Agency of the Subsurface

[Image: The Heathen Gate at Carnuntum, outside Vienna; photo by Geoff Manaugh.]

Last summer, a geophysicist at the University of Vienna named Immo Trinks proposed the creation of an EU-funded “International Subsurface Exploration Agency.” Modeled after NASA or the ESA, this new institute would spend its time, in his words, “looking downward instead of up.”

The group’s main goal would be archaeological: to map, and thus help preserve, sites of human settlement before they are lost to development, natural decay, climate change, and war.

Archaeologist Stefano Campana, at the University of Siena, has launched a comparable project called Sotto Siena, or “Under Siena”—abbreviated as SOS—intended to survey all accessible land in the city of Siena.

[Image: A few of Siena’s innumerable arches; photo by Geoff Manaugh.]

That project’s goal is primarily to catalog the region’s millennia of human habitation and cultural artifacts, but, like Immo Trinks and his proposed ISEA, is also serving to document modern-day infrastructure, such as pipes, utilities, sewers, and more. (When I met Campana in Siena last year, I was interested to learn that a man who had walked over to say hello, who was introduced to me as an enthusiastic supporter of Campana’s work, was actually Siena’s chief of police—it’s not just archaeologists who want to know what’s going on beneath the streets.)

I had the pleasure of tagging along with both Trinks and Campana last year as part of my Graham Foundation grant, “Invisible Cities,” and a brief write-up of that experience is now online over at WIRED.

The article begins in Siena, where I joined Campana and two technicians from the Livorno-based firm GeoStudi Astier for a multi-hour scan of parks, piazzas, and streets, using a ground-penetrating radar rig attached to a 4WD utility vehicle.

[Images: The GPR rig we rode in that day, owned and operated by GeoStudi Astier; photos by Geoff Manaugh.]

We stayed out well past midnight, at one point scanning a piazza in front of the world’s oldest bank, an experience that brought back positive memories from my days reporting A Burglar’s Guide to the City (alas, we didn’t discover a secret route into or out of the vault, but just some fountain drains).

In Vienna, meanwhile, Trinks drove me out to see an abandoned Roman frontier-city and military base called Carnuntum, near the banks of the Danube, where he walked me through apparently empty fields and meadows while narrating all the buildings and streets we were allegedly passing through—an invisible architecture mapped to extraordinary detail by a combination of ground-penetrating radar and magnetometry.

“We want to map it all—that’s the message,” Trinks explained to me. “You’re not just mapping a Roman villa. You’re not mapping an individual building. You are mapping an entire city. You are mapping an entire landscape—and beyond.”

An estimated 99% of Carnuntum remains unexcavated, which means that our knowledge of its urban layout is almost entirely mediated by electromagnetic technology. This, of course, presents all sorts of questions—about data, machine error, interpretation, and more—that were explained to me on a third leg of that trip, when I traveled to Croatia to meet Lawrence B. Conyers.

[Image: A gorge leading away behind the archaeological site I visited on the island of Brač, Croatia; photo by Geoff Manaugh.]

Conyers is an American ground-penetrating radar expert who, when we met, was spending a couple of weeks out on the island of Brač, near the city of Split. He had traveled there to scan a hilltop site, looking for the radar signatures of architectural remains, in support of a project sponsored by the University of Colorado at Boulder.

Conyers supplies a voice of caution in the WIRED piece, advising against over-relying on expensive machines for large-scale data collection if the people hoarding that data don’t necessarily know how to filter or interpret it.

[Image: Lawrence Conyers supervises two grad students using his ground-penetrating radar gear; photo by Geoff Manaugh.]

The goal of an International Subsurface Exploration Agency could rise or fall, in other words, not just on questions of funding or public support, but on the limits of software analysis and human interpretation: are we sure that what we see on the screens of our machines is actually there, underground?

When we spoke in Siena, Campana used the metaphor of a medical biopsy, insisting that archaeologists and geophysicists will always need to excavate, not just for the recovery of historical artifacts and materials, but for verifying their own hypotheses, literally testing the ground for things they think they’ve seen there.

Archaeologist Eileen Ernenwein, co-editor of the journal Archaeological Prospection, also emphasized this to me when I interviewed her for WIRED, adding a personal anecdote that has stuck with me. During her graduate thesis research, Ernenwein explained, she found magnetic evidence of severely eroded house walls at an indigenous site in New Mexico, but, after excavating to study them, realized that the structure was only visible in the electromagnetic data. It was no less physically real for only being visible magnetically—yet excavation alone would have almost certainly have missed the site altogether. She called it “the invisible house.”

In any case, many things have drawn me to this material, but the long-term electromagnetic traces of our built environment get very little discussion in architectural circles, and I would love this sort of legacy to be more prominently considered. What’s more, our cultural obsession with ruins will likely soon begin to absorb new sorts of images—such as radar blurs and magnetic signatures of invisible buildings—signaling an art historical shift in our representation of the architectural past.

For now, check out the WIRED article, if you get a chance.

(Thanks again to the Graham Foundation for Advanced Studies in the Fine Arts for supporting this research. Related: Through This Building Shines The Cosmos.)

Through This Building Shines the Cosmos

[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.]