Follow TV Tropes


Useful Notes / Schrödinger's Cat

Go To

"Do you know that thought experiment with the cat in the box with the poison? Theory requires the cat be both alive and dead until observed. Well, I actually performed the experiment. Dozens of times. The bad news is that reality doesn't exist. The good news is we have a new cat graveyard."
GLaDOS, Portal 2: Lab Rat

The Schrödinger's Cat thought experiment is increasing in popularity as a Motif in fiction. Erwin Schrödinger's thought experiment involved a cat sealed inside a box with a Geiger counter. The Geiger counter controls a mechanism to smash a vial of toxic gas, killing the cat. A small amount of radioactive substance is placed near the Geiger counter, calibrated so that there is a 50% chance of triggering the death trap within one hour. The thing is, after an hour, until the box is open, there is no way to determine whether the cat inside is alive or dead, thus allowing the cat to be both alive and dead.

The thought experiment was originally a critique of the Copenhagen interpretation of Quantum Physics, where the cat can be living and dead at the same time as a superposition of "realities". The paradox should be obvious. Note that the paradox only exists in a flawed understanding of the Copenhagen interpretation, the classic interpretation of quantum mechanics. According to the many-worlds interpretation, what actually happens is that the entire world splits into a superposition of worlds where the cat is alive, and those where it is dead.

The reason the experiment is interesting is that in quantum mechanics, things like subatomic particles routinely exist in superpositions of states, and correct predictions of the outcomes of certain experiments can only be made by taking these effects into accountnote . The experiment posits that if we can accept that small particles (like the radioactive trigger) can be in these kinds of states, then we have to accept that large objects (like the cat) can also be in these kinds of states, raising the question of why we don't routinely observe that.

This thought experiment immediately became popular as a metaphor for uncertainty of the truth, fate, Quantum Physics, how quantum physics can do anything, and whatever the hell is inside that box. Ironically, the original experiment was used to show how stupid the idea of superposition was.

The Copenhagen interpretation says that, because of this, each particle is 50% decayed and 50% undecayed. Schrödinger thought that this idea was Insane Troll Logic, so he extended it to show: if the decay of a radioactive nucleus will set off a device which will release toxic gas into a box that contains a cat, and if (as per the Copenhagen interpretation) the nucleus is 50% decayed and 50% undecayed, the device is 50% triggered and 50% untriggered, so the cat is simultaneously 50% killed and 50% still alive.

As mentioned earlier, the supposed paradox relies on a flawed understanding of Quantum Physics. The flaw lies in not knowing what it means to observe something; observation is not the passive thing like in the world of the everyday, but an active process. In the theoretical box (no physicist would actually do this; it's highly unethical), the observer isn't the scientist, it's not even the cat; it's the Geiger counter, and it keeps the wave function collapsed into either 100% alive or 100% dead, and not 50% both. To learn more, see the Quantum Physics page. In short, the Copenhagen Interpretation doesn't predict a cat simultaneously alive and dead, but rather a cat that is fully alive until it is fully dead. To put it another way, even famous and intelligent physicists like Schrödinger can be completely wrong.

Sometimes though, it's just used to show off the writer's cleverness. Or not.

Here's a video that explains the principle in question.

As you might know, even This Very Wiki is fond of using this. It's the Trope Namer for:

Schrödinger's Cat may or may not exist in these works, you'll have to check to know for sure:

    open/close all folders 

    Anime and Manga 
  • The titular Angel's Egg makes a pretty good analogy to Schrödinger's Cat, but with the added twists that the longer time goes on without the egg hatching, the more likely that whatever was in it has become stillborn, if it ever existed at allnote , and the only way to "collapse the waveform" would be to break the egg open, killing whatever is inside it for surenote . This is what the man eventually does, with tragic consequences.
  • Done a couple of times in Yu-Gi-Oh! GX. Bastion Misawa has it as a formula on his wall (dub only) and a character uses a card which uses Schrödinger's Cat as a basis.
  • Sayonara, Zetsubou-Sensei has a whole episode about the concept which discusses it in detail.
  • Hellsing actually has a character named Schrödinger, and he has a power to be 'everywhere and nowhere' — allowing him to always be in all plot relevant spots at once, as well as to Cosmic Ret Con any damage he suffers. And he's a Cat Boy, naturally. In fact, he has a pretty big purpose beyond comic relief: He was designed to be the 'poison' against Alucard. When he offs himself and lets Alucard absorb his soul, Schrödinger can no longer tell where he is and is neither dead nor alive. This naturally also extends to Alucard, who loses the ability to manifest at all. 30 years later, however, Alucard manages to return to Hellsing by offing the 3 million plus lives in him except for Schrödinger's.
  • Noein has a lot of its premise based on Schrödinger and the idea that an outcome can be altered if it is not observed.
  • In one episode of Rascal Does Not Dream of Bunny Girl Senpai, Futaba uses this thought experiment to explain an Adolescence Syndrome case.
  • One episode of Space☆Dandy features loads of alternate versions of the main characters, in one of these Meow's counterpart was a Schrödingerian, a cat creature in a box who was alternately alive or dead.
  • In Koi Neko, Inaho the kitsune presents Shinta with a mysterious box that, when opened, will cause one of the two Naos - Cat Girls who were once kittens he looked after as a child - to disappear. The reason for this is that one of them died, but both wished to be with Shinta.

    Comic Books 
  • In Animal Man, the final issue of the Peter Milligan-penned Alternate Universe arc referred to Schrödinger's cat, and was titled "Schrodinger's Pizza."
  • In All-Star Superman, the Ultrasphinx traps Lois Lane in a state of quantum uncertainty, between life and death, unless someone can answer its riddle. Superman answers it and saves her.
  • In one The Mighty Thor story, Donald Blake references Schrödinger's cat in describing the Odinsleep, saying the sleeper is in a state between life and death.
  • Played with in The Incredible Hercules, where Amadeus Cho finds himself playing a deadly Role-Playing Game (itself a Schrödinger's Butterfly of a sort), in which his character, Mastermind Excello, encounters a box containing a cat that is literally both dead and alive in the lair of a Mad Scientist.
  • Referenced and parodied in one Empowered story where Thugboy describes Empowered as Schrödinger's Cat Girl, because of her constant mood swings regarding thinking of herself as beautiful or ugly. His friend Frank thinks that he's been reading too many of Empowered's college textbooks.

    Fan Fiction 
  • Deva Series: In Academy Blues, Laura develops a spell called "Schrodinger", which places her in a state between life a death, and allows her to literally be anywhere within a large radius. The spell is somewhat unstable, and she tends to fade in and out in different locations at random times. The spell encloses her body at the location she initiated the spell in a box of light.
  • Suzumiya Haruhi No Index: Since Haruhi is an unknowing Reality Warper, if she is asked to guess a card randomly drawn from a deck, she will always get it right, even if she guesses a card that isn't in the deck. The observers comment that it's like if someone did the Schrödinger's Cat experiment and pulled a dog out the box instead.

  • The 2001 short film The Heisenberg Principle, directed by Cris Jones, explores this is in a mystical/artistic way.
  • A Serious Man by The Coen Brothers: References to Schrödinger's Cat occurs multiple times as a general theme, both on a literal and metaphorical level. It can be seen as a metaphor for general uncertainty in the world. For instance:
    • It's discussed literally in the film since Larry is a physics teacher
    • Larry's marriage is in completely the opposite state to what he thought it was,
    • When Larry both is and isn't being bribed.
      Larry Gopnik: It doesn't make sense. Either [your son] left the money or he didn't.
      Mr. Park: Please. Accept the mystery.
    • Reb Groshkover in the opening scene is one. He is suspected to be an undead dybbuk, but no one is sure whether he is either alive or dead until he's stabbed to make sure.
    • The end: Larry has been called to discuss his MRI results and Danny may be hit by a tornado. In our minds Larry and his son are both dead and not dead.

  • A Certain Magical Index uses Schrödinger's Cat in order to explain the Esper abilities: the state of the "cat" outside of their mind is whatever the user's mind deems it to be, allowing the manifestation of the abilities. Misaka Imouto tries to name her cat Schrödinger, but Touma shoots that idea down. That name is taboo for cats. He adds that anyone who would even consider putting a cat in a box with poison gas must really hate cats.
  • In Crushed by Laura and Tom McNeal, this becomes a critical plot point after Wickham reveals his past to Audrey.
  • Discworld:
    • In the novels, Death does not understand how this would work. A pretty thing would come to pass if he couldn't tell if a cat was dead or not.
    • Pratchett makes multiple references to this. In The Unadulturated Cat, the theory is used to explain the ability of Offscreen Teleportation that all cats seem to have (apparently, the cat was so distressed by being locked in a box with radioactive materials, it became an instant expert in teleportation).
    • In Lords and Ladies the motif is spoofed once again, when the cat locked in the box turns out to be Greebo.
      Technically, a cat locked in a box may be alive or it may be dead. You never know until you look. In fact, the mere act of opening the box will determine the state of the cat, although in this case there were three determinate states the cat could be in: these being Alive, Dead, and Bloody Furious.
    • Pratchett also returns to the motif in the short story "Death and What Comes Next" when a philosopher tries to get out of his own mortality by explaining that in an infinite number of universes, there exists a version of himself that isn't about to die. Death points out the absurdity of this in multiple ways...but the most relevant is that the cat paradox counts on the cat being unobserved, and Death sees everything.
  • Dirk Gently's Holistic Detective Agency saw Dirk begin to explain Schrödinger's cat normally, before talking about how he intervened in the experiment because the cat had gone missing. Dirk turns out to be making it up to see if Richard, who has been acting very oddly, is capable of spotting complete nonsense (like someone actually performing an experiment where the outcome you're testing is what happens before you look) when he hears it.
  • This was the trilogy of novels written by Robert Anton Wilson as the successor to the original Illuminatus! trilogy. The Scrodinger's Cat trilogy explores issues of quantum physics, multiple parellel universes, fan-shaped destinies, and the Copenhagen Interpretation.
  • Eric Flint's novel The Philosophical Strangler features a very strange and enigmatic (human) character named "Schrödinger's Cat", as she wanders through life endlessly looking for (a guy named) Schrödinger, it's impossible to tell at any given moment what she's doing and where she's going. And naturally at one point she gets sealed up inside a doorless stone cell in the bottom of a dungeon. When the other protagonists tunnel in to rescue her, she is somehow no longer there.
  • Qualia the Purple has this play an important role, explaining the concept competently and using it equally so.
  • The Salmon of Doubt features half of a cat. Not a cat chopped in half and lying still, the very lively and normal-acting front part of a cat, which just kind of ends midway along. The cat's name is Gusty Winds, and near the end of what Douglas Adams had written before he died, Dirk comes across a road sign that says "Gusty winds may exist."
  • An incarnation of Schrödinger's Cat appears in Wyrm. It looks and acts a lot like the Cheshire Cat from Alice in Wonderland. But it's actually an avatar of Wyrm.

    Live-Action TV 
  • In Stargate SG-1, Carter explains why her cat is called Schrödinger to a scientifically advanced alien. (Season 1, episode 17, "Enigma"). Amusingly, the alien agrees with Schrödinger when she finishes: anyone who thinks that might be true has misunderstood the laws of physics.
  • FlashForward (2009) lets us know that Simon is a scientist because he explains it when we first meet him.
  • On The Big Bang Theory, Sheldon uses it as a metaphor about whether or not Penny and Leonard's date will be successful or not. He also gets its origin wrong, claiming it was an explanation for the Copenhagen interpretation rather than a critique of it.
  • The third season premiere of Six Feet Under opens with Nate trapped in a Mental World with recurring references to Schrödinger's Cat, highlighting the fact that he's in an in-between state while undergoing risky brain surgery and won't know where he is until he actually takes a risk and "opens the box."
  • Doctor Who
    • Series 7 seems to suggest that the whole of Time Travel is like this. Rory once called out The Doctor for not checking history books before traveling somewhere, and The Doctor says that's not how he travels. We later learn that there's some justification to The Doctor's method as he explains in "The Angels Take Manhattan" that time can be rewritten, but not once you've read it. This is further demonstrated when we see Rory's grave. Once seen, that set of events is fixed, or undoing it would cause a paradox. This is further brought home in the Series 7 finale, "The Name of The Doctor" when The Doctor explains that when you are a time traveler, there is one place you must never go. Turns out, it's your grave. Once you see when and where you will end up dead, it can't be undone. But if you have no prior knowledge of events, then you can change how they turn out without causing a paradox. It is belief in an established timeline that holds the universe and the time stream together.
    • A less wibbly—wobbly, timey–wimey example occurred in ''The Android Invasion''. The last we see of Sergeant Benton is when he's knocked out by one of the duplicates – leaving fans with a conundrum. Was the original killed so as to not interfere with the android copy, or was the original kept alive in order to maintain the copy? Seven years (and one regeneration) later, we finally got an answer in ''Mawdryn Undead'' : He is ALIVE – he made it to retirement in 1979 and went on to become a used car salesmen.
  • McGee makes a direct reference to this in the NCIS episode "Grace Period", where a suicide bomber named Yazid who has killed two NCIS agents is unknown to be either alive or dead the day before his bombing. Ducky claims he had been dead a day before he blew himself up, but the team finds evidence that he had called from a cellphone on the day he died. Turns out a different guy (whom an agent had seen walk into the building when the bomb went off) had killed Yazid the day before by suffocating him with latex, which he used to create a mold of his throat and mouth, which he then used to recreate his voice on a life-like voice emitter to call someone the day of the bombing to make the authorities think he was still alive, then he rigged Yazid's corpse with a bomb and blew him up inside a building in order to discredit his Muslim Peace Conference. Talk about a Complexity Addiction.
  • In the fourth season of Person of Interest Root references the idea when she is arguing that Shaw is still alive after performing a Heroic Sacrifice, pointing out that until they definatively know she is both alive and dead.

    Video Games 
  • Digital Devil Saga literally has a cat named Schrödinger. It makes a lot of sense when you realise it's an aspect of Seraph that achieved enlightenment.
  • In NetHack a monster known as the Quantum Mechanic will sometimes drop a box when it dies. When you open the box either a living cat will jump out or a cat corpse will be found inside. What's more, examining the code shows that which will be found is undetermined until you check — as opposed to every other container in the game, the contents of which are determined when the box is spawned.
  • Ghost Trick has a rather literal interpretation of the trope. To be exact, by the end of the game, Sissel is de-facto a dead-immortal cat.
  • Portal 2 makes several references to it. See also the Portal 2: Lab Rat entry below.
    • One of Rattman's dens early in the game has a diagram of a cat apparently jumping out of a box, with quantum physics equations scribbled all over it.
    • There's an achievement called Schrödinger's Catch, which involved catching a bouncing box before it hit the ground without knowing beforehand which way the box will bounce.
    • Also mentioned by the Fact Core during the final boss battle:
      Fact Core: The Schrödinger's Cat paradox outlines a situation in which a cat in a box must be considered, for all intents and purposes, simultaneously alive and dead. Schrödinger created this paradox as a justification for killing cats.
  • Selected randomly as a gambling device in the Money-Making Game in Kingdom of Loathing, where the winner is decided by one player guessing whether the cat is alive or dead. Of course, you don't actually get to choose.
  • Bioshock 2 makes a reference to this with an Easter Egg in Dionysus Park. In Imago Fine Arts there are multiple ice chunks made of frozen seawater and within one of them is the corpse of Schrödinger the cat. If whacked or shot, Schrödinger bleeds but never shatters making him seem both alive and dead at the same time.
  • BioShock Infinite:
    • The post-credits sequence. DeWitt thinks his daughter is in her room, but he's not sure. As he opens the door, the screen cuts to black. Given the infinite amount of universes that could exist, she is both in and not in the room, and it is left up to the player which version DeWitt finds.
    • Also, the game features something called "Reconciliation Sickness" which is, for all intents and purposes, Schrödinger's thought experiment Gone Horribly Wrong. Due to the interference of Elizabeth's extradimensional powers, the wave function doesn't collapse, causing people who are alive in one possible timeline and dead in another to become trapped in a torturous state of undeath. One such victim is Chen Lin, the Vox-aligned gunsmith.
    • The early game Voxophone "Everyman All at Once" features a theological variant of the thought experiment:
    One man goes into the waters of baptism. A different man comes out, born again. But who is that man who lies submerged? Perhaps the swimmer is both sinner and saint, until he is revealed unto the eyes of man.
    • In Burial at Sea-Episode 2, there is a hermetic chamber with the carcass of feline (presumably a cougar or a panther) inside it within Fink's lab, a reference to the experiment.
  • One scene in the second Deponia game had Rufus wondering why a cat's food bowl was outside of a locked building, whereas the cat was inside. After filling the bowl with tuna to get the cat's attention, he speculates on how the cat can be inside and outside at the same time, name-drops Schrödinger, and claims that he and Goal are witnessing quantum physics at work. The door has a cat flap.

    Visual Novels 
  • Nine Hours, Nine Persons, Nine Doors references the original paradox (albeit not by name) in the Safe End and True End. After The Reveal, Akane's discussion of how information flows and her existence are nods to the Copenhagen interpretation. The sub-tropes listed above are also used, although the player doesn't know that until afterward. The sequel, Virtue's Last Reward, actually discusses the concept in-game. K's identity is also an in-universe example. In most timelines, the person in the suit is Kyle Klim. In the cyan door pathways, however, it is Akane Kurashiki.
  • Umineko: When They Cry has this as a recurring motif, and is used to explain the fantasy scenes as something that could have happened but not necessarily did happen. The events on Rokkenjima is also refered to as this as no one except Eva knows and who chose not to reveal the truth so that Ange wouldn't find out the truth about her parents.
  • Similarly, Higurashi: When They Cry uses the cat; most notably, Frederica Bernkastel uses it in one of her poems. In that poem, the cat dies, referring to the end of Minagoroshi-hen, as well as the fate Rika encounters a few nights after the Watanagashi.

  • This Sci-ence Comic does a surprisingly comprehensive job of summing it up.
  • This xkcd strip is a Schrödinger's comic.
  • In this DM of the Rings strip, Gimli tries to abuse the concept (along with a poorly cast die) to become an UNCERTAINTY LICH.
  • Checkerboard Nightmare featured a minor character named Schrödinger the Cat. He could see all possible realities simultaneously and as a result he's completely insane.
  • This strip of Irregular Webcomic! references Schrödinger's thought experiment in the punchline, but you'll notice that the explanatory note below the comic starts off talking about Heisenberg. As DMM points out in the final paragraph, the punchline of the comic existed in a state of flux while he was writing The Rant. Later, Jamie and Adam remove the "thought" from "thought experiment" and actually set up Schrödinger's Cat with an actual box and an actual cat. Next MythBusters strip, after Jamie says there's no way to determine whether the cat is alive or dead without opening the box and observing the cat, Adam kicks it and makes it yowl.
    (Commentary) Technically, in the experimental sense, this is actually "observing" the cat. Quantum mechanics isn't quite that perverse.
  • Luke Surl explains why the cat is dead. In an earlier strip, he drew some interesting parallels with classic literature.
  • A classroom lecture on Schrödinger's Cat is given in this page of Spy6teen; and ends up being Chekhov's Gun in this comic
  • This early Dresden Codak comic.
    "Somewhere, Niels Bohr walks among us, unobserved and immortal."
    (Niels Bohr, in a purple cat disguise, is seen hiding in a bush.)
Later, thanks to guest artist Zack Weiner, Cat's Schrödinger was introduced.
  • In Portal 2: Lab Rat (the comic that ties the two Portal games together), there are a couple references.
    • GLaDOS claims to have actually done the experiment.
      GLaDOS: Do you know that thought experiment with the cat in the box with the poison? Theory requires the cat be both alive and dead until observed. Well, I actually performed the experiment. Dozens of times. The bad news is that reality doesn't exist. The good news is we have a new cat graveyard.
    • At the end of the comic, Doug Rattman compares Chell to the cat, surviving in stasis but with no guarantee she'll ever be woken up.
      Rattman: Both alive and dead, until someone opens the box.
  • Referenced in this Cyanide and Happiness comic.
  • Scenes from a Multiverse has fun with this in this strip, which briefly presents an entire civilization based on the uncertainty theory, including universal ownership of celebratory "cat boxes".
  • Captain SNES: The Game Masta has a cat named Schrödinger, whose state in Videoland cannot be determined by the residents, as it is from the real world, and it generally proceeds to make fools of everyone it meets.
  • One of the "extra" pages from Problem Sleuth depicts the Midnight Crew unleashing hundreds of these cats, existing in every possible state between alive and dead, on the Wasp Professor.
    And unfortunately for the Professor... EVERY ONE OF THOSE CAT STATES IS UNBELIEVABLY DEADLY.
  • Homestuck had a sudden perspective switch after Nepeta, the resident cat troll, attacked Ax-Crazy sober Gamzee. For the longest time, nobody knew whether she had survived the encounter. She didn't. Therefore, she was temporarily Schrödinger's Nepeta.
  • All of the above regarding Schrödinger in Hellsing also applies in Hellsing fancomic And Shine Heaven Now with one added twist: he's an I-Jin of Erwin Schrödinger.

    Web Original 
  • Linkara criticizes the experiment in one of his reviews. In his Top 15 Screw Ups video, he admits he missed the point somewhat although he does note that in the original review it was just meant to be a quick joke and he hadn't anticipated how serious so many people would take it.
  • Cecil Adams (of The Straight Dope) explains the concept in rhyme.
  • SCP-2144 is, in usual SCP fashion, an attempt to turn the trope into mild creepypasta. 2144 is a cat who is invisible to cameras, inaudible to microphones, and intangible to weighing scales, yet very lively and animate as long as it stays in an open area (humans can see/hear/touch it just fine, but they can't feel its heartbeat). If you force it into an enclosed area it immediately becomes comatose, but cameras and microphones can detect it again. Oh, and it emits deadly radiation and exhales hydrogen cyanide while comatose. Fortunately for everyone else it has an aversion to open doors and windows.

    Western Animation 
  • Used as a joke in a Futurama episode. The cops catch Erwin Schrödinger speeding with a box containing a cat, he's not clear whether it's alive or dead (until Fry opens the box and the cat claws his face), and there's also drugs in there.
  • In Rick and Morty, after a feedback loop occurs that splits reality into hypothetical possibilities, Rick shows Morty and Summer the outside filled with an endless oblivion also containing hundreds of cats that Rick claims to be Schrodinger’s cat, but assumes they both are and aren't.
  • Said by Velma in the series finale for Scooby-Doo! Mystery Incorporated while she is trying to comprehend the reveal of an alternate timeline where the Nibiru Entity never existed, and therefore never negatively influenced any of the character's lives, placing them in a happy town with no mysteries.
  • Family Guy: Parodied in "Herpe the Love Sore", where Peter is tempted to open a box meant for Quagmire.
    Peter: You know, Lois, physicists believe there are two alternate universes: one in which I don't open the box, and one in which I do.
    (transition to alternate reality)
    Peter: I'm not gonna open the box. (Lois shoots him)
    (transition back to normal reality)
    Peter: I'm gonna open the box.
  • Teen Titans Go!: Parodied in "Quantum Fun". Robin lectures the other Titans about the experiment and decides to recreate it with Beast Boy serving as the cat. While Robin declares that Beast Boy is neither alive nor dead as long as they don't open the box, Beast Boy's ghost rises out of the closed box. Raven quickly revives him.

    Real Life 
  • A famous quote by Stephen Hawking: "When I hear about Schrödinger's cat, I reach for my gun." note to explains:
    This represents the thoughts of many physicists, because there are several aspects the thought experiment that bring up issues. The biggest problem with the analogy is that quantum physics typically only operates on the microscopic scale of atoms and subatomic particles, not on the macroscopic scale of cats and poison vials.
  • Also, physicists such as John Gribbin (author of In Search of Schrödinger's Cat and Schrödinger's Kittens) wonder at what point particles go from being "quantum" to "ordinary". How big do you have to be to be normal? How small do you have to be to be in two places at once? note 
  • The rise of Quantum Mechanics Can Do Anything has led to references to the original thought experiment in unrelated fields. One publication in political science asks the reader to imagine international structure by invoking Schrödinger's cat and the Uncertainty Principle.
  • An entry in the Style Invitational (humor contest in the Washington Post) from 2010:
    Curiosity only collapsed the quantum superposition of Schrödinger's cat into a definite state. What killed it was leaving it in a box for a week.
  • Cracked used a punchline in this article:
    The cat just dies, and you're just an asshole.

Alternative Title(s): Schroedingers Cat