Solar Energy

Solar Energy, radiation produced by nuclear fusion reactions deep in the Sun’s core. The Sun provides almost all the heat and light Earth receives and therefore sustains every living being.


Solar energy travels to Earth through space in discrete packets of energy called photons (Electromagnetic Radiation). On the side of Earth facing the Sun, a square kilometer at the outer edge of our atmosphere receives 1,400 megawatts of solar power every minute, which is about the capacity of the largest electric-generating plant in Nevada. Only half of that amount, however, reaches Earth’s surface. The atmosphere and clouds absorb or scatter the other half of the incoming sunlight. The amount of light that reaches any particular point on the ground depends on the time of day, the day of the year, the amount of cloud cover, and the latitude at that point. The solar intensity varies with the time of day, peaking at solar noon and declining to a minimum at sunset. The total radiation power (1.4 kilowatts per square meter, called the solar constant) varies only slightly, about 0.2 percent every 30 years. Any substantial change would alter or end life on Earth.

SOLAR ENERGY STORAGE DEVICES
Because of the intermittent nature of solar radiation as an energy source, excess solar energy produced during sunny periods must be stored. Insulated tanks commonly store this energy in hot water. Batteries often store excess electric energy produced from wind or photovoltaic devices. One possibility for the future is the use of excess solar-generated electric energy as a supplemental source for existing power networks. Uncertain economics and reliability, however, make this plan difficult to implement.

Mountain Climbing

Mountain Climbing, ascending mountains, most commonly as a recreational activity. Mountain climbing is popular worldwide, wherever hills rise high enough to provide challenge. The activity’s rewards include the physical exertion it requires, the satisfaction of overcoming difficulties by working with others, the thrill of reaching a summit, and the unobstructed view from a mountaintop. Exploration and research are other reasons that people climb mountains.

Ascents can be either non technical (a hike up a path or a scramble over rocks, not requiring the safety of a rope), or technical (a climb up more difficult terrain that requires the use of rope and other specialized equipment). This article focuses on technical climbs, which involve all the elements of simple hikes but also require advanced knowledge and equipment. Making technical climbs is also known as mountaineering.

Since ancient times, people have viewed mountain peaks as towering objects of myth, spiritual inspiration, and romantic beauty. Early peoples made ascents only to hunt game, to rescue lost or strayed animals, or to gain a military advantage over an enemy. Eventually, the unknown and inaccessible ceased to be something to be feared and avoided, and the conquest of the major mountain peaks and ranges of the world began. Mountaineering as a sport was born on August 8, 1786, with the first ascent of Mont Blanc (4807 m/15,771 ft), one of Europe’s tallest peaks. Since that ascent, mountain climbing has evolved into three related sports: alpine climbing, ice climbing, and rock climbing. These sports require the same fundamental techniques.

Rock Climbing Equipment

Rock climbing shoes resemble toughened ballet slippers, made of supple leather or synthetic materials. They have sticky rubber soles, and toes and heel-liners made of rubber. All climbing shoes and slippers should be fitted snugly around the foot. Climbers use gymnastic chalk (magnesium carbonate) to dry sweat from their hands and fingers while climbing. The white powder is carried in a small pouch called a chalk bag that is attached to the climber’s harness.

Because rock climbing requires plenty of innovative, supple movements, clothing should be lightweight, comfortable, and nonrestricting. T-shirts, shorts, and tights made of cotton, Lycra-cotton blends, and other synthetic materials are popular. Rock climbers also use athletic tape to protect fingers, knuckles, and wrists during difficult climbs.

History of Mountaineering

People have long climbed mountains for necessary daily activities such as retrieving lost animals and hunting, but technical climbing as a sport has a much shorter history. The sport’s history is often described in terms of first ascents, the conquering of previously unscaled mountains or, on mountains that have already been climbed, the accomplishment of previously untried and unclimbed routes.

After the ascent of Mont Blanc in 1786, people began to organize expeditions to make first ascents. Some of the most challenging mountains were found in the Himalayas of Central Asia, which contain many of the world’s highest peaks. In 1953 New Zealand climber Sir Edmund Hillary and Sherpa Tenzing Norgay made the first ascent of the world’s highest mountain, the Himalayan peak Mount Everest (8848 m/29,028 ft). A year later Italian mountaineers Achille Compagnoni and Lino Lacedelli ascended the world’s second highest mountain, K2 (8611 m/28,250 ft).

As more of the world’s mountains were climbed for the first time, mountaineers sought to challenge themselves by using more difficult routes and by climbing with less assistance from climbing partners. Italian mountaineer Reinhold Messner and Austrian climber Peter Habeler became the first to scale Everest without bottled oxygen in 1978. Two years later Messner returned to climb Everest completely alone and without oxygen.

During the 1980s and 1990s ascents became even more daring, and some climbers attempted to ascend different series of related summits. In 1985 American climber Dick Bass became the first mountaineer to climb the highest mountain on each of the seven continents, collectively referred to as the Seven Summits. In 1986 Messner finally completed his goal of climbing the 14 highest mountains in the world—a feat that took him 17 years to accomplish. All are higher than 8000 m (26,247 ft) and located in Nepal, Pakistan, China, and Tibet.

United States Air Force

United States Air Force, the branch of the United States armed forces responsible for conducting military operations in air and space. The United States Air Force was formed from the Army Air Corps in 1947. The Air Force plays a critical role in the defense of the United States through control of air and space. The Air Force deploys aircraft to fight enemy aircraft, bomb enemy targets, provide reconnaissance, and transport soldiers for the other armed services. The Air Force also maintains most of the country’s nuclear forces, including a fleet of strategic bombers that carry nuclear weapons and land-based nuclear missiles. In addition, the Air Force launches and maintains a wide variety of military satellites.

In 2003 there were approximately 368,000 airmen (the term for both men and women soldiers) in the U.S. Air Force, including about 4,000 cadets at the United States Air Force Academy near Colorado Springs, Colorado. About one of every five members of the Air Force is an officer. In 2003 there were more than 150,000 civilians working for the Department of the Air Force, with another 181,000 Air Reserve and Air National Guard personnel.

THE LIFE OF AN AIRMAN

United States Air Force airmen include commissioned officers and enlisted members. In 2003 there were about 76,000 officers (including cadets at the Air Force Academy) and 292,000 enlisted members. Roughly one-fifth of all Air Force personnel were female. African Americans made up about 15 percent of the total Air Force, Hispanic Americans about 4 percent, and Native Americans, Pacific Islanders, and other minority groups about 4 percent of the total force. Homosexuals can serve in the Air Force, but they must conform to the U.S. military’s “don’t ask, don’t tell” policy. Under this policy, homosexuals will not be sought out for expulsion from the Air Force, but they may be forced to leave the service if their sexual orientation becomes known.

Stock Car Racing

Although stock cars race in several countries, the class is most associated with the United States because of the powerful public presence of the National Association for Stock Car Auto Racing (NASCAR), the sport's governing body. Stock car racing was once associated primarily with the southern United States, but now enjoys a national audience. Stock cars were similar to conventional cars when this type of racing began, just prior to World War II (1939-1945). But since NASCAR was founded in the late 1940s there has been a trend away from street cars. Despite relatively normal outward appearances, today’s stock cars are pure racing machines that can reach speeds of up to 200 mph (322 km/h). Originally run on beaches and dirt tracks, NASCAR races are now held on paved ovals and, in major events, on high-banked super speedways. The major stock car racing events are the Daytona 500, run in Daytona Beach, Florida, and the World 600, in Charlotte, North Carolina. NASCAR’s marquee racing series is the Winston Cup.


Stock car racing’s fan base grew rapidly in the 1990s. One factor is that stock car drivers are generally more accessible to fans than F1 or sports car drivers. In addition, stock car drivers and their cars—familiar names such as Dodge, Ford, Chevrolet, and Pontiac—usually receive better American media coverage than other forms of racing. While some of the most successful stock car drivers retired in the 1990s, such as Richard Petty and Bobby Allison, younger drivers, such as Jeff Gordon, Ricky Rudd, Tony Stewart, Dale Earnhardt, Jr., and Kevin Harvick have replaced them as stars of the sport. Stock car racing below the NASCAR level is a thriving sport in the United States, bolstered by a well-established fan base. These stock cars run on many of the same tracks that are used for other racing series.

Therapy

Therapy, any of various techniques used in the treatment of physical or mental illnesses. Therapy is used not only during the course of a disease but also after recovery if the patient suffers lingering effects. Although some disorders may be treated by only one form of therapy, a combination of therapeutic techniques is often required.

In treating physical diseases, probably the most common form of therapy in Western medicine is chemotherapy, or drug therapy. The many drugs available range from commonly used compounds like aspirin, which reduces fever and relieves pain, to the complex chemicals used in the treatment of cancer. Some physical conditions can be corrected through surgery while others may be effectively treated by radiotherapy, which involves the use of X rays or other types of radiation . Radiotherapy is frequently used in the treatment of cancer, often in combination with surgical treatment and chemotherapy. Therapeutic methods drawn from non-Western traditions are collectively referred to as alternative medicine and include techniques such as chiropractic, acupuncture, and homeopathy.

Like physical disorders, mental illnesses may be treated with drugs, particularly antidepressants. However, while drugs help relieve the patient’s symptoms, they seldom cure the underlying problems. More useful therapies include techniques that rely heavily on verbal and emotional communication. Collectively referred to as psychotherapy, these techniques help the patient to express, understand, and cope with underlying problems that are not due to physical disease. Emotionally disturbed children who cannot express their problems verbally may be treated by play therapy. The children are encouraged to engage in certain forms of recreation or to act out scenes on the theory that this process will reveal their feelings. Similar treatment, sometimes called psychodrama, may be used to help adults.

The final stage in treatment of physical and mental illnesses is often rehabilitation. This may include physical therapy, which involves exercise, massage, and the application of heat and water (hydrotherapy) to improve or restore functioning to damaged and weakened parts of the body. People with disabilities also benefit from recreational and occupational therapy, which helps people master their personal and work-related activities, such as buttoning clothes or cooking while seated in a wheelchair. Speech therapy is given to people who have speech problems of physical or psychological origin. In addition, people with disabilities may require psychotherapy to help them overcome the emotional and psychological problems that are sometimes associated with disability.

Domain Name System

Domain Name System (DNS), in computer communications, a method of translating Internet addresses so that computers connected in the Internet can find each other. A DNS server translates a numerical address assigned to a computer (such as 207.46.228.91) into a sequence of words, and vice versa. A DNS name, written in lowercase letters with words separated by periods, takes the form of username@computer.zonename . Username is the name or account number used to log on. The hostname (Whitehouse in the example above) is the name of the computer or Internet provider; it may consist of several parts. Zonename indicates the type of organization. Common zone names include com (commercial organization), edu (educational), gov (government), and net (networking organization).

Space Telescope

Space Telescope, telescope or other astronomical detector mounted on an artificial satellite that orbits Earth. In the late 20th century astronomers’ view of the universe was revolutionized because of observations made by telescopes in orbit. Compared to Earth-based telescopes, space telescopes offer a much clearer view of astronomical objects because the instruments are far above Earth’s turbulent, distorting atmosphere. Telescopes in orbit can also cover the entire celestial sphere, while portions of the sky may not be accessible to stationary ground-based telescopes, depending on their location on Earth.

Space telescopes also have access to a wider part of the electromagnetic spectrum (see Electromagnetic Radiation), including X rays, gamma rays, ultraviolet light (see Ultraviolet Radiation), and much of the infrared spectrum (see Infrared Radiation). Each of these spectra offers a new window onto the universe that carries a wealth of information about planets, stars, and galaxies, and also the processes that shape them. Phenomena such as active galaxies and black holes cannot be fully understood without comparing data from across the electromagnetic spectrum.

Space telescopes range in complexity from small satellites, which often survey the entire sky, to larger “observatory-class” satellites, which can target particular objects. These larger satellites generally require more intensive control from scientists on the ground, who choose objects to be studied and help point the satellites in the correct direction.

The World's Endangered Languages

By Doug Whalen and K. David Harrison
As the second millennium comes to a close, more than 6,000 distinct human languages are in use worldwide. Many linguists predict that by the year 2100, only half of these languages will still be spoken—a loss of one language every 12 days.

Why are languages disappearing? The most fundamental reason is increased contact among formerly isolated human societies. Languages need isolation to develop and to maintain their distinctive characteristics. When isolation ends, local languages tend to disappear along with traditional ways of life.

Many indigenous peoples and linguists are working to halt this trend, which threatens to diminish the world’s cultural and linguistic heritage. Much of a society’s history and culture is contained in its language. To lose an ancestral language is to weaken the links to the ancestors themselves. As languages disappear, a wealth of culture, art, and knowledge disappears with them. The world’s many languages also offer anthropologists a unique resource for studying how humans spread across the Earth. Much of what is known about the historical movement of human beings comes from the study of languages that were spoken by ancient peoples of the Earth.