Best Information About Titanic Disaster

Titanic Disaster:                           

 one of the worst maritime disasters in history. The British luxury liner Titanic (46,000 gross tons) of the White Star Line, on its maiden voyage from Southampton to New York City, struck an iceberg about 153 km (about 95 mi) south of the Grand Banks of Newfoundland just before midnight on April 14, 1912. Of the more than 2220 persons aboard, about 1513 died, including the American millionaires John Jacob Astor, Benjamin Guggenheim, and Isidor Straus.
The ship had been proclaimed unsinkable because of its 16 watertight compartments. Nevertheless, the iceberg sufficiently damaged the Titanic to make it sink in less than three hours. Subsequent investigations found that the ship had been steaming too fast in dangerous waters, that lifeboat space had been provided for only about half of the passengers and crew, and that the Californian, close to the scene, had not come to the rescue because its radio operator was off duty and asleep. These findings led to many reforms, such as lifeboat space for every person on a ship, lifeboat drills, the maintenance of a full-time radio watch while at sea, and an international ice patrol.
The sinking of the Titanic has been the subject of several books and films, but not until September 1985 was the actual wreck found resting under about 3800 m (about 12,000 ft) of water. The area was photographed by a joint French-United States expedition through the use of robot submersibles equipped with television cameras (see Deep-Sea Exploration, Submersible Craft). In July 1986 the U.S. researchers explored the Titanic in the three-person Alvin submersible; they took pictures of the interior, but recovered no artifacts. The following year a controversial French salvage effort retrieved dishes, jewels, currency, and other artifacts, which were exhibited in Paris in September 1987.
Although these visits brought back haunting photographs and artifacts, no one had ever been able to thoroughly assess the damage caused by the Titanics collision with the iceberg. Historians had long thought the sinking of the vessel resulted from massive damage to the ships steel hull. Experts have since found evidence, however, that it was the location, rather than the extent, of the damage that caused the ship to sink. An expedition in August 1996 set out to examine the wreckage and to locate and study the damage to the hull. Sonar experts, naval architects (including one from the shipyard that built the Titanic), a microbiologist, and historians of the shipwreck were among the experts accompanying the expedition. The purpose was to determine whether the ship broke apart on the surface, to what extent flaws in the steel used to build the Titanics hull contributed to the disaster, and how long the wreck is likely to survive on the ocean floor. The expedition also attempted to raise a 28 sq m (about 300 sq ft) section of the Titanics hull, but a storm and a broken rope sent the piece plunging back to the ocean bottom.
According to the 1996 expeditions experts, the bow portion of the Titanic had struck the seabed at an angle and slid across it, plowing up sediments that covered the damaged area of the hull. To overcome this obstacle, the 1996 expedition used sophisticated sonar equipment, known as a sub-bottom profiler, to determine the extent and nature of the damage. Sonar uses reflected sound waves instead of light waves to “see” objects. Because sound waves can both penetrate material and reflect off material of differing density in different ways, the sonar was able to provide an image of what lay behind the sediments.
The Titanic was considered practically unsinkable because its hull was divided into 16 watertight compartments. The ship was designed to stay afloat with any two adjacent compartments or the front four compartments (which were smaller in volume) flooded. As a result, many authors of books on the disaster thought that only a huge tear, perhaps 90 m (300 ft) long, could have caused the 269 m (882 ft) ship to sink. But Edward Wilding, a naval architect, testified in the wake of the disaster that the total area damaged by the iceberg was small and probably did not exceed 1 sq m (about 12 sq ft). Others, however, did not believe that so large a ship could be undone by so little damage, and so the myth of the huge gash began. Previous expeditions found no sign of a gash, however, and the latest sonar findings confirmed Wildings belief that the damage was slight: six thin breaches spread out along a 35 m (110 ft) section of the hull with a total surface area of about 1 sq m (about 12 sq ft). The ruptures punctured six watertight compartments and were spread strategically along riveted seams.
A 1991 expedition had also retrieved samples of the Titanics steel for analysis. Tests determined that the steels poor resistance to impact, a quality known as impact strength, combined with its chemical makeup, made the steel brittle. This problem was compounded by the fact that the Titanic was operating in unusually cold waters for that time of year. When exposed to near-freezing temperatures, tests showed that the steel became extremely brittle. The August 1996 expedition confirmed these findings and applied them to the question of whether the Titanic broke apart before sinking.
At the time of the Titanics sinking there were conflicting reports as to whether the ship broke up at the surface or sank intact. All of the ships surviving officers said the Titanic sank intact. A number of passengers, however, said that the ship broke up at the surface. Earlier expeditions established that the ship was in two pieces on the ocean floor, but some experts had theorized that the ship broke up on its way to the bottom. There was even a claim that there might be a third piece.
Based on the new findings about the nature of the damage sustained by the Titanic and the quality of the steel used in the hull, naval architects set out to determine the stresses that might have prevailed as the ship sank. The architects used a computer simulation of stresses in the hull, known as a finite element model. The simulation showed that the weight of the waterlogged bow would have generated enough stress to cause failures in the Titanics steel plates as the ship sank, confirming reports that the ship broke apart before sinking. Also, the 1996 expedition located a third piece of the ship, indicating that the ship broke in two places.
Another series of tests performed in 1998 on some iron rivets brought back from the site found excess amounts of slag, a metal waste product added in small amounts to give iron strength. However, too much slag makes iron brittle, and there is evidence that weak rivets may have also contributed to the ruptures.
Great forces conspired to sink the Titanic, but scientists found that tiny ones will cause it to collapse and eventually disappear. In the 85 years since the Titanic sank, iron-eating microbes have slowly sapped the strength from the Titanics structure. Eventually the wreck will no longer be able to support its own weight.
Disaster, in this article, a sudden, accidental event that causes many deaths and injuries. Most disasters also result in significant property damage. Common natural causes of disasters include earthquakes, floods, hurricanes and typhoons, and tornadoes. Tsunamis (popularly, but incorrectly, known as tidal waves), volcanic eruptions, wildfires, and landslides and avalanches rank among the other natural forces that sometimes create disasters.
Not all disasters are produced by the forces of nature. Many modern-day disasters involve accidents aboard passenger-carrying airplanes, ships, or railroads. Other “man-made” disasters can be traced to the collapse of buildings, bridges, tunnels, and mines, as well as to explosions and fires unintentionally triggered by humans.

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Best Information About Rabbits And Their Types

Rabbits and Hares,




 common name for certain small, furry mammals with long ears and short tails. Although the names rabbit and hare are often used interchangeably, in zoological classification the species called rabbits are characterized by the helplessness of their offspring, which are born naked and with closed eyes, and by their gregarious habit of living in colonies in underground burrows. (The exception is the cottontail of North America, which does not dig burrows; its nest is on the surface, usually in dense vegetation, and it is not social.) Species designated zoologically as hares are born furred and with open eyes, and the adults merely construct a simple nest and rarely live socially. Furthermore, the hare is generally larger than the rabbit and has longer ears with characteristic black markings. Moreover, the skulls of rabbits and hares are distinctly different.
Distributed throughout the world, hares and rabbits have many common characteristics. Both groups breed prolifically, bearing four to eight litters a year, with three to eight young in each litter, have a period of gestation lasting about a month, reach sexual maturity in about six months, and have a life span of about ten years. These animals, which weigh from about 1 to 5 kg (about 2 to 11 lb) and attain a length of about 30 to 60 cm (about 12 to 24 in), feed mainly on herbs, tree bark, and vegetables. They prefer to live in regions where the soil is loose and dry and where brushwood offers shelter. Although rabbits and hares are valued as game by hunters, as food, and for their fur, they often are pests to farmers whose trees and crops they destroy. The species commonly found in the United States are the cottontail, the snowshoe rabbit, the jackrabbit, and the domestic rabbit.

II  COTTONTAIL

The chief wild rabbit of North America is the cottontail. Its name is derived from the white undersurface of its short tail, which resembles a puff of cotton. The cottontail is noted for remaining motionless to avoid notice when it senses danger. The rabbit, which swims well, also evades enemies by plunging into lakes or streams.

III  SNOWSHOE

The varying hare, known popularly as the snowshoe rabbit, is distributed widely throughout North America. In winter it is pure white except for black ear tips, and in summer it is reddish-brown. The young snowshoe weighs 85 g (3 oz) at birth and develops so rapidly that it crawls on the second day after birth and hops on the third day. Adult males, called bucks, fight one another with their teeth when they court the same females, which are known as does. Although largely herbivorous, the adult snowshoe rabbit may eat mice and carrion.

IV  JACKRABBIT One species of jackrabbit, the black-tailed jackrabbit, is found in the western parts of the United States and Canada. The fastest of the rabbits and hares, jackrabbits achieve speeds of about 70 km/h (about 45 mph) and can bound some 4.5 to 6 m (some 15 to 20 ft) in a single jump. Because this species competes with grazing animals for food, livestock owners in the western United States have undertaken great drives to reduce the hare population, which has been estimated to be as high as 3100 per sq km (8000 per sq mi). Jackrabbits may carry tularemia, a bacterial disease that can be fatal to humans.
The varying hare, known popularly as the snowshoe rabbit, is distributed widely throughout North America. In winter it is pure white except for black ear tips, and in summer it is reddish-brown. The young snowshoe weighs 85 g (3 oz) at birth and develops so rapidly that it crawls on the second day after birth and hops on the third day. Adult males, called bucks, fight one another with their teeth when they court the same females, which are known as does. Although largely herbivorous, the adult snowshoe rabbit may eat mice and carrion.
V  DOMESTIC RABBIT
At least 66 varieties of the domesticated rabbit are derived from a wild rabbit native to Europe and Africa. Some varieties are Angora, Belgian, Dutch, Himalayan, lop, Siberian, Patagonian, silver-tip, Polish, and Flemish. The domesticated rabbit has extremely diverse characteristics, varying in color through every grade, shade, and mixture, from pure white to all black; in coat from very short to long, silky hair capable of being woven; and in style of ears from the prick ear—erect, small and almost as stiff as metal—to the floppy, broad, soft-skinned lopped ear, which hangs to the ground. Domestic rabbits warn one another of danger by thumping on the ground with their hind feet. They are bred as pets, for genetic studies, for laboratory experimentation, and for their meat and furs; domestic rabbits furs are sold under the trade names of arctic seal, clipped seal, and lapin.Rabbits have been introduced to South America, Java, Australia, New Zealand, and various oceanic islands around the world. A significant instance of the rapid distribution of rabbits can be found in the present abundance of rabbits in Australia and New Zealand. In New Zealand, seven rabbits were first turned out near Invercargill, apparently about 1860. They soon spread to both countries and multiplied so rapidly that rabbit control became a serious problem. In Australia a virus deadly only to true rabbits was developed, and in 1951 decimation of the rabbit population began through the artificial promotion of this virus infection, known as myxomatosis. The project met with success only in areas with sufficient water to serve as breeding grounds for mosquitoes, which transmit the virus. However, the disease spread to Europe, killing rabbits in Britain, Belgium, and France, where the animal serves useful purposes.

Scientific classification: Rabbits and hares belong to the family Leporidae of the order Lagomorpha. Cottontails are classified in the genus Sylvilagus. The snowshoe rabbit is classified as Lepus americanus, the black-tailed jackrabbit as Lepus californicus, and the wild rabbit of Europe and Africa as Oryctolagus cuniculus.

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The Sun And It s Introduction Find The Best Online Information

Sun,


                                                   


 closest star to Earth. The Sun is a huge mass of hot, glowing gas. The strong gravitational pull of the Sun holds Earth and the other planets in the solar system in orbit. The Sun’s light and heat influence all of the objects in the solar system and allow life to exist on Earth.
The Sun is an average star—its size, age, and temperature fall in about the middle of the ranges of these properties for all stars. Astronomers believe that the Sun is about 4.6 billion years old and will keep shining for about another 7 billion years.
For humans, the Sun is beautiful and useful, but also powerful and dangerous. As Earth turns, the Sun rises over the eastern horizon in the morning, passes across the sky during the day, and sets in the west in the evening. This movement of the Sun across the sky marks the passage of time during the day (see Sundial). The Sun’s movement can produce spectacular sunrises and sunsets under the right atmospheric conditions. At night, reflected sunlight makes the Moon and planets bright in the night sky.
The Sun provides Earth with vast amounts of energy every day. The oceans and seas store this energy and help keep the temperature of Earth at a level that allows a wide variety of life to exist. Plants use the Sun’s energy to make food, and plants provide food for other organisms. The Sun’s energy also creates wind in Earth’s atmosphere. This wind can be harnessed and used to produce power.While it lights our day and provides energy for life, sunlight can also be harmful to people. Human skin is sensitive to ultraviolet light emitted from the Sun. Earth’s atmosphere blocks much of the harmful light, but sunlight is still strong enough to burn skin under some conditions (see Burn). Sunburn is one of the most important risk factors in the development of skin cancers, which can be fatal. Sunlight is also very harmful to human eyes. A person should never look directly at the Sun, even with sunglasses or during an eclipse. The Sun influences Earth with more than just light. Particles flowing from the Sun can disrupt Earth’s magnetic field, and these disruptions can interfere with electronic communications.
Characteristics of the Sun, The distance between the sun and the earth varies because the earth travels in an elliptical rather than circular orbit. The distance is roughly 100 times the sun’s diameter. Turbulence in the photosphere forms granules of various sizes and sunspots. Temperature is a measure of kinetic energy. The dense plasma in the center of the sun is roughly 2500 times hotter than the surface. Gases in the corona have escaped from the sun’s surface and have a very high velocity. The sun’s spectral type, G2, indicates that it is composed of hydrogen, helium, calcium,iron and other metals.
II PHYSICAL CHARACTERISTICS
The Sun is large and massive compared to the other objects in the solar system. The Sun’s radius (the distance from its center to its surface) is 695,508 km (432,169 mi), 109 times as large as Earth’s radius. If the Sun were hollow, a million Earths could fit inside it. The Sun has a mass of 1.989 × 1027 metric tons. This number is very large. Written out, it would be the digits 1989 followed by 24 zeroes. The Sun is 333,000 times as massive as Earth is. Despite its large mass, the Sun has a lower density, or mass per unit volume, than Earth. The Sun’s average density is only 1.409 g/cu cm (1.188 oz/cu in), which is a quarter of the average density of Earth.
The Sun produces an enormous amount of light. It generates 3.83 × 1026 watts of power in the form of light. In comparison, an incandescent lamp emits 60 to 100 watts of power. The temperature of the outer, visible part of the Sun is 5500°C (9900°F).
From Earth the Sun looks small, because it is far away. Its average distance from Earth is 150 million km (93 million mi). Light from the Sun takes about eight minutes to reach Earth. This light is still strong enough when it reaches Earth, however, to damage human eyes when viewed directly. The Sun is much closer to Earth than any other star is. The Sun’s nearest stellar neighbor, Proxima Centauri (part of the triple star Alpha Centauri), is 4.3 light-years from our solar system, meaning light from Proxima Centauri takes 4.3 years to reach the Sun. The Sun is so much closer to Earth than all other stars are that the intense light of the Sun keeps us from seeing any other stars during the day.

A  Importance to Earth
Earth would not have any life on it without the Sun’s energy, which reaches Earth in the form of heat and light. This energy warms our days and illuminates our world. Green plants absorb sunlight and convert it to food, which these plants then use to live and grow. In this process, the plants give off the oxygen that animals breathe. Animals eat these plants for nourishment. All plant and animal life relies on the Sun’s presence
The Sun also provides—directly or indirectly—much of the energy on Earth that people use for fuel (see Solar Energy). Devices called solar cells turn sunlight into electricity. Sunlight can heat a gas or liquid, which can then be circulated through a building to heat the building. The energy stored in fossil fuels originally came from the Sun. Ancient plants used sunlight as fuel to grow. Animals consumed these plants. The plants and animals stored the energy of sunlight in the organic material that composed them. When the ancient plants and animals died and decayed, this organic material was buried and gradually turned into the petroleum, coal, and natural gas people use today. The Sun’s energy produces the winds and the movements of water that people harness to produce electricity (see Wind Energy; Water Power). The Sun heats Earth’s oceans and land, which in turn heat the air and make it circulate in the atmosphere as wind. The Sun fuels Earth’s water cycle, evaporating water from the oceans, seas, and lakes. This water returns to the ground in the form of precipitation, flowing back to the oceans through the ground and in rivers. The energy of water’s motion in rivers can be harnessed with dams.

B  Role in the Solar System

The Sun’s gravitational pull holds the solar system together. The planets, asteroids, comets, and dust that make up our solar system are strongly attracted to the Sun’s huge mass. This gravitational attraction keeps these bodies in orbit around the Sun. The Sun also influences the solar system with its diffuse outer atmosphere, which expands outward in all directions. This expanding atmosphere fills the solar system with a constant flow of tiny, fast, electrically charged particles. This flow is called the solar wind. The region through which the solar wind blows is called the heliosphere. Estimates vary about the extent of the heliosphere, ranging from about 86 to about 100 times the distance between Earth and the Sun. Interstellar winds may give the heliosphere an egg shape. The solar wind spreads out as it leaves the Sun. The point at which the solar wind is so diffuse that it stops having an effect on its surroundings is called the heliopause. The heliopause marks the outer edge of the solar system. Within the heliosphere, the Sun provides most of the heat and light that are present, and the particles in the solar wind interact with the planets and satellites in the solar system. The solar wind causes auroras—displays of colored light—in the atmosphere of Earth’s polar regions. The solar wind also carries remnants of the Sun’s magnetic field, which affect the magnetic fields of the planets and larger satellites. The solar wind pushes the planets’ magnetic fields away from the Sun, turning them into elongated, windsock shapes. For more information, see the Solar Wind section of this article.

III  THE SUN AS A STAR
The Sun is extremely important to Earth and to our solar system, but on the scale of the galaxy and the universe, the Sun is just an average star. It is one of hundreds of billions of stars in our galaxy, the Milky Way, which is just one of more than 100 billion galaxies in the observable universe
The Sun’s Place in the Milky Way
The Milky Way Galaxy contains about 400 billion stars. All of these stars, and the gas and dust between them, are rotating about a galactic center. Stars that are farther away from the center move at slower speeds and take longer to go around it.

The Sun is located in the outer part of the galaxy, at a distance of 2.6 × 1017 km (1.6 × 1017 mi) from the center. The Sun, which is moving around the center at a velocity of 220 km/s (140 mi/s), takes 250 million years to complete one trip around the center of the galaxy. The Sun has circled the galaxy more than 18 times during its 4.6-billion-year lifetime.

B  Comparisons with Other Stars
A star is a ball of hot, glowing gas that is hot enough and dense enough to trigger nuclear reactions, which fuel the star. In comparing the mass, light production, and size of the Sun to other stars, astronomers find that the Sun is a perfectly ordinary star. It behaves exactly the way they would expect a star of its size to behave. The main difference between the Sun and other stars is that the Sun is much closer to Earth.Most stars have masses similar to that of the Sun. The majority of stars’ masses are between 0.3 to 3.0 times the mass of the Sun. Theoretical calculations indicate that in order to trigger nuclear reactions and to create its own energy—that is, to become a star—a body must have a mass greater than 7 percent of the mass of the Sun. Astronomical bodies that are less massive than this become planets or objects called brown dwarfs. The largest accurately determined stellar mass is of a star called V382 Cygni and is 27 times that of the Sun.The range of brightness among stars is much larger than the range of mass. Astronomers measure the brightness of a star by measuring its magnitude and luminosity. Magnitude allows astronomers to rank how bright, comparatively, different stars appear to humans. Because of the way our eyes detect light, a lamp ten times more luminous than a second lamp will appear less than ten times brighter to human eyes. This discrepancy affects the magnitude scale, as does the tradition of giving brighter stars lower magnitudes. The lower a star’s magnitude, the brighter it is. Stars with negative magnitudes are the brightest of all. Magnitude is given in terms of absolute and apparent values. Absolute magnitude is a measurement of how bright a star would appear if viewed from a set distance away. By convention, this distance is 10 parsecs, or 32.6 light-years. Apparent magnitude measures how bright a star appears from Earth. The Sun’s absolute magnitude is 4.8. The brightest known stars have absolute magnitudes of about -9 (lower magnitudes mean brighter stars), and the dimmest known stars have absolute magnitudes of about 20. The apparent magnitude of the Sun is -26.72. The apparent magnitude of the brightest star in Earth’s night sky, Sirius, is -1.46. The dimmest stars that can be seen from Earth with unaided eyes have apparent magnitudes of about 6.
Astronomers also measure a star’s brightness in terms of its luminosity. A star’s absolute luminosity or intrinsic brightness is the total amount of energy radiated by the star per second. Luminosity is often expressed in units of watts. The Sun’s absolute luminosity is 3.86 × 1026 watts. The absolute luminosity of stars ranges from one thousandth of the luminosity of the Sun to 10 million times that of the Sun.Another way of measuring brightness is to measure the amount of light that reaches an observer. This measurement is called apparent brightness or apparent luminosity. Apparent luminosity depends on the absolute luminosity of a star and the distance from the star to the observer. Apparent luminosity becomes smaller as distance from the star to the observer becomes larger. From Earth, the apparent luminosity of the Sun is 10 billion times greater than the apparent luminosity of the next brightest star, Sirius, because the Sun is so much closer to Earth. The radius of the Sun is about average among stars. The radii of most stars fall between 0.2 and 15 times the Sun’s radius, although some giant stars are hundreds of times larger than the Sun. Larger stars usually have larger absolute luminosities.We receive much more energy from the Sun than from other stars, because the Sun is so nearby. The Sun’s proximity also allows scientists to study its face in detail. A modest telescope can resolve solar structures that are 700 km (400 mi) across—about the distance from Boston, Massachusetts, to Washington, D.C. That level of detail is comparable to seeing the features on a coin from 1 km (0.6 mi) away. Other stars are so distant that the details on their surfaces remain unresolved with even the largest telescopes.

C  Composition of the Sun

The Sun is a second-generation star, meaning that some of its material came from former stars. Some stars in our galaxy are nearly as old as the expanding universe, which scientists believe originated in the big bang explosion about 14 billion years ago (see Big Bang Theory). In contrast, the Sun is only 4.6 billion years old.The first stars were composed only of the hydrogen and helium produced in the early universe. These stars are called first-generation stars. Although hydrogen is also the main ingredient of the Sun, it contains heavier elements, such as carbon, nitrogen, and oxygen, as well. These elements formed inside first-generation stars that lived and died before the Sun was born. When these massive, short-lived stars used up their internal fuel, they exploded and ejected the heavier elements into interstellar space. The Sun formed from this material, making it a second-generation star.

D  The Sun’s Remote Past and Distant Future
The Sun and planets in our solar system formed when a rotating cloud of dust and gas in space collapsed, or condensed, due to the gravitational attraction between the particles in the cloud. A nearby supernova explosion may have triggered the collapse, or a random fluctuation in the density of the cloud may have started the process. The Sun formed at the center of the spinning cloud, while the debris that condensed into planets formed a flattened disk revolving around the Sun. When the Sun reached its present size about 4.6 billion years ago, it was hot enough inside to ignite the nuclear reactions that make it glow.
The Sun cannot shine forever, because it will eventually use up its present fuel. The nuclear fusion reactions that make the Sun glow (for more information, see the section entitled The Sun’s Energy in this article) depend on the element hydrogen, but the hydrogen in the Sun’s core will eventually run out. Nuclear reactions have converted about 37 percent of the hydrogen originally in the Sun’s core into helium. Astronomers estimate that the Sun’s core will run out of hydrogen in about 7 billion years.
The Sun will grow steadily brighter as time goes on and more helium accumulates in its core. Even as the supply of hydrogen dwindles, the Sun’s core must keep producing enough pressure to keep the Sun from collapsing in on itself. The only way it can do this is to increase its temperature. The increase in temperature raises the rate at which nuclear reactions occur and makes the Sun brighter. In 3 billion years, the Sun will be hot enough to boil Earth’s oceans away. Four billion years thereafter, the Sun will have used up all its hydrogen and will balloon into a giant star that engulfs the planet Mercury. At this point in its life, the Sun will be a red giant star. The Sun will then be 2,000 times brighter than it is now, and hot enough to melt Earth’s rocks. At this time the outer solar system will get warmer and more habitable. The icy moons of the giant planets may warm enough to be covered by water instead of ice.
When the giant Sun uses up its fuel, it will no longer be able to support the weight of its inner layers, and they will begin to collapse toward the core, eventually producing a small, dense, cool star called a white dwarf. The Sun will then have about the same radius as Earth has, but it will be much denser and more massive than Earth. The Sun will become a white dwarf star about 8 billion years from now. After it becomes a white dwarf, it will cool slowly for billions of years, eventually becoming so cool that it will no longer emit light.

IV  THE SUN’S ENERGY

The Sun produces an amazing amount of light and heat through nuclear reactions (Nuclear Energy). The process that produces the Sun’s energy is called nuclear fusion. In nuclear fusion, two atoms come together to produce a heavier atom. Fusion reactions release energy and tiny elementary particles.

A  Scale of the Sun’s Energy 

In just one second the Sun emits more energy than humans have used in the last 10,000 years. The Sun has been shining relatively steadily for 4.6 billion years. Until the early 20th century, humans did not know of any process that could explain the energy production of the Sun. Even if a fire, such as those that occur on Earth, were as large as the Sun, the fire would consume the mass of the Sun in a few thousand years.

Scientists now know that the Sun is mainly composed of hydrogen, the lightest and most abundant element in the universe. The Sun contains an enormous amount of hydrogen, however, which makes the Sun very massive. All matter inside the Sun is gravitationally attracted to all the other matter in the Sun, and this attraction tends to pull the Sun’s mass together. This inward pull creates high pressures and temperatures inside the Sun.

The center is so violent and hot that collisions between atoms break the hydrogen atoms apart into their subatomic ingredients. A hydrogen atom is made up of a nucleus that contains a positively charged proton, and a negatively charged electron that orbits the nucleus. In the Sun, collisions separate the electron from the nucleus, freeing each to move about the solar interior. The positively charged nuclei, or protons, are called ions. A gas in which particles are ionized, or have electric charges, is called plasma. Scientists often consider plasma, such as the material inside the Sun, to be a fourth state of matter—the three more familiar states of matter are gas, liquid, and solid. See also Atom.

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Information About Different Cats Of The World

Cat,

 small, mainly carnivorous animal, Felis catus, member of the family Felidae, popular as a household pet, and valuable for killing mice and rats. Like other members of the cat family, the domestic cat has retractile claws; keen hearing and smell; remarkable night vision; and a compact, muscular, and highly supple body. Cats possess excellent memory and exhibit considerable aptitude for learning by observation and experience. The natural life span of a domestic cat is about 15 years.
Most authorities believe that the shorthaired breeds of domestic cat are derived from the Caffre cat, Felis libyca, a species of African wildcat domesticated by the ancient Egyptians perhaps as early as 2500 bc and transported by the Crusaders to Europe, where it interbred with the indigenous smaller wildcats. The longhaired breeds may have sprung from the Asian wildcat, Felis manul. Over the centuries, cats have remained virtually the same in size, weighing about 3.6 kg (about 8 lb) when full-grown, and have preserved their instinct for solitary hunting.
A Physiology of the Cat
The body of a domestic cat is extremely flexible; its skeleton contains more than 230 bones (the human skeleton, although much larger, contains 206 bones), and its pelvis and shoulders are more loosely attached to its spine than in most other quadrupeds. The cats great leaping ability and speed are due in part to its powerful musculature. Its tail provides balance when jumping or falling.
The cats claws are designed for catching and holding prey. The sharp, hooked, retractile claws are sheathed in a soft, leathery pocket at the end of each toe, and are extended for fighting, hunting, and climbing. The cat marks its territory by scratching and scenting trees or other objects; its claws leave visible scratch marks, and the scent glands on its paw pads leave a scent mark.
The cats teeth are designed for biting, not for chewing. Its powerful jaw muscles and sharp teeth enable the cat to deliver a killing bite to its prey.
B  Senses
The cats vision is exceptionally well adapted for hunting, especially at night. It has excellent night vision; extensive peripheral vision; and binocular vision, which enables it to accurately judge distances. The cats daylight vision is not as good as that of humans; cats see movement much more easily than detail, and are thought to see only a limited range of colors.
The cats hearing is extremely sensitive. It can hear a wide range of sounds, including those in the ultrasonic range. Its ears are less sensitive to lower frequencies, which may explain why some domestic cats are more responsive to female voices than to male voices. The cat can turn its ears to focus on different sounds.
The cat has a highly developed sense of smell, which plays a vital role in finding food and in reproduction. Many of the social signals of domestic cats take the form of scents; for example, male cats can apparently smell a female cat that is receptive to male cats from a distance of hundreds of meters or yards.
The cats sense of taste is peculiarly specialized: it has little ability to detect sweetness, but is extremely sensitive to slight variations in the taste of water. The cats tongue is covered with rough protuberances, or papillae, that it uses to rasp meat from bones. It also uses its tongue to groom itself.
The cats whiskers, or vibrissae, are extremely sensitive to the slightest touch, and are used for testing obstacles and sensing changes in the environment. In extremely dim light, a cat may feel its way by using its whiskers.
C  Reproduction
The domestic cat usually reaches puberty at around nine or ten months of age. A sexually mature female cat goes into heat, or estrus, several times a year; during estrus, she is both receptive to, and attractive to, male cats. The gestation period of the cat is about 65 days; the average litter consists of 4 kittens. Kittens are born blind, deaf, and helpless. Their eyes open at 8 to 10 days of age, and they begin to be weaned about 6 weeks after birth.
D  Coat Colors
The domestic cats original coat color was probably grayish-brown with darker tabby stripes, a color that provides excellent camouflage in a variety of environments. All other coat colors and patterns are the result of genetic mutations; for example, solid coat colors such as black and blue are the result of a gene that suppresses tabby stripes; an orange coat is the result of a gene that transforms black pigment to orange; and a solid white coat is the result of a gene that completely suppresses all formation of pigment.
Two pigments, black and orange, form the basis for all coat colors in the modern domestic cat. These pigments may be combined with each other or with white (the absence of pigment). A single gene, the O (Orange) gene, determines whether a cats coat contains black or orange pigment. The O gene can be thought of as a switch that is either on (orange) or off (black). The gene is located on the X chromosome, so its inheritance is sex-linked.
III  CAT BREEDS
About 40 varieties, or breeds, of domestic cats are recognized internationally. Although the various cat breeds often differ dramatically in coat length and overall look, they vary less in size than do dog breeds. The smallest cat breeds weigh about 2 to 3 kg (about 5 to 7 lb) when full-grown; the largest weigh about 7 to 9 kg (about 15 to 20 lb). So far, attempts to develop miniature or giant domestic cat breeds have been unsuccessful.
A  Breed Origins
 Many domestic cat breeds, including the Maine coon, Manx, Russian blue, and Siamese, began as a naturally occurring variety of domestic cat native to a specific geographic area. Others, such as the Himalayan, are artificially created breeds, the result of generations of careful breeding for a desired look. Some relatively new breeds, including the curly-coated Rex breeds, the hairless Sphynx, the fold-eared Scottish fold, and the curl-eared American curl, began with a genetic mutation and were then developed by selective breeding into a distinct breed.
B  Breed Standards
For each domestic cat breed, there is an official standard of perfection registered with different cat associations that describes the ideal cat of that breed and its distinctive features; lists desirable and undesirable characteristics; and mentions faults that, in a cat show, could result in penalty or disqualification. For example, in the Siamese breed standard, the eyes are described as almond-shaped and slanting toward the nose; a tendency to squint is penalized, and crossed eyes are a disqualifying fault.
Breed standards differ slightly from cat association to cat association, and not all cat associations recognize every breed. To become recognized in a particular cat association, a breed must first be accepted for provisional status by that association. To become recognized for championship competition, the breed must complete a rigorous set of requirements that differ from association to association.
IV  THE CARE OF CATS
Cats are known for their ability to fend for themselves in the wild, but household pets, dependent on human beings for care and feeding, require considerable attention. Educational materials on the care of cats and responsible cat ownership are available through bookstores and local humane societies.
A  General Care
Although cats have a reputation for being relatively independent, domestic cats require love and attention from their owners. A balanced daily diet, such as that provided by high-quality commercial cat food, is essential for health and longevity, as is a regular supply of fresh water. Regular cleaning of litter pans is necessary to prevent disease; some cats will refuse to use a badly soiled litter pan. Cats claws should be trimmed frequently. To prevent damage to furniture, cats that live indoors should be provided with a scratching post, preferably covered with a rough material such as sisal rope. Cats use their tongues to clean their coats, and they normally swallow any loose hair. All cats, including shorthairs, should be brushed weekly to remove loose hair; this will help prevent hairballs from forming in their stomachs. A few longhaired breeds, such as the Persian and the Himalayan, require daily combing to prevent their long, soft fur from matting.
B  Neutering or Spaying
Every year hundreds of thousands of unwanted domestic cats and kittens are destroyed because homes cannot be found for them. To avoid contributing to this problem, a cat should be altered (surgically treated to make it incapable of reproducing) unless it is a registered, pedigreed member of a responsible breeding program. A female cat is spayed (altered by removing the uterus and ovaries); a male cat is neutered (altered by removing the testicles). Cats that have been altered are healthier and easier to live with. Unaltered females may be susceptible to uterine infections and ovarian cysts; unaltered cats of both sexes may mark their territory by spraying urine. Some veterinarians recommend altering cats as young as 12 weeks of age, while others recommend waiting until the animal reaches sexual maturity (at six to ten months of age). Current veterinary research indicates that early altering has little negative effect on a cats health; a low-quality diet, however, can cause serious urinary tract problems.
C  Indoors vs. Outdoors
Some domestic cat owners choose to keep their cats indoors; others permit their cats to go outdoors some or all of the time. The decision of whether to allow a cat outdoors is a personal one; cats that have been declawed, however, and those that have not been altered, should not be allowed outdoors unless confined to a covered enclosure.
Cats that are allowed outside have some degree of freedom and independence, and may enjoy hunting small animals and interacting with other cats; they get plenty of exercise and are unlikely to become bored or lonely. The outdoors, however, poses many hazards to cats, even in rural areas. An outdoor cat may be struck by a car, poisoned by common pesticides, or injured by other animals (other cats, dogs, and, in some areas, wild animals such as coyotes). In addition, the cat may be exposed to the fatal feline diseases that are endemic in the stray cat population. According to some authorities, a cat that is permitted outdoors has an average life expectancy of 2 to 3 years; conversely, the average life expectancy of an indoor cat is about 15 years.
Although an indoor cat does not enjoy the same freedom as an outdoor cat, many indoor cats live happy and complete lives. It is easier to keep a cat indoors if it has not become accustomed to going out. Indoor cats need exercise just as outdoor cats do. Some cats can be trained to use a harness leash. Often, the easiest way to provide an indoor cat with exercise and stimulation is to provide a feline companion.
D  Cat Diseases
Domestic cats are susceptible to a variety of viral and bacterial diseases. Fortunately, many common feline diseases can be controlled by a regular system of inoculation. Cats may also suffer from external parasites such as fleas and mites, and from intestinal parasites (worms). Cats can contract rabies from infected prey or other infected animals, but such instances are rare.
Upper respiratory infections are a common feline illness and can sometimes be fatal, especially in young kittens. Vaccines provide some protection against the following upper respiratory diseases: feline viral rhinotracheitis (FVR), feline calicivirus (FCV), and chlamydia (feline pneumonitis).
Panleukopenia (feline infectious enteritis) is a highly contagious, often fatal disease characterized by a sudden onset and severe gastrointestinal symptoms such as vomiting and diarrhea. Vaccination is the only effective way to control the disease.
Feline leukemia virus (FeLV) is a fatal, contagious disease that is spread by direct contact. A cat with feline leukemia may have a variety of symptoms, including general malaise, weight loss, anemia, and fever. An infected cat may transmit the disease to other cats before it develops clinical symptoms itself. A blood test can detect whether a cat has been infected. Although a vaccine is available, the most reliable way to prevent a cat from contracting feline leukemia is to keep it from coming into contact with FeLV-positive cats.
Feline infectious peritonitis (FIP) is an inflammation of the peritoneum (lining of the abdomen). Although FIP is contagious, some cats appear to develop a natural immunity to it. An infected cat may be a symptomless carrier. Once a cat develops symptoms, the disease is invariably fatal. There is no reliable blood test for FIP, but a vaccine is now available.
E  Inoculations
Cats can be successfully inoculated against many serious feline diseases. Kittens should be inoculated against rhinotracheitis, calicivirus, panleukopenia, and, optionally, chlamydia. Most veterinarians recommend a series of two or three inoculations, given every 3 weeks starting at 6 weeks of age. After 12 weeks of age, a kitten may also be inoculated against rabies, feline leukemia, and feline infectious peritonitis. Inoculations should be repeated annually to maintain immunity.
V  SHOWING AND JUDGING CATS
Many owners, even those of mixed-breed cats, enjoy exhibiting their cats at shows. Judges at cat shows must be trained and certified. Purebred cats are judged on health, temperament, and how well they fit the official standard for their breed. Mixed-breed cats are judged on health, temperament, and general appearance. All cats are expected to be amenable to handling; a cat may be disqualified if it bites or otherwise injures a judge.
A  Cat Associations
A cat association is an organization that registers cats and kittens, selects cat show judges, and schedules cat shows. There are various cat associations in the United States, including the Cat Fanciers Association (CFA), The International Cat Association (TICA), and the American Cat Fanciers Association (ACFA). The largest of these groups, the CFA, registers more than 80,000 cats and kittens annually. All of the cat associations operate independently; cat clubs, breeders, and exhibitors choose which associations they wish to join and whose breed standards and rules they wish to follow.
B  Cat Shows
An increasing number of local, regional, and national cat shows are held throughout the year in the United States, with hundreds of cats competing for awards. Owners show their cats for fun and to gain a reputation among other exhibitors and breeders. Cat shows typically do not award monetary prizes, and the entry fees and travel expenses can be expensive.
Although exact show rules and procedures vary from association to association, the general format is the same. There are four categories of competition: purebred kittens, purebred adults, purebred alters (cats that have been neutered or spayed), and household pets (mixed-breed cats or kittens).
A single cat show may have as many as 20 or more different judges; usually, a cat is judged by every judge in the show. At cat shows in the United States, each judge has his or her own ring—an area consisting of 10 to 15 numbered cages and a judging table. Cats wait in cages in another area of the show hall, called the benching area. The owners bring the cats to the ring when called and place them in the judging cages. The judge takes each cat out of its cage in turn, places it on the judging table, and examines the cat carefully to make sure that it is healthy and meets the standard for that breed. After judging each cat within a particular class or breed, the judge gives out preliminary awards, such as Best of Color or Best of Breed. After judging all the cats in a category, the judge gives top awards to the ten best cats in that category. Each judge works independently, and judges opinions sometimes differ markedly.
VI  CAT LORE
Cats and humans have interacted for thousands of years. These animals have figured in the history of many nations, are the subject of much superstition and legend, and are a favorite subject of artists and writers.
A  History and Legend
Cats became objects of worship in ancient Egypt because of their ability to keep down the rodent population in the countrys economically important grain fields along the Nile. The Egyptian cat goddess Bast, or Bastet, became associated with fertility and childbearing. Egyptian cats were also used for sport by their owners. Attached to leashes, these animals hunted birds for the family table; a boomerang flung by the master brought the birds down and the cats, unleashed, would retrieve them. Because they were economically useful and were believed to ensure many children for a family, cats were so revered that they were mummified and buried either with their owners or in specially designated cemeteries.
Despite Egyptian laws that forbade the removal of the sacred cats, Phoenician sailors smuggled them out of the country. Cats were traded along with other treasures from the Middle East and in antiquity could be found throughout the Mediterranean area. Archaeological evidence indicates that the Romans were the first to bring cats to the British Isles.
Throughout much of the Middle Ages, cats were feared and hated. Because of their nocturnal habits, they were believed to consort with the devil. This association with witchcraft has been responsible for many acts of cruelty toward cats through the centuries. The Renaissance, in contrast, was the golden age for cats. Almost everyone owned one, from members of royal families and their staffs down to the peasantry.
The first domestic cats in North America arrived with the colonists and were employed to keep the rodent population under control in the settlers fields, barns, and homes. Cats are said to have played an important part in keeping rats out of the California gold mines.
In India cats often played an important part in religious or occult ceremonies. In South America the Inca revered sacred cats; cats are represented in pre-Columbian Peruvian artifacts. Cats continue to be worshiped as deities in countries such as Thailand and China.
B  Cats in Art and Literature
Egyptian tomb paintings and sculpture are the earliest representations of the domestic cat. Images of cats appear on Greek coins of the 5th century bc; cats were later depicted in Roman mosaics and paintings and on earthenware, coins, and shields. The 8th-century Irish manuscript of the Gospels, the Book of Kells, has a representation of cats and kittens in one of its illuminations. Later artists, such as the Italian artist Leonardo da Vinci and his German contemporary Albrecht Dürer, are among the many who included cats in their works.
Although the Old Testament makes no mention of cats, the Babylonian Talmud tells of their admirable qualities and encourages the breeding of cats “to help keep the houses clean.” Memorable literary cats include the British writer Rudyard Kiplings “Cat That Walked by Himself” (one of the Just So Stories, 1902), the delightful cats of Old Possums Book of Practical Cats (1939) by the Anglo-American poet T. S. Eliot, and the Cheshire Cat, joint creation of the English writer Lewis Carroll and the illustrator Sir John Tenniel in the childrens classic Alices Adventures in Wonderland (1865). Many contemporary comic strips and animated cartoons also contain feline characters that delight ailurophiles (lovers of cats) of all ages.

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