A machine is a tool consisting of one or more parts that is constructed to achieve a particular goal. Machines are powered devices, usually mechanically, chemically, thermally or electrically powered, and are frequently motorized. Historically, a device required moving parts to classify as a machine; however, the advent of electronics technology has led to the development of devices without moving parts that are considered machines.
The word "machine" is derived from the Latin word machina, which in turn derives from the Doric Greek μαχανά (machana), Ionic Greek μηχανή (mechane) "contrivance, machine, engine" and that from μῆχος (mechos), "means, expedient, remedy". The meaning of machine is traced by the Oxford English Dictionary to an independently functioning structure and by Merriam-Webster Dictionary to something that has been constructed. This includes human design into the meaning of machine.
A simple machine is a device that simply transforms the direction or magnitude of a force, but a large number of more complex machines exist. Examples include vehicles, electronic systems, molecular machines, computers, television and radio.
Simple machines
Table of simple mechanisms, from Chambers' Cyclopedia, 1728. Simple machines provide a "vocabulary" for understanding more complex machines.
The idea that a machine can be broken down into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane.
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines (such as steam engines) burn a fuel to create heat which is then used to create motion. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air and others, such as wind-up toys use elastic energy. In biological systems, molecular motors like myosins in muscles use chemical energy to create motion.
An electrical machine is the generic name for a device that converts mechanical energy to electrical energy, converts electrical energy to mechanical energy, or changes alternating current from one voltage level to a different voltage level.
Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible and is usually applied to information and signal processing. Similarly, the ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a working system.
Computers store and manipulate the flow of electrons, with patterns in this storage and flow being interpreted as information manipulation. See State machine and Turing machine.
Charles Babbage designed various machines to tabulate logarithms and other functions in 1837. His Difference engine is the first mechanical calculator. This machine is considered to be the forerunner of the modern computer though none of them were built in his lifetime.
Study of the molecules and proteins that are the basis of biological functions has led to the concept of a molecular machine. For example, current models of the operation of the kinesin molecule that transports vesicles inside the cell as well as the myocin molecule that operates against actin to cause muscle contraction; these molecules control movement in response to chemical stimuli.
Researchers in nano-technology are working to construct molecules that perform movement in response to a specific stimulus. In contrast to molecules such as kinesin and myosin, these nano-machines or molecular machines are constructions like traditional machines that are designed to perform in a task.
