Scientific Discoveries: c. 1900 - Present

AP Concept: 6.1 Science and the Environment
Key Concepts
  • Researchers made rapid discoveries in science that spread quickly
Medical Advances
  • The discovery of vaccines, antibiotics, and new surgical techniques improved life expectancy and eradicated many previously-deadly diseases in wealthy countries
    • Alexander Fleming discovered penicillin in the 1920s, a naturally growing substance that could attack bacteria, and scientists replicated and improved on his results to discover that penicillin could cure serious infections
    • By the late 1940s, penicillin became widely available in wealthy countries, and scientists began researching other forms of antibiotics to cure diseases
    • While inoculation against diseases with vaccines had been occurring since the 18th century, it greatly increased during the 20th century
    • It became standard for children to be inoculated against diphtheria, measles, mumps, and other previously dangerous diseases
    • The World Health Organization (WHO) launched global programs aimed at inoculating children around the world
  • Nevertheless, impoverished countries continue to suffer from diseases such as tuberculosis, cholera, and malaria, though many of these diseases no longer threaten wealthy countries
Technological Advances
  • Technological advances in cities also improved life expectancy and quality
  • While Western cities had been developing sewage systems in the 19th century, they began to develop more expansive systems for treating sewage in the early 20th century
  • This discovery drastically reduced the incidence of water-borne diseases in urban populations
  • Advances in agriculture transformed farming throughout the world
  • Between the 1940s and 1960s, the innovations of the Green Revolution were credited with saving over a billion people from starvation, especially in the developing world
  • Research, development, and technology transfer initiatives led to the development of high-yielding varieties of cereal grains, expansion of irrigation infrastructure, and the use of synthetic fertilizers and pesticides
  • These developments greatly increased agricultural output throughout the world
  • New methods of communication and transportation profoundly reduced problems associated with geographic distance
  • Radio, television, and the Internet allowed faster communication, while automobiles and airplanes allowed faster transportation
  • Advances in energy technology revolutionized industrial productivity
  • The use of oil and nuclear power allowed greater productivity, but had significant environmental costs
  • New scientific theories, such as Einstein's theory of relativity, led to significant advances in human understanding

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Migration: c. 1750 - c. 1900