Planetary engineering on the largest scale might one day reveal itself to us through the observation of a Dyson sphere or other vast object created by an advanced civilization. But it’s interesting to think about alternative strategies for using celestial energies, strategies that assume vast powers at the disposal of mankind as projected into the distant future. Thus an interesting proposal from the Swiss theorists M. Taube and W. Seifritz, who consider what to do about the Sun’s eventual evolution into a planet-swallowing red giant.
A Sunshade and a Planetary Shift
Considering the possibilities of preserving the Earth during the Sun’s transition into a brighter and much larger object, the authors discuss alternatives like raising the Earth’s orbit to a safer distance or using a parasol to shield the planet from its rays. That might tide us over for a few billion years beyond the point where an unprotected Earth could survive as a habitable place. But the paper only begins here. After the sunshade, the authors go on to discuss their plan to create an artificial sun in the Kuiper Belt, where an Earth slowly moved into an outer orbit by gravitational swing-by techniques can eventually find its new home in a stable orbit around a life-giving source of heat and light. Call it an ArtSun, as they do, and ponder how much science fiction it might inspire.
Imagine, for example, an Earth gradually being shifted to a new orbit over a period of perhaps tens of millions of years as the Sun begins its inexorable growth to engulf the inner planets. And imagine our world, as the authors do, illuminated for the duration of the journey by a ring of fusion power stations encircling the planet at an orbital distance of 350,000 kilometers. This ring of whatever materials are best suited for the job is inescapably reminiscent of Larry Niven’s Dyson-esque Ringworld, though on a much smaller scale, and suggests a level of planetary engineering as beyond our present capabilities as the Large Hadron Collider would have been beyond the imaginings of Greek philosophers.
Given the changes in technology that make even a thousand years from now a vista too remote to analyze, it’s hard to know what might have transpired in a billion years, much less the five billion the authors contemplate during which the parasol might shield the Earth, or the billions beyond that it could survive around the new star. But the question is worth pondering from the standpoint of SETI, I think, where we might think about what an advanced civilization might do given enough time and powerful enough tools. And Taube and Seifritz’ ArtSun is a marvelous creation in any case, made up of gas giants culled from other stars. Surely that would throw an interesting astronomical signature?
Creating Sol II
The idea here is that within twenty light years of the Solar System there ought to exist enough planetary systems with gas giants, many of them much larger than our own Jupiter, to cull for use in the new stellar creation. Here’s the plan:
Some hundreds of such ‘gas giants’ will be transported to the Kuiper Belt by means of the ‘swing-by’ technique and fused together to form an ‘ArtSun’ which will ignite when its mass passes over a certain value. Unmanned spacecraft under fully autonomous control will explore those planetary systems and will find the corresponding asteroids for the ‘swing-by’ technique to accelerate the suited ‘gas giants’ out of their planetary systems. DD-fusion will be the source of energy for all these enterprises whereby deuterium will be separated out from the atmosphere of the ‘gas giant’. Although we do not know how to ignite a DD-explosive reaction for a Dyson-like space ship without the help of fissionable material we proceed on the assumption that we will have found a method in the far future.
Coincidentally, Adam Crowl just sent me links to two papers by Friedwardt Winterberg discussing DD fusion — creating propulsion solely through the non-fission ignition of pure deuterium — and thus opening up manned exploration of the entire Solar System. But more on this another day, because I’m not ready to leave Taube and Seifritz without a few more details about creating new stars. The duo discuss fusing twenty imported gas giants to create an M-class star, with the potential of using up to 100 such planets to create a G5 star not so different from the Sun. The M-dwarf would seem to be easier but a bit more problematic:
Under the assumption we let rotate Earth around such a Red Dwarf illuminated with the same ‘solar constant’ as today, we find a sidereal period for Earth being only 6.91% of a year, i.e. only 25.2 days but the not yet answered question is whether the photosynthesis will work satisfactorily under the red light.
Yes, and we’d best keep photosynthesis fully operational. On the other hand, an M-dwarf offers a tremendously increased lifetime over a G-class star. The authors go on to consider how to power up the fusion devices that will keep the Earth illuminated during its long orbit-shifting journey to 50 AU. All the deuterium to run these and the planet-shifting operations around other stars will come from a familiar source (familiar, at least, if you know the history of Project Daedalus, the British Interplanetary Society’s starship design) — the atmosphere of Jupiter and perhaps Saturn. Given the future technologies we’re discussing here, mining outer system atmospheres for fuel would doubtless be a trivial operation.
Moving a Planet, or Moving Off-Planet?
Would an advanced civilization ever embark on such a task? If it did, would the astronomical signature of planetary re-location be something today’s astronomers in our own Solar System could flag as the likely sign of extraterrestrial engineering? My own guess, from a parochial 21st Century perspective, is that a civilization with the ability to travel to another solar system to move a gas giant to ours probably has the ability to consider massive re-location of population as needed to the nearest available habitable planet, or indeed, moving into vast space-based habitats that could survive a red giant’s depredations.
The authors choose planetary migration because they believe only a small number of Earth’s inhabitants could be evacuated via the creation of a starship. But their model is Freeman Dyson’s upgraded Project Orion vehicle from a classic 1968 paper, one that would carry a 10,000 ton payload at 10,000 kilometers per second via Orion-like nuclear bomb detonations. It’s hard to believe that a civilization that might survive billions of years into the future would be limited by 1968 starship design (a design that Dyson himself later gave up on as being unworkable). If anyone is around in five billion years, protected by Taube and Seifritz’ sunshade and hoping to avoid a swelling Sun, I think they’ll be opting for interstellar transport away from a soon to be devastated Earth.
But it’s fascinating to speculate on alternatives. Take a look at the discussion of planetary orbit changing using asteroid swing-bys, and ponder the risks of setting a large asteroid on a near-miss trajectory that, given the slightest mistake, could end all life on the planet anyway. One thing you can say about Taube and Seifritz — they’re not at all afraid to think big. And it’s worth your time looking this one up for the imaginative tinkering with the future that gets us thinking ultra-long-term, not to mention prompting those good SF story ideas. The paper is Taube and Seifritz, “The search for a strategy for mankind to survive the solar Red Giant catastrophe,” available online. That Dyson paper, by the way, is “Interstellar transport,” Physics Today 21, (October, 1968), pp. 41-45. And have a look at Crowlspace for other options for red giant survival.