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} }) </script> </div> </form> </fieldset> <article class="entryArticle content STeditorial"> <header class="entryHeader icon-theme"> <h1 class="entryTitle">Thought Experiment </h1> </header><p class='tagLine'>Entry updated 18 March 2024. Tagged: Theme.</p><div class="browsingBtns"> <span> <input class="button PNI previous" type="button" onclick="window.location.href='/next.php?id=p&entry=thought_experiment'" value="Prev" /> </span> <span> <input class="button PNI next" type="button" onclick="window.location.href='/next.php?&entry=thought_experiment'" value="Next" /> </span> <span> <input class="button PNI incoming" type="button" onclick="window.location.href='/incoming.php?entry=thought_experiment'" value="About This Entry" title="What links to the entry; contributor initials explained; how to cite; other information" /> </span> </div> <p>In <a href="/entry/physics">Physics</a>, a thought experiment or <i>Gedankenexperiment</i> is a common means of exploring the implications of scientific assumptions without resorting to actual apparatus. Einstein's development of <a href="/entry/relativity">Relativity</a> employed thought experiments about light signals exchanged between observers whose relative speed was a significant fraction of the speed of light, not easily attained by any real observer or (at that time) measuring device. The first conscious crafting of something like a thought experiment in fiction may be the novel <i>Die Wahlverwandtschaften</i> ["Elective Affinities"] (<b>1809</b> 2vols; trans R Dillon Boylan as <i>Elective Affinities</i> <b>1854</b>) by Wolfgang von Goethe (1749-1832), where the chemical theory that some species "tend" to combine provides an excuse for an induced <i>ménage a quatre</i> whose participants are hidden away in a country house, which Goethe describes as a "chemical retort" where their interactions can be observed in isolation, though the sexual liaisons generated (see <a href="/entry/sex">Sex</a>) prove deadly: humans do not flourish in a state of love. In science fiction, any story which uses sf devices to expound or illuminate a scientific principle may be described as a thought experiment.</p> <p>Such stories range from the didactic whimsy of George <a href="/entry/gamow_george">Gamow</a>'s <i>Mr Tompkins in Wonderland; Or, Stories of C, G & H</i> (stories 1938-1939 <i>Discovery</i>; <b>1939</b> chap) – dealing with <a href="/entry/relativity">Relativity</a>, <a href="/entry/gravity">Gravity</a> and quantum physics – to Hal <a href="/entry/clement_hal">Clement</a>'s less obtrusive exposition of high gravity in <i>Mission of Gravity</i> (April-July 1953 <a href="/entry/asf">Astounding</a>; cut <b>1954</b>; text restored with additions and one added story, as coll <b>1978</b>) and of variously chaotic weather and quasi-weather systems in <i>Close to Critical</i> (May-July 1958 <a href="/entry/asf">Astounding</a>; <b>1964</b>), <i>Star Light</i> (June-September 1970 <a href="/entry/analog">Analog</a>; <b>1971</b>) and <i>Still River</i> (<b>1987</b>). A K <a href="/entry/dewdney_a_k">Dewdney</a>'s <i>The Planiverse: Computer Contact with a Two-Dimensional World</i> (<b>1984</b>) downplays storytelling in favour of gleefully imagined <a href="/entry/flatland">Flatland</a> science – the design, for example, of a workable two-dimensional steam engine. John E <a href="/entry/stith_john_e">Stith</a>'s <i>Redshift Rendezvous</i> (<b>1990</b>) develops one of the <i>Mr Tompkins</i> conceits with a version of <a href="/entry/hyperspace">Hyperspace</a> whose very low speed of light makes <a href="/entry/relativity">Relativity</a> effects an aspect of everyday life; Stephen <a href="/entry/baxter_stephen">Baxter</a>'s <i>Raft</i> (September/October 1989 <a href="/entry/interzone">Interzone</a>; much exp <b>1991</b>) outdoes <i>Mission of Gravity</i> with its depiction of an <a href="/entry/alternate_cosmos">Alternate Cosmos</a> whose gravitational constant is so large that humans can sense one anothers' pull and <a href="/entry/stars">Stars</a> are only a mile or two across.</p> <p>In <a href="/entry/mathematics">Mathematics</a>, sf thought experiments can give a sense of the vastness of numbers. The "infinite monkey theorem" whereby – given infinite time – a randomly typing monkey or team of monkeys will eventually generate the complete works of <a href="/entry/shakespeare_william">Shakespeare</a> is an old favourite. This features briefly as an actual if unsuccessful physical experiment within an Oxford college in Edmund <a href="/entry/crispin_edmund">Crispin</a>'s detective tale <i>The Case of the Gilded Fly</i> (<b>1944</b>; vt <i>Obsequies at Oxford</i> <b>1945</b>); is amusingly dramatized in R A <a href="/entry/lafferty_r_a">Lafferty</a>'s "Been a Long, Long Time" (December 1970 <a href="/entry/fantastic">Fantastic</a>), whose action stretches over an almost unimaginable <a href="/entry/time_abyss">Time Abyss</a>; and is spoofed in Russell Maloney's "Inflexible Logic" (February 1940 <i>The New Yorker</i>). Similarly vast and hard to comprehend is the titular <a href="/entry/libraries">Library</a> of Jorge Luis <a href="/entry/borges_jorge_luis">Borges</a>' "The Library of Babel" (in <i>El jardín de senderos que se bifurcan</i>, coll <b>1942</b>), which in effect contains all possible outcomes of the monkeys' stochastic efforts. Everything is there and nothing can be found (see <a href="/entry/information_theory">Information Theory</a>), even when the hypothetical library is digitized and made computer-searchable as in David <a href="/entry/langford_david">Langford</a>'s "The Net of Babel" (February 1995 <a href="/entry/interzone">Interzone</a>).</p> <p>Sociological and cultural-anthropological thought experiments in sf are very numerous and diverse. Unusual human societies – of which Jack <a href="/entry/vance_jack">Vance</a> was a particularly prolific creator – are regularly encountered on remote <a href="/entry/islands">Islands</a>, <a href="/entry/space_habitats">Space Habitats</a>, and planets settled during the <a href="/entry/colonization_of_other_worlds">Colonization of Other Worlds</a>.</p> <p>One famous ethical thought experiment known as the Trolley Problem has seen various sf dramatizations. In the simplest formulation, a runaway trolley will kill several people tied to the track ahead, unless a bystander makes the decision to pull a lever that diverts the trolley to a side track where it will kill just one person who would otherwise have survived. The protagonist of Carl <a href="/entry/jacobi_carl">Jacobi</a>'s "Tepondicon" (Winter 1946 <a href="/entry/planet_stories">Planet Stories</a>) is offered the choice of escaping with a great treasure or saving the people of seven plague-stricken cities at the cost of his own life; we are not told his decision, but in Tom <a href="/entry/godwin_tom">Godwin</a>'s "The Cold Equations" (August 1954 <a href="/entry/asf">Astounding</a>) the hapless girl stowaway in space is ejected into vacuum so that an entire colony threatened by (again) plague can receive medical supplies. One episode of <i>The</i> <a href="/entry/good_place_the">Good Place</a> (<i>2016-2020</i>) is titled "The Trolley Problem" (<i>2017</i>), featuring both discussion and realistic simulations of the thought experiment.</p> <p>A "real" thought experiment which has fascinated many sf authors is the Schrödinger's Cat paradox. This dramatizes the quantum-physics concept that the wave function representing a physical system is a superposition of possible outcomes which does not "collapse" into a particular state until observed. Should the <a href="/entry/cats">Cat</a> in the box, whose death <i>may</i> have been triggered by an unpredictable quantum event (radioactive decay whose detection releases <a href="/entry/poisons">Poison</a> gas), be regarded as in a mixed state – neither alive nor dead until the box is opened by an observer? Sf explorations of the theme include Douglas <a href="/entry/adams_douglas">Adams</a>'s whimsical <i>Dirk Gently's Holistic Detective Agency</i> (<b>1987</b>), Greg <a href="/entry/bear_greg">Bear</a>'s "Schrödinger's Plague" (29 March 1982 <a href="/entry/analog">Analog</a>), George Alec <a href="/entry/effinger_george_alec">Effinger</a>'s "Schrödinger's Kitten" (September 1988 <a href="/entry/omni">Omni</a>), Ursula <a href="/entry/le_guin_ursula_k">Le Guin</a>'s "Schrödinger's Cat" (in <i>Universe 5</i>, anth <b>1974</b>, ed Terry <a href="/entry/carr_terry">Carr</a>), F Gwynplaine <a href="/entry/macintyre_f_gwynplaine">MacIntyre</a>'s "Schrödinger's Cat-Sitter" (July/August 2001 <a href="/entry/analog">Analog</a>) and Rudy <a href="/entry/rucker_rudy">Rucker</a>'s "Schrödinger's Cat" (30 March 1981 <a href="/entry/analog">Analog</a>). Robert Anton <a href="/entry/wilson_steve">Wilson</a>'s 1979-1981 <b>Schrödinger's Cat</b> trilogy deals with a labyrinth of <a href="/entry/parallel_worlds">Parallel Worlds</a>. A large "Schrödinger cat box" is used for randomly delayed human execution in Dan <a href="/entry/simmons_dan">Simmon</a>'s <i>Endymion</i> (<b>1996</b>). In a chapter of <i>Flatterland: Like Flatland Only More So</i> (<b>2001</b>), Ian <a href="/entry/stewart_ian">Stewart</a> examines and debunks the seeming paradox, explaining that the cat/box quantum system is sufficiently large that any mixed state would almost instantaneously collapse or "decohere".</p> <p>"Maxwell's Demon" was propounded by the physicist James Clerk Maxwell (1831-1879) as a thought experiment in thermodynamics, whose second law states that <a href="/entry/entropy">Entropy</a> (disorder) must always increase. The tiny imaginary demon acts as gatekeeper between two gas-filled chambers, allowing fast (hot) molecules to pass in one direction but not the other so that in apparent violation of thermodynamics one chamber grows ever hotter and the other ever colder. (A more sophisticated analysis shows that the overall entropy must in fact increase, because to distinguish fast from slow molecules the demon in effect needs a flashlight whose energy output adds more entropy to the system than the selection process removes. John Lowell dramatized this argument in comic verse as "The Diabolical Heating Scheme of J C Maxwell" [in <i>More Random Walks in Science</i>, anth <b>1982</b>, ed Robert L Weber].) Such demons are harnessed in Joseph <a href="/entry/samachson_joseph">Samachson</a>'s "A Feast of Demons" (March 1958 <a href="/entry/galaxy">Galaxy</a>) as by William Morrison, which features a demonstration in which one side of a vat of liquid spontaneously freezes while the other boils, and goes on to postulate entropic and anti-entropic demons which respectively cause accelerated ageing and <a href="/entry/rejuvenation">Rejuvenation</a>. Larry <a href="/entry/niven_larry">Niven</a> also actualizes Maxwell's Demon – as a joke – in the fantasy vignette "Unfinished Story No. 1" (in <i>All the Myriad Ways</i>, coll <b>1971</b>).</p> <p>Notable twenty-first-century examples of thought-experiment sf include Ted <a href="/entry/chiang_ted">Chiang</a>'s "Exhalation" (in <i>Eclipse 2</i>, anth <b>2008</b>, ed Jonathan <a href="/entry/strahan_jonathan">Strahan</a>), with its melancholy evocation of how a mechanical sentience in a nearly-sealed <a href="/entry/pocket_universe">Pocket Universe</a> might deduce the nature of <a href="/entry/entropy">Entropy</a>, and Greg <a href="/entry/egan_greg">Egan</a>'s <i>Incandescence</i> (<b>2008</b>), demonstrating in unsparing detail how low-tech dwellers in a closed environment where conventional astronomical observations are unavailable could nevertheless reason their way to general <a href="/entry/relativity">Relativity</a>. Such ambitious sf thought experiments can convey an austere, almost purely intellectual <a href="/entry/sense_of_wonder">Sense of Wonder</a>.</p> <p>A relevant anthology is <i>Gedanken Fictions: Stories on Themes in Science, Technology, and Society</i> (anth <b>2000</b>) edited by Thomas A <a href="/entry/easton_thomas_a">Easton</a>. [DRL]</p> <p><b>see also:</b> <a href="/entry/feminism">Feminism</a>; <a href="/entry/iconoclasm">Iconoclasm</a>; <a href="/entry/metaphysics">Metaphysics</a>; <a href="/entry/satire">Satire</a>.</p> <p><b>previous versions of this entry</b></p> <ul><li><a href='https://web.archive.org/web/*/http://www.sf-encyclopedia.com/entry/thought_experiment' target='_blank'>Internet Archive</a></li></ul><br /><br /></article></div> <div class="sideBarsWrapper"> <div class="sideBarsColsWrapper clearfix"> <div class="column sideBar12 clearfix"> <div class="columnForm"><aside id="blogFeed" class="widget"> <div class="content STeditorial clearfix"> <h2>Recently visited entries<span style="background:url(/images/thingSFE2.png) !important"></span></h2><ul style='width: 50%; float: left;'> </ul> <p align=center style="float:right; padding-top:20px; padding-bottom:20px;">ISSN 3049-7612<br /> <a href="/facts.php?id=logo"> <img src="/images/VitMan.gif" width=150 height=150 title="Click for larger version of this SFE logo"></a><br /> <b><a href="/donate.php"><img src="/images/Paypal-Donate.gif" WIDTH="92" HEIGHT="26" BORDER="0" /></a><br /><a href="/">Home/Welcome page</a></b></p><div style="margin-bottom:10px;"></div></div> </aside><aside id="blogFeed" class="widget"> <div class="content STeditorial clearfix"> <h2><i>SFE</i> Special Features<span></span></h2><p style="margin-top: 10px;"><input type="button" value="What’s New" style="width: 150px !important;" class="button primary" onclick="window.location.href='/whatsnew.php'">  Latest entries; 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