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The world’s most famous cat seems to be everywhere—and nowhere. It appears on cartoons, T-shirts, board games, puzzle boxes, and glow-in-the-dark coffee cups. There’s even a gin named after the celebrity animal—boasting “a strong backbone of juniper.”
But its origin story is almost as mysterious as the scientific principle it was enlisted to illustrate. While Austrian physicist Erwin Schrödinger concocted the conceit of the cat, he was not the one who popularized it. The fictitious animal only really entered wider public consciousness after American science-fiction and fantasy writer Ursula K. Le Guin published a short story called “Schrödinger’s Cat,” 50 years ago. It was just one of dozens of works published by Le Guin, who died in 2018 after a long and celebrated career.
Schrödinger originally invented the cat image as a gag. If true believers in quantum mechanics are right that the microworld’s uncertainties are dispelled only when we observe it, Schrödinger felt, this must also sometimes happen in the macroworld, an absurdity that violates common sense. Writing in a paper published in 1935 in the German-language journal Naturwissenschaften, he presented his famous cat-in-a-box image to demonstrate just how foolish this notion was.
For a while, few paid attention. According to an Ngram search of Google Books carried out by Steven French, a philosopher of science at the University of Leeds, there were no citations of the phrase “Schrödinger’s cat” in the literature for almost 20 years. As French describes in his 2023 book, A Phenomenological Approach to Quantum Mechanics, the first reference appeared in a footnote to an essay by the Austrian philosopher Paul Feyerabend in the 1957 book Observation and Interpretation in the Philosophy of Physics.
Schrödinger originally invented the cat image as a gag.
The American philosopher and logician Hilary Putnam first learned of Schrödinger’s cat around 1960. “I always assumed the physics community was familiar with the idea,” Putnam later recalled, but he found few who were. In his 1965 paper “A philosopher looks at quantum mechanics,” Putnam called it “absurd” to say that human observers determine what exists. But he was unable to refute the idea.
Invoking Schrödinger’s image, Putnam found that we are indeed unable to say, “that the cat is either alive or dead, or for that matter that the cat is even a cat, as long as no one is looking.” Putnam had another worry, too. Quantum formalism required that if he looked at a quantum event, it would throw him into superposition, the limbo of being in various states at the same time. Putnam concluded at the time that, “no satisfactory interpretation of quantum mechanics exists today.”
It was another decade before the cat and its bizarre implications leapt into popular culture. In 1974 Le Guin published The Dispossessed, an award-winning book about a physicist whose new, relativistic theory of time draws him into the politics of the pacifist-anarchist society in which he lived. According to author Julie Phillips, who is writing a biography of the fantasy writer, Le Guin read up on relativity theory to help her make her character’s “theory of simultaneity” sound plausible.
“My best guess,” Phillips wrote in an email to me, “is that she discovered Schrödinger’s cat while doing research for the novel.” Le Guin, it appears, seems to have read Putnam’s article around 1972. “The Cat & the apparatus exist, & will be in State 0 or State 1, IF somebody looks,” Le Guin wrote in a note to herself. “But if he doesn’t look, we can’t say they’re in State 0, or State 1, or in fact exist at all.”
Unlike Putnam, Le Guin was entranced by the implied uncertainties and appreciated the fantastic nature of Schrödinger’s image. “If we can say nothing about the definite values of micro-observables, when not measuring them, except that they exist, then their existence depends on our observation & measurement,” she wrote in her notes.
In “Schrödinger’s Cat,” which Le Guin finished in September 1972 but didn’t publish for another two years, an unnamed narrator senses that “things appear to be coming to some sort of climax.” A yellow cat appears. The narrator grieves but doesn’t know why. A musical note makes her want to cry but she doesn’t know for what—and thinks the cat knows but is unable to tell her. She then remembers Michelangelo’s painting The Last Judgment, of a man dragged down to hell who clamps a hand over one eye in horror but keeps the other eye open and clear. The doorbell rings and in walks Rover, a dog.
Rover pulls a box out of his knapsack with a quantum-mechanical gadget that will either shoot or not shoot the cat once it gets inside and the lid is closed. Before we open the lid, Rover says, the cat is neither dead nor alive. “So it is beautifully demonstrated that if you desire certainty, any certainty, you must create it yourself.”
The narrator is not sure. Don’t we ourselves get “included in the system,” aren’t we still inside an even bigger box? She’s reminded of the Greek legend of Pandora, who opens her box and lets out all its evil contents. She and Rover open the lid—but find the box empty.
The house roof flies off “just like the lid of a box” and “the unconscionable, inordinate light of the stars” shines down. The narrator finally identifies the musical note, whose tone has become much clearer now that the stars are visible. The narrator wonders whether the cat knows what it was they had lost.
Le Guin’s story was soon followed by fictional and non-fictional treatments of quantum mechanics by other writers in which Schrödinger’s cat is a major figure. Examples include Robert Anton Wilson’s Schrödinger’s Cat Trilogy; H.R. McGregor’s Schrödinger’s Baby: A Novel; Adam Felber’s Schrödinger’s Ball: A Novel; Ryan Boudinot’s Blueprints of the Afterlife. There have also been a number of short stories including F. Gwynplaine MacIntyre’s “Schrödinger’s Cat-Sitter” from 2001.
Phillips calls Le Guin’s “Schrödinger’s Cat” a “slight, playful story with an undercurrent of sorrow,” and warned me not to overthink it. “You could think of it as ‘a fantasy writer looks at quantum mechanics,’” she explained, adding that Le Guin wrote in her journal that fantasy as a genre and physics as a science are approaches to reality that reject common sense. “I think,” Phillips concluded, “she may have been playing around with her sense, at that moment, that physics was another way of expressing the fantastic.”
If so, Le Guin certainly found the right image. 
Reprinted with permission from Physics World.
Lead image: K. Cozy Bear / Shutterstock
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