20th century

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The Earth as seen from Apollo 17 in December 1972. The second half of the 20th century saw humanity's first space exploration.

The 20th century was a century that began on January 1, 1901[1] and ended on December 31, 2000.[2] It was the tenth and final century of the 2nd millennium. It is distinct from the century known as the 1900s which began on January 1, 1900 and ended on December 31, 1999.

The 20th century was dominated by a chain of events that heralded significant changes in world history as to redefine the era: flu pandemic, World War I and World War II, nuclear power and space exploration, nationalism and decolonization, the Cold War and post-Cold War conflicts; intergovernmental organizations and cultural homogenization through developments in emerging transportation and communications technology; poverty reduction and world population growth, awareness of environmental degradation, ecological extinction;[3][4] and the birth of the Digital Revolution. It saw great advances in communication and medical technology that by the late 1980s allowed for near-instantaneous worldwide computer communication and genetic modification of life.

Global total fertility rates, sea level rise and ecological collapses increased; the resulting competition for land and dwindling resources accelerated deforestation, water depletion, and the mass extinction of many of the world's species and decline in the population of others; consequences which are now being dealt with. It took over two-hundred thousand years of human history up to 1804 for the world's population to reach 1 billion;[5] world population reached an estimated 2 billion in 1927; by late 1999, the global population reached 6 billion.[6] Global literacy averaged 80%; global lifespan-averages exceeded 40+ years for the first time in history, with over half achieving 70+ years (three decades longer than it was a century ago).[7]

Overview

Map of the British Empire (as of 1910). At its height, it was the largest empire in history.

The century had the first global-scale total wars between world powers across continents and oceans in World War I and World War II. Nationalism became a major political issue in the world in the 20th century, acknowledged in international law along with the right of nations to self-determination, official decolonization in the mid-century, and related regional conflicts.

The century saw a major shift in the way that many people lived, with changes in politics, ideology, economics, society, culture, science, technology, and medicine. The 20th century may have seen more technological and scientific progress than all the other centuries combined since the dawn of civilization. Terms like ideology, world war, genocide, and nuclear war entered common usage. Scientific discoveries, such as the theory of relativity and quantum physics, profoundly changed the foundational models of physical science, forcing scientists to realize that the universe was more complex than previously believed, and dashing the hopes (or fears) at the end of the 19th century that the last few details of scientific knowledge were about to be filled in. 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 a few decades. These developments were made possible by the exploitation of fossil fuel resources, which offered energy in an easily portable form, but also caused concern about pollution and long-term impact on the environment. Humans explored space for the first time, taking their first footsteps on the Moon.

World powers and empires in 1914, just before the First World War

Mass media, telecommunications, and information technology (especially computers, paperback books, public education, and the Internet) made the world's knowledge more widely available. Advancements in medical technology also improved the health 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 itself in a short time. However, these same wars resulted in the destruction of the imperial system. For the first time in human history, empires and their wars of expansion and colonization ceased to be a factor in international affairs, resulting in a far more globalized and cooperative world. The last time major powers clashed openly was in 1945, and since then, violence has seen an unprecedented decline.[8]

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 20th century.

Summary

Technological advancements during World War I changed the way war was fought, as new inventions such as tanks, chemical weapons, and aircraft modified tactics and strategy. After more than four years of trench warfare in western Europe, and 20 million dead, the powers that had formed the Triple Entente (France, Britain, and Russia, later replaced by the United States and joined by Italy and Romania) emerged victorious over the Central Powers (Germany, Austria-Hungary, the Ottoman Empire and Bulgaria). In addition to annexing much of the colonial possessions of the vanquished states, the Triple Entente exacted punitive restitution payments from them, plunging Germany in particular into economic depression. The regime of Tsar Nicholas II was overthrown during the conflict, Russia became the first communist state, and the Austro-Hungarian and Ottoman empires were dismantled at the war's conclusion.

Ukraine, early days of the 1941 Nazi invasion. The Soviet Union lost around 27 million people between 1941 and 1945,[9] almost half of all World War II deaths.

At the beginning of the period, Britain was the world's most powerful nation,[10] having acted as the world's policeman for the past century. Fascism, a movement which grew out of post-war angst and which accelerated during the Great Depression of the 1930s, gained momentum in Italy, Germany and Spain in the 1920s and 1930s, culminating in World War II, sparked by Nazi Germany's aggressive expansion at the expense of its neighbors. Meanwhile, Japan had rapidly transformed itself into a technologically advanced industrial power. Its military expansion into eastern Asia and the Pacific Ocean culminated in a surprise attack on the United States, bringing it into World War II. After some years of dramatic military success, Germany was defeated in 1945, having been invaded by the Soviet Union and Poland from the east and by the United States, the United Kingdom, Canada, and Free France from the west. The war ended with the dropping of two atomic bombs on Japan. Japan later became a western ally with an economy based on the manufacture of consumer goods and trade. Germany was divided between the Western powers (West Germany) and the Soviet Union; all areas recaptured by the Soviet Union (East Germany and eastward) became Soviet puppet states under communist rule. Meanwhile, Western European countries were influenced by the American Marshall Plan and made a quick economic recovery, becoming major allies of the United States under capitalist economies and relatively democratic governments.

World War II left about 60 million people dead. When the conflict ended in 1945, the United States and the Soviet Union emerged as the major world powers. Allies during the war, they soon became hostile to one another as the competing ideologies of communism and democratic capitalism occupied Europe, divided by the Iron Curtain and the Berlin Wall. The military alliances headed by these nations (NATO in North America and Western Europe; the Warsaw Pact in Eastern Europe) threatened each other with total war in what was called the Cold War (1947–91). The period was marked by a new arms race, and nuclear weapons were produced in the tens of thousands, sufficient to end most human life on the planet had a large-scale nuclear exchange ever occurred. The size of the nuclear arsenals is believed by many historians to have staved off war between the two, as the consequences were too great to bear. The policy of massive nuclear attack, knowing a similar counterattack would be forthcoming, was called mutually assured destruction (MAD). However, several proxy wars, such as the Korean War (1950–1953) and the Vietnam War (1955–1975), were waged as the United States implemented its worldwide "containment" policy against communism.

Albert Einstein is often regarded as the father of modern physics.

After World War II, most of the European-colonized world in Africa and Asia gained independence in a process of decolonization. Meanwhile, the wars empowered several nations, including the UK, USA, Russia, China and Japan, to exert a strong influence over many world affairs. American culture spread around the world with the advent of the Hollywood motion picture industry, Broadway, rock and roll, pop music, fast food, big-box stores, and the hip-hop lifestyle. Britain continued to influence world culture, including the British Invasion—The Rolling Stones, The Beatles—into American music, leading many rock bands from other countries (such as Swedish ABBA) to sing in English. The western world and parts of Asia enjoyed a post–World War II economic expansion. After the Soviet Union collapsed under internal pressure in 1991, the communist governments of the Eastern bloc were dismantled, followed by awkward transitions into market economies.

Following World War II, the United Nations, successor to the League of Nations, was established as an international forum in which the world's nations could discuss issues diplomatically. It enacted resolutions on such topics as the conduct of warfare, environmental protection, international sovereignty, and human rights. Peacekeeping forces consisting of troops provided by various countries, with various United Nations and other aid agencies, helped to relieve famine, disease, and poverty, and to suppress some local armed conflicts. Europe slowly united, economically and, in some ways, politically, to form the European Union, which consisted of 15 European countries by the end of the 20th century.

In the last third of the century, concern about humankind's impact on the Earth's environment made environmentalism popular. In many countries, especially in Europe, the movement was channeled into politics through Green parties. Increasing awareness of global warming began in the 1980s, commencing decades of social and political debate.

The computer is a major technological advancement in this century.

The nature of innovation and change

Due to continuing industrialization and expanding trade, many significant changes of the century were, directly or indirectly, economic and technological in nature. Inventions such as the light bulb, the automobile, and the telephone in the late 19th century, followed by supertankers, airliners, motorways, radio, television, antibiotics, frozen food, computers and microcomputers, the Internet, and mobile telephones affected people's quality of life across the developed world. Scientific research, engineering professionalization and technological development drove changes in everyday life.

Social change

Martin Luther King, Jr., an African American civil rights leader.

At the beginning of the century, strong discrimination based on race and sex was significant in general society. Although the Atlantic slave trade had ended in the 19th century, the fight for equality for non-white people in white-dominated societies of North America, Europe, and South Africa continued. During the century, the social taboo of sexism fell. By the end of the 20th century, women had the same legal rights as men in many parts of the world, and racism had come to be seen as abhorrent.[11] Attitudes towards homosexuality also began to change in the later part of the century.

The world at the end of the 20th century

Communications and information technology, transportation technology, and medical advances had radically altered daily lives. Europe appeared to be at a sustainable peace for the first time in recorded history. The people of the Indian subcontinent, a sixth of the world population at the end of the 20th century, had attained an indigenous independence for the first time in centuries. China, an ancient nation comprising a fifth of the world population, was finally open to the world in a new and powerful synthesis of west and east, creating a new state after the near-complete destruction of the old cultural order. With the end of colonialism and the Cold War, nearly a billion people in Africa were left in new nation states after centuries of foreign domination.

The world was undergoing its second major period of globalization; the first, which started in the 18th century, having been terminated by World War I. Since the US was in a dominant position, a major part of the process was Americanization. The influence of China and India was also rising, as the world's largest populations were rapidly integrating with the world economy.

Terrorism, dictatorship, and the spread of nuclear weapons were some issues requiring attention. The world was still blighted by small-scale wars and other violent conflicts, fueled by competition over resources and by ethnic conflicts. Despots such as Kim Jong-il of North Korea continued to lead their nations toward the development of nuclear weapons.

Disease threatened to destabilize many regions of the world. New viruses such as SARS and West Nile continued to spread. Malaria and other diseases affected large populations. Millions were infected with HIV, the virus which causes AIDS. The virus was becoming an epidemic in southern Africa.

Based on research done by climate scientists, the majority of the scientific community consider that in the long term environmental problems may threaten the planet's habitability.[12] One argument is that of global warming occurring due to human-caused emission of greenhouse gases, particularly carbon dioxide produced by the burning of fossil fuels.[13] This prompted many nations to negotiate and sign the Kyoto treaty, which set mandatory limits on carbon dioxide emissions.

World population increased from about 1.6 billion people in 1901 to 6.1 billion at the century's end.[14][15]

Wars and politics

Map of territorial changes in Europe after World War I (as of 1923).

The number of people killed during the century by government actions was in the hundreds of millions. This includes deaths caused by wars, genocide, politicide and mass murders. The deaths from acts of war during the two world wars alone have been estimated at between 50 and 80 million. Political scientist Rudolph Rummel estimated 262,000,000 deaths caused by democide, which excludes those killed in war battles, civilians unintentionally killed in war and killings of rioting mobs.[16] According to Charles Tilly, "Altogether, about 100 million people died as a direct result of action by organized military units backed by one government or another over the course of the century. Most likely a comparable number of civilians died of war-induced disease and other indirect effects."[17] It is estimated that approximately 70 million Europeans died through war, violence and famine between 1914 and 1945.[18]

Richard Nixon and Leonid Brezhnev aboard the USS Sequoia, June 19, 1973
Hong Kong, under British administration from 1842 to 1997, is one of the original four Asian tigers.

Culture and entertainment

I and the Village by Marc Chagall, a modern painter.
  • As the century began, Paris was the artistic capital of the world, where both French and foreign writers, composers and visual artists gathered. By the end of the century New York City had become the artistic capital of the world.
  • Theater, films, music and the media had a major influence on fashion and trends in all aspects of life. As many films and much music originate from the United States, American culture spread rapidly over the world.
  • 1953 saw the coronation of Queen Elizabeth II, an iconic figure of the century.
  • Visual culture became more dominant not only in films but in comics and television as well. During the century a new skilled understanding of narrativist imagery was developed.
  • Computer games and internet surfing became new and popular form of entertainment during the last 25 years of the century.
  • In Literature, science fiction, fantasy (with well-developed fictional worlds, rich in detail), and alternative history fiction gained unprecedented popularity. Detective fiction gained unprecedented popularity in the interwar period. In the United States in 1961 Grove Press published Tropic of Cancer a novel by Henry Miller redefining pornography and censorship in publishing in America.

Music

The invention of music recording technologies such as the phonograph record, and dissemination technologies such as radio broadcasting, massively expanded the audience for music. Prior to the 20th century, music was generally only experienced in live performances. Many new genres of music were established during the 20th century.

Led Zeppelin are widely considered one of the most successful, innovative, and influential rock groups in history.

The world's most popular / famous music artists of the 20th century include : Louis Armstrong, Duke Ellington, Bing Crosby, ABBA, The Beach Boys, The Beatles, Harry Belafonte, Little Richard, Chuck Berry, James Brown, Miles Davis, Bob Dylan, Jimi Hendrix, Michael Jackson, Elton John, Robert Johnson, Led Zeppelin, Queen, Madonna, Bob Marley, Charlie Parker, Pink Floyd, Elvis Presley, The Rolling Stones, Frank Sinatra, Stevie Wonder, Tupac Shakur, Nirvana (band), The Notorious B.I.G.,Amr Diab , Fairuz, Umm Kulthum,Abdel Halim Hafez and many more.

Film, television and theatre

Film as an artistic medium was created in the 20th century. The first modern movie theatre was established in Pittsburgh in 1905.[23] Hollywood developed as the center of American film production. While the first films were in black and white, technicolor was developed in the 1920s to allow for color films. Sound films were developed, with the first full-length feature film, The Jazz Singer, released in 1927. The Academy Awards were established in 1929.

Charlie Chaplin in his 1921 film The Kid, with Jackie Coogan.

Art and Architecture

Sport

  • The popularity of sport increased considerably—both as an activity for all, and as entertainment, particularly on television.
  • The modern Olympic Games, first held in 1896, grew to include tens of thousands of athletes in dozens of sports.
  • The FIFA World Cup was first held in 1930, and was held every 4 years after World War II.

Science

Mathematics

The pioneer of computer science, Alan Turing

Multiple new fields of mathematics were developed in the 20th century. In the first part of the 20th century, measure theory, functional analysis, and topology were established, and significant developments were made in fields such as abstract algebra and probability. The development of set theory and formal logic led to Gödel's incompleteness theorems.

Later in the 20th century, the development of computers led to the establishment of a theory of computation.[24] Other computationally-intense results include the study of fractals[25] and a proof of the four color theorem in 1976.[26]

Physics

Astronomy

  • A much better understanding of the evolution of the universe was achieved, its age (about 13.8 billion years) was determined, and the Big Bang theory on its origin was proposed and generally accepted.
  • The age of the solar system, including Earth, was determined, and it turned out to be much older than believed earlier: more than 4 billion years, rather than the 20 million years suggested by Lord Kelvin in 1862.[27]
  • The planets of the solar system and their moons were closely observed via numerous space probes. Pluto was discovered in 1930 on the edge of the solar system, although in the early 21st century, it was reclassified as a plutoid instead of a planet proper, leaving eight planets.
  • No trace of life was discovered on any of the other planets in our solar system (or elsewhere in the universe), although it remained undetermined whether some forms of primitive life might exist, or might have existed, somewhere. Extrasolar planets were observed for the first time.

Biology

Norman Borlaug, father of the Green Revolution, is often credited with saving over a billion people worldwide from starvation.

Medicine

A stamp commemorating Alexander Fleming. His discovery of penicillin had changed the world of modern medicine by introducing the age of antibiotics.

Notable diseases

Energy and the environment

Oil field in California, 1938. The first modern oil well was drilled in 1848 by Russian engineer F.N. Semyonov, on the Apsheron Peninsula north-east of Baku.
  • The dominant use of fossil sources and nuclear power, considered the conventional energy sources.
  • Widespread use of petroleum in industry—both as a chemical precursor to plastics and as a fuel for the automobile and airplane—led to the geopolitical importance of petroleum resources. The Middle East, home to many of the world's oil deposits, became a center of geopolitical and military tension throughout the latter half of the century. (For example, oil was a factor in Japan's decision to go to war against the United States in 1941, and the oil cartel, OPEC, used an oil embargo of sorts in the wake of the Yom Kippur War in the 1970s).
  • The increase in fossil fuel consumption also fueled a major scientific controversy over its effect on air pollution, global warming, and global climate change.
  • Pesticides, herbicides and other toxic chemicals accumulated in the environment, including in the bodies of humans and other animals.
  • Overpopulation and worldwide deforestation diminished the quality of the environment.

Engineering and technology

First flight of the Wright Flyer I, December 17, 1903, Orville piloting, Wilbur running at wingtip.

One of the prominent traits of the 20th century was the dramatic growth of technology. Organized research and practice of science led to advancement in the fields of communication, engineering, travel, medicine, and war.

  • The number and types of home appliances increased dramatically due to advancements in technology, electricity availability, and increases in wealth and leisure time. Such basic appliances as washing machines, clothes dryers, furnaces, exercise machines, refrigerators, freezers, electric stoves, and vacuum cleaners all became popular from the 1920s through the 1950s. The microwave oven became popular during the 1980s and have become a standard in all homes by the 1990s. Radios were popularized as a form of entertainment during the 1920s, which extended to television during the 1950s. Cable and satellite television spread rapidly during the 1980s and 1990s. Personal computers began to enter the home during the 1970s–1980s as well. The age of the portable music player grew during the 1960s with the development of the transistor radio, 8-track and cassette tapes, which slowly began to replace record players. These were in turn replaced by the CD during the late 1980s and 1990s. The proliferation of the Internet in the mid-to-late 1990s made digital distribution of music (mp3s) possible. VCRs were popularized in the 1970s, but by the end of the 20th century, DVD players were beginning to replace them, making the VHS obsolete by the end of the first decade of the 21st century.
  • The first airplane was flown in 1903. With the engineering of the faster jet engine in the 1940s, mass air travel became commercially viable.
  • The assembly line made mass production of the automobile viable. By the end of the 20th century, billions of people had automobiles for personal transportation. The combination of the automobile, motor boats and air travel allowed for unprecedented personal mobility. In western nations, motor vehicle accidents became the greatest cause of death for young people. However, expansion of divided highways reduced the death rate.
  • The triode tube, transistor and integrated circuit successively revolutionized electronics and computers, leading to the proliferation of the personal computer in the 1980s and cell phones and the public-use Internet in the 1990s.
  • New materials, most notably stainless steel, Velcro, silicone, teflon, and plastics such as polystyrene, PVC, polyethylene, and nylon came into widespread use for many various applications. These materials typically have tremendous performance gains in strength, temperature, chemical resistance, or mechanical properties over those known prior to the 20th century.
  • Aluminum became an inexpensive metal and became second only to iron in use.
  • Semiconductor materials were discovered, and methods of production and purification developed for use in electronic devices. Silicon became one of the purest substances ever produced.
  • Thousands of chemicals were developed for industrial processing and home use.

Space exploration

American Buzz Aldrin during the first moonwalk in 1969. The relatively young aerospace engineering industries rapidly grew in the 66 years after the Wright brothers first flight.
  • The Space Race between the United States and the Soviet Union gave a peaceful outlet to the political and military tensions of the Cold War, leading to the first human spaceflight with the Soviet Union's Vostok 1 mission in 1961, and man's first landing on another world—the Moon—with America's Apollo 11 mission in 1969. Later, the first space station was launched by the Soviet space program. The United States developed the first reusable spacecraft system with the Space Shuttle program, first launched in 1981. As the century ended, a permanent manned presence in space was being founded with the ongoing construction of the International Space Station.
  • In addition to human spaceflight, unmanned space probes became a practical and relatively inexpensive form of exploration. The first orbiting space probe, Sputnik 1, was launched by the Soviet Union in 1957. Over time, a massive system of artificial satellites was placed into orbit around Earth. These satellites greatly advanced navigation, communications, military intelligence, geology, climate, and numerous other fields. Also, by the end of the 20th century, unmanned probes had visited the Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and various asteroids and comets. The Hubble Space Telescope, launched in 1990, greatly expanded our understanding of the Universe and brought brilliant images to TV and computer screens around the world.
  • The Global Positioning System, a series of satellites that allow land-based receivers to determine their exact location, was developed and deployed.[30]

Religion

Economics

See also

References

  1. ↑ "Twentieth Century's Triumphant Entry". The New York Times. January 1, 1901
  2. ↑ "The 21st Century and the 3rd Millennium When Did They Begin?". United States Naval Observatory. Retrieved 2013-06-07.
  3. ↑ Wilson, E.O., The Future of Life (2002) ( ISBN 0-679-76811-4). See also: Leakey, Richard, The Sixth Extinction : Patterns of Life and the Future of Humankind, ISBN 0-385-46809-1
  4. ↑ "The Sixth Extinction - The Most Recent Extinctions". Archived from the original on 2015-12-18.
  5. ↑ "World Population to Hit Milestone With Birth of 7 Billionth Person". PBS NewsHour. Retrieved 11 February 2018.
  6. ↑ "World population hits 6 billion". 4 March 2004. Retrieved 11 February 2018.
  7. ↑ "Quiz: Population 7 Billion—Could We All Fit in One City?". 30 October 2011. Retrieved 11 February 2018.
  8. ↑ Pinker, Stephen (2011). The Better Angels of Our Nature. Viking. ISBN 978-0-670-02295-3.
  9. ↑ Mark Harrison (2002). Accounting for War: Soviet Production, Employment, and the Defence Burden, 1940–1945. Cambridge University Press. p. 167. ISBN 0-521-89424-7
  10. ↑ Ferguson, Niall (2004). Empire: The rise and demise of the British world order and the lessons for global power. New York: Basic Books. ISBN 0-465-02328-2.
  11. ↑ Fleegler, Robert L. Theodore G. Bilbo and the Decline of Public Racism, 1938-1947 Archived 2009-02-06 at the Wayback Machine.. Retrieved 23 December 2014
  12. ↑ Smith, J.B.; et al. "Ch. 19. Vulnerability to Climate Change and Reasons for Concern: A Synthesis". Extreme and Irreversible Effects. Sec 19.6. , in IPCC TAR WG2 2001
  13. ↑ "Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750." (p 11) "From 1750 to 2011, CO2 emissions from fossil fuel combustion and cement production have released 375 [345 to 405] GtC to the atmosphere, while deforestation and other land use change are estimated to have released 180 [100 to 260] GtC." (p 10), IPCC, Climate Change 2013: The Physical Science Basis - Summary for Policymakers, Observed Changes in the Climate System, p. 10&11, in IPCC AR5 WG1 2013.
  14. ↑ "World Population: Historical Estimates of World Population". United States Census Bureau. December 19, 2013. Retrieved 2015-01-09.
  15. ↑ "World Population: Total Midyear Population for the World: 1950-2050". United States Census Bureau. December 19, 2013. Retrieved 2015-01-09.
  16. ↑ Democide See various exclusions
  17. ↑ Charles Tilly (2003). "The politics of collective violence" Cambridge University Press. p. 55. ISBN 0-521-53145-4.
  18. ↑ Gary Rodger Weaver (1998). Culture, Communication, and Conflict. Simon & Schuster. p. 474. ISBN 0-536-00373-4
  19. ↑ Geoffrey A. Hosking (2001). "Russia and the Russians: a history". Harvard University Press. p. 469. ISBN 0-674-00473-6
  20. ↑ "The Other Killing Machine". The New York Times. May 11, 2003
  21. 1 2 "China's great famine: 40 years later". British Medical Journal 1999;319:1619–1621 (December 18 )
  22. ↑ Thee, Marek (1976). "The Indochina Wars: Great Power Involvement - Escalation and Disengagement". Journal of Peace Research. Sage Publications. 13 (2): 117. ISSN 1460-3578. JSTOR 423343. (Subscription required (help)).
  23. ↑ "You saw it here first: Pittsburgh's Nickelodeon introduced the moving picture theater to the masses in 1905". Pittsburgh Post-Gazette. 18 June 2005. Retrieved 11 February 2018.
  24. ↑ 1906-1976., Boyer, Carl B. (Carl Benjamin), (1991). A history of mathematics. Merzbach, Uta C., 1933-, Rogers D. Spotswood Collection. (2nd ed. [rev.] ed.). New York: Wiley. ISBN 0471543977. OCLC 23823042.
  25. ↑ Devaney, Robert L. (1998). A first course in chaotic dynamical systems : theory and experiment (6. printing. ed.). Reading, Mass. [u.a.]: Addison-Wesley. ISBN 0-201-55406-2.
  26. ↑ Kenneth Appel; Wolfgang Haken (26 July 1976). "Every Planar Map is Four-Colorable" (PDF). Bulletin of the American Mathematical Society.
  27. ↑ Thomson, Sir William (1862). "On the Age of the Sun's Heat". Macmillan's Magazine. 5: 288–293.
  28. 1 2 3 "The Nobel Prize in Physiology or Medicine 1962". NobelPrize.org. Nobel Media AB. Retrieved November 5, 2011.
  29. 1 2 3 4 "James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin". Science History Institute. Retrieved 20 March 2018.
  30. ↑ "Global Positioning System History". 2012-10-27. Retrieved 2018-02-07.

Further reading

  • Brower, Daniel R. and Thomas Sanders. The World in the Twentieth Century (7th Ed, 2013)
  • Grenville, J. A. S. A History of the World in the Twentieth Century (1994). online free
  • Hallock, Stephanie A. The World in the 20th Century: A Thematic Approach (2012)
  • Pollard, Sidney, ed. Wealth and Poverty: an Economic History of the 20th Century (1990), 260pp; global perspective online free
  • Stearns, Peter, ed. The Encyclopedia of World History (2001)
  • UNESCO (February 28, 2008). "The Twentieth Century". History of Humanity. VII. Routledge. p. 600. ISBN 978-0-415-09311-8.
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