Unbuild Your Own Solar System

by Duncan Lunan

Between 3 and 5 a.m. on Wednesday, August 9th, I took part in a long-distance video interview with Jimmy Church of the ‘Fade to Black’ programme in the USA.  There were three main topics which we discussed.  The first was the Sighthill Stone Circle, which has been extensively covered in Orkney News over the last three years.  The second was the mediaeval mystery of the Green Children of Woolpit  (Orkney News, June 19th and 26th, 2022), and the third was the mysterious interstellar object ’Oumuamua, on which I recently published a major article in the May/June issue of the US magazine Analog.  I’ve promised another for Orkney News in due course.  From there we went on to a more general discussion about interstellar civilisations.

Prof. Nikolai Kardashev postulated that there are three SETI-related levels of high-technology civilisation:  Type 1 controls the matter and energy of a planet, Type 2 the resources of a Solar System, and Type 3 the resources of a galaxy.  (N.S. Kardashev, ‘Transmission of Information by Extraterrestrial Civilisations’, in G.M. Tovmasyan, ed., Extraterrestrial Civilisations, Israeli Program for Scientific Translations, 1967.)  The ultimate example of a Type 2 is generally taken to be Prof. Freeman Dyson’s suggestion that an advanced civilisation might break up the planets of its solar system and build a shell around its star, to utilise all the matter and energy available to it  (Fig. 1) – hence the late Chris Boyce’s title for it, which I’ve used as my heading.  (F.J. Dyson, ‘Search for Artificial Stellar Sources of Infrared Radiation’ (Science, Vol. 131, 1959, reprinted in A.G.W. Cameron, ed., Interstellar Communication, Benjamin, New York, 1963.) 

Other scientists pointed out that with any imaginable technology a solid Dyson sphere was a scientific impossibility, because unless it had near-infinite strength it would shear if it rotated, and collapse if it did not. Dyson replied that he meant all along not to build a solid shell, but to surround the star with a shell of artificial asteroids  (Fig. 2). (‘The Search for Extraterrestrial Technology’ in R.E. Marshak, ed., Perspectives in Modern Physics, Interscience Publishers, 1966.)  Any interested reader can track down both papers and decide for themselves what he actually meant.  SF writers have always gone for the solid version, as far as I know. But even if it could be done, there are strong practical arguments against it.

Speaking to the Astronomers of the Future Club in Troon, in January 2022, Prof. Michael A. Garrett of Jodrell Bank suggested that a Kardashev 2 or 3 civilisation would be detectable, because it would use so much energy that it would disturb the infrared-to-radio power law for star formation in galaxies.  I’m not so sure about that:  in the ASTRA discussions leading to my book Man and the Planets (1983, Fig. 3), we agreed that ‘control’ implies restraint, or at least the possibility of it, as opposed to Freeman Dyson’s nightmarish vision of intelligence as ‘a purposeless technological cancer’, bringing destruction to one planetary system after another. 

Fig. 3. Man and the Planets, 1983, cover by Gavin Roberts, Waverider approaching Titan

A civilisation which was compelled to break up its planets to provide living space for population expansion cannot be said to be in control of its situation.  Chris Boyce’s ideas about the future of mind-machine interactions suggested a situation to us in which such a scenario might be desirable, or even necessary, but using one bad idea to meet the consequences of another is no recipe for survival.  Even the resources of an asteroid sphere must eventually be exhausted, after which fragmentation must follow, with asteroids cannibalising one another, until all that’s left is a great shroud of debris which the Sun gradually smooths into a vast, peaceful equatorial ring.  We concluded that to achieve true Kardashev 2 status a civilisation would have to become conservationist, and if Kardashev 2s collectively evolved to Kardashev 3s they would be galactic gardeners, not industrialists.  That may make them a great deal harder to detect – indeed, since we don’t see the wreckage of their failures, the proof of their success may be that we can’t see them out there.  We don’t see the wreckage of ‘megastructures’, on interplanetary scale or larger, much less a ruined galaxy like the Milky Way of Arthur C. Clarke’s The City and the Stars.  

In 1967 the late Andy Nimmo went to work in Zambia for several years, and left me his collection of science fiction magazines.  The same year my family moved house in Troon, and at the end of the move, in a bedroom piled at random with books and magazines, to calm down before sleep I picked a magazine off the nearest pile, which happened to be the January 1960 issue of Fantastic Stories.  The editorial by Norman Lobsenz was called ‘Keep out Private Solar System’, and featured the publication of Freeman Dyson’s paper, the previous year.  How long would it be, asked Lobsenz, before the idea featured in science fiction – and to the best of my knowledge it still hadn’t, seven years later.  Thinking it over, I recalled that in The Young Traveller in Space by Arthur C. Clarke, one of the books which cemented my fascination with astronomy and spaceflight 14 years earlier  (Fig. 4), he had stated that a straight flight from one planet to another when they were at opposition, both in line with the Sun, would require almost infinite energy.  Putting that together with what I’d learned since, from further reading and from Dr. Archie Roy’s lectures in astronautics and astrodynamics in first-year astronomy at Glasgow University, it would be virtually impossible for a rocket vehicle in orbit within a Dyson Sphere to land on the shell. 

The story sold to Galaxy, and the editors asked for my background because they were impressed by the rigorous Maths underlying it.  Too honest perhaps for my own good, I confessed that I’d calculated the ship’s orbital period from a very basic equation in Clarke’s story ‘Jupiter Five’, and the rest was back-of-the-envelope selection of the velocity vectors.  Despite that, the editors of Galaxy were sufficiently impressed to give ‘The Moon of Thin Reality’ the cover, in June 1970  (July in the UK edition), by a big-name artist, Jack Gaughan  (Fig. 5).  This caused immediate interest in my work – who’s the new guy who gets a Gaughan cover on his first published story? – and I realised that if ever I was to go full-time as a writer, this was the time.  I became self-employed at the beginning of October 1970, promptly selling my next three stories to Galaxy before the 1971 postal strike cut me off from the US market, and I took to writing nonfiction instead.

Throughout the month that my characters were inside the Dyson sphere, they kept up efforts to contact the occupants of the shell or at least their computer systems, all to no avail.  It may be no coincidence but an intuitive judgment, that for a long time all subsequent Dyson civilisation stories known to me, including Larry Niven’s Ringworld  (Fig. 6), Frederik Pohl’s ‘Cuckoo’ and the Next Generation episode that brought back Scotty  (Fig. 7), have portrayed them as collapsed.  The late Bob Shaw’s Orbitsville specifically portrayed one as a trap, a honeypot built to lure in starfaring cultures which might otherwise compete with the builders.  Once settled on the inside, such a culture has no material resources to draw on and can’t even see the stars any more.  While the solid sphere, Ringworld or even the asteroid swarm offer a huge range of alternative habitats, still everyone lives inside a sphere, a ring or an asteroid.  As Bill Ramsay said in the ASTRA discussions, “Going to a singularity is always dangerous”.  Iain M. Banks has portrayed thriving ‘Orbital’ rings in his Culture novels, but even they are vulnerable to warfare, with immense loss of property and life, as in Look to Windward  (Fig. 8). 

Dyson spheres could be no less vulnerable to natural hazards.  The technology which could create a Dyson structure could probably protect it from incoming comets, but the idea that there could be ‘stray planets’ orbiting freely in interstellar space was first advocated by Harlow Shapley  (Fig. 9).  Some, he suggested, might be large enough to have molten interiors and solid crusts  (Fig. 10), perhaps even supporting life  (Fig. 11).  (‘Crusted Stars and Self-heating Planets’, Matematica y Fisica Teorica Serie A 14, 1962). 

In a series of collaborations with Poul Anderson, the artist Chesley Bonestell created a cover for Analog in May 1968, featuring an icebound stray planet passing close to a star, with violent results on its surface  (Fig. 12).  The first possible example of a stray planet was found in 2016;  possible ones were indicated by gravitational lensing within the Kepler space observatory’s study field  (Fig. 13);  more have been found by the PanSTAARS observatory on Hawaii, and the one in Fig. 14 featured in NASA’s series of retro space tourism posters  (Fig. 15).  Wikipedia lists 33 possible ones, 4 of them doubtful but quite a few confirmed, but the accompanying article suggests that there could be far more, possible hundreds of thousand times as many in the Galaxy as there are stars, and many of them in the range between Jupiter and the smallest brown dwarf and red dwarf stars.  Even if one didn’t hit an outer planet, as H.G. Wells depicted in The Star, or pass through an asteroid swarm or hit a Ringworld or sphere, the disruptive effects of its gravitation could be catastrophic.

In 2017 there was a stir about KIC 8462852 (Tabby’s Star), which exhibited strange, erratic dips in brightness, leading to suggestions that it’s being orbited by alien ‘megastructures’.  Alternative explanations such as giant comets or debris from colliding planets were not accepted because either would generate large quantities of dust, not detected in the infrared signature of the star.  Nor could they account for a slow overall dimming of the star, over the 20th century at least, which was discovered when records were searched.  As it happens, ordinary-sized comets were then detected orbiting another class F star, like Tabby’s, 800 light-years away.  That’s only one-third nearer than Tabby’s, and their events don’t look like the Tabby’s Star dimmings  (Matt Williams, ‘Astronomers Find Comets Orbiting a Star 800 Light-years Away’, Universe Today, 30th October 2017).

A team at the University of Antioquia in Columbia suggested that there’s a gas giant planet about the size of Neptune in close orbit around Tabby’s Star  (about 0.1 AU from it), with a tilted ring around it which oscillates under the star’s pull, so that its occultations of the star’s light would follow a complex pattern.  (M. Sucerquia et al, ‘Anomalous Lightcurves of Young Tilted Exorings’, Monthly Notices of the Royal Astronomical Society, preprint 5th September 2017;  Matt Williams, ‘Is the “Alien Megastructure” around Tabby’s Star Actually a Ringed Gas Giant?’, Universe Today, 28th August 2017.)  But to account for the observed dimmings of the star, the ring would have to be a large one.

Fig. 16. Hypothetical uneven ring of dust orbiting KIC 8462852, also known as Boyajian’s Star or Tabby’s Star

Alternatively there could be a very large ring surrounding the whole star, but warped due to the presence of undiscovered gas giant planets  (Fig. 16), suggested by an international team including the discoverer Tabitha Boyajian  (Matt Williams, ‘Not an Alien Megastructure, a Cloud of Dust on a 700-day Orbit’, Universe Today, 6th October 2017).  The dust particles would be large, suggested by a dimming of the star in ultraviolet rather than a brightening in infrared.  But the hypothesis needs the giant comets as well, to explain the shorter dimmings – there were three in 2017 – and can’t explain the occasional freak brightenings of the star which were also discovered in the records (‘News Update:  Tabby’s Star Continues to Misbehave as Explanations Flounder’, Universe Today, November 2017.)  

‘Tabby’s’ is an F-type Main Sequence star which wouldn’t be expected to vary like that.  More massive than the Sun, it would be shorter-lived, burning out by the time it was the Sun’s age.  The late Prof. Krafft Ehricke suggested that evolution would proceed faster in such high-energy environments, and the Galaxy would belong to the F-star civilisations because they’d have the incentive to develop interstellar travel  (‘Astrogenic Environments’, Spaceflight, January 1972).  A Tabby’s Star civilisation may have opted for a stay-at-home Dyson Sphere, but on the arguments above, that would be a serious mistake for any advanced culture to make.  For the moment, at least, the warped dust cloud hypothesis holds sway.

Fig. 17. Asteroid sphere filling

Thinking about how a Dyson civilisation might nevertheless come into being, Dyson himself described how the planet Mercury might be dismantled as a first step  (in ‘The Search for Extraterrestrial Technology’ above).  He didn’t go on to suggest how it might be done for the other planets  (Fig. 17).  In The Next Ten Thousand Years  (Cape, 1974), Adrian Berry suggested that free-floating fusion reactors in the atmosphere of Jupiter might turn its hydrogen into iron asteroids which could be launched into space  (Fig. 18),  But since he proposed dismantling Mercury to shield Earth from the radiation from the Jupiter operation, it was hard to see how the rest of the planet could be prevented from boiling off into space.  The gases might be gathered and processed by factories in space  (Fig. 19), but still the losses would surely be excessive.  Berry’s proposal did give us the idea for a less violent process which could lead to making Jupiter’s outer layers habitable  (Fig. 20 – see ‘Jupiter’, ON, September 5th 2021), which seems an altogether better plan.

One suggestion for getting round the construction problem is to build the Dyson structure not as a solid sphere, but out of plates  (Fig. 21). 

Fig. 21. Dyson hexagons

For his novella ‘Empress of Starlight’  (Analog, Nov/Dec 2018, reprinted in Around Alien Stars, Brief Candle Press, 2019, Fig. 22), he proposed a new method of building a smaller Dyson sphere, with much less mass and harnessing much more energy  (Fig. 23).  His version would consist of flexible, interlinked hexagons  (Fig. 24), sustained by sunlight pressure and therefore self-correcting if disturbed  (unlike Niven’s Ringworld.  I was one of the critics who pointed that out, and he revised his scenario in Ringworld Engineers, 1980). 

Used as a phased optical array, it would have extraordinary resolving power as a space telescope  (Fig. 25).  But used as a transmitter, what it could do is truly scary. 

Fig. 25. Dyson array resolution and beam power

In his novella, an army of robots is using the technique to weaponise the stars, with the ability to hit targets 11 metres across from a distance of 300 light-years  (Fig. 26).  We never find out who’s behind it or what unimaginable threat they’re seeking to counter, but whatever it is, it must be something much worse than the ‘Empress’ of the title, who only wants, like Garbo, ‘to be alone’.  Gerry Nordley’s ideas may make Dyson structures more practicable, but let’s hope there’s never a need for them in that way, or we could be back to the vision of a ruined Galaxy that I mentioned at the beginning.

Fig. 26. Dyson array resolving power from theta Circini, 276ly

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