Robert Fludd’s 1618 “water screw” perpetual motion machine dating atmos clocks a 1660 wood engraving. This device is widely credited as the first recorded attempt to describe such a device in order to produce useful work, that of driving millstones.
Perpetual motion is motion of bodies that continues indefinitely. A perpetual motion machine is a hypothetical machine that can do work indefinitely without an energy source. These laws of thermodynamics apply regardless of the size of the system. Thus, machines that extract energy from finite sources will not operate indefinitely, because they are driven by the energy stored in the source, which will eventually be exhausted. A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out.
In 2017, new states of matter, time crystals, were discovered in which on a microscopic scale the component atoms are in continual repetitive motion, thus satisfying the literal definition of “perpetual motion”. The history of perpetual motion machines dates back to the Middle Ages. For millennia, it was not clear whether perpetual motion devices were possible or not, but the development of modern theories of thermodynamics has shown that they are impossible. Despite this, many attempts have been made to construct such machines, continuing into modern times. Modern designers and proponents often use other terms, such as “over unity”, to describe their inventions. Oh ye seekers after perpetual motion, how many vain chimeras have you pursued? Go and take your place with the alchemists.
There is a scientific consensus that perpetual motion in an isolated system violates either the first law of thermodynamics, the second law of thermodynamics, or both. As a result, the thermal efficiency—the produced work power divided by the input heating power—cannot be greater than one. The output work power of heat engines is always smaller than the input heating power. The rest of the heat energy supplied is wasted as heat to the ambient surroundings.
The thermal efficiency therefore has a maximum, given by the Carnot efficiency, which is always less than one. The efficiency of real heat engines is even lower than the Carnot efficiency due to irreversibility arising from the speed of processes, including friction. Statements 2 and 3 apply to heat engines. Other types of engines which convert e. Machines which comply with both laws of thermodynamics by accessing energy from unconventional sources are sometimes referred to as perpetual motion machines, although they do not meet the standard criteria for the name. By way of example, clocks and other low-power machines, such as Cox’s timepiece, have been designed to run on the differences in barometric pressure or temperature between night and day.EnableInternalCSP_request