Editing Perpetual motion (section)

{{Short description|Work being continuously done without an external input of energy}}
{{Other uses}}
{{Redirect|Perpetual Motion Machine}}
{{Redirect|Free energy device|other meanings of "free energy"|Free energy (disambiguation){{!}}Free energy}}
[[Image:WaterScrewPerpetualMotion.png|thumb|right|250px|[[Robert Fludd]]'s 1618 "water screw" perpetual motion machine from a 1660 wood engraving. It is widely credited as the first attempt to describe such a device.{{notetag|Although the machine would not work, the idea was that water from the top tank turns a [[water wheel]] (bottom-left), which drives a complicated series of gears and shafts that ultimately rotate the [[Archimedes' screw]] (bottom-center to top-right) to pump water to refill the tank. The rotary motion of the water wheel also drives two grinding wheels (bottom-right) and is shown as providing sufficient excess water to lubricate them.}}<ref name="sciam" />]]

[[File:Something for nothing (1940).ogv|thumb|thumbtime=18|upright=1.1|''Something for Nothing'' (1940), a short film featuring [[Rube Goldberg]] illustrating the [[U.S. Patent Office]]'s policy regarding perpetual motion machines (and the power efficiency of [[gasoline]])]]
'''Perpetual motion''' is the motion of bodies that continues forever in an unperturbed system. A '''perpetual motion machine''' is a hypothetical machine that can do work indefinitely without an external [[energy]] source. This kind of machine is impossible, since its existence would violate the [[first law of thermodynamics|first]] and/or [[second law of thermodynamics|second]] laws of thermodynamics.<ref name="Derry">{{cite book
  | last = Derry
  | first = Gregory N. 
  | title = What Science Is and How It Works
  | publisher = Princeton University Press
  | page = 167
  | url = https://books.google.com/books?id=Dk-xS6nABrYC&q=%22perpetual+motion&pg=PA167
  | isbn = 978-1400823116| date = 2002-03-04 
  }}</ref><ref name="Roy">{{cite book
  | last = Roy
  | first = Bimalendu Narayan 
  | title = Fundamentals of Classical and Statistical Thermodynamics
  | publisher = John Wiley & Sons
  | year = 2002
  | page = 58
  | url = https://books.google.com/books?id=mpmLUjAVua4C&q=%22perpetual+motion&pg=PA58
  | isbn = 978-0470843130| bibcode = 2002fcst.book.....N 
  }}</ref><ref>{{cite web|url=http://oxforddictionaries.com/definition/perpetual%2Bmotion?q=perpetual+motion |title=Definition of perpetual motion |publisher=Oxforddictionaries.com |date=2012-11-22 |access-date=2012-11-27}}{{dead link|date=September 2022|bot=medic}}{{cbignore|bot=medic}}</ref><ref>Point, Sébastien. [https://skepticalinquirer.org/2018/01/free-energy-when-the-web-is-freewheeling/ "Free energy: when the web is freewheeling".] ''Skeptikal Inquirer'', January–February 2018.</ref> These [[laws of thermodynamics]] apply regardless of the size of the system. Thus, machines that extract energy from finite sources cannot 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 [[End of the Sun|burn out]].

In 2016,<ref name="technologyreview.com">{{Cite web|url=https://www.technologyreview.com/2016/10/04/157185/physicists-create-worlds-first-time-crystal/|title = Physicists Create World's First Time Crystal}}</ref> new states of matter, [[time crystal]]s, were discovered in which, on a microscopic scale, the component atoms are in continual repetitive motion, thus satisfying the literal definition of "perpetual motion".<ref name="Grossman 2012">{{cite web|last1=Grossman|first1=Lisa|title=Death-defying time crystal could outlast the universe|url=https://www.newscientist.com/article/mg21328484-000-death-defying-time-crystal-could-outlast-the-universe/|work=New Scientist|archive-url=https://archive.today/20170202104619/https://www.newscientist.com/article/mg21328484-000-death-defying-time-crystal-could-outlast-the-universe/|archive-date=2017-02-02|date=18 January 2012|url-status=dead}}</ref><ref name="Cowen 2012">{{cite web|last1=Cowen|first1=Ron|title="Time Crystals" Could Be a Legitimate Form of Perpetual Motion|url=https://www.scientificamerican.com/article/time-crystals-could-be-legitimate-form-perpetual-motion/|work=Scientific American|archive-url=https://archive.today/20170202101455/https://www.scientificamerican.com/article/time-crystals-could-be-legitimate-form-perpetual-motion/|archive-date=2017-02-02|date=27 February 2012|url-status=dead}}</ref><ref name="Powell 2013">{{cite journal|last1=Powell|first1=Devin|title=Can matter cycle through shapes eternally?|journal=Nature|year=2013|issn=1476-4687|doi=10.1038/nature.2013.13657|s2cid=181223762|url=http://www.nature.com/news/can-matter-cycle-through-shapes-eternally-1.13657|archive-url=https://archive.today/20170203080014/http://www.nature.com/news/can-matter-cycle-through-shapes-eternally-1.13657|archive-date=2017-02-03|url-status=dead|url-access=subscription}}</ref><ref name="Gibney 2017">{{cite journal|last1=Gibney|first1=Elizabeth|title=The quest to crystallize time|journal=Nature|volume=543|issue=7644|year=2017|pages=164–166|issn=0028-0836|doi=10.1038/543164a|bibcode=2017Natur.543..164G|pmid=28277535|s2cid=4460265}}</ref> However, these do not constitute perpetual motion machines in the traditional sense, or violate thermodynamic laws, because they are in their quantum [[ground state]], so no energy can be extracted from them; they exhibit motion without energy.