NAVIGATION The sailors of antiquity studied the night sky. Reading the sky map, they could sail away from sight of the shore, knowing that steering by certain reliable stars would bring them home. This crude, practical application of ASTRONOMY allowed the adventurous to sail into the unknown with a reasonable chance of finding their way. Wind-powered ships risked longer voyages, tempted by the knowledge, trade, and new settlements offered by distant lands. The maps of the known world expanded as the blanks were filled in by the reports of the sailors who had mastered NAVIGATION. CONSTRUCTION Advancing beyond the use of mud bricks and mortar to build homes and walls, ancient engineers responded to the need for stronger, more elaborate structures by developing new techniques and skills in CONSTRUCTION. The preferred building material became stone. These new skills made possible the aqueducts, city walls, palaces, temples, bridges, and roads that still stand today in many places, testaments to the ancient builders. In CIVILIZATION, Construction allows Settler units to construct Fortresses. HORSEBACK RIDING Horses are believed to have been first domesticated in the great plains of northern Asia. Mounted horsemen from this region migrated into the more civilized parts of Europe and Asia, often driving out or enslaving the inhabitants. Where the horse could be raised, HORSEBACK RIDING was extremely useful as a source of power and means of transportation. It proved especially valuable in battle, making the rider much more imposing and mobile. Mounted warriors were part of most armies until their role as scouts and Cavalry was superseded by vehicles and aircraft. CEREMONIAL BURIAL Groping for an explanation of the world around them, the earliest humans developed the first concepts of religion. These early forms of worship attempted to give order to the world and assign humans a role in the universe. Gradually the rites of worship grew more sophisticated with sacrifices, ceremonies, vigils, symbology, sacred items, and prayer. One significant step in the advance of worship was the CEREMONIAL BURIAL, often a preparation for an afterlife. The remains of CEREMONIAL BURIALS offer some of the most detailed information available of past civilizations. POTTERY Concomitant and essential to the Agricultural Revolution was the invention of POTTERY. For seasonal crops and domesticated animals to be really useful, sturdy and waterproof containers were necessary to hold and protect the surplus until needed. The discovery of the properties of clay, the kiln, and the potter's wheel made dependable containers possible. POTTERY was essential to the growth of substantial human populations. Without it, cities would not have been possible. ALPHABET An ALPHABET is a group of symbols that represents phonemes, sounds that humans can make or distinguish. Some ALPHABETS represent syllables. The ancestors of modern ALPHABETS are the iconographic and ideographic symbols of ancient man such as cuneiform and hieroglyphics. The modern ALPHABET of the West traces back to the Romans, then to the Greeks, and then to the Phoenicians. The ALPHABET was significant because ideas could now be transferred by being painted on pottery, carved in stone, or impressed in clay. Ideas no longer had to be exchanged face-to-face by voice or hand signals. ADVANCED FLIGHT The technology of FLIGHT advanced rapidly in the 20th Century, especially during the two World Wars when the contending nations raced against each other for air superiority. ADVANCED FLIGHT technology was a specialty of the Germans in World War II. They developed the first practical jet fighters, extremely long-ranged Bombers, and the first guided rockets. However, these innovations could not be produced in sufficient quantities to be really useful. The Allies mass-produced less innovative, but dependable, aircraft that won the air war. ASTRONOMY Perhaps the oldest of the sciences, ASTRONOMY originated by observing the regularity of celestial movements. The earliest astronomers were priests who were often able to use the predictability of events to maintain their power. Ancient Greek students of ASTRONOMY understood that the Sun was the center of the Solar System, made reasonable estimates for the size and distance of the Sun and Moon, and made a close estimate of the size of the Earth. These facts not rediscovered in the West for over one thousand years. Much later, ASTRONOMY became important in timekeeping and NAVIGATION. ATOMIC THEORY Greek philosophers first proposed that matter was composed of tiny, indivisible particles in constant motion. However, this concept was not popular at the time, especially with Aristotle, and disappeared. Independently, ATOMIC THEORY was revived in the 19th Century. Advances in PHYSICS, especially the development of quantum mechanics, provided a satisfactory explanation for the behavior of electrons and other sub-atomic particles. An understanding of ATOMIC THEORY made possible the development of NUCLEAR FISSION and atomic weapons. AUTOMOBILE The first practical AUTOMOBILES were developed in the late 19th Century, although experiments with steam-powered wagons had been carried out over one hundred years earlier. The critical invention that made the AUTOMOBILE a success was the internal COMBUSTION engine. This relatively small but powerful engine could be mounted within the frame of the "horseless carriage" and drive the wheels. The AUTOMOBILE had a tremendous impact on the economy and lifestyles of the rich Western nations, and it also revolutionized warfare. Armed and armored AUTOMOBILES, known as tanks, became a dominant weapon on the battlefield. BANKING Modern BANKING arose during the Renaissance among the merchant families of the Italian city-states who were benefiting from the increase in TRADE, both within Europe and with the Middle East. The wealthy merchants pooled their surplus money into a Bank, and loaned cash at interest to other commercial enterprises. The availability of this capital for investment made many new businesses possible and helped accelerate economic growth. BANKING was even more important after the Industrial Revolution due to the even larger capital investments required by the newly rising industrial CORPORATIONS. BRIDGE BUILDING An important measure of the advancement of any civilization was the internal CONSTRUCTION improvements built to facilitate trade and communication. The Roman Empire was renowned for its roads, aqueducts, and other structures that linked the frontiers to the capital. BRIDGE BUILDING was greatly advanced by the Romans, and rediscovered in the West by medieval engineers many years later. The first IRON bridge was built in England in the late 18th Century, and BRIDGE BUILDING techniques advanced rapidly to meet the demands of the expanding RAILROADS of the 19th Century. BRONZE WORKING BRONZE is an alloy of copper and other metals, mainly tin. BRONZE WORKING technology grew out of experiments with copper ore, which was often found pure enough in ancient times to be worked into metal objects. Experiments with the distinctive greenish copper ore led to mixtures of metals into BRONZE. The new metal proved much more useful than copper because it was harder, less brittle, and could hold a sharper edge. It made better, less costly tools, and was very useful for making weapons and armor. The first societies possessing BRONZE weapons had a distinct advantage over those armed with stone or copper. CHEMISTRY The basis for modern CHEMISTRY was laid by the pseudo-science of alchemy, which attempted to turn base metals into gold and silver through the agency of an elixir or Philosopher's Stone. Alchemy periodically surfaced and degenerated until the real science of CHEMISTRY was found to have economically useful applications. CHEMISTRY was also spurred by the practical needs of MEDICINE and the theoretical considerations of natural PHILOSOPHY. CHIVALRY CHIVALRY was a system of ethical ideals that grew out of FEUDALISM. It established a code of behavior for the landed class of mounted warriors, known as Knights. The chief chivalric virtues were piety, honor, valor, courtesy, chastity, and loyalty. These represented a fusion of Christian and military morality and became the basis for gentlemanly conduct. The zenith of CHIVALRY were the Crusades, a series of invasions of the Middle East that attempted to recapture the Holy Land from the Muslims. CHIVALRY was enhanced by monastic orders of knighthood, including the Knights Templar and Knights Hospitaler. CODE OF LAWS As populations and cities grew, the need grew for the establishment of rules of conduct within the newly organized societies. After the development of the ALPHABET, these rules were written down along with the punishments that kept them enforced. The earliest known such codes existed in Babylon, India, and Palestine. Roman law was the first to distinguish between public law, in which the state is involved, and private law, concerning disputes between citizens. U.S. law was greatly influenced by the work of Sir William Blackstone, who stressed the natural rights of the individual. COMBUSTION The development of the internal COMBUSTION engine was a great advance of the Industrial Age. Relying on the volatility of new fuels made available by the REFINING of oil, these compact engines developed great power. They were essential to the development of the AUTOMOBILE and aircraft because previous engines were too bulky to be practical. In addition, the internal COMBUSTION engine was extremely efficient in generating power for the fuel it consumed, which allowed vehicles, aircraft, and ships to travel reasonable distances. COMMUNISM COMMUNISM developed as a system of social organization where the real property (land) and means of production (factories) were owned by all. Experiments with this system appeared at various times in the past, but COMMUNISM in the world today arose from the often appalling living conditions that came into being for the factory workers during the Industrial Age. Outrage over the greed of the new capitalists and the poverty of the workers led to the Communist Manifesto of Marx and Engels that predicted the rise of a classless society. COMMUNISM has failed so far to fulfill its promise of an egalitarian society based on working-class values. COMPUTERS A COMPUTER is a device capable of performing a series of arithmetic or logical operations. It is distinguished from a calculator by being programmable and capable of storing and retrieving data. COMPUTERS are made possible by previous advances in MATHEMATICS and continuing developments in ELECTRONICS. Significant advances in COMPUTER technology take place at an amazing pace. COMPUTERS have proven useful and necessary in many applications, including huge computations, entertainment, information storage, cryptography, and and control of ROBOTS. CONSCRIPTION Compulsory enrollment in the armed forces, or CONSCRIPTION, was introduced in France during the Revolution. It was thought necessary and equitable by the new government surrounded by enemies. In the era of national mobilization for war that followed, wartime CONSCRIPTION was instituted by many nations, including most major participants in the World Wars. In the U.S., peacetime CONSCRIPTION was maintained for nearly 30 years following World War II. CURRENCY As cities grew, their internal economies became more complicated. People specialized in their labors, some producing grain, some pottery, some bricks, etc. A system of barter developed so that the wares and services of one individual could be exchanged for those of another. In response to the need for a medium of exchange, and for more sophisticated ways to store purchasing power and set standards of value, CURRENCY came into use. The first satisfactory CURRENCY was coinage made from electrum, a naturally occurring alloy of gold and silver. DEMOCRACY A system of government where all of the people share in directing the activities of the state was called a DEMOCRACY. This type of government first arose in some of the ancient Greek city-states, though slaves and women did not participate. The modern DEMOCRACIES of the West developed over time, tracing back to the Magna Carta agreement signed by King John of England in the 13th Century. Government run by elected representatives of the people was the basic concept of modern DEMOCRACY. DEMOCRACY made possible unprecedented personal and economic freedom, and the world's strongest economies to date. ELECTRICITY The phenomenon of ELECTRICITY has been witnessed by humans since the dawn of time in the form of lightning, static ELECTRICITY, and MAGNETISM, but only in the last two hundred years has the energy of charged particles been harnessed. Electric current is a flow of electrons from an electromotive force, such as a battery or generator, that possesses a negative charge. The current flows through a conductor of electricity (a copper wire for example) to a positive terminal that attracts the charge. Along the way, the electric current can be made to provide power and do work. ELECTRONICS ELECTRONICS is the science of understanding and ENGINEERING the controlled flow of electrons in electronic currents. Historical breakthroughs that have occurred in ELECTRONICS include the electronic tube, semiconductor, transistor, and integrated circuits. These made possible COMPUTERS, advanced weapons, improved radars, and communication receivers, as well as more efficient techniques in power generation and transmission. ENGINEERING The science of ENGINEERING originated with the civil engineers, who built bridges, roads, aqueducts, and other structures, and the military engineers, who built fortifications and weapons. Over time, ENGINEERING came to mean the design, CONSTRUCTION, and operation of the structures and machines of industry, warfare, and day-to-day life. Engineers were the people who put the new advances of knowledge to practical use. They were people not only good with their hands, but also with their heads. The ENGINEERING problem-solver was most likely to discover a new INVENTION and lead the advance of knowledge. EXPLOSIVES EXPLOSIVES were discovered during experiments with GUNPOWDER and CHEMISTRY in the search for stable and powerful chemicals for industrial and military applications. An EXPLOSIVE is a chemical that undergoes a rapid COMBUSTION, and produces much heat and gas. The heat causes the gas to rapidly expand, thereby exerting the pressures of an explosion. Some EXPLOSIVES are mixtures of combustibles that are ignited. Others contain unstable molecules that can undergo an EXPLOSIVE decomposition called a detonation. The former type is used as propellants for bullets and fireworks, while the latter is used in warheads and rock blasting. FEUDALISM In the unsettled times that followed the collapse of Charlemagne's Frankish empire, a new social and political system arose in Europe, called FEUDALISM. Derived from the concept of MONARCHY, it was a hierarchial system where each succeeding stratum owed allegiance to those above. At the bottom were the serfs, who worked the land for the lord of the local manor. The local lord in turn managed the land for the lord above him, and so on to the king, who actually owned all the land. The people at the bottom of the hierarchy were protected by those above, and in return served their masters. FEUDALISM led to the code of CHIVALRY and the mounted Knight. FLIGHT Sustained, self-powered motion through the air, or FLIGHT, has tantalized humans since the dawn of time. Despite many experiments and attempts at flying, it wasn't until the development of the internal COMBUSTION engine that the laws of PHYSICS could be made to work for man's quest. Just after the turn of the 20th Century, Orville and Wilbur Wright made the first four controlled, sustained flights at Kitty Hawk, N.C. The technology of FLIGHT advanced rapidly. Within a relatively few years, aircraft were circling the globe, safely delivering passengers and mail at record speeds. FUSION POWER Nuclear FUSION is the process by which two atomic nuclei combine to form one heavier atomic nucleus, giving off tremendous energy in the process. The difficulty with sustaining this thermonuclear reaction is that it requires very high temperatures for initiation and fuel containment. An answer to part of the problems of FUSION may lie in the development of SUPERCONDUCTORS. Nuclear FUSION offers great promise as a source of electric power because a safe fuel is available in large quantities and the process does not create the radioactive waste that plagues Nuclear FISSION. In CIVILIZATION, FUSION POWER eliminates the risk of a Nuclear Power Plant meltdown. GENETIC ENGINEERING One of the hopes in the search for a cure for cancer and many other diseases and disorders comes from GENETIC ENGINEERING, a new field of study in science and MEDICINE. GENETIC ENGINEERING is a group of techniques that manipulate the genetic material of living cells. Gene splicing is a technique for transporting genetic material from one species to another. Other techniques include cell fusion and nuclear transplantation. The hope is that DNA, the basic genetic material for all life, may prove to be repairable and changeable. Then all genetic disorders would no longer be permanent, but curable. GUNPOWDER GUNPOWDER is a chemical mixture of saltpeter, sulphur, and charcoal. When ignited, it burns so rapidly that it explodes if contained to any degree. GUNPOWDER is believed to have been developed by the Chinese as early as the 9th Century, but did not reach Europe until the 1300's. The Chinese appear to have used it almost exclusively for fireworks, but the competing and aggressive Europeans turned it into weapons that revolutionized warfare. Musketeers and Cannon brought an end to the battlefield dominance of heavy Cavalry and also ended recurring invasions of barbarians from Asia. HORSEBACK RIDING The HORSE was first domesticated by tribesmen on the Asian steppes. It was used by these tribes for transportation and warfare, and with its help they overwhelmed the proto-civilizations just rising in southeast Europe and the Middle East. HORSEBACK RIDING was in turn acquired by the conquered peoples and this skill accompanied the spread of civilization. In areas where the HORSE could be bred, it was extremely useful for transport and agriculture. Only in the last one hundred years has the HORSE been replaced by motor vehicles as a draft animal and mount for Cavalry. INDUSTRIALIZATION The invention of the STEAM ENGINE and other technology, especially the RAILROAD, led to the INDUSTRIALIZATION of the West. INDUSTRIALIZATION was the use of machines to dramatically increase the productivity of workers. Industry became concentrated in factories, allowing new products to become available in huge quantities. INDUSTRIALIZATION revolutionized living standards, but not always for the better. The new worker class often suffered a grinding, subservient existence that eventually fostered the social philosophy of COMMUNISM and the more practical LABOR UNION. Both were attempts to improve the lot of workers. INVENTION The contrivance of a previously unknown device, method, or process is known as an INVENTION. The advance of technical knowledge is essentially the discovery of new INVENTIONS. The history of civilization shows that the spread of LITERACY and the rise of ENGINEERING specialists were critical to the acceleration of new technology. ENGINEERING is the practical employment of INVENTION, and people who do this work are often the ones who identify the need for further advance and achieve it. The progress of a society is a measure of how well it encourages and adapts new INVENTIONS. IRON WORKING Building on the experience of their BRONZE WORKING, ancient smelters learned IRON WORKING, the manufacture and fabrication of a much more useful metal. Iron ore was extremely common compared to copper and tin, and IRON was harder, less brittle, and could hold a much sharper edge. It was an ideal material for tools and weapons. Some observers consider the development of IRON WORKING to have been a key step in the advance of civilization. It made workers much more efficient and was found useful in many new applications. LABOR UNION With the rise of MASS PRODUCTION in the Industrial Age, the balance of power between owners and workers swung too far in favor of the owners. The rising worker class often found themselves stuck in poor working and living conditions while the owners grew rich. In response to this inequity the LABOR UNION arose, an attempt by the workers to bind their interests together and collectively bargain with ownership for better working conditions and economic status. After much turmoil, the LABOR UNIONS were able to achieve a working balance of power with ownership and improve the worker's lot. LITERACY The development of WRITING made available a critical new tool for the advance of knowledge, but, like all tools, it was only useful if employed. The greater the percentage of the population that was LITERATE, the greater the advantage that could be taken from WRITING. Where only priests and scribes were LITERATE, all others had to share knowledge slowly, by face-to-face contact. When a high percentage of the population was LITERATE, as in classical Greece, the economy benefited and the advance of knowledge accelerated. MAGNETISM The force of attraction or repulsion between various substances, especially iron, is due to the motion of electric charges and is known as MAGNETISM. A MAGNETIC object normally has two poles, a north-seeking pole and a south- seeking pole, named because a freely floating MAGNET orients itself in the Earth's MAGNETIC field along a north-south axis. MAGNETISM may have been discovered in China, but its important application in the mariner's compass occurred in 12th Century Europe. Later work with MAGNETISM was important in the discovery of PHYSICS and ELECTRICITY. MAPMAKING MAPMAKING was an offshoot of the development of the ALPHABET. With this technology if became possible to record the location of important places and features on animal skins, clay tablets, tree bark, or other materials, and thus pass on this information to others. This was especially useful to seamen, who often ventured far from home along strange coasts with their only guide being the MAPS made by those who had sailed there previously. MAPMAKING encouraged travel and exploration by making it less risky. It was the beginning of the skills that became the science of NAVIGATION. MASONRY The aggregation of people into the first cities required permanent buildings. To fill the need for these structures, some of the new city dwellers became expert in the techniques of MASONRY. This technology utilized rocks and mud bricks, cementing these materials into buildings and walls. With experience, their buildings grew larger and more elaborate, walls became more imposing, and the work became more permanent and pleasing to the eye. Years of experience led to more sophisticated techniques of CONSTRUCTION. MASS PRODUCTION Following the advent of INDUSTRIALIZATION, factory owners developed new techniques to make production more efficient. Henry Ford is credited with one major advance, the installation of MASS PRODUCTION assembly lines in his AUTOMOBILE plants. In this case, the object being assembled, a car, was carried along conveyor belts to the various workstations, where each worker expertly performed his part of the assembly. When the car reached the end of the line, it was fully built. Techniques such as this resulted in dramatic increases in worker productivity as long as the workers were content. MATHEMATICS From the earliest ALPHABETS, some symbols came to represent the concept of numbers. MATHEMATICS arose from the needs of agriculture and commerce to keep track of quantities, accounts, and measurements. Farmers needed to know the size of the yield from their fields. Traders needed to know what they had available for barter and the rates of exchange. MASONS needed to know the dimensions of the structure they were building. The development of MATHEMATICS was critical to the future advance of PHYSICS and other sciences. MEDICINE The study of the body and healing was first developed into a science by the Greeks. Hippocrates, considered the father of MEDICINE, based his studies of the human body on observation and reasoning. His studies were just one of many breakthroughs that resulted from the flowering of Greek PHILOSOPHY. Though some of his beliefs were incorrect, many modern medical students take the Hippocratic Oath upon graduation, swearing to uphold his principles. MEDICINE and alchemy were the basis for the developing science of CHEMISTRY. METALLURGY The science of METALLURGY became especially important after the development of GUNPOWDER, as the European powers vied with one another for the latest technological advance in weapons. Research in METALLURGY was conducted by the private smelters and UNIVERSITIES. The result was artillery and naval guns superior to any in the world. This development was an important factor in the rise of European states as world powers. METALLURGY later led to the discovery of STEEL and other metals. MONARCHY The MONARCHY developed from the absolute rule of the prehistoric tribal chief. This type of absolutism evolved first into a hereditary and lifelong right to rule, and was later claimed as a divine right. The MONARCHY was made possible by the enforcement of LAWS put in place by the rulers and their supporters who had the most to gain from maintaining control. It was more practical than the despotism it often replaced because the ruler's power was not absolute and arbitrary, but generally dispensed through an aristocratic class of local rulers. The aristocrats served as a check on the ruler's power, blocking projects not in their own interest. MYSTICISM As populations and knowledge grew, a new class of spiritual advisors arose to satisfy the need for less formal, state-centered rites of worship. The priests and priestesses of MYSTICISM, often called oracles, claimed union with the divine through meditation and trance-like contemplation. MYSTICISM offered for the first time the hope of personal salvation and immortality, concepts important in the development of later RELIGIONS. NUCLEAR FISSION NUCLEAR FISSION occurs when a fissionable atomic nucleus absorbs a neutron, becomes unstable, and splits into two new nuclei. In the process, tremendous energy is given off as heat, light, and radioactivity. The first use of NUCLEAR FISSION was in warfare, where the heat and shock wave of uncontrolled fission produced an unprecedented weapon, the atomic bomb. Later, controlled NUCLEAR FISSION was employed to provide enough heat to power the generation of electricity in a NUCLEAR POWER Plant. The dangers and risks associated with NUCLEAR POWER have so far limited its employment. NUCLEAR POWER The development of NUCLEAR POWER was an attempt to find a peaceful application for the energy released by NUCLEAR FISSION. The heat given off created steam that drove electric turbines, producing electricity. NUCLEAR POWER held the promise of being cleaner and less costly than burning fossil fuels. However, the radioactive materials consumed in the process were extremely lethal, the disposal of nuclear waste was difficult, and the risk of nuclear meltdown could not be eliminated. Continuing work may lead to a safer application. For example, employing reactors built on the principles of nuclear FUSION, rather than FISSION, may yet provide safe, clean power. PHILOSOPHY In ancient Greece, LITERACY and interest in the natural world was common in an expanding upper class that devoted much of its leisure time to debate. Popular topics for discussion were the reality, causes, and principles of thinking and being, better known as PHILOSOPHY. These debates considered the facts independent of the traditional religious dogmas of the day, and opened the door to examination of a wide range of new ideas. The writings of many of these early Greek philosophers, including Plato and Aristotle, have been luckily preserved. It has been said that all PHILOSOPHY after Plato was no more than footnotes to his work. PHYSICS The study of PHYSICS came into being from abstract theories of MATHEMATICS and the practical experience of engineers and sailors. Concerned with the study of matter and energy, and the relationships between them, classical PHYSICS dealt with phenomena within the bounds of normal observation: motion, acoustics, thermodynamics, and optics. These studies in turn led to further advances in areas such as MAGNETISM and ELECTRICITY. Modern PHYSICS is primarily concerned with the behavior of matter and energy under extreme conditions or at extreme scales. PLASTICS One of the spinoffs of research in the REFINING of oil was the discovery of PLASTICS, organic compounds that can be molded under heat and pressure. PLASTICS appeared to be wonders of the Industrial Age and were found to be cheap and sturdy substitutes for more traditional materials in all manner of uses. But the widespread use of PLASTICS led to environmental problems because the material does not decay. Disposal by incineration was complicated because it melts, clogs equipment, and may give off harmful fumes. RAILROAD The RAILROAD resulted from the successful marriage of a promising new technology, the STEAM ENGINE, and a growing need: fast, safe, and inexpensive transportation. RAILROADS applied the unprecedented power of the locomotive to the pulling of trains of loaded wagons over rails. This resulted in a dramatic increase in the amount of cargo that a few men could move quickly and over great distances. RAILROADS were a critical contributor to INDUSTRIALIZATION. They not only made it easier to obtain raw materials and reach markets, but the search for better equipment spurred innovation that benefited many other industries. RECYCLING Although scrap metals and other materials have been reused in manufacturing processes for some time, only recently has RECYCLING become a household concern. Increasing world populations and the flow of products off the MASS PRODUCTION lines are threatening to choke our planet in refuse and pollution. In the DEMOCRACIES of the West, the richest nations and the most wasteful, a movement is underway to reuse as much refuse as possible. When RECYCLED, old newspapers used again spare trees, plastic bottles save oil, and aluminum cans save electricity. RECYCLING reduces costs and pollution, thereby improving the quality of life. REFINING Mineral tar and petroleum have been known throughout history, but little use was found for either until it was discovered through CHEMISTRY that oil could be REFINED into chemicals with a wide variety of uses. The primary application of oil derivatives was as fuel for internal COMBUSTION engines that powered the AUTOMOBILE and other machines. Oil had to await the Industrial Revolution before its potential could be realized, because large CORPORATIONS could afford the investments in AUTOMOBILE production and REFINING that were required. RELIGION The evolution of RELIGION traces back to elementary forms of belief and practice concerning the extraordinary, the mysterious, and the supernatural. RELIGION gave people an object of devotion, a code of social behavior, and a reference for the individual within the group and the universe. Acceptance of the teachings of RELIGION brought peace of mind and the ability to get on with the work of life, because the terrifying questions of the unknown were contained. The advance of knowledge that followed the development of WRITING and the study of PHILOSOPHY led to the great RELIGIONS of the modern world. ROBOTICS Advances in COMPUTER technology have made possible the new science of ROBOTICS, which was previously the realm of science fiction. ROBOTICS concerns the design and building of machines capable of mimicking some modicum of human action. These machines can sense changes in their environment and take limited action based on this information. ROBOTS are essentially computer-controlled machine tools that can be programmed to perform tasks such as welding car parts. They are especially useful for tasks that are monotonous, dangerous, or tiring, where they are often more productive than their human counterparts. ROCKETRY Although experiments with ROCKETRY trace back to Chinese fireworks powered by GUNPOWDER one thousand years ago, most of our current knowledge was developed in the 20th Century. A ROCKET is propelled by the ejection of gases created by the COMBUSTION of on-board fuel. The COMBUSTION creates great pressure that is vented through the rear, and this thrust against the front interior of the COMBUSTION chamber pushes the ROCKET forward. The first practical guided ROCKETS were used in World War II. More recently, ROCKETS have been used to propel intercontinental ballistic weapons and launch spacecraft. SPACE FLIGHT Following the development of the first guided missiles in World War II, the science of ROCKETRY advanced to the point where direct space exploration became possible. SPACE FLIGHT advanced from simple sub-orbital flights to manned missions to the Moon. Work continues today on building space stations and reusable space vehicles. In the near future there may be a manned mission to Mars. In succeeding generations, new advances may make manned travel to other star systems practical. STEAM ENGINE Some of the properties of steam have been known since ancient times, but it took thousands of years of groundwork in PHYSICS and the practical skills of a few INVENTORS to build a working STEAM ENGINE. The beauty and value of this engine was that it could do the work of many men. A STEAM ENGINE operator could have his strength multiplied enormously by tapping the heat energy released by burning coal. The STEAM ENGINE was the prerequiste for the Industrial Revolution, leading to the spread of Factories and RAILROADS around the world. STEEL With the Industrial Revolution came new needs for metals, both as construction materials and for fabrication into products. The rise of RAILROADS especially spurred research in METALLURGY for a metal that could be fashioned into cheap, strong rails and bridges. Eventually, the secret of STEEL was discovered, and it was found to be a nearly perfect construction material. However, it could not be made cheaply until INDUSTRIALIZATION brought the resources and machines together at one time. In turn, STEEL led to great changes in the world, including enormous skyscrapers, armored warships, and the AUTOMOBLE. SUPERCONDUCTOR When electric current is passed through a conductor, such as a copper wire, a small but significant amount of the current is lost to resistance. When certain substances are cooled to temperatures near absolute zero, this resistance disappears. This phenomenon is called superconductivity, and a substance with no electrical resistance is a SUPERCONDUCTOR. If such a material could be found that worked at something nearer normal temperatures, its discovery might revolutionize everyday life by greatly reducing the cost of energy and making hosts of new inventions practical. THE CORPORATION The RAILROADS, iron mongers, and other businesses that launched the Industrial Revolution grew into great enterprises within a generation, far outstripping the resources of a single owner. The huge capital investments that INDUSTRIALIZATION required were met in the West by CORPORATIONS of stockholders that had access to sophisticated BANKING systems. These large industrial enterprises now dominate world business. Though often considered wasteful, conspiratory, and beyond the law, they are generally efficient and innovative, or they are soon out of business. THE REPUBLIC The concept of THE REPUBLIC first appeared in ancient Rome, where the local provinces sent representatives to the Senate to govern the nation. The head of state in a REPUBLIC was an elected representative, not a MONARCH. The concept was revived in the Constitution of the United States, and many nations of significant size and diverse make-ups have adopted something similar. THE REPUBLIC allowed unprecedented freedom, at least to a significant portion of the citizens, and this in turn often fostered strong economic growth. THE WHEEL One of the five great simple machines, the WHEEL and axle greatly increased the load that a human or animal could pull by lowering the resistance to movement. The WHEEL was also quickly turned into a weapon of war after its invention, especially in the adaptation of the Chariot. In addition to its use in transport, the WHEEL became a vitally important tool in ENGINEERING and in the Industrial Age. In the pre-Columbian New World, the WHEEL only appeared in children's toys, partly because the mountainous terrain of South America made it less practical. THEORY OF GRAVITY The attracting force that exists between any two particles of matter is called gravity. This force exists throughout the universe and explains the behavior of both the apple that fell on Newton's head and the orbit of the Earth around the Sun. The THEORY OF GRAVITY is credited to Sir Isaac Newton, who first recognized that gravitation was universal. His work opened the door to later scientists including Albert Einstein, who developed the Theory of Relativity, and the men who developed ATOMIC THEORY. TRADE One of the oldest and most widespread social institutions is the exchange of goods, or TRADE. At the most basic level of TRADE, two people exchange items with each other. Ideally, the items given are in surplus and the items received are desired. The result is that both are better off, having exchanged extras for something wanted. People, as well as nations, normally have a comparative advantage over others in the production of some good or service. Through TRADE, this advantage benefits both parties. TRADE has also proven very important in the exchange of ideas. UNIVERSITY The first UNIVERSITIES were founded in the Middle Ages by ecclesiastical or royal initiative to train young men in law, theology, and medicine. The modern UNIVERSITY consists of several faculties, or colleges, each with a specific curriculum. Traditionally, only UNIVERSITIES granted graduate degrees, but that distinction is now blurred. During the 20th Century many UNIVERSITIES, especially in the U.S., received large government grants for scientific and technological research, especially research related to weapons. WRITING The development of WRITING is considered one of the most important advances of civilization. From that point, history began, as defined by written records first inscribed on clay tablets or carved into stone. The significance of WRITING is that it allowed ideas and knowledge to be stored and passed on over distance and time, far removed from the originator. Prior to this, communication had to take place face-to-face. WRITING greatly accelerated the advance of knowledge because what was known in the past did not have to be relearned by each new generation. END