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{{For|the album by Off Minor|The Heat Death of the Universe}} {{Short description|Possible fate of the universe}}
{{About|the entropic exhaustion of the universe|other uses|Heat Death of the Universe (disambiguation)}}
{{Physical cosmology|expansion}}
{{For the| heat related illness or death| Hyperthermia}}
{{Redirect|Big Freeze}}


{{Multiple issues|
The '''heat death of the universe''' is a plausible ] in which the ] has diminished to a state of no ] and therefore can no longer sustain processes that increase entropy. Heat death does not imply any particular ]; it only requires that temperature differences or other processes may no longer be exploited to perform ]. In the language of ], this is when the universe reaches ] (maximum ]).
{{Original research|date=September 2020}}
{{Update|date=August 2021}}
{{Expand Chinese|date=August 2021|topic=sci}}
}}


{{Physical cosmology|expansion}}
If the topology of the universe is ], or if ] is a positive ] (both of which are supported by current data), the universe will continue expanding forever and a heat death is expected to occur,<ref name="Plait 2008">Plait, Philip ''Death From the Skies!'', Viking Penguin, NY, ISBN 978-0-670-01997-7, p. 259</ref> with the universe cooling to approach equilibrium at a very low temperature after a very long time period.


The '''heat death of the universe''' (also known as the '''Big Chill''' or '''Big Freeze''')<ref>, ''WMAP's Universe'', ]. Accessed online July 17, 2008.</ref><ref>{{Cite book |last=Dyer |first=Alan |title=Insiders: Space |date=2007-07-24 |publisher=] Books for Young Readers |isbn=978-1-4169-3860-6 |pages=40–41 |language=en}}</ref> is a ] on the ], which suggests the ] will evolve to a state of no ], and will therefore be unable to sustain processes that increase ]. Heat death does not imply any particular ]; it only requires that temperature differences or other processes may no longer be exploited to perform ]. In the language of ], this is when the universe reaches ].
The hypothesis of heat death stems from the ideas of ], who in the 1850s took the ] as ] loss in ] (as embodied in the first two ]) and extrapolated it to larger processes on a universal scale.


If the ] of the universe is ], or if ] is a positive ], the universe will continue expanding forever, and a heat death is expected to occur,<ref name="DftS">
==Mechanism of heat death==
{{Cite book
Initially, the universe has the maximal (''i.e.'', zero) potential energy, and the minimal (''i.e.'', zero) actual energy. Such a universe is in a state of '''heat death''' and exists as a uniform blanket of zero-temperature heat. According to the ], heat tends to pass from hotter to colder bodies. So, when a portion of the zero&#8209;temperature heat self&#8209;gravitationally shrinks to a nonzero temperature, a half of the resultant nonzero&#8209;temperature heat becomes radiated into the colder ambient vacuum, at which point the particle of nonzero&#8209;temperature heat undergoes self&#8209;gravitational shrinkage to a still higher temperature.<ref>Böhm-Vitense, Erika. . CUP, 1992, p. 29. "After each infinitesimal step of collapse the star has to wait until it has radiated away a half of the released gravitational energy before it can continue to contract."</ref> Thus the temperature difference between the self&#8209;gravitationally shrinking particle and the ambient vacuum increases, which increases the rate of heat loss and thereby accelerates the particle's self&#8209;gravitational shrinkage:
| title = Death from the Skies!
] in '']'']]
| last = Plait
{{pull quote|<p>All change is relative. The universe is expanding relatively to our common material standards; our material standards are shrinking relatively to the size of the universe. The theory of the "expanding universe" might also be called the theory of the "shrinking atom". ...</p>
| first = Philip
<p>Let us then take the whole universe as our standard of constancy, and adopt the view of a cosmic being whose body is composed of intergalactic spaces and swells as they swell. Or rather we must now say it keeps the same size, for he will not admit that it is he who has changed. Watching us for a few thousand million years, he sees us shrinking; atoms, animals, planets, even the galaxies, all shrink alike; only the intergalactic spaces remain the same. The earth spirals round the sun in an ever&#8209;decreasing orbit. It would be absurd to treat its changing revolution as a constant unit of time. The cosmic being will naturally relate his units of length and time so that the velocity of light remains constant. Our years will then decrease in geometrical progression in the cosmic scale of time. On that scale man's life is becoming briefer; his threescore years and ten are an ever&#8209;decreasing allowance. Owing to the property of geometrical progressions an infinite number of our years will add up to a finite cosmic time; so that what we should call the end of eternity is an ordinary finite date in the cosmic calendar. But on that date the universe has expanded to infinity in our reckoning, and we have shrunk to nothing in the reckoning of the cosmic being.</p>
| publisher = Viking Adult
We walk the stage of life, performers of a drama for the benefit of the cosmic spectator. As the scenes proceed he notices that the actors are growing smaller and the action quicker. When the last act opens the curtain rises on midget actors rushing through their parts at frantic speed. Smaller and smaller. Faster and faster. One last microscopic blurr of intense agitation. And then nothing.<ref>Eddington, Arthur. . CUP, 1933, pp.&nbsp;90–92</ref>}}
| isbn = 978-0-670-01997-7
When the above-described exponentially accelerating "evaporation" of ever-hotter particles comes to an end, the universe again has the maximal (''i.e.'', zero) potential energy, and the minimal (''i.e.'', zero) actual energy. Such a universe is in a state of '''heat death''' and exists as a uniform blanket of zero-temperature heat. The 13.8&#8209;billion&#8209;year&#8209;long gravitational life cycle then begins anew. And so ''ad infinitum''.
| publication-date = 16 October 2008
| page = 259
| author-link = Phil Plait
| title-link = Death from the Skies!
| year = 2008
}}</ref> with the universe cooling to approach equilibrium at a very low temperature after a long time period.

The hypothesis of heat death stems from the ideas of ] who, in the 1850s, took the ] as ] loss in nature (as embodied in the first two ]) and ] it to larger processes on a universal scale. This also allowed Kelvin to formulate the ], which disproves an infinitely old universe.<ref name="On the Age of the Sun's Heat"/>


==Origins of the idea== ==Origins of the idea==
The idea of heat death stems from the ], of which one version states that entropy tends to increase in an ]. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will ] approach a state where all ] is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature towards the ] (energy transformation) of ] (motion) into ]; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.
{{Nature timeline}}
The idea of heat death was first proposed in 1851 by ], who theorized further on the mechanical energy loss views of ] (1824), ] (1843), and ] (1850). It stems from the ], which states that ] tends to pass from hotter to colder bodies and eventually becomes uniformly distributed. As an elementary particle of matter (such as a proton) self&#8209;gravitationally shrinks, its heat becomes condensed ("augmented") to a higher temperature and then radiated away into the ambient vacuum:
{{pull quote|Although mechanical energy is indestructible, there is a universal tendency to its dissipation, which produces throughout the system a gradual '''augmentation''' and diffusion of heat, cessation of motion and exhaustion of the potential energy of the material Universe.<ref>Thomson, William. ''Macmillan's Magazine'', 5&nbsp;March 1862, pp. 388–93</ref>}}
At first, the prevailing opinion was that the heat death of the universe was in the distant future, because stars initially had high temperatures and cooled progressively with time, so that the rate of heat loss exponentially decreased. This insouciant view was overturned by ], who in 1870 discovered that the temperature of a self&#8209;gravitating perfect-gas sphere is inversely proportional to its radius: ''rT''(''r'')&nbsp;=&nbsp;''constant''. This equation is known as Lane's law.<ref>Reid, Neill I. Hawley, Suzanne L. . Springer, 2013, p. 84</ref> For example, when the sphere's radius (''r'') decreases tenfold, the sphere's temperature (''T'') increases tenfold:
{{pull quote|Lane reached the apparently paradoxical result that a star by losing heat and contracting actually grew hotter. A star shrinking under gravitation to half its linear size and remaining built on the same model, or "homologous" (i.e., the densities at two corresponding points at any two stages remaining the same fraction of the mean density) would be eight times as dense, and the internal pressures would be sixteen times as great as the overlying material is attracted four times as strongly and its weight is held up on only a quarter of the area. From the formula connecting temperature with pressure and density, given earlier in the chapter, it will be seen that the temperature in this example would be twice as great. By such reasoning, Lane concluded that as stars get smaller they grow hotter to withstand gravitation and resist collapse.<ref>Doig, Peter. . Hutchinson, 1947, p. 76</ref>}}


The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer ] in 1777 in his writings on the history of astronomy and in the ensuing correspondence with ]. In Bailly's view, all planets have an ] and are now at some particular stage of cooling. ], for instance, is still too hot for life to arise there for thousands of years, while the ] is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.<ref>
The ] (1879) dictates that the rate at which a unit surface area of the self&#8209;gravitationally condensing sphere radiates away heat is proportional to the fourth power of the sphere's temperature. So, even after taking into account that the sphere's surface area decreases a hundredfold (as the square of the radius), Lane's law implies that, '''when the self&#8209;gravitating sphere's radius shrinks tenfold, the sphere's total radiative heat loss per unit time increases a hundredfold'''.
{{Cite book
|title = A History of Modern Planetary Physics: Nebulous Earth
|last = Brush
|first = Stephen G.
|author-link = Stephen G. Brush
|publisher = Cambridge University Press
|year = 1996
|isbn = 978-0-521-44171-1
|volume = 1
|page =
|url = https://archive.org/details/historyofmodernp0000brus/page/77
}}</ref>


The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of ] (1824), ] (1843) and ] (1850). Thomson's views were then elaborated over the next decade by ] and ].<ref name="Energy and Empire" />
In 1983, numerical calculations on large computers predicted that as the temperature is raised the colour&#8209;repelling physical vacuum should flip into the simple vacuum, of which protons consist, at a temperature of 2&nbsp;×&nbsp;10<sup>12</sup> K.<ref>Willis, Bill. . ''New Scientist'', 3 October 1983, p. 10</ref> According to the ], a body as hot as the proton must be radiating away its energy at a frantic pace and shrink accordingly. From the perspective of observers consisting of such rapidly shrinking protons, intergalactic spaces must appear to be expanding with exponential acceleration. On 5 April 2016, ] ''et al.'' announced that, over the three years since 21 March 2013, when the ] published the local ] value, the apparent expansion of intergalactic spaces had unexpectedly accelerated by nine per cent.<ref>Hirsch, Arthur. . ''Hub'', 3 June 2016</ref> The proton's heat death is coming apace and hastening.

In 1974, ] applied the above&#8209;described principle of heat death to black holes and found that they, too, radiate away their energy (]) and consequently shrink in size; the smaller a black hole becomes, the faster it radiates away its remaining energy.


===History=== ===History===
The idea of heat death of the universe derives from discussion of the application of the first two ] to universal processes. Specifically, in 1851 ] (Lord Kelvin) outlined the view, as based on recent experiments on the dynamical ], that "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."<ref>Thomson, William. (1851). ", with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam." Excerpts. , Transactions of the Royal Society of Edinburgh, March, 1851; and Philosophical Magazine IV. 1852. </ref> The idea of the heat death of the universe derives from discussion of the application of the first two ] to universal processes. Specifically, in 1851, ] outlined the view, as based on recent experiments on the dynamical ]: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."<ref>Thomson, Sir William. (1851). Excerpts. , '']'', March 1851, and '']'', 1852. This version from ''Mathematical and Physical Papers'', vol. i, art. XLVIII, pp. 174.</ref>
] originated the idea of universal heat death in 1852.]] ] originated the idea of universal heat death in 1852.]]


In 1852, Thomson published '']'' in which he outlined the rudiments of the ] summarized by the view that mechanical motion and the energy used to create that motion will tend to dissipate or run down, naturally.<ref>Thomson, William (1852). "" Proceedings of the Royal Society of Edinburgh for April 19, 1852, also Philosophical Magazine, Oct. 1852. </ref> The ideas in this paper, in relation to their application to the age of the ] and the dynamics of the universal operation, attracted the likes of ] and ]. The three of them were said to have exchanged ideas on this subject.<ref name="Smith">Smith, Crosbie & Wise, Matthew Norton. (1989). ''Energy and Empire: A Biographical Study of Lord Kelvin''. (). Cambridge University Press.</ref> In 1862, Thomson published "On the age of the Sun’s heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the ]) and the universal dissipation of energy (the ]), leading to diffusion of heat, cessation of useful motion (]), and exhaustion of ] through the material universe while clarifying his view of the consequences for the universe as a whole. In a key paragraph, Thomson wrote: In 1852, Thomson published ''On a Universal Tendency in Nature to the Dissipation of Mechanical Energy'', in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down.<ref>Thomson, Sir William (1852). '']'' for 19 April 1852, also '']'', Oct. 1852. This version from ''Mathematical and Physical Papers'', vol. i, art. 59, pp. 511.</ref> The ideas in this paper, in relation to their application to the age of the ] and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject.<ref name="Energy and Empire">
{{Cite book
|title = Energy and Empire: A Biographical Study of Lord Kelvin
|last1 = Smith
|first1 = Crosbie
|last2 = Wise
|first2 = M. Norton
|publisher = Cambridge University Press
|year = 1989
|isbn = 978-0-521-26173-9
|page = 500
|author-link2 = M. Norton Wise
}}</ref> In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the ]) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion (]), and exhaustion of ], "lost irrecoverably" through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:


<blockquote>The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of ] into ] and hence into ], than to a single finite mechanism, running down like a clock, and stopping for ever.<ref>Thomson, William. (1862). "", Macmillan’s Mag., 5, 288–93; PL, 1, 394–68.</ref></blockquote> {{blockquote|The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of ] into ] and hence into ], than to a single finite mechanism, running down like a clock, and stopping for ever.<ref name="On the Age of the Sun's Heat">
{{Cite magazine
| last = Thomson
| first = Sir William
| date = 5 March 1862
| title = On the Age of the Sun's Heat
| url = https://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html
| magazine = ]
| volume = 5
| pages = 388–93
}}</ref>}}
The clock's example shows how Kelvin was unsure whether the universe would eventually achieve ]. Thompson later speculated that restoring the dissipated energy in "'']''" and then usable work&nbsp;– and therefore revert the clock's direction, resulting in a "rejuvenating universe"&nbsp;– would require "a creative act or an act possessing similar power".<ref name="britannica.com">{{cite web|url=https://www.britannica.com/biography/William-Thomson-Baron-Kelvin |publisher=Encyclopædia Britannica |author=Harold I. Sharlin |date=13 December 2019 |access-date=24 January 2020 |title=William Thomson, Baron Kelvin}}</ref><ref>{{cite magazine |last1=Otis |first1=Laura |year=2002 |title=Literature and Science in the Nineteenth Century: An Anthology |url= https://oxfordworldsclassics.com/view/10.1093/owc/9780199554652.001.0001/isbn-9780199554652 |magazine=OUP Oxford |volume=1 |pages=60–67}}</ref> Starting from this publication, Kelvin also introduced the ] (Kelvin's paradox), which challenged the classical concept of an infinitely old universe, since the universe has not achieved its thermodynamic equilibrium, thus further work and ] are still possible. The existence of stars and temperature differences can be considered an empirical proof that the universe is not infinitely old.<ref name="Thompson2015">'''' Thompson and Clausius, ], 2015.</ref><ref name="On the Age of the Sun's Heat"/>


In the years to follow both Thomson’s 1852 and the 1865 papers, Helmholtz and Rankine both credited Thomson with the idea, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "''heat death''" (Helmholtz) which will be the "''end of all physical phenomena''" (Rankine).<ref name="Smith" /><ref> (Helmholtz and Heat Death, 1854)</ref> In the years to follow both Thomson's 1852 and the 1862 papers, ] and ] both credited Thomson with the idea, along with his paradox, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "heat death" (Helmholtz), which will be the "end of all physical phenomena" (Rankine).<ref name="Energy and Empire" /><ref>
{{Cite web
|url = http://webplaza.pt.lu/fklaess/html/HISTORIA.HTML
|title = Physics Chronology
|archive-url = https://web.archive.org/web/20110522124507/http://webplaza.pt.lu/fklaess/html/HISTORIA.HTML
|archive-date = 22 May 2011
}}</ref>{{Unreliable source?|date=September 2018}}


==Current status== ==Current status==
{{see also|Entropy#Cosmology|Entropy (arrow of time)#Cosmology}} {{See also|Entropy#Cosmology|Entropy (arrow of time)#Cosmology}}
Proposals about the final state of the universe depend on the assumptions made about its ], and these assumptions have varied considerably over the late 20th century and early 21st century. In a hypothesized ] that continues expanding indefinitely, a heat death is expected to occur.<ref name="Plait 2008"/> If the cosmological constant is zero, the universe will approach absolute zero temperature over a very long timescale. However, if the cosmological constant is ], as appears to be the case in recent observations, the temperature will asymptote to a non-zero, positive value and the universe will approach a state of maximum entropy.<ref>], ], ]: </ref>


Proposals about the final state of the universe depend on the assumptions made about its ultimate fate, and these assumptions have varied considerably over the late 20th century and early 21st century. In a hypothesized ] that continues expanding indefinitely, either a heat death or a ] is expected to eventually occur.<ref name="DftS" /><ref>{{Cite web |last=Consolmagno |first=Guy |date=2008-05-08 |title=Heaven or Heat Death? |url=https://www.thinkingfaith.org/articles/20080508_1.htm |url-status=live |archive-url=https://web.archive.org/web/20231116170349/https://www.thinkingfaith.org/articles/20080508_1.htm |archive-date=2023-11-16 |access-date=2008-10-06 |website=Thinking Faith |language=en}}</ref> If the ] is zero, the universe will approach ] temperature over a ''very'' long timescale. However, if the cosmological constant is ], the temperature will asymptote to a non-zero positive value, and the universe will approach a state of maximum ] in which no further ] is possible.<ref>
The "heat death" situation could be avoided if there is a method or mechanism to regenerate ] atoms from ], ] or other sources in order to avoid a gradual running down of the universe due to the conversion of matter into energy and heavier elements in ].<ref>] 1918. On stellar evolution. Astrophys. J. 48: 35-49</ref><ref>{{cite journal |last1=Macmillan |first1=William D. |title=Some Mathematical Aspects of Cosmology |journal=Science |volume=62 |issue=1596 |pages=96–9 |year=1925 |pmid=17752724 |doi=10.1126/science.62.1596.96 |bibcode=1925Sci....62..121M }}</ref>
{{Cite journal
|last1 = Dyson
|first1 = Lisa
|author-link = Lisa Dyson
|last2 = Kleban
|first2 = Matthew
|author-link2 = Matthew Kleban
|last3 = Susskind
|first3 = Leonard
|author-link3 = Leonard Susskind
|date = 12 November 2002
|title = Disturbing Implications of a Cosmological Constant
|journal = ]
|volume = 2002
|issue = 10
|page = 011
|doi = 10.1088/1126-6708/2002/10/011
|bibcode = 2002JHEP...10..011D
|arxiv = hep-th/0208013
|s2cid = 2344440
}}</ref>


==Time frame for heat death== == Time frame for heat death ==
{{Main article|Future of an expanding universe}} {{Main|Future of an expanding universe}}


The theory suggests that from the "]" through the present day, ] and ] in the universe are thought to have been concentrated in ]s, ], and ]s, and are presumed to continue to do so well into the future. Therefore, the universe is not in ], and objects can do physical work.<ref name="A dying universe">
From the ] through the present day, matter and ] in the universe are thought to have been concentrated in ]s, ], and ]s, and are presumed to continue to be so well into the future. Therefore, the universe is not in thermodynamic equilibrium and objects can do physical ].<ref name=dying>{{cite journal|title=A dying universe: the long-term fate and evolution of astrophysical objects|author=Fred C. Adams and Gregory Laughlin|journal=Reviews of Modern Physics |volume=69 |issue=2 |pages=337–372 |date=1997 |bibcode=1997RvMP...69..337A |doi=10.1103/RevModPhys.69.337| arxiv=astro-ph/9701131}}.</ref><sup>,&nbsp;§VID.</sup> The decay time for a supermassive ] of roughly 1 galaxy-mass (10<sup>11</sup>&nbsp;]es) due to ] is on the order of ]&nbsp;years,<ref name=page>Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole, Don N. Page, ''Physical Review D'' '''13''' (1976), pp. 198–206. {{doi|10.1103/PhysRevD.13.198}}. See in particular equation (27).</ref> so ] can be produced until at least that time. After that time, the universe enters the so-called ], and is expected to consist chiefly of a dilute gas of ]s and ]s.<ref name=dying /><sup>§VIA</sup> With only very diffuse matter remaining, activity in the universe will have tailed off dramatically, with extremely low energy levels and extremely long time scales. Speculatively, it is possible that the universe may enter a second ] epoch, or, assuming that the current ] state is a ], the vacuum may decay into a lower-energy state.<ref name=dying /><sup>,&nbsp;§VE.</sup> It is also possible that entropy production will cease and the universe will reach heat death.<ref name=dying /><sup>,&nbsp;§VID.</sup> Possibly another universe could be created by random ]s or ] in roughly <math>10^{10^{10^{56}}}</math> years.<ref>Carroll, Sean M. and Chen, Jennifer (2004). {{cite arXiv | title = Spontaneous Inflation and Origin of the Arrow of Time | eprint = hep-th/0410270| last1 = Carroll| first1 = Sean M.| last2 = Chen| first2 = Jennifer| year = 2004}}</ref> Over an infinite time, there would be a spontaneous ] ''decrease'' via the ]{{citation needed|date=August 2016}}, ],<ref>http://arxiv.org/pdf/astro-ph/0302131.pdf?origin=publication_detail</ref><ref>{{Cite journal|arxiv=1205.1046|title=Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures.org|journal=International Journal of Modern Physics B|volume=27|issue=1345032|pages=1345032|last1= Werlang|first1=T.|last2= Ribeiro|first2=G. A. P.|last3=Rigolin|first3=Gustavo|year=2012|doi=10.1142/S021797921345032X|bibcode=2013IJMPB..2745032W}}</ref> and ].<ref>{{cite web|url=http://www.researchgate.net/publication/2215242_Spontaneous_entropy_decrease_and_its_statistical_formula|title=Spontaneous entropy decrease and its statistical formula|author=Xiu-San Xing|date=1 November 2007|work=ResearchGate}}</ref><ref>{{cite web|url=http://iopscience.iop.org/1475-7516/2007/01/022|title=Sinks in the landscape, Boltzmann brains and the cosmological constant problem - Abstract - Journal of Cosmology and Astroparticle Physics - IOPscience|work=iop.org}}</ref>
{{Cite journal
| last1 = Adams
| first1 = Fred C.
| author-link = Fred Adams
| last2 = Laughlin
| first2 = Gregory
| author-link2 = Gregory P. Laughlin
| year = 1997
| title = A dying universe: the long-term fate and evolution of astrophysical objects
| journal = ]
| volume = 69
| issue = 2
| pages = 337–72
|arxiv = astro-ph/9701131
|bibcode = 1997RvMP...69..337A
|doi = 10.1103/RevModPhys.69.337
| s2cid = 12173790
}}</ref><sup>:§VID</sup> The decay time for a ] of roughly 1 galaxy mass (10<sup>11</sup>&nbsp;]es) because of Hawking radiation is in the order of ]&nbsp;years,<ref name="page">
See in particular equation (27) in {{Cite journal
| last = Page
| first = Don N.
| author-link = Don Page (physicist)
| date = 15 January 1976
| title = Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole
| journal = ]
| volume = 13
| issue = 2
| pages = 198–206
| bibcode = 1976PhRvD..13..198P
| doi = 10.1103/PhysRevD.13.198
}}</ref> so entropy can be produced until at least that time. Some large ]s in the universe are predicted to continue to grow up to perhaps 10<sup>14</sup> {{solar mass}} during the collapse of ]s of galaxies. Even these would evaporate over a timescale of up to 10<sup>106</sup> years.<ref>
{{Cite journal
| last = Frautschi
| first = Steven
| date = 13 August 1982
| title = Entropy in an Expanding Universe
| url = http://www.informationphilosopher.com/solutions/scientists/layzer/Frautschi_Science_1982.pdf
| journal = ]
| volume = 217
| issue = 4560
| pages = 593–9
| jstor = 1688892
| quote = Since we have assumed a maximum scale of gravitational binding—for instance, superclusters of galaxies—black hole formation eventually comes to an end in our model, with masses of up to 10<sup>14</sup>{{solar mass}} ... the timescale for black holes to radiate away all their energy ranges ... to 10<sup>106</sup> years for black holes of up to 10<sup>14</sup>{{solar mass}}
| bibcode = 1982Sci...217..593F
| doi = 10.1126/science.217.4560.593
| pmid = 17817517
| s2cid = 27717447
}}</ref> After that time, the universe enters the so-called ] and is expected to consist chiefly of a dilute gas of ]s and ]s.<ref name="A dying universe" /><sup>:§VIA</sup> With only very diffuse matter remaining, activity in the universe will have tailed off dramatically, with extremely low energy levels and extremely long timescales. Speculatively, it is possible that the universe may enter a second ] epoch, or assuming that the current ] is a ], the vacuum may decay into a lower-].<ref name="A dying universe" /><sup>:§VE</sup> It is also possible that entropy production will cease and the universe will reach heat death.<ref name="A dying universe" /><sup>:§VID</sup>


It is suggested that, over vast periods of time, a spontaneous ] ''decrease'' would eventually occur via the ],<ref>{{Cite journal|last=Poincaré|first=Henri|date=1890|title=Sur le problème des trois corps et les équations de la dynamique.|journal=Acta Mathematica|volume=13|pages=A3–A270}}</ref> ],<ref>
==Controversies==
{{Cite journal |last=Tegmark |first=Max |author-link=Max Tegmark |year=2003 |title=Parallel Universes |journal=] |volume=288 |issue=2003 |pages=40–51 |arxiv=astro-ph/0302131 |bibcode=2003SciAm.288e..40T |doi=10.1038/scientificamerican0503-40 |pmid=12701329}}</ref><ref>
] wrote that the phrase 'entropy of the universe' has no meaning because it admits of no accurate definition.<ref name = "Uffink 2003">Uffink, J. (2003). Irreversibility and the Second Law of Thermodynamics, Chapter 7 of ''Entropy'', p. 129 of Greven, A., Keller, G., Warnecke (editors) (2003), ''Entropy'', Princeton University Press, Princeton NJ, ISBN 0-691-11338-6. Uffink writes: "The importance of Planck's ''Vorlesungen über Thermodynamik'' (Planck 1897) can hardly be estimated. The book has gone through 11 editions, from 1897 until 1964, and still remains the most authoritative exposition of classical thermodynamics."</ref><ref name="Planck 101">] (1897/193). </ref> More recently, Grandy writes: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence."<ref name="Grandy 2008 151">, ISBN 978-0-19-954617-6, p. 151.</ref> According to Tisza: "If an isolated system is not in equilibrium, we cannot associate an entropy with it."<ref>] (1966). ''Generalized Thermodynamics'', M.I.T Press, Cambridge MA, p. 41.</ref> Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system".<ref>Buchdahl, H.A. (1966). ''The Concepts of Classical Thermodynamics'', Cambridge University Press, Cambridge UK, p. 97.</ref> According to Gallavotti: "... there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state."<ref>Gallavotti, G. (1999). ''Short Treatise of Statistical Mechanics'', Springer, Berlin, ISBN 9783540648833, p. 290.</ref> Discussing the question of entropy for non-equilibrium states in general, Lieb and Yngvason express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way."<ref>Lieb, E.H., Yngvason, J. (2003). The entropy of classical thermodynamics, Chapter 8 of Greven, A., Keller, G., Warnecke (editors) (2003). ''Entropy'', Princeton University Press, Princeton NJ, ISBN 0-691-11338-6, page 190.</ref> In the opinion of Čápek and Sheehan, "''no'' known formulation applies to ''all'' possible thermodynamic regimes."<ref>Čápek, V., Sheehan, D.P. (2005). ''Challenges to the Second Law of Thermodynamics: Theory and Experiment'', Springer, Dordrecht, ISBN 1-4020-3015-0, p. 26.</ref> In Landsberg's opinion, "The ''third'' misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations, and lie beyond the scope of this book."<ref>Landsberg, P.T. (1961). ''Thermodynamics, with Quantum Statistical Illustrations'', Wiley, New York, p. 391.</ref>
{{Cite journal
| last = Tegmark
| first = Max
| date = May 2003
| author-link = Max Tegmark
| title = Parallel Universes
| journal = ]
| volume = 288
| issue = 5
| pages = 40–51
| arxiv = astro-ph/0302131
| bibcode = 2003SciAm.288e..40T
| doi = 10.1038/scientificamerican0503-40
| pmid = 12701329
}}</ref><ref>
{{Cite journal
| last1 = Werlang
| first1 = T.
| last2 = Ribeiro
| first2 = G. A. P.
| last3 = Rigolin
| first3 = Gustavo
| year = 2013
| title = Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures.
| journal = ]
| volume = 27
| issue = 1n03
| page = 1345032
| arxiv = 1205.1046
| bibcode = 2013IJMPB..2745032W
| doi = 10.1142/S021797921345032X
| s2cid = 119264198
}}</ref> and ].<ref>
{{Cite arXiv
| title = Spontaneous entropy decrease and its statistical formula
| author = Xiu-San Xing
| date = 1 November 2007
| eprint = 0710.4624
| class =cond-mat.stat-mech
}}</ref><ref>
{{Cite journal
| last = Linde
| first = Andrei
| year = 2007
| title = Sinks in the landscape, Boltzmann brains and the cosmological constant problem
| journal = ]
| volume = 2007
| issue = 1
| page = 022
| arxiv = hep-th/0611043
| bibcode = 2007JCAP...01..022L
| doi = 10.1088/1475-7516/2007/01/022
| citeseerx = 10.1.1.266.8334
| s2cid = 16984680
}}</ref> Through this, another universe could possibly be created by random ]s or ] in roughly <math>10^{10^{10^{56}}}</math> years.<ref>
{{Cite arXiv
| eprint = hep-th/0410270
| first1 = Sean M.
| last1 = Carroll
| first2 = Jennifer
| last2 = Chen
| title = Spontaneous Inflation and Origin of the Arrow of Time
| date = October 2004
}}{{bibcode|2004hep.th...10270C}}
</ref>


==Opposing views==
A recent analysis of entropy states that "The entropy of a general gravitational field is still not known," and that "gravitational entropy is difficult to quantify." The analysis considers several possible assumptions that would be needed for estimates, and suggests that the visible universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor.<ref>{{Cite journal| first = Chas A. | last = Egan | first2 = Charles H. | last2 = Lineweaver| title = A Larger Estimate of the Entropy of the Universe| journal = The Astrophysical Journal | volume = 710 | issue = 2 | pages = 1825–1834 | arxiv = 0909.3983 | date = 2009| doi = 10.1088/0004-637X/710/2/1825 | bibcode = 2010ApJ...710.1825E }}</ref> Another writer goes further; "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."<ref>{{cite journal | last1 = Smolin | first1 = L. | authorlink = Lee Smolin | year = 2014 | title = Time, laws, and future of cosmology | url = | journal = Physics Today | volume = 67 | issue = 3 | pages = 38–43 | doi=10.1063/pt.3.2310|bibcode = 2014PhT....67c..38S }}</ref>
] wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition.<ref>
{{Cite book
| title = Entropy (Princeton Series in Applied Mathematics)
| last = Uffink
| first = Jos
| publisher = Princeton University Press
| year = 2003
| isbn = 978-0-691-11338-8
| editor-last = Greven
| editor-first = Andreas
| editor-last2 = Warnecke
| editor-first2 = Gerald
| editor-last3 = Keller
| editor-first3 = Gerhard
| page = 129
| chapter = Irreversibility and the Second Law of Thermodynamics
| quote = The importance of Planck's Vorlesungen über Thermodynamik (Planck 1897) can hardly be estimated. The book has gone through 11 editions, from 1897 until 1964, and still remains the most authoritative exposition of classical thermodynamics.
}}</ref><ref>
{{Cite book |last=Planck |first=Max |url=https://archive.org/stream/treatiseonthermo00planrich#page/100/mode/2up |title=Treatise on Thermodynamics |publisher=Longmans, Green |year=1903 |location=London |page=101 |translator-last=Ogg |translator-first=Alexander |author-link=Max Planck}}</ref> In 2008, Walter Grandy wrote: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence."<ref>
{{Cite book
| title = Entropy and the Time Evolution of Macroscopic Systems
| last = Grandy
| first = Walter T. Jr.
| publisher = Oxford University Press
| year = 2008
| isbn = 978-0-19-954617-6
| page = 151
| url = https://books.google.com/books?id=SnMF37J50DgC
}}</ref> According to ], "If an isolated system is not in equilibrium, we cannot associate an entropy with it."<ref>
{{Cite book
| title = Generalized Thermodynamics
| last = Tisza
| first = László
| author-link = László Tisza
| publisher = MIT Press
| year = 1966
| isbn = 978-0-262-20010-3
| page = 41
}}</ref> ] writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system".<ref>
{{Cite book
| title = The Concepts of Classical Thermodynamics
| last = Buchdahl
| first = H. A.
| publisher = Cambridge University Press
| year = 1966
| isbn = 978-0-521-11519-3
| page = 97
| author-link = Hans Adolf Buchdahl
}}</ref> According to ], "there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state".<ref>
{{Cite book
| title = Statistical Mechanics: A Short Treatise
| last = Gallavotti
| first = Giovanni
| publisher = Springer
| year = 1999
| isbn = 978-3-540-64883-3
| page = 290
| author-link = Giovanni Gallavotti
}}</ref> Discussing the question of entropy for non-equilibrium states in general, ] and ] express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way."<ref>
{{Cite book |last1=Lieb |first1=Elliott H. |title=Entropy |series=Princeton Series in Applied Mathematics |last2=Yngvason |first2=Jakob |publisher=Princeton University Press |year=2003 |isbn=978-0-691-11338-8 |editor-last=Greven |editor-first=Andreas |page=190 |chapter=The Entropy of Classical Thermodynamic |author-link=Elliott H. Lieb |author-link2=Jakob Yngvason |editor-last2=Warnecke |editor-first2=Gerald |editor-last3=Keller |editor-first3=Gerhard}}</ref> In Peter Landsberg's opinion: "The ''third'' misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations."<ref>
{{Cite book
| title = Thermodynamics with Quantum Statistical Illustrations
| last = Landsberg
| first = Peter Theodore
| publisher = Interscience Publishers
| year = 1961
| isbn = 978-0-470-51381-1
| edition = First
| page = 391
}}</ref>

A 2010 analysis of entropy states, "The entropy of a general gravitational field is still not known", and "gravitational entropy is difficult to quantify". The analysis considers several possible assumptions that would be needed for estimates and suggests that the ] has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor.<ref>
{{Cite journal
| last1 = Egan
| first1 = Chas A.
| last2 = Lineweaver
| first2 = Charles H.
| title = A Larger Estimate of the Entropy of the Universe
| journal = ]
| publication-date = 3 February 2010
| volume = 710
| issue = 2
| pages = 1825–34
| arxiv = 0909.3983
| bibcode = 2010ApJ...710.1825E
| doi = 10.1088/0004-637X/710/2/1825
| year = 2010
| s2cid = 1274173
}}</ref> ] goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems."<ref>
{{Cite journal
| last = Smolin
| first = Lee
| author-link = Lee Smolin
| year = 2014
| title = Time, laws, and future of cosmology
| journal = ]
| volume = 67
| issue = 3
| pages = 38–43
| bibcode = 2014PhT....67c..38S
| doi = 10.1063/pt.3.2310
}}</ref> This point of view is also supported by the fact of a recent{{when|date=October 2022}} experimental discovery of a stable non-equilibrium steady state in a relatively simple closed system. It should be expected that an isolated system fragmented into subsystems does not necessarily come to thermodynamic equilibrium and remain in non-equilibrium steady state. Entropy will be transmitted from one subsystem to another, but its production will be zero, which does not contradict the ].<ref>
{{Cite journal
| last1 = Lemishko
| first1 = Sergey S.
| last2 = Lemishko
| first2 = Alexander S.
|title = Cu2+/Cu+ Redox Battery Utilizing Low-Potential External Heat for Recharge
| journal = ]
| publication-date = 30 January 2017
| volume = 121
| issue = 6
| pages = 3234–3240
| doi = 10.1021/acs.jpcc.6b12317
| year = 2017
}}</ref><ref>
{{Cite journal
| last1 = Lemishko
| first1 = Sergey S.
| last2 = Lemishko
| first2 = Alexander S.
|title = Non-equilibrium steady state in closed system with reversible reactions: Mechanism, kinetics and its possible application for energy conversion
| journal = ]
| publication-date = 8 February 2020
| volume = 2
| doi = 10.1016/j.rechem.2020.100031
| year = 2020
| page = 100031
| doi-access = free
}}</ref>

==In popular culture==
{{no footnotes|section|date=November 2023}}
In Isaac Asimov's 1956 short story '']'', humans repeatedly wonder how the heat death of the universe can be avoided.

In the 1981 ''Doctor Who'' story "]", the Doctor realizes that the Logopolitans have created vents in the universe to expel heat build-up into other universes—"Charged Vacuum Emboitments" or "CVE"—to delay the demise of the universe. The Doctor unwittingly travelled through such a vent in "]".

In the 1995 computer game '']'', based on the ] ], it is stated that AM, the malevolent supercomputer, will survive the heat death of the universe and continue torturing its immortal victims to eternity.

In the 2011 anime series '']'', the antagonist ] reveals he is a member of an alien race who has been creating ] for millennia in order to harvest their energy to combat entropy and stave off the heat death of the universe.

In the last act of '']'', the player encounters an alien race known as the Ea who have lost all hope in the future and any desire to live further, all because they have learned of the eventual heat death of the universe and see everything else as pointless due to its probable inevitability.

The overarching plot of the '']'' concerns the Photino Birds' efforts to accelerate the heat death of the universe by accelerating the rate at which stars become white dwarves.

The 2019 hit indie video game '']'' has several themes grappling with the idea of the heat death of the universe, and the theory that the universe is a cycle of big bangs once the previous one has experienced a heat death.

In Singularity Immemorial<ref>{{Cite web |title=PNC Story - IOP Wiki |url=https://iopwiki.com/PNC_Story#Chapter_12:_Singularity_Immemorial |access-date=2024-09-11 |website=iopwiki.com}}</ref> — the 7th main story event of a mobile game ] — the plot is about a virtual sector made to simulate space exploration and the threat of the heat death of the universe. The simulation uses an imitation of Neural Cloud's virus entities known as the Entropics as a stand in for the effects of a heat death.


==See also== ==See also==
* {{Annotated link|Arrow of time}}
{{div col|2}}
* {{Annotated link|Big Bang}}
* ]
* {{Annotated link|Big Bounce}}
* ]
* {{Annotated link|Big Crunch}}
* ]
* {{Annotated link|Big Rip}}
* ]
* {{Annotated link|Chronology of the universe}}
* ]
* {{Annotated link|Cyclic model}}
* ]
* {{Annotated link|Entropy as an arrow of time|Entropy (arrow of time)}}
* ]
* {{Annotated link|Fluctuation theorem}}
* ]
* {{Annotated link|Graphical timeline from Big Bang to Heat Death}}
* ]
* {{Annotated link|Heat death paradox}}
* ]
* {{Annotated link|The Last Question|''The Last Question''}}
* ]
* {{Annotated link|Timeline of the far future}}
* '']''
* {{Annotated link|Orders of magnitude (time)}}
* ]
* {{Annotated link|Thermodynamic temperature}}
{{div col end}}


==References== == References ==
{{Reflist|30em}} {{Reflist|30em}}

{{Big Bang timeline}} {{Big Bang timeline}}
{{Portal bar|Astronomy|Solar System|Space}}


{{Global catastrophic risks}}
]

]
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}

{{Authority control}}

]
] ]
]
] ]

Latest revision as of 20:34, 3 January 2025

Possible fate of the universe This article is about the entropic exhaustion of the universe. For other uses, see Heat Death of the Universe (disambiguation). For heat related illness or death, see Hyperthermia. "Big Freeze" redirects here. For other uses, see Big Freeze (disambiguation).
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Part of a series on
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Subject history

The heat death of the universe (also known as the Big Chill or Big Freeze) is a hypothesis on the ultimate fate of the universe, which suggests the universe will evolve to a state of no thermodynamic free energy, and will therefore be unable to sustain processes that increase entropy. Heat death does not imply any particular absolute temperature; it only requires that temperature differences or other processes may no longer be exploited to perform work. In the language of physics, this is when the universe reaches thermodynamic equilibrium.

If the curvature of the universe is hyperbolic or flat, or if dark energy is a positive cosmological constant, the universe will continue expanding forever, and a heat death is expected to occur, with the universe cooling to approach equilibrium at a very low temperature after a long time period.

The hypothesis of heat death stems from the ideas of Lord Kelvin who, in the 1850s, took the theory of heat as mechanical energy loss in nature (as embodied in the first two laws of thermodynamics) and extrapolated it to larger processes on a universal scale. This also allowed Kelvin to formulate the heat death paradox, which disproves an infinitely old universe.

Origins of the idea

The idea of heat death stems from the second law of thermodynamics, of which one version states that entropy tends to increase in an isolated system. From this, the hypothesis implies that if the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. In other words, according to this hypothesis, there is a tendency in nature towards the dissipation (energy transformation) of mechanical energy (motion) into thermal energy; hence, by extrapolation, there exists the view that, in time, the mechanical movement of the universe will run down as work is converted to heat because of the second law.

The conjecture that all bodies in the universe cool off, eventually becoming too cold to support life, seems to have been first put forward by the French astronomer Jean Sylvain Bailly in 1777 in his writings on the history of astronomy and in the ensuing correspondence with Voltaire. In Bailly's view, all planets have an internal heat and are now at some particular stage of cooling. Jupiter, for instance, is still too hot for life to arise there for thousands of years, while the Moon is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases.

The idea of heat death as a consequence of the laws of thermodynamics, however, was first proposed in loose terms beginning in 1851 by Lord Kelvin (William Thomson), who theorized further on the mechanical energy loss views of Sadi Carnot (1824), James Joule (1843) and Rudolf Clausius (1850). Thomson's views were then elaborated over the next decade by Hermann von Helmholtz and William Rankine.

History

The idea of the heat death of the universe derives from discussion of the application of the first two laws of thermodynamics to universal processes. Specifically, in 1851, Lord Kelvin outlined the view, as based on recent experiments on the dynamical theory of heat: "heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect."

Lord Kelvin originated the idea of universal heat death in 1852.

In 1852, Thomson published On a Universal Tendency in Nature to the Dissipation of Mechanical Energy, in which he outlined the rudiments of the second law of thermodynamics summarized by the view that mechanical motion and the energy used to create that motion will naturally tend to dissipate or run down. The ideas in this paper, in relation to their application to the age of the Sun and the dynamics of the universal operation, attracted the likes of William Rankine and Hermann von Helmholtz. The three of them were said to have exchanged ideas on this subject. In 1862, Thomson published "On the age of the Sun's heat", an article in which he reiterated his fundamental beliefs in the indestructibility of energy (the first law) and the universal dissipation of energy (the second law), leading to diffusion of heat, cessation of useful motion (work), and exhaustion of potential energy, "lost irrecoverably" through the material universe, while clarifying his view of the consequences for the universe as a whole. Thomson wrote:

The result would inevitably be a state of universal rest and death, if the universe were finite and left to obey existing laws. But it is impossible to conceive a limit to the extent of matter in the universe; and therefore science points rather to an endless progress, through an endless space, of action involving the transformation of potential energy into palpable motion and hence into heat, than to a single finite mechanism, running down like a clock, and stopping for ever.

The clock's example shows how Kelvin was unsure whether the universe would eventually achieve thermodynamic equilibrium. Thompson later speculated that restoring the dissipated energy in "vis viva" and then usable work – and therefore revert the clock's direction, resulting in a "rejuvenating universe" – would require "a creative act or an act possessing similar power". Starting from this publication, Kelvin also introduced the heat death paradox (Kelvin's paradox), which challenged the classical concept of an infinitely old universe, since the universe has not achieved its thermodynamic equilibrium, thus further work and entropy production are still possible. The existence of stars and temperature differences can be considered an empirical proof that the universe is not infinitely old.

In the years to follow both Thomson's 1852 and the 1862 papers, Helmholtz and Rankine both credited Thomson with the idea, along with his paradox, but read further into his papers by publishing views stating that Thomson argued that the universe will end in a "heat death" (Helmholtz), which will be the "end of all physical phenomena" (Rankine).

Current status

See also: Entropy § Cosmology, and Entropy (arrow of time) § Cosmology

Proposals about the final state of the universe depend on the assumptions made about its ultimate fate, and these assumptions have varied considerably over the late 20th century and early 21st century. In a hypothesized "open" or "flat" universe that continues expanding indefinitely, either a heat death or a Big Rip is expected to eventually occur. If the cosmological constant is zero, the universe will approach absolute zero temperature over a very long timescale. However, if the cosmological constant is positive, the temperature will asymptote to a non-zero positive value, and the universe will approach a state of maximum entropy in which no further work is possible.

Time frame for heat death

Main article: Future of an expanding universe

The theory suggests that from the "Big Bang" through the present day, matter and dark matter in the universe are thought to have been concentrated in stars, galaxies, and galaxy clusters, and are presumed to continue to do so well into the future. Therefore, the universe is not in thermodynamic equilibrium, and objects can do physical work. The decay time for a supermassive black hole of roughly 1 galaxy mass (10 solar masses) because of Hawking radiation is in the order of 10 years, so entropy can be produced until at least that time. Some large black holes in the universe are predicted to continue to grow up to perhaps 10 M☉ during the collapse of superclusters of galaxies. Even these would evaporate over a timescale of up to 10 years. After that time, the universe enters the so-called Dark Era and is expected to consist chiefly of a dilute gas of photons and leptons. With only very diffuse matter remaining, activity in the universe will have tailed off dramatically, with extremely low energy levels and extremely long timescales. Speculatively, it is possible that the universe may enter a second inflationary epoch, or assuming that the current vacuum state is a false vacuum, the vacuum may decay into a lower-energy state. It is also possible that entropy production will cease and the universe will reach heat death.

It is suggested that, over vast periods of time, a spontaneous entropy decrease would eventually occur via the Poincaré recurrence theorem, thermal fluctuations, and fluctuation theorem. Through this, another universe could possibly be created by random quantum fluctuations or quantum tunnelling in roughly 10 10 10 56 {\displaystyle 10^{10^{10^{56}}}} years.

Opposing views

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. In 2008, Walter Grandy wrote: "It is rather presumptuous to speak of the entropy of a universe about which we still understand so little, and we wonder how one might define thermodynamic entropy for a universe and its major constituents that have never been in equilibrium in their entire existence." According to László Tisza, "If an isolated system is not in equilibrium, we cannot associate an entropy with it." Hans Adolf Buchdahl writes of "the entirely unjustifiable assumption that the universe can be treated as a closed thermodynamic system". According to Giovanni Gallavotti, "there is no universally accepted notion of entropy for systems out of equilibrium, even when in a stationary state". Discussing the question of entropy for non-equilibrium states in general, Elliott H. Lieb and Jakob Yngvason express their opinion as follows: "Despite the fact that most physicists believe in such a nonequilibrium entropy, it has so far proved impossible to define it in a clearly satisfactory way." In Peter Landsberg's opinion: "The third misconception is that thermodynamics, and in particular, the concept of entropy, can without further enquiry be applied to the whole universe. ... These questions have a certain fascination, but the answers are speculations."

A 2010 analysis of entropy states, "The entropy of a general gravitational field is still not known", and "gravitational entropy is difficult to quantify". The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought. This is because the analysis concludes that supermassive black holes are the largest contributor. Lee Smolin goes further: "It has long been known that gravity is important for keeping the universe out of thermal equilibrium. Gravitationally bound systems have negative specific heat—that is, the velocities of their components increase when energy is removed. ... Such a system does not evolve toward a homogeneous equilibrium state. Instead it becomes increasingly structured and heterogeneous as it fragments into subsystems." This point of view is also supported by the fact of a recent experimental discovery of a stable non-equilibrium steady state in a relatively simple closed system. It should be expected that an isolated system fragmented into subsystems does not necessarily come to thermodynamic equilibrium and remain in non-equilibrium steady state. Entropy will be transmitted from one subsystem to another, but its production will be zero, which does not contradict the second law of thermodynamics.

In popular culture

This section includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. Please help improve this section by introducing more precise citations. (November 2023) (Learn how and when to remove this message)

In Isaac Asimov's 1956 short story The Last Question, humans repeatedly wonder how the heat death of the universe can be avoided.

In the 1981 Doctor Who story "Logopolis", the Doctor realizes that the Logopolitans have created vents in the universe to expel heat build-up into other universes—"Charged Vacuum Emboitments" or "CVE"—to delay the demise of the universe. The Doctor unwittingly travelled through such a vent in "Full Circle".

In the 1995 computer game I Have No Mouth, and I Must Scream, based on the Harlan Ellison short story of the same name, it is stated that AM, the malevolent supercomputer, will survive the heat death of the universe and continue torturing its immortal victims to eternity.

In the 2011 anime series Puella Magi Madoka Magica, the antagonist Kyubey reveals he is a member of an alien race who has been creating magical girls for millennia in order to harvest their energy to combat entropy and stave off the heat death of the universe.

In the last act of Final Fantasy XIV: Endwalker, the player encounters an alien race known as the Ea who have lost all hope in the future and any desire to live further, all because they have learned of the eventual heat death of the universe and see everything else as pointless due to its probable inevitability.

The overarching plot of the Xeelee Sequence concerns the Photino Birds' efforts to accelerate the heat death of the universe by accelerating the rate at which stars become white dwarves.

The 2019 hit indie video game Outer Wilds has several themes grappling with the idea of the heat death of the universe, and the theory that the universe is a cycle of big bangs once the previous one has experienced a heat death.

In Singularity Immemorial — the 7th main story event of a mobile game Girls' Frontline: Neural Cloud — the plot is about a virtual sector made to simulate space exploration and the threat of the heat death of the universe. The simulation uses an imitation of Neural Cloud's virus entities known as the Entropics as a stand in for the effects of a heat death.

See also

References

  1. WMAP – Fate of the Universe, WMAP's Universe, NASA. Accessed online July 17, 2008.
  2. Dyer, Alan (2007-07-24). Insiders: Space. Simon & Schuster Books for Young Readers. pp. 40–41. ISBN 978-1-4169-3860-6.
  3. ^ Plait, Philip (2008). Death from the Skies!. Viking Adult (published 16 October 2008). p. 259. ISBN 978-0-670-01997-7.
  4. ^ Thomson, Sir William (5 March 1862). "On the Age of the Sun's Heat". Macmillan's Magazine. Vol. 5. pp. 388–93.
  5. Brush, Stephen G. (1996). A History of Modern Planetary Physics: Nebulous Earth. Vol. 1. Cambridge University Press. p. 77. ISBN 978-0-521-44171-1.
  6. ^ Smith, Crosbie; Wise, M. Norton (1989). Energy and Empire: A Biographical Study of Lord Kelvin. Cambridge University Press. p. 500. ISBN 978-0-521-26173-9.
  7. Thomson, Sir William. (1851). "On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule's equivalent of a Thermal Unit, and M. Regnault's Observations on Steam" Excerpts. , Transactions of the Royal Society of Edinburgh, March 1851, and Philosophical Magazine IV, 1852. This version from Mathematical and Physical Papers, vol. i, art. XLVIII, pp. 174.
  8. Thomson, Sir William (1852). "On a Universal Tendency in Nature to the Dissipation of Mechanical Energy" Proceedings of the Royal Society of Edinburgh for 19 April 1852, also Philosophical Magazine, Oct. 1852. This version from Mathematical and Physical Papers, vol. i, art. 59, pp. 511.
  9. Harold I. Sharlin (13 December 2019). "William Thomson, Baron Kelvin". Encyclopædia Britannica. Retrieved 24 January 2020.
  10. Otis, Laura (2002). "Literature and Science in the Nineteenth Century: An Anthology". OUP Oxford. Vol. 1. pp. 60–67.
  11. Laws of Thermodynamics Thompson and Clausius, Oxford University Press, 2015.
  12. "Physics Chronology". Archived from the original on 22 May 2011.
  13. Consolmagno, Guy (2008-05-08). "Heaven or Heat Death?". Thinking Faith. Archived from the original on 2023-11-16. Retrieved 2008-10-06.
  14. Dyson, Lisa; Kleban, Matthew; Susskind, Leonard (12 November 2002). "Disturbing Implications of a Cosmological Constant". Journal of High Energy Physics. 2002 (10): 011. arXiv:hep-th/0208013. Bibcode:2002JHEP...10..011D. doi:10.1088/1126-6708/2002/10/011. S2CID 2344440.
  15. ^ Adams, Fred C.; Laughlin, Gregory (1997). "A dying universe: the long-term fate and evolution of astrophysical objects". Reviews of Modern Physics. 69 (2): 337–72. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/RevModPhys.69.337. S2CID 12173790.
  16. See in particular equation (27) in Page, Don N. (15 January 1976). "Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole". Physical Review D. 13 (2): 198–206. Bibcode:1976PhRvD..13..198P. doi:10.1103/PhysRevD.13.198.
  17. Frautschi, Steven (13 August 1982). "Entropy in an Expanding Universe" (PDF). Science. 217 (4560): 593–9. Bibcode:1982Sci...217..593F. doi:10.1126/science.217.4560.593. JSTOR 1688892. PMID 17817517. S2CID 27717447. Since we have assumed a maximum scale of gravitational binding—for instance, superclusters of galaxies—black hole formation eventually comes to an end in our model, with masses of up to 10M☉ ... the timescale for black holes to radiate away all their energy ranges ... to 10 years for black holes of up to 10M☉
  18. Poincaré, Henri (1890). "Sur le problème des trois corps et les équations de la dynamique". Acta Mathematica. 13: A3 – A270.
  19. Tegmark, Max (2003). "Parallel Universes". Scientific American. 288 (2003): 40–51. arXiv:astro-ph/0302131. Bibcode:2003SciAm.288e..40T. doi:10.1038/scientificamerican0503-40. PMID 12701329.
  20. Tegmark, Max (May 2003). "Parallel Universes". Scientific American. 288 (5): 40–51. arXiv:astro-ph/0302131. Bibcode:2003SciAm.288e..40T. doi:10.1038/scientificamerican0503-40. PMID 12701329.
  21. Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo (2013). "Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures". International Journal of Modern Physics B. 27 (1n03): 1345032. arXiv:1205.1046. Bibcode:2013IJMPB..2745032W. doi:10.1142/S021797921345032X. S2CID 119264198.
  22. Xiu-San Xing (1 November 2007). "Spontaneous entropy decrease and its statistical formula". arXiv:0710.4624 .
  23. Linde, Andrei (2007). "Sinks in the landscape, Boltzmann brains and the cosmological constant problem". Journal of Cosmology and Astroparticle Physics. 2007 (1): 022. arXiv:hep-th/0611043. Bibcode:2007JCAP...01..022L. CiteSeerX 10.1.1.266.8334. doi:10.1088/1475-7516/2007/01/022. S2CID 16984680.
  24. Carroll, Sean M.; Chen, Jennifer (October 2004). "Spontaneous Inflation and Origin of the Arrow of Time". arXiv:hep-th/0410270.Bibcode:2004hep.th...10270C
  25. Uffink, Jos (2003). "Irreversibility and the Second Law of Thermodynamics". In Greven, Andreas; Warnecke, Gerald; Keller, Gerhard (eds.). Entropy (Princeton Series in Applied Mathematics). Princeton University Press. p. 129. ISBN 978-0-691-11338-8. The importance of Planck's Vorlesungen über Thermodynamik (Planck 1897) can hardly be estimated. The book has gone through 11 editions, from 1897 until 1964, and still remains the most authoritative exposition of classical thermodynamics.
  26. Planck, Max (1903). Treatise on Thermodynamics. Translated by Ogg, Alexander. London: Longmans, Green. p. 101.
  27. Grandy, Walter T. Jr. (2008). Entropy and the Time Evolution of Macroscopic Systems. Oxford University Press. p. 151. ISBN 978-0-19-954617-6.
  28. Tisza, László (1966). Generalized Thermodynamics. MIT Press. p. 41. ISBN 978-0-262-20010-3.
  29. Buchdahl, H. A. (1966). The Concepts of Classical Thermodynamics. Cambridge University Press. p. 97. ISBN 978-0-521-11519-3.
  30. Gallavotti, Giovanni (1999). Statistical Mechanics: A Short Treatise. Springer. p. 290. ISBN 978-3-540-64883-3.
  31. Lieb, Elliott H.; Yngvason, Jakob (2003). "The Entropy of Classical Thermodynamic". In Greven, Andreas; Warnecke, Gerald; Keller, Gerhard (eds.). Entropy. Princeton Series in Applied Mathematics. Princeton University Press. p. 190. ISBN 978-0-691-11338-8.
  32. Landsberg, Peter Theodore (1961). Thermodynamics with Quantum Statistical Illustrations (First ed.). Interscience Publishers. p. 391. ISBN 978-0-470-51381-1.
  33. Egan, Chas A.; Lineweaver, Charles H. (2010). "A Larger Estimate of the Entropy of the Universe". The Astrophysical Journal. 710 (2) (published 3 February 2010): 1825–34 . arXiv:0909.3983. Bibcode:2010ApJ...710.1825E. doi:10.1088/0004-637X/710/2/1825. S2CID 1274173.
  34. Smolin, Lee (2014). "Time, laws, and future of cosmology". Physics Today. 67 (3): 38–43 . Bibcode:2014PhT....67c..38S. doi:10.1063/pt.3.2310.
  35. Lemishko, Sergey S.; Lemishko, Alexander S. (2017). "Cu2+/Cu+ Redox Battery Utilizing Low-Potential External Heat for Recharge". The Journal of Physical Chemistry C. 121 (6) (published 30 January 2017): 3234–3240. doi:10.1021/acs.jpcc.6b12317.
  36. Lemishko, Sergey S.; Lemishko, Alexander S. (2020). "Non-equilibrium steady state in closed system with reversible reactions: Mechanism, kinetics and its possible application for energy conversion". Results in Chemistry. 2 (published 8 February 2020): 100031. doi:10.1016/j.rechem.2020.100031.
  37. "PNC Story - IOP Wiki". iopwiki.com. Retrieved 2024-09-11.
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