Automobiles are self-propelled motor vehicles designed to run primarily on roads. Usually they have four wheels and an internal combustion engine fueled by gasoline, a liquid petroleum product.
The automobile industry is one of the largest and most important industries in the world. It is an integral part of the economy, providing employment to millions of workers and being a significant source of revenue for many other industries.
A large number of engineers and scientists work on research and development of automobiles to improve the body, chassis, engine, drivetrain, control systems, safety systems and emission-control systems. These engineers and scientists are essential for bringing the automobile to its full potential.
Cars evolved as a result of the invention of the internal combustion engine by Dutch scientist Christiaan Huygens in the late 1600s. He developed a system that combined a piston, a crankshaft and an exhaust valve to generate the power needed to turn a wheel.
Eventually, a large number of small manufacturers began to manufacture automobiles to meet the growing demand for vehicles. This resulted in a rapid increase in the technology used by automobiles. Some of the most important innovations included electric ignition and the electric self-starter (both by Charles Kettering, for the Cadillac Motor Company in 1910-1911), independent suspension and four-wheel brakes.
During the 1920s, automobiles became a major force in the American economy. They ended rural isolation, brought new businesses to the roadside and stimulated tourism and travel-related industries. These industries created jobs and paved the way for urban amenities such as service stations, roadside restaurants and motels. The automobile also contributed to the construction of streets and highways, one of the largest public works projects in history.