Physics metaphors don’t work, or so I recently claimed. Metaphors always fail; they cut corners in reshaping our perception. But are certain physics metaphors defective simply because they cannot be experimentally confirmed? To illustrate this idea, I mentioned the famous metaphor for how the Higgs field gives particles mass, which is likened to fans mobbing – and slowing – celebrities as they walk across a room.
I know from actual experience that this is false. Having been within metres of filmmaker Spike Lee, composer Stephen Sondheim, and actors Mia Farrow and Denzel Washington, I’ve seen fans have many different reactions to the presence of nearby celebrities in motion. If the image were strictly true, I’d have to check which celebrities were about each morning to know what the hadronic mass would be that day.
I therefore invited Physics World readers to propose other potentially empirically defective physics metaphors, and received dozens of candidates. Technically, many are similes rather than metaphors, but most readers, and myself, use the two terms interchangeably. Some of these metaphors/similes were empirically confirmable and others not.
Shoes and socks
Michael Elliott, a retired physics lecturer from Oxford Polytechnic, mentioned a metaphor from Jakob Schwichtenberg’s book No-Nonsense Quantum Mechanics that used shoes and socks to explain the meaning of “commutation”. It makes no difference, Schwichtenberg wrote, if you put your left sock on first and then your right sock; in technical language the two operations are said to commute. However, it does make a difference which order you put your sock and shoe on.
“The ordering of the operations ‘putting shoes on’ and ‘putting socks on’ therefore matters,” Schwichtenberg had written, meaning that “the two operations do not commute.” Empirically verifiable, Elliott concluded triumphantly.
A metaphor that was used back in 1981 by CERN physicist John Bell in a paper addressed to colleagues requires more footgear and imagination. Bell’s friend and colleague Reinhold Bertlmann from the University of Vienna was a physicist who always wore mismatched socks, and in the essay “Bertlmann’s socks and the nature of reality” Bell explained the Einstein–Podolsky–Rosen (EPR) paradox and Bell’s theorem in terms of those socks.
If Bertlmann stepped into a room and an observer noticed that the sock on his first foot was pink, one could be sure the other was not-pink, illustrating the point of the EPR paper. Bell then suggested that, when put in the wash, pairs of socks and washing temperatures could behave analogously to particle pairs and magnet angles in a way that conveyed the significance of his theorem. Bell bolstered this conclusion with a scenario involving correlations between spikes of heart attacks in Lille and Lyon. I am fairly sure, however, that Bell never empirically tested this metaphor, and I wonder what the result would be.
Out in space, the favourite cosmology metaphor of astronomer and astrophysicist Michael Rowan-Robinson is the “standard candle” that’s used to describe astronomical objects of roughly fixed luminosity. Standard candles can be used to determine astronomical distances and are thus part of the “cosmological distance ladder” – Rowan-Robinson’s own metaphor – towards measuring the Hubble constant.
Retired computer programmer Ian Wadham, meanwhile, likes Einstein’s metaphor of being in a windowless spacecraft towed by an invisible being who gives the ship a constant acceleration. “It is impossible for you to tell whether you are standing in a gravitational field or being accelerated,” Wadham writes. Einstein used the metaphor effectively – even though, as an atheist, he was convinced that he would be unable to test it.
I was also intrigued by a comment from Dilwyn Jones, a consultant in materials science and engineering, who cited a metaphor from the 1939 book The Third Policeman by Irish novelist Flann O’Brien. Jones first came across O’Brien’s metaphor in Walter J Moore’s 1962 textbook Physical Chemistry. Atoms, says a character in O’Brien’s novel, are “never standing still or resting but spinning away and darting hither and thither and back again, all the time on the go”, adding that “they are as lively as twenty leprechauns doing a jig on top of a tombstone”.
But as Jones pointed out, that particular metaphor “can only be tested on the Emerald Isle”.
Often metaphors entertain as much as inform. Clare Byrne, who teaches at a high school in St Albans in the UK, tells her students that delocalized electrons are like stray dogs – “hanging around the atoms, but never belonging to any one in particular”. They could, however, she concedes “be easily persuaded to move fast in the direction of a nice steak”.
Giving metaphors legs
I ended my earlier column on metaphors by referring to poet Matthew Arnold’s fastidious correction of a description in his 1849 poem ”The Forsaken Merman”. After it was published, a friend pointed out to Arnold his mistaken use of the word “shuttle” rather than “spindle” when describing “the king of the sea’s forlorn wife at her spinning-wheel” as she lets the thing slip in her grief.
The next time the poem was published, Arnold went out of his way to correct this. Poets, evidently, find it imperative to be factual in metaphors, and I wondered, why shouldn’t scientists? The poet Kevin Pennington was outraged by my remark.
“Metaphors in poetry are not the same as metaphors used in science,” he insisted. “Science has one possible meaning for a metaphor. Poetry does not.” Poetic metaphors, he added are “modal”, having many possible interpretations at the same time – “kinda like particles can be in a superposition”.
I was dubious. “Superposition” suggests that poetic meanings are probabilistic, even arbitrary. But Arnold, I thought, was aiming at something specific when the king’s wife drops the spindle in “The Forsaken Merman”. After all, wouldn’t I be misreading the poem to imagine his wife thinking, “I’m having fun and in my excitement the thing slipped out of my hand!”
My Stony Brook colleague Elyse Graham, who is a professor of English, adapted a metaphor used by her former Yale professor Paul Fry. “A scientific image has four legs”, she said, “a poetic image three”. A scientific metaphor, in other words, is as stable as a four-legged table, structured to evoke a specific, shared understanding between author and reader.
A poetic metaphor, by contrast, is unstable, seeking to evoke a meaning that connects with the reader’s experiences and imagination, which can be different from the author’s within a certain domain of meaning. Graham pointed out, too, that the true metaphor in Arnold’s poem is not really the spinning wheel, the wife and the dropped spindle but the entirety of the poem itself, which is what Arnold used to evoke meaning in the reader.
That’s also the case with O’Brien’s atom-leprechaun metaphor. It shows up in the novel not to educate the reader about atomic theory but to invite a certain impression of the worldview of the science-happy character who speaks it.
The critical point
In his 2024 book Waves in an Impossible Sea: How Everyday Life Emerges from the Cosmic Ocean, physicist Matt Strassler coined the term “physics fib” or ”phib”. It refers to an attempted “short, memorable tale” that a physicist tells an interested non-physicist that amounts to “a compromise between giving no answer at all and giving a correct but incomprehensible one”.
The criterion for whether a metaphor succeeds or fails does not depend on whether it can pass empirical test, but on the interaction between speaker or author and audience; how much the former has to compromise depends on the audience’s interest and understanding of the subject. Metaphors are interactions. Byrne was addressing high-school students; Schwichtenberg was aiming at interested non-physicists; Bell was speaking to physics experts. Their effectiveness, to use one final metaphor, does not depend on empirical grounding but impedance matching; that is, they step down the “load” so that the “signal” will not be lost.
Building on historical lessons for space governance, urgent action is needed to address escalating threats. Today, we face a dangerous gap in space security: our deterrence frameworks are obsolete for borderless domains, like space. Meanwhile, U.S. intelligence warns that Russia’s “satellite inspectors” may be prototype anti-satellite (ASAT) weapons, and Russian electronic warfare systems continue to […]
SAN FRANCISCO – Solar energy startup Solestial won a $1.2 million Space Force contract to develop novel arrays for small satellites. Under a SpaceWerx award announced July 16, Solestial will optimize silicon solar cells and power modules for speedy integration and assembly. In addition, Solestial will develop electrical interconnectors. The project will culminate in Solestial […]
SpaceX provided a lift for a competitor in the satellite broadband sector with the Falcon 9 launch of spacecraft for Amazon’s Project Kuiper constellation July 16.
It’s rare for protestors to show up outside NASA headquarters in Washington — and even rarer when they include a Pokémon character. But on the morning of June 30, about 60 people gathered on the corner of 4th and E Streets SW, waving signs and shouting through a bullhorn, seeking to attract the attention of […]
The second law of thermodynamics demands that if we want to make a clock more precise – thereby reducing the disorder, or entropy, in the system – we must add energy to it. Any increase in energy, however, necessarily increases the amount of waste heat the clock dissipates to its surroundings. Hence, the more precise the clock, the more the entropy of the universe increases – and the tighter the ultimate limits on the clock’s precision become.
This constraint might sound unavoidable – but is it? According to physicists at TU Wien in Austria, Chalmers University of Technology, Sweden, and the University of Malta, it is in fact possible to turn this seemingly inevitable consequence on its head for certain carefully designed quantum systems. The result: an exponential increase in clock accuracy without a corresponding increase in energy.
Solving a timekeeping conundrum
Accurate timekeeping is of great practical importance in areas ranging from navigation to communication and computation. Recent technological advancements have brought clocks to astonishing levels of precision. However, theorist Florian Meier of TU Wien notes that these gains have come at a cost.
“It turns out that the more precisely one wants to keep time, the more energy the clock requires to run to suppress thermal noise and other fluctuations that negatively affect the clock,” says Meier, who co-led the new study with his TU Wien colleague Marcus Huber and a Chalmers experimentalist, Simone Gasparinetti. “In many classical examples, the clock’s precision is linearly related to the energy the clock dissipates, meaning a clock twice as accurate would produce twice the (entropy) dissipation.”
Clock’s precision can grow exponentially faster than the entropy
The key to circumventing this constraint, Meier continues, lies in one of the knottiest aspects of quantum theory: the role of observation. For a clock to tell the time, he explains, its ticks must be continually observed. It is this observation process that causes the increase in entropy. Logically, therefore, making fewer observations ought to reduce the degree of increase – and that’s exactly what the team showed.
“In our new work, we found that with quantum systems, if designed in the right way, this dissipation can be circumvented, ultimately allowing exponentially higher clock precision with the same dissipation,” Meier says. “We developed a model that, instead of using a classical clock hand to show the time, makes use of a quantum particle coherently travelling around a ring structure without being observed. Only once it completes a full revolution around the ring is the particle measured, creating an observable ‘tick’ of the clock.”
The clock’s precision can thus be improved by letting the particle travel through a longer ring, Meier adds. “This would not create more entropy because the particle is still only measured once every cycle,” he tells Physics World. “The mathematics here is of course much more involved, but what emerges is that, in the quantum case, the clock’s precision can grow exponentially faster than the entropy. In the classical analogue, in contrast, this relationship is linear.”
“Within reach of our technology”
Although such a clock has not yet been realized in the laboratory, Gasparinetti says it could be made by arranging many superconducting quantum bits in a line.
“My group is an experimental group that studies superconducting circuits, and we have been working towards implementing autonomous quantum clocks in our platform,” he says. “We have expertise in all the building blocks that are needed to build the type of clock proposed in in this work: generating quasithermal fields in microwave waveguides and coupling them to superconducting qubits; detecting single microwave photons (the clock ‘ticks’); and building arrays of superconducting resonators that could be used to form the ‘ring’ that gives the proposed clock its exponential boost.”
While Gasparinetti acknowledges that demonstrating this advantage experimentally will be a challenge, he isn’t daunted. “We believe it is within reach of our technology,” he says.
Solving a future problem
At present, dissipation is not the main limiting factor for when it comes to the performance of state-of-the-art clocks. As clock technology continues to advance, however, Meier says we are approaching a point where dissipation could become more significant. “A useful analogy here is in classical computing,” he explains. “For many years, heat dissipation was considered negligible, but in today’s data centres that process vast amounts of information, dissipation has become a major practical concern.
“In a similar way, we anticipate that for certain applications of high-precision clocks, dissipation will eventually impose limits,” he adds. “Our clock highlights some fundamental physical principles that can help minimize such dissipation when that time comes.”
New research released by the UK Space Agency underscores the country’s growing reliance on satellite technologies, which supported industries accounting for about 18% of national GDP.
Connexion
Science Magazine
Discover Mag
