitness, military and police applications, courier services, bicycle racing, and bicycle stunts.


A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled vehicle, commonly wheeled, that does not operate on rails (such as trains or trams) and is used for the transportation of people or cargo.

The vehicle propulsion is provided by an engine or motor, usually an internal combustion engine or an electric motor, or some combination of the two, such as hybrid electric vehicles and plug-in hybrids.

As of 2011, there were more than one billion motor vehicles in use in the world, excluding off-road vehicles and heavy construction equipment.[3][4][5] The US publisher Ward’s estimates that as of 2019, there were 1.4 billion motor vehicles in use in the world.


A road–rail vehicle is a dual-mode vehicle which can operate both on rail tracks and a conventional road. They are also called hi-rail, from highway and railway, or variations such as high-rail, HiRail, Hy-rail, etc.

They are often converted road vehicles, keeping their normal wheels with rubber tires, but fitted with additional flanged steel wheels for running on rails. Propulsion is typically through the conventional tires, the flanged wheels being free-rolling; the rail wheels are raised and lowered as needed. Purpose-built road–rail vehicles also exist.


Watercraft, also known as water vessels or waterborne vessels, are vehicles used in and on water, including boats, ships, hovercraft, and submarines. Watercraft usually have a propulsive capability (whether by sail, oar, paddle, or engine) and hence are distinct from a simple device that merely floats, such as a log raft.


An aircraft is a vehicle or machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil,[2] or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors, and hot air balloons.

The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.


The sweet and fleshy product of a tree or other plant that contains seed and can be eaten as food.

A fruit is the part of a plant that has seeds and flesh (edible covering). A fruit is normally sweet (or sometimes sour) and can be eaten in its raw (uncooked) state. Fruit are the way plants disseminate their seeds.


There are two criteria for the classification of fruits:

* Whether the carpels present in gynoecium are free or in a fused state.
* One or more flower takes part in the formation of fruit.



Simple fruits

These fruits develop from the monocarpellary ovary or multicarpellary syncarpous ovary. Only one fruit is formed by the gynoecium. Simple fruits are of two types

• Fleshy Fruits: In fleshy fruits, the fruit wall is differentiated into epicarp, mesocarp, and endocarp. These fruits develop from superior or inferior syncarpous gynoecium.
• Dry Fruits: The pericarp of simple dry fruits is usually quite dry and hard. It is not differentiated into the three layers of epicarp, mesocarp and endocarp. In some dry fruits, this pericarp is broken down and the seeds are scattered or dispersed. These fruits are dehiscent fruits.

In some fruits, the pericarp is further arranged into one or more seeded segments. Such fruits are schizocarpic fruits. In some fruits, the pericarp is not observed to be dehisced even after maturing/ripening. Such fruits are indehiscent Fruits.

Aggregate fruits

These are the fruits that develop from the multicarpellary apocarpous ovary. It becomes a fruitlet because each carpel is separated from one another in the apocarpous ovary. These fruits make a bunch of fruitlets which is known as etaerio.

* Etaerio of follicles: Each fruit or etaerio is a follicle. Eg. Calotropis, Catharanthus, Magnolia -e. In calotropis, the stigma is fused or joined in carpellary ovary and ovaries of ovules are separated. It means only two follicles are present in etaerio.

* Etaerio of achenes: In this aggregate fruit, each fruit is an achene. Eg. Ranunculus, Strawberry, Rose, Lotus. In lotus, the thalamus becomes spongy and some achenes are embedded in it. In strawberry, the thalamus is fleshy and we can find small achenes on its surface.

* Etaerio of berries: It is an aggregate of small berries. Eg. Polyalthia, Annona squamosa (Custard-apple). In the etaerio of Annona, all the berries are arranged densely on the thalamus.

* Etaerio of drupes: In this type of fruit, many small drupes develop from different carpels. Eg. Raspberry. In this type carpel of apocarpous ovary form drupe fruit.

Composite fruits

All composite fruits are false fruits. In these fruits, generally, there are many ovaries and other floral parts combining to form the fruit. These are of two types:

*Sorosis: These fruits develop from spike, spadix or catkin inflorescence. Examples inJackfruit fruit, Kevda (screwpine). In jackfruit (Kathal) pistillate flowers are developed around the peduncle. In fruit formation, the pericarp becomes spongy and fused.
*Sycosis: These fruits develop from hypanthodium inflorescence. Receptacle becomes hollow and has a pore. Numerous small scales surround the pore. Eg. Ficus species Peepal


* Most fruits are naturally low in fat, sodium, and calories. …
* Fruits are sources of many essential nutrients that many people don’t get enough of, including potassium, dietary fiber, vitamin C, and folate.
* Diets rich in potassium may help to maintain healthy blood pressure.


Earth is the third planet from the Sun and the only astronomical object known to harbor and support life. About 29.2% of Earth’s surface is land consisting of continents and islands. The remaining 70.8% is covered with water, mostly by oceans, seas, gulfs, and other salt-water bodies, but also by lakes, rivers, and other freshwater, which together constitute the hydrosphere. Much of Earth’s polar regions are covered in ice. Earth’s outer layer is divided into several rigid tectonic plates that migrate across the surface over many millions of years, while its interior remains active with a solid iron inner core, a liquid outer core that generates Earth’s magnetic field, and a convective mantle that drives plate tectonics


A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of the earth. Many techniques have been developed to present world maps that address diverse technical and aesthetic goals.[

Charting a world map requires global knowledge of the earth, its oceans, and its continents. From prehistory through the Middle ages, creating an accurate world map would have been impossible because less than half of Earth’s coastlines and only a small fraction of its continental interiors were known to any culture.

Maps of the world generally focus either on political features or on physical features. Political maps emphasize territorial boundaries and human settlement.


The world religions paradigm was developed in the United Kingdom in the 1960s, where it was pioneered by phenomenological scholars like Ninian Smart. It was designed to broaden the study of religion away from its heavy focus on Christianity by taking into account other large religious traditions around the world. The paradigm is often used by lecturers instructing undergraduate students in the study of religion and is also the framework used by school teachers in the UK and other countries.

Since the late twentieth century, the paradigm has faced critique by scholars of religion like Jonathan Z. Smith, some of whom have argued for its abandonment. Critics have argued that the world religions paradigm is inappropriate because it takes the Protestant variant of Christianity as the model for what constitutes religion; that it is tied up with discourses of modernity, including modern power relations; that it encourages an uncritical understanding of religion; and that it makes a value judgement as to what religions should be considered “major”. Others have argued that it remains useful in the classroom, so long as students are made aware that it is a socially constructed category.


In sociolinguistics, a world language is a language that is geographically widespread and makes it possible for members of different language communities to communicate. The term may also be used to refer to constructed international auxiliary languages such as Esperanto.

English is the foremost—and by some accounts only—world language. Beyond that, there is no academic consensus about which languages qualify; Arabic, French, Russian, and Spanish are other possible world languages. Some authors consider Latin to have formerly been a world language.


World history or global history as a field of historical study examines history from a global perspective. It emerged centuries ago; leading practitioners have included Voltaire (1694-1778), Hegel (1770-1831), (1818-1883) and Arnold J. Toynbee (1889-1975). The field became much more active (in terms of university teaching, text books, scholarly journals, and academic associations) in the late 20th century.

It is not to be confused with comparative history, which, like world history, deals with the history of multiple cultures and nations, but does not do so on a global scale. World history looks for common patterns that emerge across all cultures. World historians use a thematic approach, with two major focal points: integration (how processes of world history have drawn people of the world together) and difference (how patterns of world history reveal the diversity of the human experience).



* A tree is a tall plant with woody tissue. Trees gather light for photosynthesis through their leaves; this process creates “food” for the tree.

* Most of a tree trunk is dead tissue and serves only to support the weight of the tree crown. The outside layers of the tree trunk are the only living portion. The cambium produces new wood and new bark.

* The band of tissue outside of the cambium is the phloem. Phloem transports new materials (the sugars created from photosynthesis) from the crown to the roots. Dead phloem tissue becomes the bark of a tree.

* The band of tissue just inside of the cambium is the xylem, which transports water from the roots to the crown. Dead xylem tissue forms the heartwood, or the wood we use for many different purposes.

*Every year, trees grow two annual rings. In the spring, usually a wider and thinner-walled layer called springwood forms. In the summer, a thicker-walled layer, called summerwood, develops. Annual rings are typical in temperate forest trees.


* Leaves – broadleaf or needles; primary location for photosynthesis and production of hormones and other chemicals.
* Twigs and Branches – support structures for leaves, flowers and fruits.
* Crown – the upper part of the tree composed of leaves, twigs, branches, flowers and fruit.
* Flowers – the site of reproduction. Trees can be male, female or both. Conifers, however, do not have petals and typical flower structures.
* Fruits and Seeds – all trees have seeds, most are inside of the fruit.
* Trunk – generally a single “stem,” but can be multiple-stemmed. Main functions are materials transport and support.
* Bark – main function is to protect the living tissue called cambium from damage.
* Roots – two main functions: (1) collect nutrients and water and (2) anchor the tree


* At the twig tips (apical meristem)
* At the root tips (root apical meristem)
* At the cambium (old xylem cells become heartwood, old phloem cells become bark)


• Trees for food

• Lumber and paper

• Fire wood

• Shade

• Beauty and interest

• Wind break, sound barrier and privacy

• Medicine and cooking