There is a wonderful moment in Larry Niven’s 1970 novel Ringworld when protagonist Louis Wu is first shown an image of an artificial ring completely encircling a star. These days the concept of a Dyson sphere is well established as a way for a civilization to capture as much energy as possible from the host star, but back then I had never heard of the concept. Dyson thought both a solid shell and a ring would be unstable and believed the best form for his concept was what he described as “…a loose collection or swarm of objects traveling on independent orbits around the star.” In that sense, Niven’s Ringworld wasn’t really Dysonian, but I found it staggering.
What a place! An engineered ring the diameter of Earth’s orbit fully 1.6 million kilometers wide, giving a habitable inner surface equal to about three million Earth-sized planets. A broader backdrop for science fiction adventure could scarcely be imagined unless it were a full-blown Dyson sphere. And indeed, Ringworld became the venue for a number of subsequent novels that tied into the collection of futuristic lore Niven called Known Space.
Speaking of science fiction authors reminds me that Dyson himself harked back to Olaf Stapledon, whose 1937 novel Star Maker seems to have given him his inspiration. In fact, Dyson has opined (I believe this was at the Starship Century symposium in San Diego) that ‘Stapledon sphere’ would be a more accurate name for the idea. Here’s Stapledon’s original read on Dyson spheres as a common outcome in a galaxy, viewed by the visionary protagonist as he witnesses events of the far future, when civilization “…began to avail itself of the energies of its stars upon a scale hitherto unimagined”:
“Not only was every solar system now surrounded by a gauze of light traps, which focused the escaping solar energy for intelligent use, so that the whole galaxy was dimmed, but many stars that were not suited to be suns were disintegrated, and rifled of their prodigious stores of sub-atomic energy.”
Addendum: Dyson’s talk in San Diego, which I had initially mis-reported as having been made in London, is available at the Starship Century site — click on the link to the videos.
Capturing all the power of a host star is a marker for a civilization that has reached Type II in Nikolai Kardashev’s classification of intelligent civilizations. Type III — this is what Stapledon depicts in the passage above — can tap the energy resources of its entire galaxy. Dyson Spheres would be vast indeed, but the various searches that have thus far been undertaken for them have relied on the amount of infrared radiation such an object would produce (see, among a number of articles in the archives here, Toward an Interstellar Archaeology, which talks about Richard Carrigan’s leading role in conceiving and mounting this search).
The White Dwarf Alternative
We have no Dyson sphere detections as of now, but speculative work on the concept continues, as revealed in a new paper from ?brahim Semiz and Salim O?ur (Bo?aziçi University, Istanbul), forwarded to me recently by Adam Crowl. The duo posit a new take on Dyson spheres in which they are built around not G-class stars like our Sun but white dwarfs. Building around a white dwarf offers a number of possible solutions to Dyson sphere problems. And it turns out there are many of these.
Consider: If we somehow built a true sphere in the Solar System with a 1 AU radius, the gravity of the Sun would, according to the authors, be a miniscule 5 X 10-4 g. Inhabitants would be faced with microgravity. Rotating a Dyson Sphere would be one way out of the problem, but doing this would leave the equatorial regions as the truly usable surfaces, which would make it more sensible to build a ring-like structure in the first place rather than an all encompassing sphere that was largely useless. A system of independently rotating rings might be imagined but seems gratuitously complex.
The authors are aware of the instability that would plague both a Dyson sphere and a ring, but their paper isn’t about finding solutions to these problems but arguing for a different central object, which has advantages of its own. A white dwarf is much smaller than a G-class star, but applying Dysonian principles here would still give us a similar way of capturing energy while providing, by the authors’ estimate, 105 times the living area of a planet on the outside shell while not subjecting inhabitants to microgravity. A possible scenario is a civilization surviving the red giant stage of its star and returning to construct a Dyson Sphere around the white dwarf that eventually emerged.
From the paper:
…the red giant stage is also quite long, about a billion years for a solar-mass star (it decreases with mass), so it might seem that life/intelligence/civilization could also develop during that stage. However, conditions like radiative flux and stellar wind, even the mass of the star, are quite variable during the red giant phase, as opposed to the main-sequence period, when they are stable. Hence, while the astronomically-long-term outlook of an intelligent civilization is subject of conjecture, a civilization set to build a Dyson Sphere as discussed in this work would probably arise during the main sequence period of its star, and find ways to survive the red giant stage; maybe temporarily migrating to an orbit farther from its star, either to a planet, or failing/rejecting that, to orbital habitats a la O’Neill. In fact, such an effort would provide the experience needed before undertaking the construction of the Dyson Sphere around the eventual white dwarf.
We wind up with a 106 kilometer-scale Dyson Sphere with the inhabitants living on the outer shell as an alternative to the more common Dyson Sphere of fiction and speculation, one that would still be theoretically detectable through its infrared emissions but a much greater challenge because of its lower power. Its smaller size also means the white dwarf Dyson Sphere needs less construction material, with a 10-meter thick shell requiring approximately the mass of a single terrestrial planet. The required compressive strength of building materials for such a rigid sphere is also higher, demanding an extra means of support about which the authors choose not to speculate.
The paper is Semiz and O?ur, “Dyson Spheres around White Dwarfs,” available on the arXiv site as a preprint.
A step up from a Dyson Sphere (from the point of view of gravity) would be a “suprastellar world”. The late Paul Birch had a website (mirror here: http://buildengineer.com/www.paulbirch.net/index_orig.html with a paper in the “papers” section, called “Supramundane Planets”: http://buildengineer.com/www.paulbirch.net/SupramundanePlanets.pdf
The basic idea is to construct a stationary shell around a star at the one-gee level, with thousands or tens of thousands of layers, each using an appropriate fraction of the star’s energy output. The whole structure is supported against the star’s gravity by means of what Birch called “Dynamic Compression Members” which while not solid, would have virtually unlimited compressive strength.
Paul Birch’s papers had originally appeared in the Journal of the British Interplanetary Society in the 1980s and 1990s, but sadly appear to have been almost forgotten since then. If you have not yet read them, I highly recommend them — I would even suggest that his ideas are worth a Centauri Dreams article or two!
The required compressive strength of building materials for such a rigid sphere is also higher, demanding an extra means of support about which the authors choose not to speculate.
I understand the attraction of a vast, wide open space. Bob Shaw’s “Orbitsville” provides a good sense of size of a Dyson sphere. But in practice, it is going to be a lot easier to make a swarm of rotating structures. Materials will be within physical constraints, the swarm can be built incrementally, environmental conditions can be diverse, emulating any environment one wishes, and isolation will reduce chances of epidemics or other rogue organisms or technologies.
The other advantage of rotating habitats is that they can be built with many concentric levels too, massively increasing the available living space. Just like a skyscraper offer a lot of living space comapred to land.
Spinning a Ringworld or a section of a Dyson sphere to produce a centripetal force, so that inhabitants on the surface would have one gee acceleration on them, while in an interesting concept, is quantitatively difficult.
If the radius is 1 AU then the tangential velocity of the ring has to be about 1000 km/s in order to produce 1 gee. That’s 33 times faster than the Earth spins around the sun, more than the speed of the sun around the galaxy. It’s about as fast as the fastest stars go, and they are going that fast because they were expelled from center of the galaxy, so are on their way out.
I would be a bit nervous of having a structure as large as these near such a powerful gravitational field of a white dwarf. I get at 1 sol mass and an orbital distance of 500 000 km an orbital velocity of around 550 km/s!, even car massed boulders have energies comparable to atomic munitions. Keeping the structure in place around the star would be the least of your problems.
@ James Benford – At 1000 km/s, you have almost free STL star flight. Another ring around another star could even capture the ship. A mere 1300 years to alpha Centauri.
Of course you have to solve a lot of engineering problems to build the ring :)
If the purpose of a Dyson Sphere is two-fold – collect all the energy of a star and expand living space, why must the same structure do double duty? Why not collect the energy with a light weight solar collector, its position maintained by radiation pressure. The habitats can then be spinning structures located anywhere outside the collector sphere, with energy beamed to them. These habitats could be huge (planetary diameter sized) with very many layers of living space to vastly expand the living surfaces. Or just cover an existing planet with multi-kilometer high structures. For example, with a 10 km high structure all over Earth, with each layer perhaps 100 m high, you get 100x the current earth’s surface. Getting rid of excess heat might be a problem, depending on how much lighting and electrical energy is needed for each layer. (You could grow a lot of mushrooms in lightless farms for food if needed). Some layers would be used to recreate ecosystems, perhaps even ones from the ancient eras, all isolated from each other).
As Jim Benford points out, spinning rings would have very high rim velocities. High enough, in fact, that interstellar travel becomes conceivable just letting go from the perimeter.
On the other hand, the rim velocity available with conventional materials is a paltry 2 km/s, befor the ring (spoke, cylinder, sphere, whatever) breaks apart under its own centrifugal force…
I heard tell that there is a mathematical, physical paper on why you can’t have SOLID rings in equilibrium around some planetary body. I was wondering, does anyone here happen to know where I might find this research paper so that I could take a gander at it ? Paul would you by any chance have any resources that could find out the name of the research paper(s) that would explain the theory behind why such a thing is not possible ?
There is a different type of “Dyson Sphere” that has been proposed (I’ve forgotten where) that involves a shell built at the 1g radius around a gas giant planet. This would require a lot less raw material to build and still provide plenty of living space. Such a thing might be detectable by us as a very large, very low density transiting planet.
Paul Birch’s Supra-Stellar discussions are certainly the most appropriate to this concept. His Supra-Self, which has sufficient self-gravity to not require an Under-World, is vast on a scale that boggles the mind – over ~2 light-years wide, with 10 million levels, a mass of ~1 trillion Suns, and time-dilation at its core so extreme that time runs 1/2500 as quickly as it does here on Earth. Unsurprisingly, many of its levels hover not far from their event horizons.
The plural of dwarf is dwarves.
Niven’s “Bigger than Worlds” described a range of huge space habitats. My favorite was the Topopolis: An extremely long O’Neil colony wrapped around a star like a ball of yarn. The radius of curvature around the star is large enough that no problems are caused by it rotating on it’s elongated, curved axis, while the colony could travel along it’s axis at orbital velocity, or perhaps slightly higher in order to support the remaining structure against gravity.
Far more practical than a simple spherical surface, allowing for full Earth gravity if desired with conventional materials and engineering, and can be constructed with all necessary redundancies so that it won’t catastrophically fail.
Re Mark’s comment above:
Dictionaries accept both ‘dwarfs’ and ‘dwarves,’ though ‘dwarfs’ is the older and more commonly encountered form. Tolkien seems to be the one who, relatively recently, popularized ‘dwarves.’
Why hang around a white dwarf when you can hang around a red dwarf and have a large efficient fusion reactor below, if you run low on fuel just add more hydrogen.
(From fiction) Iain M. Banks’ orbitals seems more practical and, though still impossible for us, perhaps more theoretically tractable. Put a relatively small(!) ring in orbit around a star, orient it edge on and spin it. The spin provides gravity and the sequence of plates and gaps (empty spans with cables and/or “fields”) provide equal intervals of day and night.
Re Tolkien: He wrote (I forget where now) that his choice of ‘dwarves’ was deliberately done to distinguish those people from dwarfs.
As a Brit educated in the 1950’s and 1960’s, I learned that plurals of roof, hoof, dwarf etc was rooves, hooves and dwarves. This has increasingly changed to roofs, hoofs and dwarfs.
@william – I think the instability comes from the problem that if the ring shifts position at all, then gravity will increasingly pull on the side nearest the star. There are no counterbalancing forces to return it to a stable state. A ring therefore cannot be statically stable, but must be dynamically adjusted to maintain its position with the star in its exact center. A planet OTOH, can change velocity so that its orbit is stable even if highly elliptical.
Robert (Bob) Shaw wrote a book around 1970 which explored the interior of a Dyson Sphere. I still have my copy.
I like the Brett/Niven Topopolis idea. It can be formed by organic growth as many individual orbiting O’Neil cylinders are tied together into a ring, then multiple rings, and ultimately the “ball of yarn” construct, all the while remaining in orbit.
There is no expenditure of energy or material strain to speak of compared to a cloud of free-flying colonies. An important incentive to form a chain over free flight would be collision avoidance, which becomes increasingly important as the number of colonies grows.
One thing gets me about a Dyson sphere vs a ring structure – why does everyone think they are mutually exclusive? You can build two ultra-thin hemispheric mirrors around your star that are supported only the pressure of light, then between them place your thick (rotating?) Ringworld. This light absorbing Earth-like ring would have to be placed much further out than a conventional Ringworld or Dyson sphere, but given perfect mirrors, this world would end being exactly the same surface area as a conventional, closer in Dyson sphere.
Another thing that disturbs me is that everyone keeps repeating the idea of building a conventional Dyson sphere or ring at 1AU, when most of you know that 2AU is the correct figure for Sol. For those who don’t here is a hint: the Earth has four times more area than the disk it presents to the Sun. Another hint: we might not notice it because we sleep through most of it, but Earth has a night – one that has no use to us once we do a tiny bit of genetic engineering on our plants.
Paul, I just googled “dwarves” and “dwarfs”. You’re completely right! Dwarfs returned ~16 million results to only ~11 million for Dwarves. This is really surprising to me! After leaf/leaves, loaf/loaves, etc, it’s hard to imagine dwarf/dwarves isn’t the standard!
Thanks for answering, though. This is how we learn things :)
@Rob Henry. Ring worlds are often depicted as having shades orbiting sunward so that day/night cycles are simulated. For a sphere the mechanism would be more complex. But having the ring orbit at 2 AU would mean 1/4 sunlight intensity which would not be Earthlike. I would think that radiators would be the way to go to get rid of any excess heat if that is your concern. For Dyson swarms using rotating habitats 1 AU is what you would want.
Ron S said on March 24, 2015 at 12:07
“(From fiction) Iain M. Banks’ orbitals seems more practical and, though still impossible for us, perhaps more theoretically tractable. Put a relatively small(!) ring in orbit around a star, orient it edge on and spin it. The spin provides gravity and the sequence of plates and gaps (empty spans with cables and/or “fields”) provide equal intervals of day and night.”
Iain. M. Banks’ ‘Orbitals’ differ slightly from the above insofar as his orbitals aren’t aligned edge-on to the star.
Niven had his Ringworld night/day cycle provided by an inner-ring of evenly spaced occulting plates connected with monofilament wires and spun at the correct rate so their shadows gave nighttimes on the Ringworld. Banks, however, had his much smaller(!… still ginormous!)orbitals inclined at the appropriate angle so that as it rotated once a day a spot on the inside surface would rotate into sunlight giving a dawn as the sun would rise over the rim-mountains. The sun would then arc up into the sky and seem to approach the thin band of the opposite night side of the orbital up at the zenith at local noon. As the ring rotates the sun lowers until a sunset is seen on the same rim just further along (say the sunrise is anti-spinward then the sunset would be further along the spinward direction), then there is a night time for that spot inside the bracelet-world… a night that would be awesome with the sunlit ribbon stretching vertically from horizon to horizon, becoming very thin at the zenith as you look past the dot that is the Hub.
You can approximate any latitude on a planet by varying the inclination… you like low winter sun that never climbs higher than 10 deg then incline the Orbital 80 deg to its ecliptic so it seems to roll along its orbit… if you prefer higher, summer-like sun angles of around 85 degrees (say, like the tropics on Earth) then only bump the Orbital’s inclination up by 5 degrees. I’m english and live at 50 Deg N so I’d gladly live on that latter Orbital, ha ha.
The Hub houses an all-powerful ‘Mind’ that regulates everything so it would keep the Orbital optimally aligned to prevent any day-long nights around the two Solstices.
So, Banksian ‘Plates’ are built (and may be inhabited first), then several Plates are moved into position and connected to form the Orbital… any gaps are temporarily shored up with the ‘fields’ until completed… then the outside is used for transit systems around the circumference and, if you visited ‘Vavatch’ (be quick) you could eternally circumnavigate it on the ocean-liner of your choice on its inner, continuous sea. Cool.
Mark writes:
Hey, no problem. The reason I knew both spellings were acceptable was that some time back, when writing about brown dwarfs, I looked at my wife and said ‘how do you spell the plural of dwarf?’ That set about a chase through the Net looking for an answer!
For Niven’s Ringworld, the shadow squares were solar power generators for the various systems. If not needed for that, they could deflect light from the shadowed regions to the illuminated regions, doubling illumination during the day.
The acceleration of the Sun’s gravity at about Earth’s orbit is only about 0.0006 of Earth’s gravity. If you were to take 99.94% of the mass used to make a ringword, and make it stationary ballast, the remaining fraction could serve as a thin magnetically levitated living space rotating at high speed. At the scale we’re talking, a magnetic bearing could have a gap of planetary dimensions, and still function, so the required precision wouldn’t be awful.
For less luminous objects than the Sun, the ratio of the primary’s gravity to the desired Earth gravity would be higher, and a smaller proportion of the mass would be needed as ballast.
So, I think something that kind of resembles Ringworld could be built without use of Unobtainium. But it would be a horribly, horribly inefficient use of the mass, and subject to the sort of catastrophic failure no long term habitat for humanity should ever tolerate.
No Alex Tolley, not a quarter daylight intensity, but a quarter that of perpetual-tropical-midday sun. The tropics is so hot that we generate too much cloud cover and it begins to reduce photosynthetic efficiency, so might as well dial that down a bit anyway. Obviously, average daylight intensity on a horizontal surface on Earth would be half that midday figure, even in the absence of a light absorbing atmosphere.
If we desire 12 whole hours of total darkness and 12 of daylight (for some random reason) , then we still have to place our conventional-type sphere/ring at root 2 AU. If it is a more sensible shading of 8hrs/24hrs then we are getting to 1.63AU. You might as well call it ‘a bit less than 2’ even with an elaborate and unnecessary night generation indulgence.
@Rob Henry – I’m not clear what the problem you are concerned about. Is it intensity. or energy dissipation? Intensity can be varied in a number of ways, including inclination (see Zambelli above), shades, etc. If heat dissipation, unlike planets, energy can be radiated from the “night side”. So 1 AU looks fine to me. as temperature can be controlled in a number of ways.
Now if you are arguing for a simple system without
cont..
any dynamic systems that is stable, then that may require a different radius.
@Brett Bellmore, this levitated layer balanced by ballast is my reasoning too, but in the absence of a white dwarf it is a bit hard for a conventional Ringworld. Normally we would give them an unbounded atmosphere, which at ground on Earth weighs ten tons per square metre. So it seems a thick rotating layer might be necessary anyway, unless they live in a balloon.
Note that even with hemispheric mirrors, the 1 solar mass WD Ringworld would be closer in than 1AU, and so the mass ratio of a balancing layer much lower. Also note that light pressure would not be high enough to keep my mirrors in place, until the whole hemispheric mirror is in place.
@Alex Tolley, my biggest worry is energy dissipation – people really would cook here. Next is excessive cloud formation. Think of how much cover there is in the tropics, now add just a few extra degrees.
Once your stream bath gets to 40C (and at 1AU with Zenith sun it will) all humans will die if they venture outdoors for more than a few minutes. In our ringworld deserts, day temperatures will get much higher than that, but we should be able to survive a little longer. At night temperatures should get lower than our worst deserts on Earth (since they would be even dryer), which are around -20C.
Also note that Earth CO2 is only a trace gas and its levels can hardly be lowered further, it being easier (for our plants) and safer to raise them (even 1%, or 30 times their present levels should be fine for us). We could raise ringworlds albedo but Earth is already pretty shiny, and once again we are relying on almost total cloud cover to save us. So much for photosynthesis!
I am starting to think that 2AU is too close in.
Mark Z: You’re right. I mistook something I read in one of his books about orbital construction to be about the final product. In any case it just shows there are perhaps simpler approaches than Dyson rings and spheres.
Ron S…
“…there are perhaps simpler approaches than Dyson rings and spheres.”
I agree with you 100%. I know we deal with such über-engineering when we discuss such things but I have a really hard time imagining how any race would ever be able to construct a solid Stapledon/Dyson sphere or, for that matter, a Ringworld à la Niven (this particular primate also knows why would I expect anything different? tee hee). But then again, so long as there isn’t anything in the laws of nature to prevent structures like this being constructed and maintained then the sky’s the limit… especially if that sky is stuck to the inside of a Sphere!
Dyson Swarms of O’Neil habitats on the other hand, way easier to cogitate.
At Rob Henry,
I think the sunshades solve your heat dissipation problem. Instead of just day/night reflectors as usually depicted, add in partial shades between the night reflectors that reduce the intensity. This can be made to mimic the conditions of almost any latitude at I AU apart from solar inclination.
If the ground still heats up, then active cooling can be achieved using refrigeration and heat radiation to the shielded side of the ring.
My sense is that these are minor issues compared to construction of the ring. O’Neill swarms make much more sense to me as a realistic way to harvest the stars energy.
Alex Tolley writes “My sense is that these are minor issues compared to construction of the ring.”
To me that demands a yes and no reply. Yes – from an engineering view you are spot on. From an economic view deflecting three quarters of all incident sunlight is identical behaviour to burning banknotes. Putting your ring or swarm at 1AU undermines the entire point of building the ring in the first place.
@Rob Henry – the idea that the ring should be > 1AU really demands a real discussion. Any thought of developing the idea further?
Brett:
A ring of orbiting O’Neil style cylindrical colonies attached end to end does not require Unobtainium, is easy to build up incrementally, provides artificial gravity of any desired strength, uses material efficiently, and resembles Ringworld to some extent. The land area could even be contiguous, if the individual cylinders were fused into a continuous tube. And if you kept growing it, eventually the resulting “ball of yarn” could resemble a Dyson sphere, still no Unobtainium needed. Main advantage over a “swarm”: Collision avoidance.
If we created our own stars, fusion reactors on a much smaller scale, we could use more space in the solar system and interstellar space than been confined to a region of space around a sun. In effect we could create free floating structures like Bernal spheres that have large volumes and have fusion reactors that power a light source with specific wavelengths of light for photosynthesis and our own optical sensors as not all of the spectrum is used by animals and other organisms. When these spheres move out of the solar system slowly they could still see an image of our sun by using telescopes to high resolution by combining many different spheres images. It would seem the swarm idea of colonies that more outwards slowly would be more practical to an advanced alien race intent on its population expansion than a large ring or star encasing sphere that would require high maintenance. It is these orbiting colonies that we may see transiting their stars as there would be many and they would be much easier to spot than an IR signature.
A New Type of Dyson Sphere May Be Nearly Impossible to Detect
Maddie Stone
Saturday 4:00 pm
Over fifty years ago, physicist Freeman Dyson proposed an awesome, if slightly insane, idea: That an advanced alien civilization might construct a massive, energy-harvesting sphere around its star, and bunk up inside.
Scientists have never given up on Dyson spheres—we’ve even conducted a few legitimate searches for their infrared heat signatures. Now, physicists Ibrahim Semiz and Salim Ogur may have an explanation for why we can’t seem to find the megastructures. If Dyson spheres exist, they’re probably a lot smaller than we thought.
Since Dyson first proposed his massive space habitats, scientists have tried to imagine how such structures could physically work. By and large, researchers have focused on Dyson spheres encircling Sun-like stars. But this scenario poses a few major, and perhaps insurmountable, problems. For starters, such a sphere would have to be built at a distance of roughly 1 AU, the same distance between the Earth and the Sun. That means the structure would be utterly massive, requiring huge volumes of material to construct.
What’s more, the surface of the sphere would experience only minuscule levels of gravity. To live on it, humans would either need substantial genetic modification, or some sort of advanced artificial gravity system, the likes of which we haven’t been able to piece together, even theoretically.
Full article here:
http://gizmodo.com/a-new-type-of-dyson-sphere-may-be-nearly-impossible-to-1694258669
I like the idea of a white dwarf Dyson Sphere/Supramundane world. Sirius b has the mass of the Sun. I actually think this sort of Dyson would be easier to detect because it would have to reflect visible light off of itself. The light would come from the white dwarf, be focused through a hole in its surface then reflected back on the outside of the sphere by a convex parabolic mirror.
http://www.newmars.com/forums/viewtopic.php?pid=124431#p124431
For energy collection, I’ recommend building a Dyson around Gacrux, a red giant 88 light years away with the luminoscity of 1500 Suns, as it has the mass of only a little over 1 Sun, it should be easy to support the shell by radiation pressure alone against its feeble gravity at 38 AU radius.