The world’s most famous cat is everywhere. 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 “lovely aromas of fresh mint and lemon zest”, with notes of basil, blueberries, cardamom and lemon-thyme – and “a strong backbone of juniper” – it’s yours for just £42.95 for 500 ml.

You know whom I’m talking about. But despite its current ubiquity, the fictitious animal only really entered wider public consciousness after the US science-fiction and fantasy writer Ursula K Le Guin published a short story called “Schrödinger’s cat” exactly 50 years ago. Le Guin, who died in 2018 at the age of 88, was a widely admired writer, who produced more than 20 novels and over 100 short stories.

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 – and that’s ridiculous. Writing in a paper published in 1935 in the German-language journal Naturwissenschaften (23 807), he presented his famous cat-in-a-box image to show why such a notion is foolish.

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 in the UK, 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 philosopher Paul Feyerabend in the 1957 book Observation and Interpretation in the Philosophy of Physics edited by Stephan Körner.

The American philosopher and logician Hilary Putnam (1926–2016) first learned of Schrödinger’s image 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 himself into superposition. Putnam concluded that “no satisfactory interpretation of quantum mechanics exists today”.

Enter Le Guin

It was to be another decade before the cat and its bizarre implications jumped into popular culture. In 1974 Le Guin published The Dispossessed (1974), 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 Julie Phillips, who is writing a biography of Le Guin, she read up on relativity theory to make her character’s “theory of simultaneity” sound plausible.

“My best guess,” Phillips wrote in an e-mail 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 in about 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.”

Le Guin was entranced by the implied uncertainties and appreciated the fantastic nature of Schrödinger’s image

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.”

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 a yet 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 note, whose tone is now much clearer once the stars are visible. The narrator wonders whether the cat knows what it was they lost.

Le Guin’s story was soon followed by other fictional and non-fictional treatments of quantum mechanics in which Schrödinger’s cat is a major figure. Examples include the Schrödinger’s Cat Trilogy (Robert Anton Wilson, 1979); Schrödinger's Baby: a Novel (H R McGregor, 1999); Schrödinger’s Ball (Adam Felber, 2006); Blueprints of the Afterlife (Ryan Budinot, 2012). There have also been a number of short stories including F Gwynplaine MacIntyre’s “Schrödinger's cat-sitter” from 2001.

The critical point

Phillips called 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 unerringly found the right image.

The post Ursula Le Guin: the pioneering author we should thank for popularizing Schrödinger’s cat appeared first on Physics World.

In 1983 officials from San Diego City Council in California voted to install high-pressure sodium (HPS) streetlights that emitted a full spectrum of visible light. The existing, low-pressure sodium (LPS) streetlights gave off only a narrow, yellowish band, and it was hoped that the HPS lights would brighten streets and reduce crime. Makes sense, right?

However, astronomers at the 200-inch Hale telescope on Palomar Mountain, about 100 km away, were appalled, saying light pollution would blind their instrument. While they could readily filter out the narrow band of wavelengths from LPS lights, this was impossible with HPS lamps. “It would have the same effect as taking a sledgehammer and knocking out half of it,” complained one scientist who studied quasars, fearing it was “the beginning of the end”.

One member of San Diego’s council defended its action, claiming that local citizens didn’t like the existing lights and feared for their safety. “All we’re doing is responding to our constituents who are telling us that they don’t want yellow lights,” the council member said. “I’m for technology. But I’m also for the people of San Diego.”

In 1984 the council reversed its decision and approved the LPS lights. Delighted astronomers even named an asteroid that had recently been discovered “3043 San Diego”. But the battle continued to rage for nearly a decade. Some LPS opponents insisted that if the astronomers really wanted the telescope they should move it elsewhere. Others derided the telescope’s value.

“Little that is done in astronomy anywhere is of any practical importance,” huffed one writer to the San Diego Union-Tribune. Another said there was “no reason whatever to inconvenience literally millions of people in Southern California so some fool astronomer can play with this particular toy”. A third demanded that San Diego citizens’ safety be put ahead of the desire to “see Venus on a cloudy night”.

Astronomers assumed they’d prevail so long as they presented their case 'factually and logically'

Other supporters of the bright lights were annoyed by how they felt they were being treated, and angered that they were being dismissed as “provincial and small-town”. At one city-council meeting they were labelled “flat-Earthers”. Eventually, in 1993, the council did a second U-turn and decided to install HPS lamps in high-crime areas – and later in other parts of the city too.

Disputed issues

Palomar astronomers were forced to cope with increasing light pollution by observing more in the infrared and by looking to the skies to within just 45 degrees of the zenith. Recounting the dispute in his 2001 book Asteroids: a History, the aerospace historian Curtis Peebles said it was tempting to think “that the political and civic leaders in one of California’s largest cities could not really do and say these things…but they did.” The asteroid, though, retained its name.

Astronomers assumed they’d prevail so long as they presented their case “factually and logically”, as Peebles put it. But facts and logic were not the only motivating concerns of the San Diego citizens. Some thought that their safety should come ahead of the telescope’s operation, others were suspicious of the instrument’s overall value compared to other important values, and still others were annoyed by the way their concerns were dismissed. As Peebles wrote, the scientists simply “never understood the people they were fighting”.

The San Diego events sound parochial, but Peebles concluded they “mirror those in the larger world”. I’ve covered a few, such as the time when the Brookhaven National Laboratory was forced to shut its research reactor in 1999 after an insignificant leak of tritium ignited anti-nuclear protests and fed political ambitions. There was also the closing of the US National Tritium Labelling Facility at the Lawrence Berkeley National Laboratory, following protests against tritium emissions that were within limits set by the US Environmental Protection Agency.

A lab’s purpose is harder to explain and justify than for more ordinary institutions

Many local institutions, such as schools, post offices or fire stations, fit into their surrounding communities in three distinct ways. First, they have a physical place, sharing air, water, streets, electricity and other services with neighbours. Second, they serve easily recognized purposes, which neighbours might feel they could not easily do without. Finally, such institutions have “personalities”, for their behaviour over time appears as more or less reliable, caring and trustworthy.

Laboratories are different. They, too, have physical places. But because they have sensitive scientific instruments, it can make labs vulnerable to activities in other nearby places. When Palomar, for example, was being planned nearly a century ago, it was sited in a then-remote location on a mountain top. But population growth and technological developments effectively shrank distances to places like San Diego, leading to intrusive interactions.

A lab’s purpose, too, is harder to explain and justify than for more ordinary institutions. Its products and services are not primarily for neighbours but the wider scientific community and can seem to be of little practical value – as the Palomar telescope did to some. Finally, a lab “lives in” a community, which means its conduct and those of its staff can be investigated and commented on by politicians and the media.

The critical point

Ensuring a lab’s place in a community therefore poses special challenges. For the Palomar astronomers, the stars seemed to be a straight shot – or as straight as the geometry of spacetime will allow. Contacting San Diego involved a more complex trajectory with several different paths. Unless these paths are identified and addressed, the events at Palomar are likely to mirror others.

The post Astronomers versus activists: the battle over San Diego’s streetlights appeared first on Physics World.