Wolfgang Mozart Biography - Facts, Birthday and Life Story

Wolfgang Mozart Biography - Facts, Birthday and Life StoryMozart, Wolfgang Amadeus (1756-1791), Austrian composer, who is considered one of the most brilliant

As a child prodigy Mozart toured Europe and became widely regarded as a miracle of nature because of his musical gifts as a performer of piano, harpsichord, and organ and as a composer of instrumental and vocal music. His mature masterpieces begin with the Piano Concerto No. 9 in E-flat Major (Jeunehomme, 1777), one of about a dozen outstanding concertos he wrote for piano. Also successful as an opera composer, Mozart wrote three exceptional Italian operas to texts by Italian librettist Lorenzo da Ponte: Le Nozze di Figaro (The Marriage of Figaro, 1786), Don Giovanni (1787), and Così fan tutte (All Women Do So, 1790). They were followed in 1791 by his supreme German opera, Die Zauberflöte (The Magic Flute).

Mozart’s works were catalogued chronologically by Austrian music bibliographer Ludwig von Köchel, who published his catalog in 1862. The numbers he assigned, which are called Köchel numbers and are preceded by the initial K, remain the standard way of referring to works by Mozart. The Jeunehomme Concerto, for example, is K. 271.

II  LIFE
and versatile composers ever. He worked in all musical genres of his era, wrote inspired works in each genre, and produced an extraordinary number of compositions, especially considering his short life. By the time Mozart died at age 35, he had completed 41 symphonies, 27 piano concertos, 23 string quartets, 17 piano sonatas, 7 major operas, and numerous works for voice and other instruments.

Mozart was born in Salzburg. From his father, violinist and composer Leopold Mozart, he received his early musical training. By age six he had become an accomplished performer on the clavier, violin, and organ and was highly skilled in sight-reading and musical improvisation. In 1762 Leopold took his six-year-old son on his first concert tour through the courts of Europe. The young Mozart absorbed the musical styles of the time through travel to Austria’s capital, Vienna; the German cities of Munich and Mannheim; Paris, France; London, England; and various centers in Italy. From 1762 to 1766, while he was often touring, he composed several symphonies, a few sacred works, and a number of sonatas for keyboard and violin.

In London in 1764 Mozart met then-popular German composer Johann Christian Bach, son of Johann Sebastian Bach. The eight-year-old Mozart played four-hand piano sonatas with Bach while sitting on the composer’s lap. The symphonies of the younger Bach and of Carl Friedrich Abel, another German composer living in London, offered models for Mozart’s first symphonies (K. 16 and K. 19), written in 1764 and 1765 when he was eight and nine years old. In 1767, at age 11, Mozart transformed piano sonatas by various composers into his first four piano concertos through the addition of interludes and episodes for orchestra. He intended these works (K. 37, K. 39, K. 40, and K. 41) for his own performance. In 1768 he composed his first opera buffa (comic opera), La finta semplice (The Simple Pretense), and his first German operetta, Bastien und Bastienne. The following year La finta semplice was performed at the palace of the Salzburg archbishop, who appointed Mozart his concertmaster.

From 1769 to 1773, Mozart made three extended journeys to Italy with his father, during which he was remarkably productive and wrote not only symphonies and operas but also string quartets and several sacred works. In Milan he was commissioned to write an opera seria—that is, a serious opera in Italian on a heroic subject. The opera, Mitridati, rè di Ponto (Mithridates, King of Pontus), was produced in 1770 in Milan under Mozart’s direction with success. Also that year the pope made Mozart a knight of the Order of the Golden Spur.

III  MUSIC

Mozart’s music can be divided into periods of stylistic assimilation and stylistic innovation. From childhood he showed skill at imitating virtually any type of music, including the sacred style of church music and the so-called galant (courtly) idiom. The elegant though often superficial galant style dominated much instrumental music of the 1760s and 1770s. Mozart’s mastery often demonstrates itself in an ability to expand and deepen the stylistic possibilities of the time. The manner in which he extended the character and form of the concerto, for instance, owes much to his experience in writing operatic arias.

High Blood Pressure (Hypertension) and Causes of High Blood Pressure: Weight, Diet, Age, and More

Blood Pressure,
High Blood Pressure (Hypertension) and Causes of High Blood Pressure: Weight, Diet, Age, and More pressure of circulating blood against the walls of the arteries (blood vessels that carry blood from the heart to the rest of the body). Blood pressure is an important indicator of the health of the circulatory system. Any condition that dilates or contracts the arteries or affects their elasticity, or any disease of the heart that interferes with its pumping power, affects blood pressure.

In a healthy human being, blood pressure remains within a certain average range. The complex nervous system mechanisms that balance and coordinate the activity of the heart and arterial muscles permit great local variation in the rate of blood flow without disturbing the general blood pressure.

Hemoglobin, the iron-protein compound that gives blood its red color, also plays a role in regulating local variation in blood pressure. Hemoglobin carries nitric oxide, a gas that relaxes the blood vessel walls. Hemoglobin controls the expansion and contraction of blood vessels, and thus blood pressure, by regulating the amount of nitric oxide to which the vessels are exposed.

Two measurements are used to describe blood pressure. Systolic pressure measures blood pressure when the heart contracts to empty its blood into the circulatory system. Diastolic pressure measures blood pressure when the heart relaxes and fills with blood. Systolic and diastolic pressure are measured in millimeters of mercury (abbreviated mm Hg) using an instrument called a sphygmomanometer. This instrument consists of an inflatable rubber cuff connected to a pressure-detecting device with a dial. The cuff is wrapped around the upper arm and inflated by squeezing a rubber bulb connected to it by a tube. Meanwhile, a health-care professional listens to a stethoscope applied to an artery in the lower arm. As the cuff inflates, it gradually compresses the artery. The point at which the cuff stops the circulation and at which no pulsations can be heard through the stethoscope is read as the systolic pressure. As the cuff is slowly deflated, a spurting sound can be heard when the heart contraction forces blood through the compressed artery. The cuff is then allowed gradually to deflate further until the blood is flowing smoothly again and no further spurting sound is heard. A reading at this point shows the diastolic pressure that occurs during relaxation of the heart. Normal blood pressure in an adult is less than 120/80 mm Hg. The first number describes systolic pressure, while the second number describes diastolic pressure.

Blood pressure is influenced by a wide range of factors and varies between individuals and in the same individual at different times. For instance, blood pressure naturally increases with age because the arteries lose the elasticity that, in younger people, absorbs the force of heart contractions. Other factors, such as emotions, exercise, or stress, may temporarily raise blood pressure.

Abnormally high blood pressure, known as hypertension, that remains untreated can lead to stroke, heart attack, and kidney or heart failure. Hypertension may have no known cause or it may result from heart or blood vessel disorders or from diseases affecting other parts of the body. Abnormally low blood pressure, known as hypotension, may be caused by shock, malnutrition, or some other disease or injury.

Mouth Disease Symptoms, Diagnosis, and Treatment

Mouth DiseaseMouth, opening in an animal's body used for taking in food. Mouths are also typically used for making
sounds, such as barks, chirps, howls, and in humans, speech. In most animals, the mouth is found on the face, near the eyes and nose.

Lips, which form the mouth's muscular opening, are an especially familiar part of the body for humans. Lips help hold food in the mouth and are used to form words during speech. They also help form facial expressions, such as smiling and frowning. Lips open wide during a yawn and squeeze together during a whistle. Lips are darker than the surrounding skin because of the many extremely small blood vessels, called capillaries, that show through the skin.

The cheeks form the sides of the mouth. They are composed of muscle tissue that is covered on the outside by skin. Like the lips, the cheeks help hold food and they also play a role in speech.

Inside the mouth is the large, muscular tongue. This extremely flexible muscle is used for eating and swallowing and also for talking. It is attached to the floor, or bottom, of the mouth. Its upper surface is covered with tiny projections, called papillae, that give the tongue a somewhat rough texture. The papillae contain tiny pores that are the site of taste buds, the receptor cells responsible for our sense of taste. There are four kinds of taste buds that are grouped together on certain areas of the tongue’s surface—those that are sensitive to sweet, salty, sour, and bitter flavors.

The roof, or top, of the mouth is called the palate. It separates the mouth from the nasal passages above it. The front part of the palate—the part closer to the lips—is made of bone covered with moist tissue, called mucous membrane. This part of the mouth is known as the hard palate. Behind the hard palate is the soft palate, a small area composed mainly of muscle tissue. During swallowing, the soft palate presses against the back of the throat, preventing food or liquid from moving upward into the nasal passages.

Teeth are used for biting into and chewing food. Their interaction with the lips and tongue helps a person speak clearly. Children have 20 primary teeth, which begin to erupt, or break through the gums, at about six months of age. At six years of age, the primary teeth start to fall out, as permanent teeth replace them. The number of permanent teeth is 32. The crown, or top, of each tooth is covered with enamel, the hardest substance in the human body.

The mouth also contains three pairs of salivary glands. These glands secrete a watery fluid called saliva, which moistens food and the tissues of the mouth. Saliva contains amylase, a digestive enzyme that starts to break down carbohydrates in food even before it is swallowed. Saliva also contains a specialized protein, or enzyme, called lysozyme, which fights bacteria.

Despite the presence of saliva, many kinds of bacteria live in the warm, moist environment of the mouth. Caring for the mouth, called oral hygiene, helps keep these bacteria from multiplying and causing illness. Daily brushing of the teeth and tongue, flossing between the teeth, and regular checkups with a dentist help keep the mouth clean and the teeth and gums healthy (see Dentistry).

The most common ailment of the mouth is tooth decay. Other disorders affecting the mouth include gingivitis, a condition marked by inflamed, infected gums; trench mouth, a severe form of gingivitis that causes bleeding ulcers in the mouth; and thrush, a fungal infection characterized by white sores in the mouth. Oral cancer is a risk for individuals who smoke or chew tobacco or who drink alcohol excessively. A small lump or thickened tissue in the mouth may indicate cancer. It should be checked by a doctor or dentist without delay, as many oral cancers can be cured if treated early.

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Mythology, GODs, Goddesses, Muses, Monsters - Infoplease, A Particular Culture,

MythologyMythology, the body of myths of a particular culture, and the study and interpretation of such myths. A
myth may be broadly defined as a narrative that through many retellings has become an accepted tradition in
a society. By this definition, the term mythology might include all traditional tales, from the creation stories of ancient Egypt to the sagas of Icelandic literature to the American folktale of Paul Bunyan.

Myths are universal, occurring in almost all cultures. They typically date from a time before the introduction of writing, when they were passed orally from one generation to the next. Myths deal with basic questions about the nature of the world and human experience, and because of their all-encompassing nature, myths can illuminate many aspects of a culture.

II  WHAT ARE MYTHS?

Although it is difficult to draw rigid distinctions among various types of traditional tales, people who study mythology find it useful to categorize them. The three most common types of tales are sagas, legends, and folktales.

When a tale is based on a great historical (or supposedly historical) event, it is generally known as a saga. Despite a saga’s basis in very distant historical events, its dramatic structure and characters are the product of storytellers’ imaginations. Famous sagas include the Greek story of the Trojan War and the Germanic epic poem the Nibelungenlied (Song of the Nibelungs).

A legend is a fictional story associated with a historical person or place. For example, many early saints of the Christian church are historical figures whose lives have been embellished with legend (see Saint Denis; Saint George). Legends often provide examples of the virtues of honored figures in the history of a group or nation. The traditional American story about young George Washington and the cherry tree—in which he could not lie about chopping it down—is best described as a legend, because George Washington is a historical figure but the story about the cherry tree is recognized today as fictional.

Folktales, a third variety of traditional tale, are usually simple narratives of adventure built around elements of character and plot—for example, the young man who slays a monster and wins the hand of a princess. The Greek tale of Perseus is a good example of this theme. He saves the Ethiopian princess Andromeda from a sea monster and then marries her. Folktales may contain a moral or observation about life, but their chief purpose is entertainment.

Myths may include features of sagas, legends, and folktales. What makes one of these tales a myth is its serious purpose and its importance to the culture. Experts usually define a myth as a story that has compelling drama and deals with basic elements and assumptions of a culture. Myths explain, for example, how the world began; how humans and animals came into being; how certain customs, gestures, or forms of human activity originated; and how the divine and human worlds interact. Many myths take place at a time before the world as human beings know it came into being. Because myth-making often involves gods, other supernatural beings, and processes beyond human understanding, some scholars have viewed it as a dimension of religion. However, many myths address topics that are not typically considered religious—for example, why features of the landscape take a certain shape.

III  COMMON TYPES OF MYTHS,

No system of classification encompasses every type of myth, but in discussing myths it is helpful to group them into broad categories. This article concentrates on three major categories: cosmic myths, myths of gods, and hero myths.

A  Cosmic Myths,

Cosmic myths are concerned with the world and how it is ordered. They seek to explain the origin of the world, universal catastrophes such as fire or flood, and the afterlife. Nearly all mythologies have stories about creation, a type of story technically known as cosmogony, meaning “birth of the world.” Creation stories also include accounts of how human beings first came into existence and how death and suffering entered human experience.

The oldest cosmogonies known today are those of Egypt and the ancient Near East. An example is the creation epic of the Babylonians, Enuma elish (When on high), which dates back to at least the 12th century bc. According to Enuma elish, in the beginning of the world there was only a watery void in which fresh waters mingled with salt waters of the sea. The fresh waters were personified as Apsu, a male being, and the salt waters as Tiamat, a female. The myth describes a conflict between these earliest gods and a younger generation that sprang from them. Ultimately the younger gods won the war, led by Marduk, a god of thunder and lightning who resembles the Greek god Zeus and the Norse god Thor. Marduk defeated the army of the elder gods and killed Tiamat—represented as a dragon—in single combat. He then split her carcass in two, forming heaven and earth from the halves, and established the sun, moon, and constellations.

Enuma elish contains several themes common to many ancient Near Eastern creation stories: the ordering of the world out of chaos, the central role of waters in the creation of the world, the victory of a divine king over enemies who represent chaos, and the creation of matter from the corpse of a world-mother. A very different type of creation story appears in the Spider Woman myth of the Native American Hopi people. According to this narrative, in the beginning the only two beings in existence were Tawa, the sun god, and Spider Woman, an earth goddess who lived in a shadowy, cavelike underworld. Human beings were created from clay by Spider Woman and animated by the gaze of Tawa. Tawa used his light and heat to create dry land, and the world took shape. Spider Woman led the humans and other creatures up to the earth’s surface, and each species was assigned its proper residence and role in the world. This myth features the common Native American theme of emergence, in which creatures emerge from the earth as if from a mother’s womb.

Other types of creation myth occur in the cosmogony of the Maya people, with its many cycles of creation and destruction, and in the ancient Hebrew account of creation by a single, all-powerful deity.

B  Myths of the GODs,

Many myths do not directly concern human beings, but focus rather on the activities of the gods in their own realm. In many mythologies the gods form a divine family, or pantheon (from the Greek pan, meaning “all,” and theos, “god”). The story of a power struggle within a pantheon is common to a large number of world mythologies—for example, the Babylonian Enuma elish centers on Marduk’s struggle for supremacy and his eventual victory over Tiamat. Greek mythology features a similar story of struggle between generations. In Greek mythology, the earliest gods were Gaea (Earth) and Uranus (Heaven), and their children were called the Titans. The eldest of the Titans, Cronus, overthrew his father and was eventually overthrown by his own son, Zeus, who became the new master of the universe. Similarly, the Aesir–the pantheon of the Norse gods—had to overcome an older group called the Vanir before gaining power. Unlike the Greek and Babylonian accounts, the Norse myth features a reconciliation between the two sides.

 In Greek mythology, Hermes (best known as the messenger of the gods) was a famous trickster.

Across cultures, mythologies tend to describe similar characters. A common character is the trickster. The trickster is recklessly bold and even immoral, but through his inventiveness he often helps human beings. In Greek mythology, Hermes (best known as the messenger of the gods) was a famous trickster. In one version of a characteristic tale, Hermes, while still an infant, stole the cattle of his half-brother Apollo. To avoid leaving a trail that could be followed, Hermes made shoes from the bark of a tree and used grass to tie them to the cattle’s hooves. When Apollo nonetheless discovered that Hermes had stolen his cattle, he was furious. In the end, Apollo was so enchanted with the music of a lyre that Hermes had made that he allowed Hermes to keep the cattle in exchange for the lyre. Other tricksters of mythology are the West African god Eshu, who tricked the supreme god Olodumare into abandoning the earth to dwell in heaven; the Indian god Krishna, whose trickery often aims at a higher moral purpose; and the Native American Coyote, who scattered the once-orderly stars in the sky and strewed the plants on earth.

Myths about the gods are as numerous as the cultures that produce them. Other types that occur across various cultures include myths about the Great Mother (for example, the Mesopotamian Ishtar, who journeys to the underworld to rescue her lost lover Tammuz); the Dying God (for example, the Egyptian Osiris, who is murdered and dismembered but ultimately resurrected); and the Savior God (for example, the Greek Prometheus, who helps humanity at the cost of incurring Zeus’s anger).
C Myths of Heroes,
Nearly all cultures have produced myths about heroes. Some heroes, such as the Greek Achilles, have one mortal and one divine parent. Others are fully human but are blessed with godlike strength or beauty. Many myths about heroes concern significant phases of the hero’s career, such as the circumstances of the hero’s birth, a journey or quest, and the return home.

The birth and infancy of a mythological hero is often exceptional or even miraculous. In the ancient Near Eastern and Mediterranean world, the births of many heroes followed similar patterns. For example, the Hebrew prophet Moses, the Greek hero Oedipus, and the Roman heroes Romulus and Remus were all exposed to the elements at birth and left to die, but miraculously survived. Other heroes were immediately able to care for themselves. In early infancy, the Greek hero Hercules strangled a pair of enormous serpents sent to kill him. The Irish Cú Chulainn, who later became a great warrior, also performed astonishing feats of strength as a child.

Most heroes set off on a quest or a journey of some kind. One of the earliest tales of a hero’s journey is the Babylonian story known as the Gilgamesh epic, written in cuneiform on 12 clay tablets in about 2000 bc. The hero, Gilgamesh, embarks on a quest for immortality. A goddess named Siduri guides him, and in the course of his adventures he must do combat with monsters and visit the world of the dead. At the end of the quest, Gilgamesh must accept mortality, which the gods allotted to human beings when they created them. In Greek and Roman mythology the stories of Jason (who sailed in quest of the Golden Fleece) and of Aeneas (who traveled from Troy to Italy to found Rome) likewise describe journeys or quests. Other narratives that may be interpreted as heroic journeys include the biblical story of the Hebrew prophet Moses, who led his people on a 40-year journey through the wilderness, and the Celtic tale of King Arthur and the quest for the Holy Grail (see Arthurian Legend).

The most famous tale of a hero’s return home is probably the ancient Greek story of Odysseus, recounted in the Odyssey by the poet Homer. When the story opens, Odysseus has been away for nearly 20 years, fighting in the Trojan War and then kept captive by the sea nymph Calypso. Back in his kingdom of Ithaca, suitors who want to marry his wife Penelope are devouring and wasting his property and plotting against his son. Zeus persuades Calypso to let Odysseus leave and return home, but the god Poseidon is angry with Odysseus and is determined to kill him. In the course of his journey, Odysseus is shipwrecked, held captive by Calypso, and nearly devoured by monsters; all his companions are killed. When he finally returns to Ithaca, penniless and without allies, he must plot the destruction of the suitors and persuade Penelope that he really is who he claims to be. Of course, he succeeds brilliantly.


Native Americans of North America (History),

Native Americans of North America, Native Americans of North America, indigenous peoples of North America. Native Americans had lived
throughout the continent for thousands of years before Europeans began exploring the “New World” in the 15th century.

Most scientists agree that the human history of North America began when the ancient ancestors of modern Native Americans made their way across a land bridge that once spanned the Bering Sea and connected northeastern Asia to North America. Scientists believe these people first migrated to the Americas more than 10,000 years ago, before the end of the last ice age (see Migration to the Americas). However, some Native Americans believe their ancestors originated in the Americas, citing gaps in the archaeological record and oral accounts of their origins that have been passed down through generations.

Native Americans excelled at using natural resources and adapting to the climates and terrains in which they lived. Over thousands of years distinct culture areas developed across North America. In the Northeast, for example, Native Americans used wood from the forests to build houses, canoes, and tools. Dense populations in the Pacific Northwest exploited the abundance of sea mammals and fish along the Pacific Coast. In the deserts of the Southwest, Native Americans grew corn and built multilevel, apartment-style dwellings from adobe, a sun-dried brick. In the Arctic, inhabitants adapted remarkably well to the harsh environment, becoming accomplished fishers and hunters.

Among the several hundred Native American groups that settled across North America, there existed, and still exists, many different ways of life and world views. Each group had distinctive social and political systems, clothing styles, shelters, foods, art forms, musical styles, languages, educational practices, and spiritual and philosophical beliefs. Nevertheless, Native American cultures share certain traits that are common to many indigenous peoples around the world, including strong ties to the land on which they live.

When European explorers and settlers began to arrive in the Americas in the 15th century, Native Americans found themselves faced with a new set of challenges. Some Native Americans learned to coexist with Europeans, setting up trade networks and adopting European technologies. Many more faced generations of upheaval and disruption as Europeans, and later Americans and Canadians, took Native American lands and tried to destroy their ways of life. During the 20th century, however, Native American populations and cultures experienced a resurgence. Today, Native Americans are working to reassert more control over their governments, economies, and cultures.

The indigenous peoples of North America are known by many terms. Most tribal peoples prefer to be identified by their tribal affiliation, such as Hopi, Onondaga, Mohawk, or Cherokee. The most common collective terms are Native American or American Indian. For many years, Indian was the most prevalent term. When Christopher Columbus and other European explorers arrived in the Americas, they thought they were in Asia, which the Spanish referred to as “the Indies.” They called the native peoples indios, as in the people of the Indies, later translated to Indian. However, some scholars believe the Europeans were not calling native peoples indios, but rather In Dios, meaning “Of God.”

The term Native American became popular in the United States in the 1960s, although some people believe it is too broad because it can refer to anyone born in the Americas, including Hawaiians and descendants of immigrants. In Canada, aboriginal people is a commonly used collective term. It refers to Indians, Métis (people of mixed indigenous and European ancestry), and Inuit. In the 1970s many Indians in Canada began calling their bands First Nations. When referring to the original inhabitants of the United States, this article uses Native Americans, American Indians, Indians, and native peoples interchangeably. When referring to the original inhabitants of Canada, the article generally uses aboriginal peoples, indigenous peoples, and native peoples.

This article divides its discussion of Native Americans into four main parts. The Culture Areas section examines Native American ways of life in ten different geographic regions. Traditional Way of Life looks at specific aspects of Native American life, such as food, clothing, and music. The History section describes the history of Native Americans in North America from the earliest times to the present day. Native Americans Today discusses contemporary life for indigenous peoples in the United States and Canada.

For a discussion of the indigenous peoples of Middle and South America, see Native Americans of Middle and South America. Other major articles on Native Americans in North America include Indian Treaties in Canada, Migration to the Americas, Native American Architecture, Native American Art, Native American Languages, Native American Literature, Native American Policy, and Native American Religions.

Rocket, Self Propelled Device As a FireWork,

Rockets and MissilesRocket, self-propelled device that carries its own fuel, as well as the oxygen, or other chemical agent,

A rocket can be as simple and small as a firework, which has a small amount of thrust, or as complex and powerful as the Saturn V rocket, which took humans to the Moon. British Congreve war rockets, which were used in the War of 1812, are referred to in a line of the United States national anthem: “And the rockets red glare…” Rockets have many applications both on Earth and in space. The most common and well-known use of rockets is for missiles—weapons that deliver explosive warheads through the air to specified targets (see Guided Missile). Rockets also have numerous peaceful purposes. Upper atmospheric research rockets, or sounding rockets, carry scientific instruments to high altitudes, helping scientists carry out astronomical research and learn more about the nature of the atmosphere. Jet-Assisted-Take-Off (JATO) rockets help lift heavily loaded planes from runways. Lifesaving rockets carry lifeline ropes to ships stranded offshore. Ships in distress can launch signal rockets to signal for help. Rocket ejection seats safely boost pilots out of jet planes during emergencies. Fireworks have provided entertainment for centuries, and model rockets form the basis of a popular hobby.

II  ROCKET USES,

People use all kinds of rockets for the same basic purpose: to carry objects through air and space. Missiles carry explosive devices to targets, while sounding rockets carry scientific instruments into the upper atmosphere. Launch vehicles boost satellites and other spacecraft into space, and smaller thruster rockets steer or stabilize spacecraft in space.

A  Missiles,

The term missile actually means any object thrown at an enemy and includes arrows, bullets, and other weapons. In modern military usage, however, missile usually means an explosive device propelled through the air by a rocket or an air-breathing engine. (Air-breathing engines differ from rockets in that rockets carry their own oxygen, while air-breathing engines get their oxygen from the air as they fly through it.)

Missiles can be launched from the ground, from airplanes, and even from submarines. Some missiles are designed to hit targets in the air, while others are built to hit targets on the ground. Some missiles, called guided missiles, have steering systems that guide them to their target.

B  Sounding Rockets,


Scientists use sounding rockets to carry scientific instruments into the upper atmosphere to take measurements of air quality, radiation from space, and other data. Many countries use sounding rockets to monitor weather and pollution. Engineers enable a rocket to reach its target altitude by shutting down the rocket at a specific height. The rocket then coasts upward until air friction and gravity stop its upward movement and cause it to fall back to Earth. The instruments usually include a radio transmitter that sends measurements back to Earth. Some sounding rockets carry parachutes that allow their controllers to recover the rocket and the instruments, but some fall back to Earth without a parachute. Engineers design a sounding rocket’s flight path so that the rocket will fall into the ocean or into an uninhabited area in order to avoid damaging property or hurting people.

C  Launch Vehicles,


Launch vehicles send satellites and other spacecraft into space. These vehicles must be far more powerful than other types of rockets, because they carry more cargo farther and faster than other rockets. To place an object into orbit around Earth, the launch vehicle must reach a velocity of about 30,000 km/h (about 18,500 mph). To escape Earth’s gravitational pull entirely and head into deep space, these rockets must attain a velocity, called an escape velocity, of about 40,000 km/h (about 25,000 mph). Engineers have found that the most efficient way for launch vehicles to reach these speeds is to use staged rockets, or rockets divided into different stages, one atop another.

D  Thrusters,

Many spacecraft use small rockets called thrusters to move around in space. Thrusters can change the speed and direction of a spacecraft. They allow a spacecraft to steer in space, to jump to a higher orbit, or to fall back to Earth.

III  HOW ROCKETS WORK,

All rockets—whether small or large, simple or complex—work by the basic principle of action and reaction, which was formulated by English scientist Sir Isaac Newton in 1687. Newton’s third law of motion states, “For every action there is an equal and opposite reaction.” In the case of the rocket, the expulsion of exhaust gases from the rear is the action, and the forward movement of the rocket is the reaction.



needed to burn its fuel. Most rockets move by burning their fuel and expelling the hot exhaust gases that result. The force of these hot gases shooting out in one direction causes the rocket to move in the opposite direction. A rocket engine is the most powerful engine for its weight. Other forms of propulsion, such as jet-powered and propeller-driven engines, cannot match its power. Rockets can operate in space, because they carry their own oxygen for burning their fuel. Rockets are presently the only vehicles that can launch into and move around in space.