Schrödinger's cat is a seemingly paradoxical thought experiment devised by Erwin Schrödinger that attempts to illustrate the incompleteness of the theory of quantum mechanics when going from subatomic to macroscopic systems.
The original formulation of Schrödinger's cat
In 1935, Schrödinger published an essay describing the conceptual problems in quantum mechanics. A brief paragraph in this essay described the cat paradox:
- One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small that perhaps in the course of one hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The Psi function for the entire system would express this by having in it the living and the dead cat (pardon the expression) mixed or smeared out in equal parts.
Adaptations in science fiction
It was not long before science-fiction writers picked up this evocative concept, often using it in a humorous vein. Several have taken the thought experiment a step further, pointing out extra complications which might arise should the experiment actually be performed.
For example, in his novel American Gods, Neil Gaiman has a character observe, "if they don't ever open the box to feed it'll eventually just be two different kinds of dead." Likewise, Terry Pratchett's Lords and Ladies adds the issue of a third possible state, in the case of Greebo, "Bloody Furious." Douglas Adams describes an attempt to enact the experiment in Dirk Gently's Holistic Detective Agency. By using clairvoyance to see inside the box, it was found that the cat was neither alive nor dead, but missing, and Dirk's services were employed in order to recover it.
In "Schrödinger's Cat-Sitter" by F. Gwynplaine MacIntyre (published in Analog magazine, July/August 2001), a time-traveler named Smedley Faversham visits the past to interview Erwin Schrödinger but gets tricked into taking care of Schrödinger's wife's cat while she is away and Schrödinger is visiting Max Planck. In attempting to take care of the cat, Faversham inadvertently locks it in a cabinet with a Geiger counter, a vial of acid, and a hammer, unintentionally enacting Schrödinger's thought experiment, but with results that remain as uncertain as in the original case.
Yet another example of the cat in popular fiction is the cat Quark, from Jeff Noon's book "Automated Alice". In it, Alice has the question "Am I real, or am I fake?" which is much like "Is it alive, or is it dead?" Near the end of the book, Alice encounters a cat named Quark, who is invisible, and got that way by being locked in a box and having a strange substance poured in, mixing it with a chameleon. The cat was both influenced by the Cheshire Cat, and Schrödinger's Cat, the Cheshire Cat and the Alice books being similar to the experiment already.
The American science-fiction writer and psychologist Robert Anton Wilson wrote the novel Schrödinger's Cat trilogy as the spiritual sequel to The Illuminatus! Trilogy. The storyline of this novel interweaves many characters who live in parallel universes. Each part of the novel is numbered as "Part One"
In Dan Simmons' books Endymion and The Rise of Endymion, one of the main protagonists is sentenced to death by being locked in a larger version of a Schrödinger's cat-box, so that random chance, rather than any single person, is responsible for his eventual death.
On a somewhat more serious level, Ian Stewart's novel Flatterland, (a sequel to Flatland) attempts to explain many concepts in modern mathematics and physics through the device of having a young female Flatlander explore other parts of the "Mathiverse." Schrödinger's Cat is just one of the many strange Mathiverse denizens she and her guide meet; the cat is still uncertain whether it is alive or dead, long after it left the box. Her guide, the Space Hopper, reassures the Cat with a modern view of quantum decoherence. Ursula K. Le Guin wrote a story entitled "Schrödinger's Cat" in 1974 (reprinted in The Compass Rose, published in 1982), which also deals with decoherence. Greg Egan's novel Quarantine, billed as "a story of quantum catastrophe," features an alternative solution to the paradox: in Egan's version of quantum mechanics, the wave function does not collapse naturally. Only certain living things—human beings among them—collapse the wave function of things they observe. Humans are therefore highly dangerous to other lifeforms which require the full diversity of uncollapsed wavefunctions to survive.
The novel OTEC is set inside an artificial reality and raises questions about quantum behavior inside simulated realities. In the simulated realities, the uncertainty principle (and Schrödinger's cat) is expected behavior. (Finite CPU limitations force the reality generator to invoke record locking on quantum level measurements of possession and energy of electrons.)
Even with a cubic mile of nano tech computer, CPU power is finite, and not wasted on real-time calculations of electron position and energy, calculations that would not be referenced in any case. OTEC also asserts that while natural realities may, or may not, have Schrödinger's cats, artificial realities must have them.
As Egan notes, Schrödinger's hypothetical cat is one of the most familiar illustrations of quantum-mechanical oddities. In Quarantine, a physicist asks the narrator, an ex-cop and private investigator, if he has ever heard of "the quantum measurement problem." The narrator is naturally confused, but when asked if he's heard of Schrödinger's cat, he replies, "Of course."
In The Cat Who Walks Through Walls
The title character (though not a main character) of R.A. Heinlein's "The Cat Who Walks Through Walls", a kitten named Pixel, is of indeterminate existence and as such, has the ability to turn up in places that are specifically sealed to outside access. When this ability is questioned, the answer is "He's Schrödinger's cat", leading to the response, "Well, tell Schrödinger to come get his cat.", or words to that effect.
Animals other than cats
Fiction writers have confined other animals besides cats in such contraptions. Dan Simmons's novel Endymion begins with hero Raul Endymion sentenced to death by imprisonment in a "Schrödinger box."
In the fortieth-anniversary Doctor Who audio drama "Zagreus" (2003), the Doctor is locked in a lead-lined box also containing cyanide in an effort to explain his situation of being neither dead nor alive. Afterwards, the Doctor does mention that he has met Schrödinger's Cat.
Kosuke Fujishima's manga series Ah! My Goddess featured a play on Schrödinger's Cat. During one storyline, a storage room was expanded to infinite proportions and the main characters encountered a Schrodinger's Whale, an extremely rare species with the ability to travel through space-time in a five-dimensional quantum state. The male lead in the series, Keiichi Morisato, befriends the whale and teaches it songs by real-life musician Matthew Sweet - but their time spent together is short, for the whale must move on or risk its safety as its wave function collapses. Because of this need to keep moving through quantum states, Schrödinger's Whales hardly ever meet, the reason they are so thin on the ground - but miraculously, Keiichi secured the future of the species by teaching it the songs. After discovering the whale had gone, he found out that it had learned Sweet's song Missing Time by itself - this gave the whales a call that they could locate each other by.
In the eroge (Japanese erotic game) Itsuka Todoku Anosora ni, made by Lump of Sugar, the setting is the main city of Koumeishi. In one story line, a main heroine, Konome, explains the story of Schrödinger's cat. Later, one can see that Koumeishi itself is the same as the situation of Schrödinger's cat: locked in space unable for anyone to come in, or leave, but the people inside are given all their basic needs. They still live in their city with some understanding of the outside world, but are unable to question their existence, or are unable to gain intention to leave. Thus Koumeishi exists as part of Tokyo, but at the same time, not a part of Tokyo.
Another, less apparent, reference to Schrödinger's cat comes from the popular collection of short, humorous stories, The Bastard Operator From Hell written by Simon Traviglia. While attempting to trick the CEO of the company that he works for into upgrading their telecomms systems, the narrator (affectionately referred to as 'the Bastard') makes up a false explanation for why the company experiences low bandwidth during a videoconferencing session: "It's a problem with Heisenberg's certainty principle of video compression... It's a famous quantum physics experiment which videoed cats in boxes. The more cats, the more certainty that you'll get quantum disturbance in video compression."
In this instance the author pays homage to Heisenberg, who ultimately influenced the creation of Schrödinger's hypothesis. It also, more obviously and more humorously, states that Heisenberg completed the experiment (which he did not even theorize) and the fact in place of the killing apparatus inside of the box there were video cameras. This would make no sense to the educated person, yet fooled his CEO because of the superior's interest in videoconferencing. While the argument that you will experience quantum disturbance in live videoconferences because of the length (or amount of cats sitting in on the session) of the session is unfounded, the rest of his statements involving an upgrade in bandwidth do 'fix' the problem.
Schrödinger's Cat used in television series
On the "Complete Monty Python's Flying Circus 16-Ton Megaset," the back of the box states "while to the uninitiated they may look like ordinary .65 oz. digital video discs, due to the unique physics of comedy (it's like quantum but with fewer dead cats), each disc actually weighs a full metaphoric ton! Please remember to lift with your knees." There is a slight reference to quantum physics and Schrödinger's cat.
In an episode entitled "The Pain in the Heart", Dr. Jack Hodgins said to Dr. Zack Addy that a crime scene is like Schrödinger's Cat. Aired 5/19/08 The lab was a crime scene, they could not disturb the scene, nor could they solve the crime without entering the lab.
In the episode "The Tangerine Factor" which aired 05/19/08, Leonard's attempt to arrange a date with Penny results in both Penny and Leonard seeking Sheldon's advice. Sheldon advises Penny that “just like Schrödinger's cat being alive or dead at same time” her date with Leonard currently has both “good and bad” probabilistic outcomes. The only way to find out is to “open the box”, in other words collapse the wave-function of an uncertain date into a specific outcome. Penny misunderstands Sheldon's argument and interprets his advice as general encouragement to go on the date. Apparently, a long session of Sheldon trying to get his point across to Penny ensues with Sheldon reciting Schrödinger's cat definition every time. Later Sheldon mentions Schrödinger's cat to Leonard who instantly gets the implied wave-function collapse as “brilliant”. (As previously established in the series when Leonard attempts to ask Leslie out “success of the whole date is determined by chemistry of good-bye kiss at the very end”.) At the appointed hour, when Leonard comes by to pick up Penny, she is clearly even more uncomfortable and concerned about going out on a date which may ruin their friendship. Leonard mentions Schrödinger's cat to Penny to which she replies she heard “far too much about Schrödinger's cat”. Leonard interprets that as sign of approval and passionately kisses Penny. Probability functions collapses into a clear determined outcome: Penny enjoys the kiss and clearly has no more fears and concerns about going out with Leonard. Recognizing her own chemistry with Leonard, Penny finally understands Schrödinger's cat analogy by mentioning "the cat is alive".
In an episode entitled "The Theory of Everything", the dead elderly couple had a gravestone for a cat named Schrödinger Martin. This is a reference to the theme of the episode, which is that everyone in the cases are connected by String Theory.
In Doctor Who
The 2007 episode 'Blink' contains a race of beings referred to as Weeping Angels. They are described as being "quantum-locked", which means they do not exist when being looked at but can prove deadly when unobserved. At one point the Doctor also mentions that he has met Schrödinger's Cat.
While Don is burdened by the possibility of him wrongly sending an innocent man to jail based on flawed evidence, his brother Charlie and Physics professor Larry remark that the evidence "proving Don right and wrong at the same time" is the "old paradox of Schrödinger's cat". Don's father then asks if that's "that Persian that keeps hiding out in [his] garage". (Episode first aired 1 April 2005)
A montage of some of Professor Farnsworth's achievements includes Schrödinger's Kit Kat Club. Episode 2ACV10 - "A Clone of my Own". Also, Episode 1ACV11 - "Mars University", depicts an actual parody of the experiment itself by having an experiment called "Witten's Dog" displayed on a blackboard at Mars University.
In the Episode "A Heart for Falsehood Framed" (Episode 25-203) Beka Valentine falls in love with a thief whose alias is Schrödinger's Cat.
In Hellsing (manga and Hellsing Ultimate)
A Nazi character in the popular manga Hellsing by Kouta Hirano resembles a young boy dressed in the manner of the Hitler Youth, with cat ears (neko-boy) named Schrödinger who has the ability to be everywhere and nowhere at the same time. It is noted in the manga that, no matter how many times they put a bullet in Schrödinger's head (Alucard and Integra have both done it) or try to kill him any other way, he cannot die because he is just like Schrödinger's cat; as long as Schrödinger believes he is alive and omnipotent, then he is, simply because he believes it to be so. He eventually commits suicide as part of the Major's plan to "poison" Alucard.
A vague character in the series, Frederica Bernkastel, writes in one of her poems about the experiment Schrödinger performed on the cat, concluding on the sad note that it died.
In House M.D.
In an episode entitled "The Right Stuff", while talking about the appearance of Allison Cameron (supposedly in Arizona), Doctor Wilson remarks, "...since she's not a dead cat, it is scientifically impossible for her to be in two places at once."
The central character Gregory House replies, "Physics joke: don't hear enough of those."
In an episode entitled "A Perfect Circle", the character Nate has a vision of watching a made-up television show that discusses the theory in brief.
Quinn has a pet cat named Schrödinger.
Samantha Carter gives a pet cat named Schrödinger to Narim, a member of the the Tollan society, who are several centuries ahead of Earth when it comes to technology. After explaining the name Schrödinger, Narim comments, that it's in his society called Kulivrian physics. After Carter asks, if Narim has studied it he replies: "Yeah, I've studied it... in among other misconceptions of elementary science."
In Yu-Gi-Oh! GX
Dr. Eisenstein uses a card known as "Schrödinger's Cat", which lets him look at the two top cards of his deck and put them back in any order he wants. This may be a result of either result of the "Schrödinger's Cat" (either life or death).
In West Wing
In Season 7 Ellie Bartlet gets married at the White House. The name of the band playing the reception is Schrödinger's Cats.
In The Sopranos
In the final episode of Season 6 "Made in America", the viewer cannot know whether or not Tony Soprano has been killed as the episode cuts to black in its final seconds. Since the viewer cannot know, Tony Soprano is both dead and alive according to quantum law, in a superposition of states. It is only if we were to view the potential shooting (or lack thereof) and determine the ultimate fate of Tony that the superposition is lost, and Tony Soprano becomes one or the other (dead or alive).
In episode 10, upon being asked to name the stray cat she found, Misaka-imōto's third choice of a name (after "Dog" and "Tokugawa Ieyasu") is "Schrödinger." Tōma Kamijō promptly responds that name is taboo for cats.
===In the movie The Chemical Wedding, written by Iron Maiden frontman, Bruce Dickinson.
In video games
A game produced by Atlus, there is a enigmatic cat-like creature revealed to have some connection to God, whom the main character can see throughout the games. His name is 'Schrodinger'.
One of the possible quotes displayed when the Rogue-class "Distract" skill is used is "Hey, is that Schrödinger's Cat on your forehead?"
In Wild Arms 3
The character of Shady the Cat, owned by a Maya Schrödinger, is based on Schrödinger's cat, and is claustrophobic as a result of the "experiment."
One of the monsters encountered in this roguelike game is called 'Quantum Mechanic', which often carries a chest. The chest either contains a cat corpse, or causes a cat to appear.
In pop'n music
A song titled Schrödinger's Cat was composed by Tomosuke Funaki for the arcade version of Pop'n Music 16 PARTY. It is accredited to being the first 43 in any arcade pop'n music game, the highest difficulty level in the series.
In Rock Band
In Half-Life 2
Barney on teleportation: I still got nightmares about that cat.
In Web Comics
- xkcd features a Schrodinger strip 
- LukeSurl.com features a Charles Dickens and Schrodinger strip 
- Piled Higher and Deeper features a Quantum Gradnamics, series 
- Cyanide and Happiness features a "90% of the General Public Won't Understand Week", strip with a reference to Schrödinger and his cat 
- The website Abstruse Goose features series of comics "Schrödinger’s Miscalculation" 
- The Order of the Stick features a strip about "Schrödinger's Ninjas" in its first book.
- Questionable Content mentions Schrodinger's cat in its own absurd extrapolation from the Copenhagen interpretation 
- The characters/creators of Three Panel Soul own a cat named Schrodinger.
- Zach Weiner's Saturday Morning Breakfast Cereal features a one panel misunderstanding Schrödinger's Cat
- Reading Day Opportunities
During an early gig in their his hometown of Reading, Reading Day Opportunities bass player Nicky Clark wore a T-Shirt emblazoned with "Schrodinger's cat is dead" on the front and "Schrodinger's cat is alive" on the back. This was demonstrative of his interest in Physics that he chose to pursue at Manchester University.
- Tears for Fears
A track titled "Schrodinger's Cat" was featured as a B-side on Tears for Fears' single, "Break it Down Again".
- ↑ E. Schrödinger, Die gegenwärtige Situation in der Quantenmechanik, Naturwissenschaftern. 23: pp. 807-812; 823-823, 844-849. (1935). English translation: John D. Trimmer, Proceedings of the American Philosophical Society 124, pp. 323-38 (1980), reprinted in Quantum Theory and Measurement, p. 152 (1983).
- ↑ http://www.gateworld.net/sg1/s1/transcripts/116.shtml
- ↑ "Schrodinger(#45)". xkcd. http://www.xkcd.com/45/. Retrieved 2008-11-08.
- ↑ "076 - What the Dickens?". lukesurl.com. http://www.lukesurl.com/archives/227. Retrieved 2008-11-08.
- ↑ "Quantum Gradnamics, pt. 3 of 3". Piled Higher and Deeper. http://www.phdcomics.com/comics/archive.php?comicid=932. Retrieved 2008-11-08.
- ↑ "90% of the General Public Won't Understand Week". Cyanide and Happiness. http://www.explosm.net/comics/949/. Retrieved 2008-11-08.
- ↑ "Schrödinger’s Infinitesimal Miscalculation". Abstruse Goose. http://abstrusegoose.com/6. Retrieved 2008-11-08.
- ↑ "Schrödinger’s Miscalculation - Part 2". Abstruse Goose. http://abstrusegoose.com/7. Retrieved 2008-11-08.
- ↑ "Schrödinger’s (emotional) Miscalculation - Part 3". Abstruse Goose. http://abstrusegoose.com/74. Retrieved 2008-11-08.
- ↑ "Powers of Observation(#715)". Questionable Content. http://questionablecontent.net/view.php?comic=715. Retrieved 2009-01-03.
- ↑ "On Force Feedback". Three Panel Soul. http://www.threepanelsoul.com/view.php?date=2007-10-08.
- ↑ "SMBC(#973)". SMBC. http://www.smbc-comics.com/?id=973#comic. Retrieved 2009-03-23.
- Poem by Cecil Adams
- Tears For Fears song lyrics Schrodinger's Cat
- A Schrodinger LOLCat goes into a wormhole
- A Schrodinger LOLcat wonders how you like it
- Proving Schrodinger wrong
- I'm in your quantum box
- Knowing the actual state of the cat
- Viennese Meow
- Discussion about the Schrödinger's Cat at the Copenhagen Interpretation Fantasy Camp: Djinn and Juicepl:Kot Schrödingera w kulturze masowej