This is possible (or would be possible) only to the extent that the multiple grids of the City layer are also interfaces to other layers of The Stack. The Earth layer provides, for example, the incredible energy necessary to feed the physical appetites of the City layer ’ s composite urbanism. Its epidermal imperative for seeing and sensing is not only a substrate to the City layer; it also becomes an operative logic of interfacial control and composition (more on this below). The Cloud layer provides the generative and reactive ambient supercomputing that makes urban envelopes and Interfaces active and brings them into other formal and informal political geographic dramas. While the Cloud may see urban nodes and fabrics as like any other material for computational expression, its main switches are themselves gathered into tight rings of intensive transcontinental hubs, centralizing bandwidth economies into a specific few cellular cities. Away from those bandwidth capitals, smaller Cloud data centers, assembly factories, fulfillment centers, call centers, and shipping ports dot more remote geographies and gather itinerant laborers into their midst (or, alternatively, protect themselves against all human contact). In special cases, Cloud platforms design their own architectural footprints by gathering their higher-level cognitive-managerial functions into megastructural corporate headquarters, often city-scale buildings with backs turned on their immediate location (more on these below). Just above the City layer in The Stack, the Address layer provides network presence for any “ thing ” within the urban landscape and for the potential of communication among them. Unlike transnational postal systems, this layer doesn ’ t address sites based on their adjacent positions on the Earth ’ s surface, and unlike the formal addressing of parties by a modern legal system, it is available to potential addressees at very different spatial or temporal scales and even degrees of physicality and abstraction. The territories of addressed instances within the larger expanse of the City layer are named, organized, and made coherent and meaningful by the Interfaces that turn maps of addressable options into practical instruments. For the User, these maps cohere the range of possible interactions and transactions not only with the City layer, but also with the Cloud and Earth layers as mediated through it; Interfaces provide a channel for the User to model and monitor his or her own position within the range that they describe. Furthermore, The Stack is not only mediated through the City layer; the entire apparatus also expresses itself at the scale of the city and the built environment, and it does so in sometimes contradictory ways, characterized as much by centralization (e.g., the continental consolidation of key bandwidth channels into meganodes and megacities) and decentralization (e.g., the global predominance of increasingly powerful mobile handsets as an essential provision for everyday urban life). <sup>11</sup>
City Layer
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