A swarm of McKendree cylinders and Deep Wells within a small Bok globule
First discovered during the early Atomic Age by the astronomer Bart Bok, Bok globules are dense, dark clouds of gas and dust scattered across interstellar space. They mass between two and fifty solar masses, are generally about a light-year across, and are a primary source of new star formation.
A Bok swarm consists of a large cloud of habitats, often numbering into the tens of millions, built within a Bok globule and using it as a source of matter and energy to support and extend the swarm. Individual swarm habitats may range in size from small Bernal spheres and O'Neill cylinders a few kilometers across all the way up to full size McKendree cylinders thousands of kilometers in length. Energy for the swarm is usually provided by a combination of standard conversion reactors and several small Deep Well Industrial Zones created on site for materials processing. Actual matter for construction and energy generation is harvested from the mass of the local Bok globule using high energy lasers to ionize the local dust and gas which is then collected via electromagnetic charge-nets and diverted to the deep well zones for transmutation into whatever elements are required.
Bok swarm culture tends to be both cosmopolitan and highly insular. The large number of habitats is home to a huge variety of societies and species, many of which are highly individualized and may not be found anywhere outside of their home swarm. At the same time, the nearest inhabited star systems may be tens of light-years away. Wormholes and Deeper interstellar beam-lines have yet to connect any of the known swarms and starships are few and far between. As a result, the average swarm inhabitant is much more likely to be interested in visiting their comparatively near neighbors, many of whom are already interesting and strange, but only a few light-minutes or hours away, than taking the time and resources required for an interstellar trip to accomplish essentially the same thing. Still, over the last thousand years or so there has been commerce between some swarms and their near stellar neighbors. In addition, those travelers who do make the journey have begun to report back on their experiences in ever growing numbers on the Known Net tourism channels. Already a few hardy entrepreneurs in the NoCoZo and Orion Federation have begun offering "new experiences for the discerning extreme vacation enthusiast" and it seems likely that the splendid isolation of the swarms will not persist for much longer.
One of the most interesting aspects of the Bok swarm phenomenon is its potential for growth. A Bok globule represents a large mass resource, mostly unconstrained by any sort of significant gravity well, and therefore readily accessible. The need to actively collect and then transmute all materials required does present challenges, but with proper logistics planning the growth potential for a determined civilization is considerable. In principle, a single Bok swarm could grow to the point of rivaling the material resources and living area of even the largest current megastructures and maintain itself for time periods comparable to the most ambitious deep time habitats. This fact has not been lost on those civilizations which most concern themselves with such things, and the relevant Net channels are seeing an increasing amount of speculation and rumor that any day now the Mutual Progress, or the Negentropists, or perhaps even the Keterists will announce some vast project centered on a Bok globule or some even grander cosmological artifact. Given the proclivities of these empires, it is perhaps only a matter of time.
Bok swarms are a comparatively recent phenomenon, dating from the mid-8700s and continuing into the Current Era. While their exact origins are unclear, the most popular current theory is that they originated from an alliance of radical elements from the Deeper Covenant, Metasoft Version Tree, and several semi-outcast Backgrounder cultures that advocated increased contact with the wider galaxy at large. Regardless of their origins, the Bok Swarm cultures seem destined to become a significant element in the future development of the Civilized Galaxy.