[4] 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.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.[5] 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).[8] 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.In a hypothesized "open" or "flat" universe that continues expanding indefinitely, either a heat death or a Big Rip is expected to eventually occur.[17] 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.The analysis considers several possible assumptions that would be needed for estimates and suggests that the observable universe has more entropy than previously thought.[35][36] 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 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.In "Singularity Immemorial",[37] 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.