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Ecumenopolises

Densely populated worlds, either planets or large megastructures

Ecumenopolis
Image from Tasp
Colossos, a densely populated shellworld at Rho1 Sagittarii; large seas of fresh water alternate with megacities on this level.
An Ecumenopolis is a world with a high density of embodied population, often largely covered with urban landscape with closely-packed urban centres. Another term for the same concept is World City. In most ecumenopolises these urban centres are separated by regions of less-populated parkland, or by seascapes, which allow the population to pursue healthy recreational pursuits, but the average population density of a typical ecumenopolis is still considerable.

Worlds with particularly high populations may be located on the surface of terrestrial planets, or floating in the oceans of water worlds, or suspended in the atmospheres of gas giants. However the most highly-populated ecumenopolises can be found on large megastructures such as Banks Orbitals or supramundane worlds. Nearly three quadrillion modosophonts live on Metropolis Ring City (about 2.8% of all embodied sophonts in the Terragen Sphere), and several megastructures in the Mutual Progress Association have populations in the trillions. Very large ecumenopolises are very rare, and most city worlds have populations in the tens of billions.

On Metropolis Ring City the average population is around 46 thousand persons per square kilometre, some smaller ecumenopolises have even denser populations, but most are somewhat less crowded, comparable to the typical urban density of a large city but covering a much larger area. Often the urban centres on an ecumenopolis are collected into tightly-packed megacities, with comparable areas of wilderness between.

Roanoke
Image from Steve Bowers
Roanoke, a city-world in the Bolobo system

Society on an Ecumenopolis

Most locations in the Terragen Sphere have a fairly low non-virtual population density, coupled with various kinds of post-scarcity economy which allow inhabitants to live a comfortable life in relatively exclusive surroundings. Even very large megastructures such as Cableville tend to have a low population density. Using hi-bandwidth communication systems, even a widely-spread culture can maintain a high level of connectivity. But some modosophonts prefer the closely-packed existence of urban culture; one expression of this tendency is the world-city.

Because they live so close to other people, the inhabitants of an ecumenopolis tend to have a large circle of friends, and an even large circle of acquaintances; most people who live on such a world utilise a range of memory applications within their exoself to keep track of the various large and complex social networks they may belong to. People who live in an Ecumenopolis almost always have a very large Dunbar number, and as many of them are long-lived individuals they will have a large database of past acquaintances that they might wish to recollect (in significant detail) and reconnect with for various reasons.

On a crowded world there are many and varied opportunities for collaboration, particular in musical, architectural and other artistic activities, and an ever-increasing variety of sporting pursuits with large numbers of participants. To improve this connectivity some citizens utilise technotelepathy and group-mind networks, and some mega-cities are organised as a collective mentality capable of interacting as a single mind as required; but numerically most citizens of ecumenopolises are single individuals capable of interacting with their fellow citizens on a variety of levels.

Even on Metropolis Ring City each citizen lives in an apartment with a minimum volume of ten thousand cubic metres per person, often stacked up into quite tall arcologies or skyscrapers that reach above the clouds, below the ring floor, or scaling the heights of the ring wall. To increase their comfort level, many citizens incorporate realistic [b]surrounds[/b] (localised virtual environments) which can increase the apparent size of their environment to an arbitrary extent. Some ecumenopolises support large numbers of virtual sophonts as well as embodied ones, increasing the size of the potential social community; other world cities have relatively few virtuals, although they often lave a large vot population which perform various tasks.

A typical ecumenopolis has extremely good personal rapid transport of all kinds, from automated cars and mobile lift capsules that can race up and down and between the tall buildings in safety; citizens often travel to various artistic and sporting events, or simply promenade along the open walkways and squares at various levels in order to see and be seen.

Public order and emergency services

Because so many people live so close together, there are significant dangers which may arise at any time. Although there is little or no financial crime because of the prevalence of post-scarcity abundance, anti-social behaviour can sometimes be a problem, and most city-worlds have automated systems that maintain public-order in various ways - mostly sophisticated vots using gentle persuasion to reduce conflicts, or non-lethal weapons such as utility foam or other mobility denial systems when that fails.

Sometimes a public event may be unexpectedly popular, and large crowds of disparate sophonts may all turn up in a restricted space such as a public square or parkland, in an event known as a 'flash crowd'. This can lead to overcrowding, and potentially to crush events and even fatalities. For this reason large numbers of crowd marshals may be deployed at short notice; sometimes sophont citizens delegated for the purpose but more often competent but non-sophont vots inside versatile bodymorphs.

A similar mixture of volunteer sophonts and vots make up the emergency services; firefighting and environmental management (every structure in a typical ecumenopolis is guaranteed against fire and environmental damage, but sometimes extreme events occur which cannot be handled by autromnatic systems); medical services and (rarely) conflict resolution. Sometimes terrorists or special interest groups may deliberately cause damage and havoc, and these events must also be resolved by specialised response units.

Urbanised Banks Orbital Megastructure

Metropolis Ring City
Image from Galaxiel
Metropolis Ring City, by far the largest of all ecumenopolises.
Metropolis Ring City houses tens of thousands of S:1 transapients, many of them tribeminds, who can organise this vast population; however some ecumenopolises, such as Kbem in the Yall-Ull system, have no transapients at all, and rely on modosophont-level organisation and resources.

Ecumenopolises require vast amounts of food, water and environmental management, almost all of which must be achieved artificially using imported or generated power. This means that they produce significant amounts of waste heat, all of which must be radiated by active means. To prevent overheating most ecumenopolises are shielded by a sunshade, often incorporating power collection systems that can help with the city-world's energy budget.

Examples of Ecumenopolises in the Terragen Sphere

Metropolis Ring City; a Banks Orbital, population 2.946 quadrillion
Colossos ; a shellworld surrounding a gas giant at Rho1 Sagittarii, population 488 trillion
Trip, a terrestrial city-world, population 4 trillion
Roanoke, a planet in the Bolobo system covered in a single city, population 36 billion.
Yumika, a city-world in the Oquendo, population 34 billion.
Kbem, an ecumenopolis habitat in the Yall Ull system, population 21 billion.
Kbem Ecumenopolis
Image from Steve Bowers
Kbem Ecumenopolis, a densely populated habitat honeycombed with habitable structures, inside and out
 
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Appears in Topics
ArchitectureHigh Tech SocietiesInfrastructure
Megascale Engineering
 
Development Notes
Text by Steve Bowers
Additional material by Grawa427
Initially published on 14 March 2025.

 
Additional Information
Ecumenopolises by Isaac Arthur
 
 
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