Bicycles were introduced in
the 19th century in Europe and now number more than a billion worldwide, twice
as many as automobiles. They are the principal means of transportation in many
regions. They also provide a popular form of recreation, and have been adapted
for use as children's toys, general fitness, military and police applications,
courier services, and bicycle racing.
The bicycle's invention has
had an enormous effect on society, both in terms of culture and of advancing
modern industrial methods. Several components that eventually played a key role
in the development of the automobile were invented for the bicycle, including ball
bearings, pneumatic tires, chain-driven sprockets, and tension-spoked wheels.
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