As metaphor, megastructures have the potential to be powerful: as explanations for real phenomena, they are petty, motivated by the same impulse which makes journalists always refer to Star Wars when writing a story about a planet with two suns, or crack feeble Doctor Who jokes when writing about the theory of time travel.
Tabby’s Star is a genuinely exciting mystery, and to read articles which rush through the halting attempts by scientists to provide an astrophysical explanation in order to get to the part where they can write about megastructures is to watch the scientific be eclipsed by the merely science-fictional.
The objects supposed to be eclipsing Tabby’s Star are always referred to as “alien megastructures”, an adjective which on first glance is redundant – the star is thousands of light years away, and humans don’t know how to build megastructures. As I argued in my megastructure post from last year, in science fiction we project the ability to construct artefacts on the scale of solar systems onto aliens or our own machine descendants to avoid the uncomfortable fact that even if we had the technology to build such monstrosities, we lack, or believe that we lack, the ability to muster the social and economic resources which they require. All megastructures are alien.
Considered in the light of what we actually know, however, the opposite is true. We don’t know if aliens exist, and we don’t know anything about what their societies and psychologies might be like. And the ability to imagine megastructures is not even a human universal: it arises from a very specific time and place, from the triumph and downfall of the dream of an ever-expanding rationalist civilisation. The megastructure is born in the communist galactic epics of Olaf Stapledon and the manic space operas of E E Doc Smith, takes flight on the dreams of Cold War theorists like Dyson and Kardashev, and begins to collapse under its own ironic weight in the middle of Larry Niven’s Ringworld series in the seventies and eighties.
When we start speculating about Dyson spheres as the explanation for astrophysical effects, rather that using them as metaphors in fiction, it’s worth listing the assumptions which underly them:
- once a civilisation becomes industrial, it will remain in a state when energy capture and expansion are its absolute priorities;
- the most plentiful source of energy in a typical solar system is the radiation from its star;
- somehow, the economic and technical means to build a Dyson sphere or swarm are achievable;
- our current knowledge of stellar astrophysics is total: in other words, there are no factors, unknown to us today, which would make building a Dyson sphere or swarm harmful or impossible
The shakiest of these assumptions seems to me to be the first. We can’t imagine alien psychology, by definition: in general, the aliens in sf are projections of racial stereotypes, whether they are warlike Hun/Klingons or austere, contemplative Vulcans. Even contemporary efforts to imagine truly inhuman aliens – the eusocial galaxy-spanning civilisation of Charles Stross’ novella “Missile Gap”, or the terrifying and asentient “scramblers” in Peter Watts’ Blindsight – are specific to the culture which created them: arising from a very early-twenty-first-century pessimism about human consciousness and society as fallible and weak, at the mercy of creatures who are better equipped to follow a biological imperative which is simply another version of the grow-expand-maximise-capture drumbeat.
The common failure in all of these dreams is the idea that we can know what aliens would do, what a civilisation with better technology or organisational skills or more ruthlessness could accomplish: this line of speculation leads to aliens who are insane caricatures or nightmarish parodies of the worst excesses of the industrial civilisation that gave birth to them.
The star AR Scorpii appears to be a binary pair of a red and white dwarf: the latter is blasting beams of electrons travelling very close to the speed of light, which, when they impact upon its companion’s surface on the side visible to Earth, cause its brightness to fluctuate violently. This explanation is only an hypothesis, like all of our ideas about the stars. I think that it’s better to contemplate the strangeness of what might be out there than to merely use these remote and strange lights as projector bulbs for the shadows cast by our human, all-too-human megastructures.