20th Century

The 20th century was the period between January 1, 1901 and December 31, 2000.

The Chinese, Russian, German, Ottoman, and Austro-Hungarian empires dissolved in the first half of the century, with all but the British, French, Portuguese, and Japanese empires collapsing during the course of World War I, and Russia transformed into the communist Soviet Union. The inter-war years saw a Great Depression cause massive disruption to the world economy. Shortly afterwards, World War II broke out, pitting the Allied powers (chiefly the Soviet Union, the United States, and the United Kingdom) against the Axis powers (Nazi Germany, the Empire of Japan, and Italy) which eventually resulted in a total victory for the Allies, at the cost of over 60 million lives, including millions of civilians, and the complete devastation of many nations. Remaining colonial empires dissolved shortly after the war. As a means of preventing future world wars, the United Nations was formed; however, competition between the two new superpowers, the Soviet Union and the United States, resulted in the Cold War, which would dominate geopolitical life for the next 45 years. The Soviet Union collapsed internally in 1991, resulting in the United States taking on sole superpower status.

The century saw a major shift in the way that vast numbers of people lived, as a result of changes in politics, ideology, economics, society, culture, science, technology, and medicine. Terms like ideology, world war, genocide, and nuclear war entered common usage. Scientific discoveries, such as the theory of relativity and quantum physics, drastically changed the worldview of scientists, causing them to realize that the universe was fantastically more complex than previously believed, and dashing the strong hopes at the end of the 19th century that the last few details of scientific knowledge were about to be filled in. Accelerating scientific understanding, more efficient communications, and faster transportation transformed the world in those hundred years more rapidly and widely than in any previous century. It was a century that started with horses, simple automobiles, and freighters but ended with high-speed rail, cruise ships, global commercial air travel and the space shuttle. Horses, Western society's basic form of personal transportation for thousands of years, were replaced by automobiles and buses within the span of a few decades. These developments were made possible by the large-scale exploitation of fossil fuel resources (especially petroleum), which offered large amounts of energy in an easily portable form, but also caused widespread concerns about pollution and long-term impact on the environment. Humans explored outer space for the first time, taking their first footsteps on the Moon.

Mass media, telecommunications, and information technology (especially computers, paperback books, public education, and the Internet) made the world's knowledge more widely available. Many people's view of the world changed significantly as they became much more aware of the struggles of others and, as such, became increasingly concerned with human rights. Advancements in medical technology also improved the welfare of many people: the global life expectancy increased from 35 years to 65 years. Rapid technological advancements, however, also allowed warfare to reach unprecedented levels of destruction. World War II alone killed over 60 million people, while nuclear weapons gave humankind the means to annihilate or significantly harm itself in a very short period of time. The world also became more culturally homogenized than ever with developments in transportation and communications technology, popular music and other influences of Western culture, international corporations, and what was arguably a true global economy by the end of the century.