Introduction to World
World, the earth with its inhabitants and their activities. Earth and world have somewhat the same meaning, but as used here earth refers to the planet while world refers to the earth as lived on and used by humankind. (For a discussion of the earth as a planet,
A great many of the subjects treated in this encyclopedia are related to the world as the home of humankind. This article is a summary of some of the world's most outstanding features, with cross references to articles giving more detailed information.
Atmosphere
The air that surrounds the earth forms the earth's atmosphere. Without an atmosphere, there would be no life on earth, nor would there be wind, clouds, rain, or fire.
Physical Features
Land. About 30 per cent of the earth's surface is land. There are 58,000,000 square miles (150,000,000 km2) of land area, divided into seven continents and thousands of islands. The larger part of the land is in the Northern Hemisphere. Spread out in this part of the world are the largest continent, Asia, and two other continents, Europe and North America. Also north of the equator are the broad, northern parts of Africa and South America. Antarctica and Australia are wholly in the Southern Hemisphere.
The surface of the land is varied. There are mountains and valleys; forests and vast treeless plains; and great sandy wastes, which are largely deserts. The highest point is the summit of Mount Everest; the lowest point is on the shore of the Dead Sea.
Water. About 70 per cent of the world is covered by water. This vast area of 139,000,000 square miles (360,000,000 km2) is made up of oceans, seas, lakes, and rivers.
Climate
The world's physical features have great influence on climate and on the activities of the people in various regions. Plains and valleys with suitable temperatures and ample moisture are conducive to farming. Some mountain ranges act as barriers to moisture-laden winds, causing ample rain on the windward side and shortage of moisture on the other side. Large lakes have a moderating effect on the atmospheric temperatures of surrounding areas—making them warmer in the winter and cooler in the summer than they would otherwise be.
Life
There are few, if any, places in the world without life of some kind. Even in Antarctica, with its bitter cold, there are penguins, mosses and lichens, and insects.
The distribution of living organisms affects human activities. A person's diet, for example, depends largely on the plants and animals easily raised in the area in which he or she lives. Often humans interfere with the natural distribution. For instance, on the vast, grassy plains of the central and western United States great herds of domestic cattle now graze where once the wild buffalo (bison) roamed. The relationship of living things to each other and to their environment is discussed in the article Ecology.
Minerals
The earth's crust is composed of minerals. From ancient times people have been extracting, by mining or quarrying, those that they found valuable. Minerals are not evenly distributed; some countries have more than enough of certain desirable minerals while other countries have very little. For instance, petroleum, one of the most valuable non-metallic minerals, is in great abundance in Iraq, Iran, and Saudi Arabia, but nearby Jordan has none.
The People
It took 200,000 years for the number of people to reach the total of 545,000,000 estimated to have been in the world in 1650. In 1950, just 300 years later, there were an estimated 2,501,000,000, and by 1995 the number had risen to 5,716,000,000. In 1650 there were about 9 persons per square mile of land (3.5 per km 2 ); in 1995 there were about 109 per square mile (42 per km2).
Experts have described the world's "population explosion" as one of the most serious problems of the future. After World War II the average annual rate of population increase rose to about 2 per cent, roughly twice what it had been before the war. The greatest increases were in developing regions of Asia, Africa, and Central and South America.
Worldwide, the growth rate has dropped since the mid-1970's (it was 1.6 per cent a year in 1990–95), but it continued to rise in Africa (to 2.8 per cent). Several African nations had growth rates of 3 per cent or more.
In early times, before the development of transportation, people lived in small, scattered bands throughout the world. According to a generally accepted theory (here given in simplified form), each group gradually developed certain physical characteristics best suited for the environment in which the people of the group lived; as the environments differed, so eventually did the people, and the various races developed.
Anthropologists do not all agree on how to classify races. However, most classifications include these three broad categories as major races: Caucasoid, Mongoloid, and Negroid.
Each of the various isolated bands of people developed its own language. Languages are often classified into families, such as the Indo-European, to which English belongs; the Sino-Tibetan, which includes Chinese; the Malayo-Polynesian; the Japanese-Korean; the Dravidian of southern India and Sri Lanka; the Afro-Asiatic, including Hebrew and Arabic; and the Ural-Altaic, including Finnish and Hungarian. In addition, there are sub-Saharan African and American Indian language families.
World History
Scientists generally agree that the world is about 4.5 billion years old, but that humans did not come into existence until comparatively recent times. Fossil remains indicate that humanlike creatures lived in Africa about 4 million years ago. Later remains from Africa, Europe, and Asia indicate that there were several species and subspecies of prehistoric humans and that they evolved from a common ancestral tree.
Prehistoric humans spent most of their time in the difficult search for food. They hunted, fished, and collected wild grains, fruits, and roots. About 9000 B. C., people of southwestern Asia began to raise sheep and plant cereals. Able to stop traveling in search of food, they made settlements and improved their farming methods so that a small area could produce food for many people. Some members of the community were now able to specialize in other work, such as pottery making, weaving, and metalworking. Trade between communities led to the development of the barter unit of value, which was probably the first kind of money.
Written History. The beginnings of recorded history date back to about 5,000 years ago, when the Sumerians invented cuneiform writing and the Egyptians invented hieroglyphics. At first, written history consisted of no more than dynastic lists, but soon commentary was added. At first the years were not numbered, but eventually the lists were dated, a development made possible by the invention of the calendar. Dynastic lists are not true history because they are not historical narratives.
During the second millennium B.C. many of the ancient Egyptian, Hittite, and Assyrian monarchs commissioned narrative histories of their reigns to be carved on monuments. The Old Testament, written by Hebrews during the first millennium B.C., was the first national history—that is, the history of an entire nation.
The ancient Greeks during the fifth century B.C. were the first to move from narration to analysis by examining causes of events, connections between them, and circumstances under which they occurred.
