Photograph by Janus Kopfstein

On a bright Saturday morning earlier this month, about thirty people gathered inside a large, dimly lit warehouse in Chelsea, hunched over smartphones, hand-drawn maps, and computer-networking equipment. Members of the group were briefed on the situation that would confront them: at about one o’clock, the Internet would go down. After that, they would be able to communicate wirelessly only through a network that they were about to create themselves.

This was only a test—a cross between a role-playing game and a fire drill. The attendees were at Eyebeam, an art and technology space, for a practice Internet apocalypse, or “Practocalypse,” intended to teach them what to do if external forces—extreme weather, tyrannical governments—cause our communications systems to fail.

The goal was to create a “wireless mesh network”—a collective of radio nodes, each one equally responsible for routing the communications of connected users. The Practocalypse version of the network would be mobile and ad hoc, relying entirely on peer-to-peer connections between devices, rather than on centralized servers. It would be a bit like a neighborhood ham-radio club, except using cell phones, laptops, and other Wi-Fi-enabled devices. Guiding the attendees were software engineers from the Guardian Project, a not-for-profit that develops free apps for resisting censorship and surveillance, and Commotion, a project for building alternative networks, which is led by the New America Foundation’s Open Technology Institute. People have already deployed similar networks in places from Tunisia to India, Detroit, and Red Hook.

It’s comforting to know that someone is preparing for Internet Armageddon, given the events of recent years. In 2011, when Hosni Mubarak, then the President of Egypt, instituted a country-wide Internet and cell-phone blackout during that country’s revolution, the concept was relatively new. These days, stories of state-mandated Internet shutdowns have become almost commonplace, forcing us to rethink networks whose resilience we once took for granted. A series of Internet outages in war-torn Syria has coincided, according to critics, with the government’s major military offensives. In Turkey, where evidence of corruption circulated on the eve of national elections, Prime Minister Recep Tayyip Erdoğan blocked access to Twitter and then YouTube, painting social media as a menace, even as millions of citizens circumvented the ban. Even the United States has toyed with the idea of an “Internet kill switch”: the Department of Homeland Security has “a shutdown and restoration process for use by commercial and private wireless networks during national crises,” though when and how it would be implemented is unclear; when the Electronic Privacy Information Center requested documents detailing the process through the Freedom of Information Act, the papers were almost entirely redacted.

Not all downtime is government-sponsored. In 2011, an elderly woman scavenging for copper accidentally severed a section of fibre-optic cable, causing Internet blackouts in parts of Georgia, Armenia, and Azerbaijan. A year later, thousands of Americans suffered lengthy outages—and worse—as Hurricane Sandy slammed into the East Coast. The storm also damaged a data center in lower Manhattan, temporarily taking down Gawker, the Huffington Post, and BuzzFeed.

Whatever the scenario, Ryan Gerety, a senior field analyst for the Open Technology Institute, told the Practocalypse participants that there is a pressing need to build local, decentralized networks. “We haven’t designed our technology to give people control of their infrastructure at all,” she said. “The normal way to communicate, even if we’re standing in the same room, is through a Google server.” Mesh networks, on the other hand, can theoretically be free from the grasp of governments and corporations.

Of course, this requires a lot of preparation. The Commotion team had already set up a tiny mesh network inside Eyebeam, broadcast by a few small Wi-Fi base stations located throughout the space. The first task of the Practocalypse was for participants to install a suite of Guardian Project apps on their phones without using the Internet. Some people in the room already had those apps on their devices, and they traded them with others using Bluetooth, near field communication (a hardware feature that lets newer phones swap data simply by touching), and a program called Kerplapp, which allows a device to make its installed apps downloadable by anyone on the local network. Unfortunately, much of this proved impossible for anyone relying on an iPhone; unlike devices running Google’s Android operating system, Apple’s platform requires all software to be installed through its heavily curated App Store. (The Guardian Project makes some, but not all, of its apps for both platforms.)

Later, the group went on a mission to extend its own network along the High Line, the elevated pedestrian park running along Manhattan’s West Side, while also tracking down several scavenger-hunt items (a “keep off the grass” sign, a condominium marked with the name George). Five people acted as human routers, carrying battery-powered Wi-Fi access points running Commotion’s software, which allowed the signal to be chained from one node to the next. The routers were said to have a range of a few city blocks, but the actual range turned out to vary, depending on factors like elevation and the positions of nearby buildings. Some Practocalypsers were able to send messages to their compatriots with an app called ChatSecure. Others concentrated on capturing the scavenger-hunt items with their smartphones, using an app called InformaCam, which records and encrypts useful metadata, in addition to images. But no one was able to relay images or text back to a node stationed on the far end of the network at Eyebeam. The Achilles’ heel of the whole endeavor, it turned out, was that there was no actual Internet apocalypse. The bustle of a pleasant Saturday afternoon on the High Line, crowded with hundreds of tourists using their devices, filled the airwaves with interference.

Still, if the group had been building a more permanent network during a full-blown Internet blackout, much of this would have become even more complicated: Which devices would relay the wireless signal? Where would we place them to guarantee fast and reliable service? How many nodes would be connected by cables, and how many could connect wirelessly? Which community members could, using their personal relationships, help expand the network?

The big lesson of the simulation was that building a post-apocalyptic network is hard. This wasn’t particularly surprising, but it was still alarming. Judging by the documents leaked by Edward Snowden, the former N.S.A. contractor, the “Internet apocalypse” might not arrive with a bang but through the slower and more subtle means of corporate centralization, censorship, and surveillance. The Internet is, by definition, a “network of networks,” one that grew over time from an American military grid to an all-encompassing infrastructure that guides our social, political, and economic activity. As we rely on the Internet to facilitate a growing list of ever more mundane activities, connecting everything from our phones to our refrigerators, we are frighteningly ill-prepared to create parallel networks of our own—the ones we may need the most.