Automobiles are four-wheeled motor vehicles that have become a major means of transportation in many countries. There are some 1.4 billion automobiles in operation worldwide, and they are used for transporting passengers and freight over long distances. Hundreds of companies produce cars, and the design and characteristics of individual models vary significantly. The modern car contains dozens of interrelated systems that must work together, including the engine, transmission, electrical system, cooling and lubrication system, wheels and tires, and chassis and body. These are all designed to support and protect the passengers, as well as to provide safety, comfort, and protection from the elements.
The automotive industry has restructured entire societies and created new forms of leisure, recreation, and business, but it has also contributed to problems such as urban sprawl (i.e., straggling, low-density development) and traffic congestion. The automobile has brought freedom of travel to individuals, but it also encourages people to live far from work or from family and friends, and it makes it difficult to maintain close connections in a large social circle.
The scientific and technical building blocks of the modern automobile date back several hundred years, to the invention of internal combustion by Dutch scientist Christiaan Huygens in the late 1600s. But it was not until the early 1900s that automobiles began to take over streets and byways in Europe and the United States, transforming personal and commercial lives. The introduction of mass production techniques, pioneered by American carmaker Henry Ford, made the automobile affordable to a wide range of Americans and revolutionized the way businesses produced other goods.