Boltzmann brain: Difference between revisions

In 1896, the mathematician [[Ernst Zermelo]] advanced a theory that the [[second law of thermodynamics]] was absolute rather than statistical.<ref>[[:de:Stephen Brush|Brush, S. G.]], ''Nebulous Earth: A History of Modern Planetary Physics'' ([[Cambridge]]: [[Cambridge University Press]], 1996), [https://books.google.com/books?id=vTBZyesS08kC&pg=PA129 p. 129].</ref> Zermelo bolstered his theory by pointing out that the [[Poincaré recurrence theorem]] shows statistical entropy in a closed system must eventually be a [[periodic function]]; therefore, the Second Law, which is always observed to increase entropy, is unlikely to be statistical. To counter Zermelo's argument, Boltzmann advanced two theories. The first theory, now believed to be the correct one, is that the universe started for some unknown reason in a low-entropy state. The second and alternative theory, published in 1896 but attributed in 1895 to Boltzmann's assistant [[Ignaz Schütz]], is the "Boltzmann universe" scenario. In this scenario, the universe spends the vast majority of eternity in a featureless state of [[Heat death of the universe|heat death]]; however, over enough [[aeon|eon]]s, eventually a very rare thermal fluctuation will occur where atoms bounce off each other in exactly such a way as to form a substructure equivalent to our entire observable universe. Boltzmann argues that, while most of the universe is featureless, humans do not see those regions because they are devoid of intelligent life; to Boltzmann, it is unremarkable that humanity views solely the interior of its Boltzmann universe, as that is the only place where intelligent life lives. (This may be the first use in modern science of the [[anthropic principle]]).<ref name="carroll2017">[[Sean M. Carroll|Carroll, S. M.]], [https://arxiv.org/abs/1702.00850 "Why Boltzmann brains are bad"] ([[Ithaca, New York]]: [[arXiv]], 2017).</ref><ref>{{cite book|last1=Bostrom|first1=Nick|author-link=Nick Bostrom| title=Anthropic Bias: Observation Selection Effects in Science and Philosophy|date=2002|publisher=Psychology Press|isbn=9780415938587|language=en|chapter=Introduction}}</ref>