Page "20th century" Paragraph 4

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.