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Thursday, May 23, 2024

To Observe the Muon Is to Experience Hints of Immortality

All people want to enact a paradigm shift, don't they? Even if it's not mRNA, or Lego, we want at least, on our one chance on Earth, to make a meme happen.

So imagine the excitement on April 7, when more than 200 physicists from seven countries convened on a Zoom call for a kind of nonexplosive gender-reveal party. What was to be disclosed was not a baby's sex but the fate of particle physics.


While the rest of the world has spent more than a year preoccupied with epidemiology, this team of physicists has spent three years collecting data for something called the Muon g-2 experiment, a much anticipated project headquartered at Fermilab, a physics and accelerator laboratory in Batavia, Illinois, that is overseen by the Department of Energy. The physicists had done their work half in the dark, with a key variable concealed. If you want a eureka badly enough, after all, you might be tempted to help the data along. Now the lights were coming on.

“We had no idea” of the outcome, Rebecca Chislett, a physicist at University College London, told Scientific American. “It was exciting and nerve-racking.”


The experiment had aimed to determine, to the finest measurement, the strength of the internal magnetic field generated by a muon, a particle similar to an electron but 200 times more massive and supremely unstable, with a lifetime of 2.2 microseconds. Muons rain down on us all the time, the indirect product of cosmic rays colliding with particles in Earth's atmosphere. But Fermilab's accelerator makes its own.

Many subatomic particles act like magnets, and the so-called Standard Model predicts the strength of their magnetism with great exactitude. To test the model, the team watched muons as they wobbled in a magnetic field and clocked whether the wobble deviated from what theory had predicted it would be. Indeed, it did. As Galileo might have said: Eppur si deviare.

In the journal Physical Review Letters, the researchers reported that the infinitesimal deviation—0.0000002 percent away from what theory stipulated—was highly significant. In its press release, Fermilab even suggested that the discovery could force us to revise our basic model of how subatomic particles work.

“The strong evidence that muons deviate from the Standard Model calculation might hint at exciting new physics. Muons act as a window into the subatomic world and could be interacting with yet undiscovered particles or forces,” read the press release. Graziano Venanzoni, a physicist at the Italian National Institute for Nuclear Physics in Pisa, called the findings “an incredible result … long awaited not only by us but by the whole international physics community.”

The known universe seemed, briefly, muonstruck. But it took only 12 days for another Italian physicist to throw cold water on the bliss. Carlo Rovelli, a founder of loop quantum gravity theory, which seeks to combine quantum mechanics and general relativity, and the author of Helgoland: Making Sense of the Quantum Revolution, which was published in English in May, wrote in The Guardian, “Physicists love to think of themselves as radical.”

This self-conception, Rovelli went on, is understandable, especially among physicists, who make their names in the outer reaches of human understanding. But it also leads labs to overhype their findings. He cited examples of would-be “discoveries” in supersymmetry that initially seemed groundbreaking but didn't live up to the hype. Rovelli especially zeroed in on the word “hint,” which appeared in that Fermilab press release. “I do not remember a time without some colleague talking about ‘hints’ that new supersymmetric particles had been ‘nearly discovered.’” The nearlys and hints, presumably, are often at a value that, unlike Fermilab's 0.0000002 percent, may not be statistically significant.

In 1807, William Wordsworth published an ode that was to Romantic poetry as the discovery of quarks was to particle physics in 1964: a breakthrough. “Intimations of Immortality from Recollections of Early Childhood” chronicles the poet's emotional detachment from nature; his blissful rediscovery of it in memories of childhood; and his bittersweet resolution that, though the Earth will die, the suggestions of deathlessness in the present moment will sustain him in his grief.

Though nothing can bring back the hour
Of splendour in the grass, of glory in the flower; 
We will grieve not, rather find 
Strength in what remains behind; 
In the primal sympathy 
Which having been must ever be; 
In the soothing thoughts that spring 
Out of human suffering; In the faith that looks through death …

An intriguing approach to literature called ecocriticism, pioneered in the 1990s by the English philosopher Jonathan Bate, argues that Romantic poetry like this ode can suggest ways to conceive of our dying planet as one that we must save—or perhaps, in sorrow, and maybe love, allow to die. But Wordsworth's poem doesn't just concern the fate of humans and the blue planet. Its subject is also intimations—what the physicists on the Muon g-2 project call “hints.”

As it happens, they are hints of the same thing: immortality.


The central contention of physics has it that the building blocks of the universe will endure even if, or even when, the humans who tally them, and the planet we live on, all die. To see into the deathless universe is to try to see nothing so flamboyant as Wordsworth's favorite daffodils and walnut groves, but to peer into the coldest spaces, the black holes and the fractional electric charge of theoretical subatomic particles. These entities have no blood flow, of course, but also no DNA; they're not susceptible to pandemics, however virulent, or the dividends and ravages of carbon. They don't live, so they don't die. To model the universe as precisely as possible is to try to see the one thing that even the strictest atheist agrees is everlasting—to try to achieve, in a lab, an intimation of immortality.

Back to the living world that's under our feet. Rovelli is right to caution against the potential delusions of those who are greedy for eurekas. But, as a fellow physicist with a radical streak, he is also sympathetic to their ambitions, a drive to “learn something unexpected about the fundamental laws of nature.” To Rovelli, whose latest book describes quantum mechanics as an almost psychedelic experience, a truly radical discovery entails the observation of phenomena that fall outside three existing frameworks in physics: quantum theory, the Standard Model of particle physics, and general relativity. Only by blowing up one of those frameworks can one achieve the kind of immortality that scientists get, the glory of someone like Einstein or Heisenberg.

But to keep looking, as Rovelli has, as Fermilab has with this study on the muon's magnetism, is also to apprehend hints. To follow hints. In that way, the physicist's work and the poet's are the same. And if Wordsworth is right, immortality can be found, of all places, in the hint—the staggering proposition by nature itself that, in spite of all the dying around us, something of all we love might be imperishable, might still flicker or shine or wobble when the rest of our world is gone.

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