A Dyson Sphere makes an extraordinary setting for science fiction. In fact, my first knowledge of the concept came from reading Larry Niven’s 1970 novel Ringworld, a book that left such an impression that I still recall reading half of it at a sitting in the drafty little parlor of a house I was renting in Grinnell, Iowa. Ringworld had just come out as a Ballantine paperback with the lovely cover you see below. I was hooked after about three pages and read deep into a night filled with wind and snow.
It could be argued, of course, that a ring made out of planetary material, a habitat so vast that it completely encircles its star, is actually one of the smaller Dyson concepts. It was in 1960 that Freeman Dyson suggested how a civilization advanced to the point of such astro-engineering might use everything it found in its solar system to create a cloud of objects, a swarm that would make the most efficient use of its primary’s light. And as you keep adding objects, you point to the ultimate outcome, a Dyson Sphere that completely envelopes the star from which it draws its energy.
A Dyson Sphere Search with IRAS
Last April I looked at Dyson spheres in the context of an article by Bruce Dorminey that considered new SETI strategies. Now I see that Richard Carrigan, a retired physicist from Fermilab, has added a new paper to the arXiv site, one that discusses the work reviewed in that earlier story. Carrigan has been examining sources identified by the Infrared Astronomical Satellite (IRAS), the idea being to look for objects that seem to be radiating waste heat in such a way that they might be Dyson Spheres of one kind or another. A fully enveloped star won’t be visible to the eye, but Carrigan’s infrared search covers the blackbody temperature region from 100 to 600 degrees Kelvin for full or partial Spheres.
The data come from an IRAS database that covers 96 percent of the sky and includes some 250,000 sources. Exciting stuff on the face of it, because unlike a conventional SETI search, a hunt for Dyson Spheres involves no necessary intent to communicate on the part of the civilization in question. And when you’re dealing with SETI, the fewer preconceptions you bring to the dance, the better. Here’s the thinking behind Carrigan’s attempt:
For a Dyson Sphere the stellar energy from the star would be reradiated at a lower temperature. If the visible light was totally absorbed by a thin “shell” a pure Dyson Sphere signature would be an infrared object with luminosity equivalent to the invisible star and a Planck or blackbody distribution with a temperature corresponding to the radius of the spherical shell formed by the cloud of objects. For a sun-like star with the shell at the radius of the Earth the temperature would be approximately 300º K.
Sorting the Evidence
A distinct signature? You would hope so, and if that is the case, we can dig through our data practicing what Carrigan delightfully calls ‘cosmic archaeology,’ using data that cover the 8 to 100 micron infrared range needed to study a Dyson Sphere’s emissions under these assumptions. Yet an identification runs into immediate problems, not the least of which is the need to differentiate any candidate from natural sources that show much the same signature. A cocoon of gas and dust around a young star, for example, might mimic an artificial source.
Carrigan goes through the possibilities — protostars, planetary nebulae, dying stars — and weighs their telltale infrared identity against a true Dyson Sphere, with notes on how to tell the natural from the potentially artificial. Here he considers the methods (italics mine):
A Dyson Sphere candidate with a blackbody distribution can have several characteristics such as a blackbody temperature, the distance from our Sun, magnitude in the infrared, and variability. It may also have a stellar signature in the visible or infrared. Slysh (1985) notes, “The confusion between red giants with thick circumstellar envelopes and possible Dyson Spheres in the IRAS survey is a serious problem, and to differentiate the two we need additional data.” …[S]ome of the source types discussed above populate the same region of an infrared color-color plot as a Dyson sphere candidate would. Non-Dyson Sphere objects can be eliminated using discriminants like spectral lines in the infrared or radio regime, implausible blackbody temperatures, established classifications, and statistical departures from a blackbody distribution.
A Dwindling List
So we still have a chance to find a true Dyson Sphere, assuming one or more are out there. If I had more money to burn, I would ring up Tibor Pacher with an offer to make another bet, this one saying that no Dyson Sphere will be found in this century. Tibor is bound to take that one, but I’ve lost several other bets recently and had better put down my cards (our other bet, on the date of the first true interstellar mission, is viewable at the Long Bets site; feel free to comment on either side of that one).
Image: A Dyson Sphere as envisioned by the producers of Star Trek: The Next Generation, from the episode “Relics.” Credit: Paramount Pictures.
Bet or no, the process of working through the database is fascinating, but the list of candidates quickly dwindles in Carrigan’s discussion. We wind up with a scant seventeen possibilities, none of them particularly promising, though worthy of further study. Carrigan comments:
This search has shown that at best there are only a few quasi-plausible Dyson Sphere signatures out of the IRAS LRS sample in the 100 < T < 600 ºK temperature region. This limit includes both pure and partial Dyson Spheres. With several possible exceptions all the “good” sources identified in this search have some more conventional explanation other than as a Dyson Sphere candidate. In spite of the fact that there are many mimics such as stars in a late dusty phase of their evolution good Dyson Sphere candidates are quite rare!
Next Steps
Where do we go from here? Compiling more on the list of seventeen Dyson candidates would be the logical next step (Carrigan discusses how). And we can search further using the more powerful Spitzer Space Telescope, an instrument with greater angular resolution than IRAS and three orders of magnitude better sensitivity in the infrared ranges needed for this work. This would extend the survey out past the center of the galaxy, but we’ll lose some of the IRAS sources, which are too bright for Spitzer’s camera to avoid saturation. And only one of the seventeen candidates Carrigan finds would be covered by such a Spitzer study.
This intriguing work reminds us how early we are in the study of Dyson Spheres, and the broader attempt to identify astro-engineering on this vast scale. The Low Resolution Spectrometer aboard the IRAS satellite was only sensitive enough to track solar-sized Dyson Spheres out to a range of some 300 parsecs, which includes a million solar-type stars. Extending that reach, and finding ways to either rule out or strengthen the case for some of Carrigan’s seventeen candidates, is work that extends our existing radio and optical SETI methods. Beefing up our infrared tools will help us determine whether a concept once considered outrageous might conceivably flag an extraterrestrial presence.
The paper is Carrigan, “IRAS-based Whole-Sky Upper Limit on Dyson Spheres,” available online.
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Wow! Seventeen candidates is pretty cool. Unlikely any will be Dyson Shells, but it’s worth dreaming.
Robert Bradbury’s Matrioshka Brains are the most likely Dyson-sized structure we’ll see if the whole post-biological paradigm obtains in this Galaxy, but he posits much lower “exhaust” temperatures, since each Shell uses the thermal radiation from the next Shell inwards, and so long as there’s a thermal gradient, net power can be generated.
He and Milan Cirkovic then postulate that ETIs will migrate to the Galactic fringe in search of a better heat sink gradient – should we be investigating large dark spheroids Out There? If They’re dumping heat from a star at 25 K then the outer shell is over 3900 AU across.
Three Points:
i) I think IR searches for advanced technological exocivilization are the way to go as they make no assumptions about the civilization except that the second law of thermodynamics applies.
ii) I don’t expect to find Dyson spheres as a space faring civilization in the transition from a Stage I Kardashev level of energy consumption to a Stage II Kardashev level of energy consumption would find it easier to colonize the Kuipier belt and Oort cloud rather than construct a Dyson sphere. Constructing a Dyson sphere would require breaking up a planet, which requires a lot more energy (and hence is more expensive) than using the in situ Hydrogen for power of the Kuipier belt and Oort cloud where you already have several Earth masses of material already broken up and ready for use. A star system with a colonized cometary belt should be lit up like a Christmas tree in the IR.
iii) Given the immense amount of time available for planetary formation before the Earth was formed (2-5 billion years) then our nearest technological neighbor is likely on average to be a very old (100s of millions to billions of years ). And given that even fairly generous galactic colonization scenarios can occur in a short time relative to this (10-50 million years), then I suspect there are no other advanced technological exocivilizations in our galaxy. Even if they left us alone, the sheer size of their waste heat output would be obvious to us. However, galaxy-wide civilizations may be detectable by looking at other galaxies for their IR excess left by old, advanced civilizations.
I would like to see an examination of this possibility. The signal may be very difficult to detect though as the IR excess from the civilization may be only a fraction of a percent of the Galaxy’s light output.
Hi Dave
David Criswell pointed out years ago that advanced civilizations would get most of their materials from the star not the planets, by “star-lifting”, thus breaking up planets isn’t necessary. Robert Bradbury’s Matrioshka Brain analysis assumes that the ETIs might do both, but conservative ETIs might retain natural planets for any number of reasons.
ERRATUM -
The 25 K radius is only about ~250 AU out NOT the 3900 AU I posted.
As Adam points out, a matroshka brain seems far more likely than any Dyson sphere. Accelerando, by Charles Stross, actually features a Matroshka Brain around Sol, happening in about a century, just following some of Ray Kurzweil’s trends, and Moore’s law and such.
The reason a Matroshka brain seems so much more likely than a Dyson Sphere is that it is so much more directly useful. As humans become more and more integrated with our computers, computational power becomes increasingly useful. At some point, it seems incredibly likely that several factors will combine to give us a matroshka brain: 1. mini-sat computers with a free energy source (the sun or planet they orbit around) would be able to offer immense parallel computational power. 2. Given the power that could be obtained even from deconstructing the asteroid belt to make such a system would offer the computational power to simulate everything on the earth several times over. 3. As people become increasingly merged with computers, they will become increasingly comfortable spending time in virtual worlds.
I thought we went through this whole discussion about the (im)practicality and risks of Dyson spheres in this very interesting thread in April (http://www.centauri-dreams.org/?p=1806, also mentioned above by Paul)?
And that we came tot the collective conclusion (or was it mainly me?) that, summarizing, Dyson spheres are quite risky and impractical (in terms of energy investment), other than incremental Dyson swarms of objects for solar/stellar energy collection.
And the same holds true, to a lesser degree, for the Oort Cloud and Kuiper Belt (I know Dave is a great fan of colonizing those ;-) ): for much less energy investment it would be possible to terraform and colonize a terrestrial planet near a sunlike star (see various estimates in mentioned thread). And particularly with much more risk-spreading. Investing so much in your own stellar system is like putting all your eggs (and a lot of them!) in one basket. And it assumes maximum energy capture as a civilization’s ulimate goal, instead of, for instance, spreading out, spreading life, intelligence and civilization, and colonize its galaxy.
I do agree with Daves point iii though.
There are two fine bets on the Long Bets site related to the discovery of extraterrestrial intelligence, but I feel there is still place for the bet suggested by Paul – is anybody out there ready to make a prediction about this? :-)
Here the links to the bets:
“The first discovery of extraterrestrial life will be someplace other than on a planet or on a satellite of a planet.”
“Evidence of extraterrestrial intelligence within the solar system will be confirmed before evidence from several light-years away.”
A culture that has harnessed the entire output of a star seems like it would be in a better position to afford the cost of sending colonists out to other stars. Also, the toolkit used to create a Dyson swarm would be more generally useful when settling other systems than one focused on terraforming planets and the gratification timescale seems like it would be much short for space structures than for terraformed planets.
I suspect that if we are talking humans, the necessary timescale for terraforming is going to make it impossible for all but a very small fraction of organizations.
One thing I noticed while playing around with broadcast power as a means of powering interstellar rockets is that phased arrays the size of a Dyson swarm have an impressively long reach. The downside (from our point of view) is that an advanced species that has a G type star/Dyson Swarm/emitter combo and which either takes a dislike to or shows a callous disregard for our well being while coveting the materials in the Earth could dismantle our planet over the course of about a week (Effective loss of habitability would occur sooner obviously) at galactic scale distances.
A Dyson swarm is certainly a possibility, in our own species’ future and the galaxy at large, Bradbury’s Matrioshka Brain concept while the most likely outcome, isn’t necessarily carved in stone.
‘Ringworld’ and its sequels are some of my most favorite Niven works too Paul.
I was recently checking the updates page of the Orion’s Arm
Web site and I came across this concept, the Nicoll-Dyson Beam:
http://eg.orionsarm.com/xcms.php?r=oaeg-view-article&egart_uid=48fe49fe47202
Apparently a Dyson Swarm’s outer layers can be turned into a
very powerful phased array laser beam. This beam could be
used to send solar sail craft at relativistic speeds across the
galaxy. It could also be used to destroy planet-sized targets
many light years from the Dyson Swarm.
Assuming such megastructures exist and that the beings who
inhabit them (organic or Artilect) might be inclined to use them
either as a means of galactic exploration, destruction, or both,
what does it say that we have yet to see either solar sail craft
coming our way, or an incredibly power beam coming to fry us?
Discuss.
A solid Dyson sphere seems unlikely. What seems more likely is that more and more artifacts would be constructed in orbit around a star (space colonies, factories, computronium clouds, space craft, junk, party poppers, etc.) such that you end up with an effective cloud of objects we could call a Dyson cloud. Most likely, all of this stuff would be along the ecliptic along with the planets and belts (since that is where the resources are and transportation is easier). So, what you have is not a ring world, but a ring cloud that might not look much different than a natural asteroid or Kuiper belt, but maybe more dense. Such an artificial ring cloud is what we should be looking for. Such a ring cloud would look like a natural belt except that it would be denser.
I have always thought that the proper strategy to find ETI is not to find their radio signals (maybe they don’t use the electromagnetic radiation for communication anymore), but to look for artifacts. Of course, I think we are alone in the Milkyway, so we have to look for ring clouds and the like in other galaxies, like the Virgo group. Given how far away that is, it is unlikely we will spot anything less than galactic-level engineering.
“The downside (from our point of view) is that an advanced species that has a G type star/Dyson Swarm/emitter combo and which either takes a dislike to or shows a callous disregard for our well being while coveting the materials in the Earth could dismantle our planet over the course of about a week.”
This sounds interesting. Could I get more details. I’m particularly interested in how you can dismantle a planet within a week by means other than a black hole.
Basically, you heat it with your interstellar beam until the planet evaporates. I will admit losses in the process will make the process last longer than output of a star/total binding energy of a planet indicates. You will lose most of the volatiles in the process and a certain fraction of the debris to effects like Poynting-Robertson drag but a considerable portion of the planet will remain in orbit around its star ready to be put to more useful purpose.
It does take the entire output of a sunlike star to do it in just a week.
We don’t see the beam coming to get us because it’s moving at C so the first we will know about it is that first brief moment as the oceans boil.
James Davis Nicoll Says:
“A culture that has harnessed the entire output of a star seems like it would be in a better position to afford the cost of sending colonists out to other stars. Also, the toolkit used to create a Dyson swarm would be more generally useful when settling other systems than one focused on terraforming planets.”
I see them as complementary rather than competing, for the very reason you mention: the energy provided by a star would enable such a civilization to travel to the stars ánd terraform planets.
“and the gratification timescale seems like it would be much shorter for space structures than for terraformed planets.”
I sincerely doubt that: the timeframes mentioned for terraforming of Mars that I have read ranged from about 300 to 1000 years, at least until the first unprotected inhabitants.
“I suspect that if we are talking humans, the necessary timescale for terraforming is going to make it impossible for all but a very small fraction of organizations.”
The returns would also be huge: a whole new planet.
The gamer in me can’t help but realize we’re looking for Halos! ;)
Although I guess I never actually thought about the possibility of such a thing being real.
Sean
Dave, this Web site discusses how long it might take to take
apart a solar system to build a Matrioshka Brain:
http://www.aeiveos.com:8080/~bradbury/MatrioshkaBrains/PlntDssmbly.html
Assuming it does not fry the recipients, a Nicoll-Dyson beam
might also make an excellent Optical METI device.
NGC 5907 has a larger amount of supposedly red dwarfs than
a spiral galaxy of its age should have, according to astronomers.
We should be investingating that star island more closely.
http://adsabs.harvard.edu/abs/1992JBIS…45..315F
“A two-stage terraforming scenario is outlined for Mars. The approach adopted differs from past methodology in two ways. It adopts a more conservative and plausible Martian volatile inventory. Possible planetary engineering solutions, including possible synergic use of terraforming techniques, are examined in detail. In the first stage, the Martian environment is modified to a state where it can support microbial and hardy plant life in approximately 200 years. While this step is conceptually similar to past scenarios, it differs greatly in detail. The second stage deals with the creation of conditions tolerable for human beings over a period of approximately 21,000 years. It is concluded that terraforming Mars is possible but not by the passive, or near-spontaneous, methods favored by some workers. A powerful industrial effort is required both on the planet’s surface and in space as will be continuing technological intervention to stabilize the postterraformed regime. “
Hi All
A Dyson Shell as an energy collector could happen long before it becomes a Habitat or a diffuse habitat halo. Gerald Nordley pointed out about 9 years ago in an “Analog” piece that self-replicating solar collectors could easily tap a large fraction of the Sun’s output within ~50 years, all without using a lot of mass (in relative terms.) He proposed using the output for propelling starships – which is fine – but it could easily do a lot more. A multi-terawatt relativistic mass-beam can devolatise regolith on Mars to make an atmosphere, move asteroids, cause fusion reactions in a Jovian and so on. And Gerald just wanted to push 30,000 kiloton starships to 0.87c per year!
Of course a terawatt beam is also a “terror”watt beam, but let’s hope security is at least as good as nuclear security is at present.
Mr. Nicoll, nice to have you aboard.
Could you point us to where you wrote about the Nicoll-Dyson
Beam concept? I am a bit skeptical about the brief information
on the idea in Wikipedia, which says the beam could destroy from
a distance of millions of light years.
Should we be really concerned about the beam from Messier 87?
“approximately 21,000 years”
Oops! A bit more than the 300-1000 years I suggested, apparently that was just for the unprotected “hardy plant life”, JDN refers to.
Indeed, that would require an entirely different kind of civilization with a truly long-term vision. Still worthwhile as a long-term investment.
@Adam: “self-replicating solar collectors could easily tap a large fraction of the Sun’s output within ~50 years” (..) “A multi-terawatt relativistic mass-beam can devolatise regolith on Mars to make an atmosphere”
Could that possibly speed up the Martian terraforming a bit?
If I recall Dyson’s original paper, it was mostly about the energy collection.
I do wish he’d not used the word “shell”, which a lot of people interpret as one solid thing, rather than some other choice of words that would make it clear we’re talking about a diffuse collection of orbiting facitilities.
As Dyson put it in his discussion with Poul Anderson in Science, Vol. 132
In reply to Maddox, Anderson, and Sloane, I would like only to add the
following points, which were omitted from my earlier communication.
1) A solid shell or ring surrounding a star is mechanically
impossible. The form of “biosphere” which I envisaged consists of a
loose collection or swarm of objects traveling on independent orbits
around the star.
From which we may deduce that Larry Niven never read this set of letters.
Should we be really concerned about the beam from Messier 87?
I know this question wasn’t meant for me, but it’s fascinating nonetheless.
Would we be able to discern astroengineering from nature if we see it?
A METI Optical Beam makes sense on many levels, an intergalactic beam from Messier 87 is akin to the Alexandrian Pharos Lighthouse, a definite “Here I am, come hither!”
Just don’t get in the beam’s path.
If the beam is high density, you can use it to power your emissarial space craft (Unfortunately the ISM in the path of the beam will be hot and diffuse so reaction mass may be scarce). Don’t think of it as a ravening beam of intergalactic destruction, think of it as an express highway to our alien buddies.
Anyway, intergalactic invasions don’t use beams. They use the A is for Andromeda scenario, to get the low tech types at the far end to do all the heavy lifting.
James,
The paper that you reference fails to take into account exponential growth. Because of the massive amount of work involved, terraforming a planet is largely impractical unless it is done involving some sort of grey goo/self replication process. A self replicating process would be significantly faster, although still likely dependent on the energy situation of the planet being targeted, i.e. terraforming inner planets would be significantly easier than terraforming outer planets, as inner planets have more solar energy available for self replicating machines to take advantage of.
Hi All
Paul Birch sprouted a few terraforming ideas in the early 1990s that deserve more attention in such discussions IMHO.
He has an unpublished paper online which discusses some very interesting technologies for terraforming Mars and Venus. He estimates that both planets could be given breathable atmospheres in ~20 years – Venus could be cooled sufficiently to cause its atmosphere to condense in about a decade using a clever cooling technique he describes.
But, as he notes, three planets in one system isn’t much for a growing civilization. He proposes some very elaborate and clever ultra-structures one of which is germane to the current discussion: a SupraSelf. The object is a multi-layered structure 1.2 lightyears across which has one-gee surface gravity from its own mass. In my mind it’s physically the ultimate artificial habitat until we learn how to make pocket Universes – for that idea check out Greg Egan’s story Borderguards.
A habitable object 1.2 light-years across would mass 2 trillion solar masses – twice the Milky Way. Such an object would be visible via its waste heat, but the red-shift would make it almost invisible – thus making for a hefty “Dark Matter” Galaxy. Birch says the inner layers (it is composed of 30 million nested shells) could have a red-shift/time-distortion factor of 2,500 making for some very curious possibilities indeed. Total area is ~200 billion trillion Earths – all of it inhabitable, unlike most of Earth. A population of 10^35 would be feasible. Surely a worthy effort for a Kardashev Type III to create over a few billennia.
Perhaps Dyson Clouds/Shells are insufficiently ambitious for our SETA efforts?
I’m quite glad that there are apparently no Dyson swarms near this location- the idea of a Nicoll-Dyson beam is a little unsettling (I’m the one who made the image for OA , by the way: yes, it is supposed to be a swarm, not a shell).
I note that Mr Nicoll calculates that these things could be effective at very long distances- so perhaps my relief is ill-founded.
Hi Steve – Nice job on bringing the Nicoll-Dyson Beam concept to
public attention.
I know Orion’s Arm is as much about creating stories which will
naturally require conflict as depicting a possible future for the
galaxy, but would you also be able to add more text on this aspect
of the Dyson Swarm’s ability to launch solar sail craft and perform
Optical METI?
I think some very interesting stories could come out of those ideas
in the process as well, without always having to resort to the need
for war and destruction. I think that just being able to build a Dyson
Swarm alone would make most other beings think twice before
attempting to bother such a society/being.
That being said, just how far could a Nicoll-Dyson Beam reach to
inflict damage? The short Wikipedia entry the OA article links to
says millions of light years, but I have questions about that. Plus
my earlier queries here on more information about the device and
its abilities have yet to be answered, thank you.
The blog Cosmic Variance recently gave its own take on the
search for Dyson Swarms here:
http://blogs.discovermagazine.com/cosmicvariance/2008/12/02/no-dyson-spheres-found-yet/
As can be seen, the author like many others is still stuck in the
mode of a Dyson Swarm only being built by and a habitat for
organic beings. Thankfully a poster updated the author early
on in the comments section with the Matrioshka Brain concept
by Robert Bradbury.
I say again, while I am certain there are plenty of organic type
intelligences in the Universe along our lines, it is the artificial ones
who will be able to and will be conducting most of the cosmic
activities that we will be able to one day recognize.
Unless all intelligences become navel-gazers and/or get lost in
virtual worlds of their own making.
And we may not be thinking widely enough in terms of the trees
(beings living on worlds around stars) keeping us from seeing the
forest (whole galaxies as living beings).
…but would you also be able to add more text on this aspect
of the Dyson Swarm’s ability to launch solar sail craft and perform
Optical METI?…
Sure; no problem.
January 19, 2009
Russia Proposes Mission to Search for Evidence of Astroengineering
Written by Ian O’Neill
It is probably the most seductive urge for mankind: search for extraterrestrial life. There are many ways to look for life; from digging into the Martian dirt with robotic landers looking for pre-biotic compounds, to building vast radio antennae to “listen” out for distant communications either leaked or transmitted deliberately from a distant star system from a developed, intelligent civilization. However, despite our best efforts, we appear to be the only form of life for hundreds of lightyears around. It is eerily quiet out there…
Although we appear to be drawing blanks so far, it doesn’t stop us from trying to work out what we should be looking for. In the quest to find a vastly advanced alien civilization, a forthcoming Russian space telescope hopes to bridge the gap between science fiction and science fact, attempting to find evidence (or lack thereof) of observable attempts of astroengineering by an alien race…
http://www.universetoday.com/2009/01/19/russia-proposes-mission-to-search-for-evidence-of-astroengineering/
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