Any sufficiently advanced extraterrestrial civilization may well find a considerable attraction in surrounding itself with a vast protective container and carrying on its activities unhindered, and perhaps even unnoticed, by the outside universe. Efficiency of energy use, possible preservation from the adverse effects of cosmic radiation and other unpleasant consequences of living in our sometimes violent galaxy, not to mention remaining hidden from any unfriendly beings who may be marauding through space – the advantages could be endless.
I touched on this subject in an early webpost in this series, The Lonely Universe Part 2: Is There Anybody There? in the context of Dyson spheres – those theoretical colossal structures which might enclose an entire star, with the inhabitants living on the inner surface of the sphere. It formed the basis of Bob Shaw’s memorable, and award-winning, 1975 science fiction novel Orbitsville, where the enormous scope offered to intelligent extraterrestrials from such a structure is clear. We see entire societies existing in such an enclosed environment, possibly not even fully realising where they are, though the task of getting out again, for a group of astronauts trapped inside, is nowhere near as straightforward as they might have wished.
In practice, the construction of such a habitat would be more likely to follow Freeman Dyson’s original idea of a series of orbiting satellites rather than a continuous sphere encasing a star, which is probably not feasible. However, Ken Roy and his colleagues have provided a smaller scale, and definitely more practical, approach to the same goal in Shell Worlds: An Approach to Terraforming Moons, Small Planets and Plutoids (JBIS, January 2009).
They showed how enclosing a small planet or large asteroid in a shell could be achieved, with compression due to gravity balanced by atmospheric pressure. A habitable environment within could enable terraforming of the planetary surface, and ultimately the development of a self-sustaining ecology. More recently, in Shell Worlds: The Question of Shell Stability (JBIS, October 2014), the same authors have confirmed that a material shell supported by atmospheric pressure would require no active measures to support it provided the planet or asteroid was large enough.
With artificial lighting to replicate sunlight, temperature could be controlled, and such a world could provide all the necessary conditions for civilized life, except perhaps for gravity which would be dictated by the size of the central body. Even then, appropriate changes, if necessary, to the physiology of the beings living there would probably not be beyond a truly advanced society. The outside of the shell would be available for industrial facilities, spaceports and so on. It would not even need to orbit a star, though the authors suggest that the quiet and peaceful conditions around red dwarf stars might be particularly appealing to a race requiring a pleasantly stable existence.
Or such a world could be free-floating in interstellar space. Inside their shell, the inhabitants might effectively travel in comfortable style, generation after generation, throughout the galaxy. Back in Odyssey 29, we talked about so-called “rogue” planets which could exist between the stars, and how we here on Earth might not even know that they are there. Anyone familiar with the classic Doctor Who serial The Tenth Planet from the mid-1960s will recall the wandering planet Mondas which arrived, rather unexpectedly, near Earth. And that turned out to be the home of the Cybermen.
An artificial shell around a world, perhaps even made with a view to concealing what lies within, could easily stand a strong chance of escaping detection. It’s just possible that an advanced alien civilization might be nearer than we think. Possibly a lot nearer. And we wouldn’t know it.
Richard Hayes, Assistant Editor (Odyssey)