A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out. 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. For example, the motions and rotations of celestial bodies such as planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy, such as solar wind, interstellar medium resistance, gravitational radiation and thermal radiation, so they will not keep moving forever. These laws of thermodynamics apply regardless of the size of the system. This kind of machine is impossible, as it would violate either the first or second law of thermodynamics, or both. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. Perpetual motion is the motion of bodies that continues forever in an unperturbed system. Patent Office's policy regarding perpetual motion machines (and the power efficiency of gasoline) Something for Nothing (1940), a short film featuring Rube Goldberg illustrating the U.S.
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