Building Dyson Spheres: an article by: GF Willmetts.

Freeman Dyson, based off Olaf Stapleton’s ‘Starmaker’ 1937 novel, proposed that an advanced civilisation needing more energy would build a shell around their star and beyond their homeplanet to take in all its energy. For the sake of names or labelling, we’ll keep to the recognised name here or ‘sphere’ or ‘shell’ as required to remind you of its shape. It isn’t just the star but also the planets out as far and including those in the goldilocks region, subject to the metabolism of the alien species. They might even be fortunate and have more than one planet capable of life. Having a confined star’s energy could speed up any form of terraforming. Even so, when you bear in mind we only utilise 1% of our star’s energy, you would have to have a serious need to confine the maximum, but let’s think on that for a moment.

Logistically, one would have to wonder how much energy would have to be expanded to mash up enough metallic rock material, let alone any other material to make such a shell. Which is sort of back-to-front as your species is already wanting to confine energy. At best, I doubt if it would be used to contain the entire star system. Then again, if you’re going to trash uninhabited outer planets that might not be a concern. If they follow a similar pattern to our Solar System, then they are likely to have gas giants so there are consequences as to what do you do with them and any repercussions if they include or exclude them from the shell. I did have a ponder on this and if the shell was in two parts, the gases from the gas giants could be used between them as a coolant or to trap some of the heat.

If the shell was enlarged to included them then the size of the shell gets ever bigger. If you are going to do some sort of stellar-building, for want of a better name, unless their home star system was perfect for this, it might be easier to select another smaller star system and build a more idealised smaller version. Any species that can build a Dyson sphere isn’t going to have problems with planetary-building. If this is nearer the galaxy’s core, then the distance between star systems is likely to be closer than what we have on the rim.

Dyson sphere
Dyson sphere

At its smallest, even a wafer-thin Dyson sphere is going to take a lot of matter. If its thicker, even more so. An alien species capable of creating such a structure will have sorted out a lot of engineering problems and would certainly have had some idea about how to achieve this way beyond what we are capable of, let alone dream up.

As we are thinking about star systems that look like our own, we might have the wrong image. Certainly star systems nearer the centre of our own galaxy might have more asteroids and material but even around a small star, why bother? If you have that advanced a civilisation, you would probably sorted out how to take advantage of anti-matter/matter conversion or playing with singularities or black holes for energy than create something so elaborate. Certainly, as we have discovered with computer technology, our demands on electricity has gone down not up, so there would be other needs than just a supply of free energy.

You would still have to consider whether any species consider encasing their star in a shell just for energy as being the only motive. A species that advanced would surely have become space-faring and certainly have colonised other planets and might well have started to explore the galaxy. Whether that means organically or through AI or other mechanical means depends on how they view their lives or have others means to circumvent mortality. To think of any alien species as being similar to ourselves in physiology, mental outlook and so forth ignores the many possibilities of alien life in the cosmos.

There would be all kinds of reasons for moving and not just because another alien species was making a hyper-space highway but you certainly would want to move away from one of more singularities or black holes that is likely to draw in your star system or even another star nearby if you thought in terms of millennia passing. Assuming, these aliens are in a denser part of the galaxies ahead of us, there would be all manner of reasons that we might not even know about. A dense level of dark energy or dark matter could also be seen as problematic. Avoiding a war with another alien species is less of a problem because of distance and creating a Dyson sphere is a multi-generation endeavour, not something that can be done overnight to escape any potential interstellar war.

Sending a generation starship out means the home species might preserve their gene pool in the galaxy but there’s never any knowledge getting back how successful this was. It would probably make more sense to take a large part if not all of your planet with you. To do that you need a heat source, so take your star with you or find a means to create a star-like source and bring the scale down to a manageable and controllable size. That would therefore make use of all the confined energy.

More of that in a while. Let’s discuss some of the problems in manufacturing a Dyson sphere. It isn’t just the question of having enough matter to create a shell large enough for the goldilocks region (that is, the inhabitable region of a star system that the alien species would live in, not necessarily similar to our own) to contain their star and home planet and any planets nearer their star.

There is still a matter of containment of all that star’s energy. Space, generally, is thought to be near absolute zero. Containing a star’s energy is likely to change that and certainly onto any physical surface it encounters. It is already thought that such a sphere would have an infra-red signature that would make it recognisable over interstellar distances. Assuming, of course, that such energy couldn’t be used. After all, the whole point of creating a Dyson sphere is to conserve as much energy as possible so why should infra-red heat be the exception unless to expel the excess heat energy?

The placing of the sphere would be knowledge of gravity and Lagrange points. The latter is where gravity is not so much neutral but where there is some stability between all planetary bodies. Even so, maintaining position would still need some energy but as its absorbing that from the star that might not seem to be a problem.

Let’s address how the Dyson sphere would be made. You wouldn’t really start off with a shell but something more akin to a ringworld or rather several of them and slowly build them up and connecting them together. The material, at least on the inside, would be dark to absorb the most energy. You might not even have to complete the shell to get the most energy but that would depend on the amount of matter available. Having a leaky Dyson sphere being more like a colander might not be so bad and would let out excess energy but we’ll assume it is completed as far as needed.

Although a star gives off energy in all directions, it would not be prudent to have a static sphere or colander or risk heat spots or damage to any weak areas. Granted, outside of planetary shadows, the shell is likely to receive energy from all directions, having it rotating would even this out. With so much surface area, having it slowly rotate should prevent that happening. The temperature of any planets within is likely to rise and without some constraints also risks making them uninhabitable which defeats the objective, unless one creates smaller partial Dyson spheres around each planet to reduce the amount of energy each planet receives. A failure in that and you would need somewhere else to live.

I’m not so sure you would want to use the inside of shell for habitation unless it was a last resort and then you’d be under not on top of it. If forced to abandon your homeplanet, it would make more sense with habitation on the outside shell and tap the energy from inside from their star than having it on the hottest side.

This will take some lateral thinking here. A substantially-sized shell such as that slowly rotating would certainly have some effect on local gravity conditions. Not so much to increase gravity inside the sphere but it would have some effect on the remaining matter or planets outside of the sphere and could well turn the remains into a belt or more orbiting the shell. A useful outer protection from comets and other interstellar matter or use a ramscoop to utilise than waste it.

The assumption has always been that a Dyson sphere would be a complete shell to conserve all the star’s energy. The problem is having too much energy and a need to vent it. Channelling the energy is a means of propulsion but then you also have to consider having enough means to move not only a star but also the planets and moons in their orbits which would be a lot trickier. Then again, an advanced alien species capable of creating such a shell would have a deeper understanding of gravity. In an expanding universe where the stars are already moving, it would simply be easier to rely on vectoring and nudge in a different direction and head towards another star. This could be to look for other sentient life or even more matter to build up the existing Dyson sphere.

Humans tend to think complete shells but the heat problem is still there and it might be easier to have two half-shells, rotating and crossing each other, ensuring that any inner planets getting a night and day. Indeed, having each planet and moon also having individual inner Dyson spheres would ensure the conservation of night and day and energy channelling. Any alien species capable of making Dyson spheres would see this as a logistical problem than anything complex. We certainly wouldn’t be in their class.

The biggest problem with a generation starship is the original crew, let alone many generations on aren’t likely to see their destination. A moving Dyson sphere gets around this problem. Recycling resources all the time, not to mention problems of discipline, genetic stock and things generally categorised in Science Fiction is a lot of effort. Taking your home star and planetary resources does at least get around this. It would still mean the generation who thought of it, unless they are long-lived, is unlikely to reach any selected destination but at least they would be going in style and carry on living normally along the way and ensure species diversity and evolution. The whole population going means never having to say goodbye.

Thinking this through, this would also explain why the search for Dyson spheres has never given any results. Everyone assumes they would stay still rather than as a means for interstellar travel.

So what happens should a Dyson sphere approach another star system, like our own, for instance. Apart from the matter of slowing down, there is a matter of effect on our own star system in terms of gravity. I doubt if the shell itself wouldn’t cause an effect if it got close but the same works both ways. It would make more sense to find a suitable Lagrange point where gravity is neutral beyond the Kuiper Belt and use more traditional spacecraft to investigate, depending on how long you can hang around.

Would we be able to recognise a Dyson sphere in transit? Investigations so far have been looking for infra-red signatures, largely for the same reasons above in venting energy. From a propulsion point of view, a Dyson sphere heading in our direction would having any energy output behind it, assuming it was coming in our direction than the direction the universe is expanding towards. However, it would be a significant mass of gravity. Although I doubt if it would show in the motion of other stars, it would distort the light travelling from them enough to give a location. Considering we are far down the pecking order on the expanding universe, an alien species wouldn’t want to come towards us unless there was a serious reason knowing what was ahead of us and postponing its fate.

That still raises the question of why we have never detected a Dyson sphere if such a thing was created. If one isn’t coming towards or away from us, they could still be vectoring in a sideways direction then we might see an energy trail depending on when it does a course correction. After all, Newton’s Laws Of Motion state it would keep going in one direction unless stopped by something else and I doubt it would need to go at the speed of light.

Something that hasn’t been considered is whether the alien species would be evolutionary static or continually evolve. They could also be taken unexpectedly by their own pandemics, over-population, revolutions or just die out. No species is beyond extinction. Uncontrolled, a Dyson sphere could have a slow but destructive course through the galaxy, especially if it vectors on other stars to draw it in a particular direction. After all, they are travelling the cosmos looking for other life, maybe similar to their own, and would have their own choices which star systems to move towards. An uncontrolled Dyson sphere with its population dead would be a serious menace or a possible means for mankind to explore the galaxy.

Considering the length of time even a Dyson Sphere would take in transit, at most it would be a blip in our star-gazing that we would consider to be something else, even if spotted in manoeuvring or just hidden amongst other star systems. The last of the big dumb objects, alas we are unlikely to see.

Of course, I could be wrong and one could manoeuvre to outside our star system. Would they stay long enough to seek out new life? That could be one of the reasons, although they might well know more about our life from broadcasts. They might not even stop but have enough time for a window to stop off and look and go back to their Dyson sphere. Would they invite any of us to go along? Mind you, if they had a few vacant planets of could even take our Earth and Moon along opens other possibilities. That would essentially be no one-way trip, unless they left us the technology to build our own but I wouldn’t be surprised if they negotiated by TV/radio long before they got here. The complications of getting another planet inside their Dyson sphere wouldn’t be difficult to do. The optimist in me would like to think they would be preserving our species by taking some if not all of us with them. Now that would be a Science Fiction dream.


© GF Willmetts 2021

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One thought on “Building Dyson Spheres: an article by: GF Willmetts.

  • Hi Geoff

    The subject matter was the basis of the cageworld books by Colin Kapp. As you say it would take a phenominal amount of material to build one let alone a set of nested spheres

    Ps . His novel the patterns of chaos is my favourite book




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