Heat death of the 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. Venus, for instance, is still too hot for life to arise there for thousands of years, while Mars is already too cold. The final state, in this view, is described as one of "equilibrium" in which all motion ceases. |author-link = Stephen G. Brush

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."

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. |author-link2 = M. Norton Wise

The clock's example shows how Kelvin was unsure whether the universe would eventually achieve thermodynamic equilibrium. Thomson later speculated that restoring the dissipated energy in "vis viva" and then usable workand 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). |archive-url = https://web.archive.org/web/20110522124507/http://webplaza.pt.lu/fklaess/html/HISTORIA.HTML |archive-date = 22 May 2011

Current status

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 theorized "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. |author-link = Lisa Dyson |author-link2 = Matthew Kleban |author-link3 = Leonard Susskind

Thermodynamic heat death is a classical-physics concept, but has been extended to quantum physics. Even when thermodynamic entropy has reached its maximum, other quantities such as quantum circuit complexity continue to increase, eventually also reaching a maximum value.

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. | author-link = Fred Adams | author-link2 = Gregory P. Laughlin See in particular equation (27) in {{Cite journal | author-link = Don Page (physicist)

It has been hypothesized that, over vast periods of time, a spontaneous entropy decrease could eventually occur via the Poincaré recurrence theorem, thermal fluctuations, | author-link = Max Tegmark

Opposing views

Max Planck wrote that the phrase "entropy of the universe" has no meaning because it admits of no accurate definition. | editor-last = Greven | editor-first = Andreas | editor-last2 = Warnecke | editor-first2 = Gerald | editor-last3 = Keller | editor-first3 = Gerhard 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." | author-link = László Tisza | author-link = Hans Adolf Buchdahl | author-link = Giovanni Gallavotti 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. | publication-date = 3 February 2010 | author-link = Lee Smolin | publication-date = 30 January 2017 | publication-date = 8 February 2020 | article-number = 100031 | doi-access = free

Philosophical views

The discovery of the principle of the heat death of the universe led to philosophical reevaluation of the place of man in the universe. In 1856, Hermann von Helmholtz suggest that it compelled humans to complete a moral destiny. Philipp Mainländer, another philosopher whose 1875 work Die Philosophie der Erlösung has been associated with the philosophy of pandeism, saw the expected heat death of the Universe as "a different, redemptive destiny for humanity: an end of suffering".

In popular culture

In Isaac Asimov's 1956 short story The Last Question, humans through the ages 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 accumulated entropy into other universes—"Charged Vacuum Emboitments" or "CVE"—to delay the demise of our universe. The Doctor unwittingly travels through such a vent in "Full Circle".

In the 1995 computer game I Have No Mouth, and I Must Scream, based on Harlan Ellison's 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 seventh main story event of the 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.

References

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