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Astronomers use tools such as telescopes, cameras, spectrographs, and computers to analyze the light that astronomical objects emit. Amateur astronomers observe the sky as a hobby, while professional astronomers are paid for their research and usually work for large institutions such as colleges, universities, observatories, and government research institutes. Amateur astronomers make valuable observations, but are often limited by lack of access to the powerful and expensive equipment of professional astronomers.
A wide range of astronomical objects is accessible to amateur astronomers. Many solar system objects—such as planets, moons, and comets—are bright enough to be visible through binoculars and small telescopes. Small telescopes are also sufficient to reveal some of the beautiful detail in nebulas—clouds of gas and dust in our galaxy. Many amateur astronomers observe and photograph these objects. The increasing availability of sophisticated electronic instruments and computers over the past few decades has made powerful equipment more affordable and allowed amateur astronomers to expand their observations to much fainter objects. Amateur astronomers sometimes share their observations by posting their photographs on the World Wide Web, a network of information based on connections between computers.
Amateurs often undertake projects that require numerous observations over days, weeks, months, or even years. By searching the sky over a long period of time, amateur astronomers may observe things in the sky that represent sudden change, such as new comets or novas (stars that brighten suddenly). This type of consistent observation is also useful for studying objects that change slowly over time, such as variable stars and double stars. Amateur astronomers observe meteor showers, sunspots, and groupings of planets and the Moon in the sky. They also participate in expeditions to places in which special astronomical events—such as solar eclipses and meteor showers—are most visible. Several organizations, such as the Astronomical League and the American Association of Variable Star Observers, provide meetings and publications through which amateur astronomers can communicate and share their observations.
It seems likely that everyday activities, such as the movements in repetitive work and in walking, were rhythmically regular enough to invite some sort of embellishment. Related breathing rhythms, chanting, or other accompaniment, such as the tapping of a walking stick while walking or the transformation of a work tool into an instrument while working, may have been early forms of music. In fact, whether sacred Native American corn-gathering songs or melodies heard in elevators or supermarkets, music still accompanies our ceremonial and everyday activities.
Scholars can only speculate about when music began or which cultures had music first. From ancient times people have told stories of its origins. The so-called music of the spheres was thought by Greek philosopher and mathematician Pythagoras in the 6th century BC—and by later classical and medieval philosophers of the Western world—to be a perfectly harmonious music, inaudible on Earth, produced by the movement of the stars and planets. In many non-Western cultures ancient thinkers understood music as part of a system of cosmological, philosophical, or scientific thought. For instance, the musical scale of ancient China, derived through arithmetic from a basic note, reflected the ancient Chinese conception of the organization of the universe. Each degree of the scale was closely related to the cardinal points (north, south, east, west), the elements, the seasons, the planets, the months of the year, colors, materials, numbers, parts of the human body, animals, smells, and so forth. The Chinese found in nature eight different sources of musical sound: metal, stone, silk, bamboo, calabash, terra cotta, skin, and wood.
Many of the elaborate melody patterns of India, called ragas, are believed to have magical or curative powers. Ragas are traditionally played at specific hours or during specific seasons; it is believed that to depart from this timetable would be harmful to the performer and audience. In some tribal societies, music appears to serve as a special form of communication with supernatural beings, and the prominent use of music in modern Christian and Jewish services may be a remnant of such a purpose. Music has always held an important role in religious rituals.
Like the glass panes in a greenhouse, certain gases in the Earth’s atmosphere permit the Sun’s radiation to heat Earth. At the same time, these gases retard the escape into space of the infrared energy radiated back out by Earth. This process is referred to as the greenhouse effect. These gases, primarily carbon dioxide, methane, nitrous oxide, and water vapor, insulate Earth’s surface, helping to maintain warm temperatures. Without these gases, Earth would be a frozen planet with an average temperature of about -18°C (about 0°F) instead of a comfortable 15°C (59°F). If the concentration of these gases rises, they trap more heat within the atmosphere, causing worldwide temperatures to rise.
Within the last century, the amount of carbon dioxide in the atmosphere has increased dramatically, largely because people burn vast amounts of fossil fuels—coal and petroleum and its derivatives. Average global temperature also has increased—by about 0.6 Celsius degree (1 Fahrenheit degree) within the past century. Atmospheric scientists have found that at least half of that temperature increase can be attributed to human activity. They predict that unless dramatic action is taken, global temperature will continue to rise by 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) over the next century. Although such an increase may not seem like a great difference, during the last ice age the global temperature was only 2.2 Celsius degrees (4 Fahrenheit degrees) cooler than it is presently.
The consequences of such a modest increase in temperature may be devastating. Already scientists have detected a 40 percent reduction in the average thickness of Arctic ice. Other problems that may develop include a rise in sea levels that will completely inundate a number of low-lying island nations and flood many coastal cities, such as New York and Miami. Many plant and animal species will probably be driven into extinction, agriculture will be severely disrupted in many regions, and the frequency of severe hurricanes and droughts will likely increase.
In 1812 Napoleon, whose alliance with Alexander I had disintegrated, launched an invasion of Russia that ended in a disastrous retreat from Moscow. Thereafter all Europe united against him, and although he fought on, and brilliantly, the odds were impossible. In April 1814, his marshals refused to continue the struggle. After the allies had rejected his stepping down in favor of his son, Napoleon abdicated unconditionally and was exiled to the Mediterranean island of Elba.
Marie Louise and his son were put in the custody of her father, the emperor of Austria. Napoleon never saw either of them again. Napoleon himself, however, soon made a dramatic comeback. In March 1815, he escaped from Elba, reached France, and marched on Paris, winning over the troops sent to capture him. In Paris, he promulgated a new and more democratic constitution, and veterans of his old campaigns flocked to his support. Napoleon asked peace of the allies, but they outlawed him, and he decided to strike first. The result was a campaign into Belgium, which ended in defeat at the Battle of Waterloo on June 18, 1815. In Paris, crowds begged him to fight on, but the politicians withdrew their support. Napoleon fled to Rochefort, where he surrendered to the captain of the British battleship Bellerophon. He was then exiled to Saint Helena, a remote island in the south Atlantic Ocean, where he remained until his death on May 5, 1821
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Excavations at Stonehenge since the 1950s suggest the monument was constructed in three main phases. The earliest phase of Stonehenge was completed by about 2900 BC. It consisted of a circular ditch 110 m (360 ft) in diameter and 1.5 m (5 ft) deep. Archaeologists believe deer antlers were used as picks to loosen the chalk bedrock. Excavated material was used to build a circular embankment along the inside rim of the ditch. Along the interior edge of the embankment the ancient architects dug 56 pits. These pits are named Aubrey Holes, after John Aubrey, who first observed them. The pits may once have held wooden posts.
In a second phase of construction, lasting from about 2900 to 2500 BC, several new timber structures arose at Stonehenge. Timber posts were erected in the flat ground at the center of the encircling ditch. Posts were also raised at a break in the ditch to the northeast, a place that served as an entrance to the site.
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I. Population Growth
Human population growth is at the root of virtually all of the world’s environmental problems. Although the growth rate of the world’s population has slowed slightly since the 1990s, the world’s population increases by about 77 million human beings each year. As the number of people increases, crowding generates pollution, destroys more habitats, and uses up additional natural resources
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Code Napoléon, designation officially applied in 1807 to the code of French civil law originally enacted in March 1804 as the Code Civil des Français and still in force in France. Properly, the term applies to the entire body of French law, as contained in five codes dealing with civil, commercial, and criminal law, promulgated between 1804 and 1811. An initial draft completed in 1793, following the outbreak of the French Revolution, was a protest against the extreme diversity in the laws then in force in different parts of France. This draft was rejected by the National Convention, but finally the task of preparing another draft was entrusted in July 1800 to a commission consisting of the most eminent jurists of France. The new draft, with some conservative features, was completed in four months. It encountered considerable opposition before it was finally enacted. It was named in honor of Napoleon, emperor of France, who had participated in the formulation.
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Retail Web sites typically include electronic catalogs that describe and display products for sale. Consumers can search for individual items or randomly browse electronic catalogs, some much larger than their mail order print counterparts. An Internet book retailer, for example, can offer millions of different book titles for sale on its Web site, far more titles than could fit into a store or that could be included cost-effectively in a print catalog.
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Electronic Commerce or e-commerce, the exchange of goods and services by means of the Internet or other computer networks. E-commerce follows the same basic principles as traditional commerce—that is, buyers and sellers come together to exchange goods for money. But rather than conducting business in the traditional way—in stores and other “brick and mortar” buildings or through mail order catalogs and telephone operators—in e-commerce buyers and sellers transact business over networked computers.
E-commerce offers buyers convenience. They can visit the World Wide Web sites of multiple vendors 24 hours a day and seven days a week to compare prices and make purchases, without having to leave their homes or offices. In some cases, consumers can immediately obtain a product or service, such as an electronic book, a music file, or computer software, by downloading it over the Internet
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The cult of Napoleon as the “man of destiny” began during his lifetime. In fact, he had begun to cultivate it during his first Italian campaign by systematically publicizing his victories. As first consul and emperor, he had engaged the best writers and artists of France and Europe to glorify his deeds and had contributed to the cult himself by the elaborate ceremonies with which he celebrated his rule, picturing himself as the architect of France’s greatest glory. He maintained that he had preserved the achievements of the Revolution in France and offered their benefits to Europe. His goal, he said, was to found a European state—a “federation of free peoples.” Whatever the truth of this, he became the arch-hero of the French and a martyr to the world. In 1840 his remains were returned to Paris at the request of King Louis-Philippe and interred with great pomp and ceremony in the Invalides, where they still lie.
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