[Image: Collage by BLDGBLOG of public domain images from NASA and the Library of Congress.]
An opportunity to explore the use of muons as a tool for architectural and archaeological imaging came up this summer while I was in Europe for my Graham Foundation project, “Invisible Cities.”
Muons are cosmic particles, similar to neutrinos, that pass through us constantly—but also through solid rock and concrete, through cathedrals, pyramids, dams, and roads. In the 1960s, physicist Luis W. Alvarez of UC Berkeley launched a whole new form of architectural imaging when he realized that, if you can capture muons as they leave various structures—in Alvarez’s case, the Pyramid of Khafre outside Cairo—then you can create an image of what they’ve just passed through.
This is now known as muography—muon photography. Muography, as I describe it in a new story published in this weekend’s Financial Times Magazine—my first cover story!—is “one part comic-book superpower, one part cosmic photography.”
Fast-forward to 2022, and muons are on the cusp of being adopted as a new tool for infrastructural inspection, allowing engineers to peer inside the supports of bridges and freeways, inside the concrete of hydroelectric dams and high-rise apartment blocks, even inside the thick, dense masonry of Renaissance cathedrals and ancient temples, looking for signs of corrosion, decay, and impending collapse.
For the Financial Times, I went to Berlin to meet an engineer leading Germany’s federal effort to test and certify muon-inspection technology, with the goal of turning an obscure physics experiment into a commercial tool. The lab I visited there was incredible, an industrial space lit by skylights in the city’s southwest suburbs, filled with massive concrete monoliths, each marked with Agnes Martin-like grids. These dense concrete slabs—modern obelisks—are used to test non-destructive imaging technologies. In the piece, I compare the lab to a Brutalist sculpture garden.
While German authorities (in this case, working with a physicist at the University of Glasgow) work to set standards and protocols for muography in the global marketplace, the most charismatic proof-of-concept for muons’ future use might come from Florence, Italy.
That’s where a muon detector will likely be installed later this year, imaging the walls of Brunelleschi’s famous dome. The cathedral there is a constantly settling, dynamic system—far from static—and the overwhelming weight of Brunelleschi’s dome has produced large cracks in the church walls below. Those cracks have been growing wider for centuries, leading to enough concern that the entire church is now enreefed with measuring devices—“giving it a solid claim as the world’s most carefully monitored structure,” as the New York Times wrote as long ago as 1987.
[Image: Looking up into Brunelleschi’s Dome, Florence; photo by Geoff Manaugh.]
Because Brunelleschi left behind no drawings or even textual descriptions of how his dome had been assembled, today’s engineers remain in the dark about how to reinforce it. With walls up to two meters thick, the masonry is too dense for traditional imaging methods, such as radar and ultrasound. But muons can easily pass through the entire cathedral; they are generated freely by natural reactions between cosmic rays and the Earth’s upper atmosphere; and they can be detected with a device that requires almost no electricity to run.
In any case, I’ve been obsessed with muons for more than a decade, so this was an absolute thrill to report. The Financial Times has a rigorous paywall, however, so it will be hard to read the piece without a subscription, but if you see a copy of the magazine kicking around at your local newsstand, grab a copy and dive into the cosmic future of large-scale architectural imaging.
[Thanks again to the Graham Foundation for Advanced Studies in the Fine Arts for funding this research. A great, but not widely known, book on Brunelleschi’s dome, with superb illustrations, is Brunelleschi’s Cupola by Giovanni Fanelli and Michele Fanelli.]