Could We Build Our Own Dyson Sphere?
Many readers have openly questioned why the behavior of the light from the star KIC 8462852 is so unusual, and they centered on the sci-fi theory of a Dyson Sphere of alien superstructures encircling the star in order to harness its energy. But if anything, a Dyson Swarm—a loose collection of a structures rather than a solid sphere—is far more likely, given the immense amount of material needed to encapsulate a star from an immense distance. But gravity is an even bigger challenge. Popular Mechanics spoke with Stuart Armstrong, a research fellow at Oxford University’s Future of Humanity Institute who has studied megastructure concepts:
The Sphere would not gravitationally bind to its star in a stable fashion. This is perhaps counterintuitive; you might think that a perfect sphere around a star would be stable. But if any part of the sphere were nudged closer to the star—say, by a meteor strike—then that part would be pulled preferentially toward the star, creating instability.
That’s too bad. If it could be stabilized, a Dyson Sphere built at 93 million miles from the sun, the same distance as the Earth, would contain about 600 million times the surface area of our planet in its interior. However, comparatively little of the surface would be habitable on account of a lack of gravity. By spinning the whole sphere, you create gravity in the form of centrifugal force along an equatorial band. But this rotation would wrack the megastructure with yet more destructive stress.
So any sphere would look much closer to this illustration by Rick Sternbach, published in Future magazine in 1979:
Could a Dyson Swarm be built around our own sun? George Dvorsky explores the tantalizing question:
[Stuart] Armstrong’s plan sees five primary stages of construction, which when used in a cyclical manner, would result in increasingly efficient, and even exponentially growing, construction rates such that the entire project could be completed within a few decades. Broken down into five basic steps, the construction cycle looks like this:
1. Get energy
2. Mine [the planet] Mercury
3. Get materials into orbit
4. Make solar collectors
5. Extract energy
The idea is to build the entire swarm in iterative steps and not all at once. We would only need to build a small section of the Dyson sphere to provide the energy requirements for the rest of the project. Thus, construction efficiency will increase over time as the project progresses. “We could do it now,” says Armstrong. It’s just a question of materials and automation.
And yes, you read that right: we’re going to have to mine materials from Mercury. Actually, we’ll likely have to take the whole planet apart. The Dyson sphere will require a horrendous amount of material-so much so, in fact, that, should we want to completely envelope the sun, we are going to have to disassemble not just Mercury, but Venus, some of the outer planets, and any nearby asteroids as well.
A reader thinks all that won’t be necessary:
Our civilization will harness fusion power LONG before we develop the ability to make a Dyson’s sphere. With fusion we essentially have the ability to make our own suns. If we don’t have enough space or run out of water, we could build fusion reactors on any moon or planet in our solar system containing water. This would be technologically much easier and far cheaper than a sphere. Fusion will provide an essentially limitless power source.
Update from a reader who’s a “PhD student in particle accelerator physics”:
I find most commentary on the KIC 8462852 is not engaging with the most distinctive feature of the signal—that it is aperiodic. To quote the paper:
KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux down to below the 20% level. The dipping activity can last for between 5 and 80 days.
This would appear to rule out orbiting objects that regularly occlude the star, whether they are naturally occurring or artificial. Even in the case of multiple objects orbiting the star with different periods, the resulting signal would be periodic. The original paper (section 4.4.3) even considers and disfavors the hypothesis that there was a recent planetary collision, with fragments orbiting the star as they break up, which would change the nature of the signal with each pass. Ultimately the signal is just too aperiodic for even that scenario (and whatever the equivalent of that scenario in alien activity would be).
Aperiodic signals are in general associated with three types of systems—random discrete events, complicated/chaotic systems, and information encoding.
1) The passing swarm of comets is an example of “random discrete events.” In this case there is no meaning in the relative timing of the dips in luminosity—its aperiodic because its different comets each time. The observations would remain aperiodic and may eventually stop.
2) An example of a chaotic system would be a solar system thrown into orbital turmoil by an external event. An example of a complicated system would be an alien transportation hub. In both cases, the occlusions are interrelated but part of a system so vast as to be rendered incomprehensible. The feature to look for is a power law. If we plot the rate of luminosity dips against the size of the luminosity dips a pattern could emerge.
3) The third possibility, information encoding, is directly associated with life. In What is Life?, Edwin Schrodinger made the case that living things are made from encoded information and that that encoded information must be stored in “aperiodic crystals”—permanent objects that deviated from simple patterns (the DNA double-helix would be discovered 9 years later). Wright and the SETI project are looking a kind of alien morse code, aperiodic patterns transmitted from a distant star. If the KIC 8462852 signal is alien morse code, 2 bit/year is an awful data transmission rate for a staggering cost. Still, I can see why SETI might want to point their radio dish in that direction.
Hope that helps.