In 1960, Freeman Dyson proposed an audacious form that future technology might take: the Dyson Sphere. It’s a simple idea, once you stop thinking in terms of “I wonder how that could be done?” and start thinking along the lines of “I wonder what is physically possible?” Dyson reasoned that an efficient civilization wouldn’t want all of the valuable energy from its home star to fly uselessly into outer space, so they would try to capture it. The solution is then obvious: a sphere of matter that encircles the entire star. It’s worth quoting a bit from Dyson’s original paper:
The material factors which ultimately limit the expansion of a technically advanced species are the supply of matter and the supply of energy. At present the material resources being exploited by the human species are roughly limited to the biosphere of the earth, a mass of the order of 5 x 1019 grams. Our present energy supply may be generously estimated at 1020 ergs per second. The quantities of matter and energy which might conceivably become accessible to us within the solar system are 2 x 1030 grams (the mass of Jupiter) and 4 x 1033 ergs per second (the total energy output of the sun).
The reader may well ask in what sense can anyone speak of the mass of Jupiter or the total radiation from the sun as being accessible to exploitation. The following argument is intended to show that an exploitation of this magnitude is not absurd. First of all, the time required for an expansion of population and industry by a factor of 1012 is quite short, say 3000 years if an average growth rate of 1 percent per year is maintained. Second, the energy required to disassemble and rearrange a planet the size of Jupiter is about 1044 ergs, equal to the energy radiated by the sun in 800 years. Third, the mass of Jupiter, if distributed in a spherical shell revolving around the sun at twice the Earth’s distance from it, would have a thickness such that the mass is 200 grams per square centimeter of surface area (2 to 3 meters, depending on the density). A shell of this thickness could be made comfortably habitable, and could contain all the machinery required for exploiting the solar radiation falling onto it from the inside.
Old news, right. What I hadn’t realized is that there is something called the Fermilab Dyson Sphere search program, led by Richard Carrigan, which recently updated its results (summarized in the title of this post). A star like the Sun radiates something pretty close to a blackbody spectrum; but if you capture all of the energy in the Sun’s radiation, and then re-radiate it from a much larger sphere (e.g. one astronomical unit in radius), it comes out at a much lower temperature — a few hundred Kelvin. Dyson therefore proposed a search strategy, looking for blackbody objects radiating in the far infrared, around 10 microns in wavelength.
And the search is now going on! Indeed, Carrigan’s most recent results were just released on astro-ph a few weeks ago:
IRAS-based whole-sky upper limit on Dyson Spheres
Authors: Richard A. Carrigan JrAbstract: A Dyson Sphere is a hypothetical construct of a star purposely cloaked by a thick swarm of broken-up planetary material to better utilize all of the stellar energy. A clean Dyson Sphere identification would give a significant signature for intelligence at work. A search for Dyson Spheres has been carried out using the 250,000 source database of the IRAS infrared satellite which covered 96% of the sky. The search has used the Calgary data collection of the IRAS Low Resolution Spectrometer (LRS) to look for fits to blackbody spectra. Searches have been conducted for both pure (fully cloaked) and partial Dyson Spheres in the blackbody temperature region 100 < T < 600 deg K. Other stellar signatures that resemble a Dyson Sphere are reviewed. When these signatures are used to eliminate sources that mimic Dyson Spheres very few candidates remain and even these are ambiguous. Upper limits are presented for both pure and partial Dyson Spheres. The sensitivity of the LRS was enough to find solar-sized Dyson Spheres out to 300 pc, a reach that encompasses a million solar- type stars.
It’s too bad the search has thus far not turned up too many promising candidates. The Fermi Paradox continues to be paradoxical.
One famous account of the first contact between an extraterrestrial civilization and the human race was told in the classic 1951 Robert Wise film, The Day the Earth Stood Still. It’s now been remade by director Scott Derrickson, starring Keanu Reeves as the alien Klaatu, and will open next Friday. In the emerging spirit of science and entertainment exchanges, there will be a panel discussion at Caltech’s Beckman Auditorium this Friday (the 5th) with Derrickson and Reeves holding up the Hollywood side of things, and roboticist Joel Burdick and I holding up the science end. Don’t quote me on this, but I think it’s at 6:00, and the movie will be screened before the panel. Should be fun.
Given that the universe of galaxies we observe is about one part in 10^{50} of the whole thing due to inflation it is possible that somewhere here and there a Dyson sphere is built. Maybe one galaxy out of a trillion at some point ends up with a star encloaked this way. Based on some work I did over 10 years ago I suspect that there might only be ~ 1000 stars in an average galaxy with a bio-planet similar to Earth and we might suspect that a small fraction of them produce intelligent life.
Dyson spheres and ring worlds? I’d frankly kiss my *** if we found something like that. It would be a major coup if optical interferometers could detect a planet similar to Earth within a few hundred light year radius around the Earth. SETI? I doubt that will materialize into anything. I will give Carrigan a point for having the temerity to a write a proposal for a Dyson sphere search.
Michio Kaku has gotten off on some of these speculations, such as intelligent actors which control entire galaxies and even more design entire cosmologies! I do tend to see this as far more in the way of science fiction than science — though science fiction can be fun. I frankly think that the exponential growth apparently argued for with these things is not sustainable. The physical manifestation of such growth leads to nonlinear feedback and chaos such as the logistics equation or the Henon-Heiles system. There are attenuating influences on any such exponential growth system, which we humans still on our planet of origin might be running into right now, that leads to strange attractor physics.
I suspect that if anything follows us humans it will be nano-bots or vonNeumann probes we might end up releasing into the solar system. I pretty strongly think we humans are not going to colonize space, for anything off Earth is simply lethal. So maybe in a billion years the solar system will be transformed by some emergent ecological-like system of self-replicating and evolving nano-bots or AI systems which stemmed from us. These might of course head off to other stars and then … ???
Lawrence B. Crowell
A ringworld around a star is a logical precursor to a full-on Dyson sphere,…
Heh, must we always let developers get their way? Save our orbitspace!
BTW, maybe we can do some space migration and ward off global warming to boot by building a ringstation around Earth. But considering how long even that would take compared to GW progression, maybe just an aluminized mylar hoop with a few compartments here and there is in order. Doable over several decades, to save the Earth?
Odani of the Aliens Says: C’mon guys–we use dark energy for our “civilizations”, ’cause there’s a lot more of it.
Sure, connect two distant galaxies by a long thread, say a dark matter tube, and dark energy pulls the galaxies apart and you extract energy!
We might want to work more provincially on the space elevator before trying that stunt! 🙂
Lawrence B. Crowell
leiam. http://teoriasdomiguel.blogspot.com/
@ Lawrence Crowell
“I pretty strongly think we humans are not going to colonize space, for anything off Earth is simply lethal. ”
It depend on what we should consider to be ” we humans”. Could Homo Erectus accept “us” into his tribe ? What about Australopithecus ? Should we consider intelligent being, with part of the consciousness inherited from or trained/nurtured by humans proper to be belonging to our lineage and therefore to be a human or at least human descendant?
Regarding Niel’s comment about the Ringworld, I saw this paper on astro-ph a while back
http://arxiv.org/abs/astro-ph/0503580
and almost immediately thought “shadow squares.”
I suppose these ideas are fun, even if they are off the wall.
As for a moon needed around a bio-planet, it might be the answer to that is found in the first StarWars movie. The rebels are situated on a lush planet that orbits a gas giant, which the Death Star is closing in on. Many Jovian planets are fairly close to their parent star, and it might be possible that bio-active planets orbit a few of these. Of course there are issues of the large radiation belts such a Jovian planet might have, whether rocky planets can form around them and so forth.
I have found it amusing that so many people think that space is a way of solving our problems on Earth. Space travel has not followed the Moore’s law very well. It cost billions of dollars to keep this ISS white elephant going which houses three people. Without some sort of change over to a Moore’s law with the energy and costs associated with space flight I think the idea of space migrations is permanently postponed.
The best way to save Earth, or more to the point to preserve our life support system here, is to stop doing a lot of things we are doing.
Lawrence B. Crowell
Serge: There are two major problems with space migrations. The first of course is energy. You can’t get around the T = 1/2mv^2 required to get to orbital or escape velocity. The other is that even if we evolve into some super-humans (a conjecture I honestly doubt for various reasons) these descendent will still be biological organisms. There is very little off Earth that is compatible with aqueous bags of proteins, lipids and saccharides … no matter how smart they are.
Lawrence B. Crowell
Will all of our “descendants’ be carbon/water based life forms? We already see organ replacements with plastics. It may be that some of our offspring are made of completely different materials than we can even envision today.
We should keep our eyes and ears open to radically different versions of intelligent information processing in the universe and not be so carbo-centric in our perspectives.
e.
Then we become like the Daleks on Dr. Who, assuming the brain is the last thing to be replaced. Well maybe, but I tend to think these ideas are somewhat suspicious.
L. C.
Of course, Dyson got the idea for the Dyson sphere from reading Starmaker, by O. Stapledon. Dyson makes this quite clear if you read his writings. However, if my memory serves me right, Stapledon wrote about wordlets circling a star along an artificial ring, sort of like a string of pearls to absorb the energy.
I am very disappointed that they’ve got Keanu ‘dude’ Reeves to play Klaatu; c’mon they could have done much better!
Sean:
Neil B. and Karl come close to a reason why searching for a Dyson Sphere makes little physical sense:
Only the portion in the plane of the solar equator would be gravitationally stable. The rest would ‘fly apart’.
For biological arguments why such a search – and SETI, are rather hopeless, see my 1982 article in Physics Today, at
http://www.pipeline.com/~lenornst/SETI.html
Did you submit your April Fools’ Day post a few months early? The Dyson sphere is a clever figment of the eponym’s imagination. What a worthless endeavor to actually look for such a thing. I thought Fermilab was cash-strapped. I guess I should go ahead and submit my DOE grant proposal to look for photon torpedo signatures in the CMB.
I hold out more hope for atmospheric spectrometry than current SETI efforts or studies such as this, fascinating as they are. We have but one example to base our entire study of what might be out there in terms of intelligent life, and I have serious doubts in our ability to anticipate what form an alien technology might take, given this abject paucity of data. Then there’s the matter of compression, which might make any EM signal of any spectrum difficult to discern from noise if it isn’t awesomely collimated and aimed straight at us.
That said, it’s perhaps less of a stretch to expect that life will leave a recognizable chemical imprint, given that we define “life” to be something that can replicate and autonomously extract energy from its environment to do so. Assuming those very basic criteria, some kind of waste should be generated, and it ought to be in an abundance difficult to explain via non-living processes. Maybe if those wastes are sufficiently esoteric, it might indicate manufacturing. At any rate, if we can just find life, any life, elsewhere, we’d hopefully have some clue, at least, of how to proceed in our search in a more-informed fashion.
Of course, if “life” doesn’t necessarily fit those basic criteria, then we really have no idea what to look for, much less how or where to look for it.
Low math: I tend to agree that looking for planets with biological signatures is likely more profitable than SETI. The search for extrasolar planets is an active business and with optical interferometers we might image planets in an entire extrasolar system. If we find a terrestrial type planet with an oxygen atmosphere and traces of methane that is a pretty good clincher for life there. From there the ETI conjecture is pretty solid, but it just might be that the closest one is in the next galaxy cluster.
I read the wikipedia article on Dyson spheres and scanned the two papers referenced here. I doubt these things exist, or at least in any abundance. The ringworld strikes me as more realistic than the whole sphere, where the word realistic here is used very liberally. The stability of the sphere is a question. It is the sophmoric problem to show a charged spherical shell has no potential change within. So containing the star in the interior is a problem. This BTW was the problem of putting a black hole in a box, where the only available “box,” at least mathematically, is the AdS. The idea of using the stellar wind or photon pressure to hold the sphere outwards, like an array of kites, might work “sort of maybe,” but would require a lot of dynamic control I should think. Think of managing the power grid here on Earth and multiplying the complexity by billions!
I suppose humans have thought there are beings in the sky for a long time. Look at old star charts, there are angels or celestial beings depicted on them. Of course there are constellations as gods and heros, some cultures saw the milky way as a path to heaven, and most religions have God or the gods up in the sky. The modern variant is the alien and UFO. The problem of course is that I do think “they” are out there. The problem is the distances might be intergalactic and too vast to ever know for sure.
So we needn’t cover our heads with aluminum foil 🙂
Lawrence B. Crowell
Well, I like chemistry because it limits the number of assumptions you have to make. Just find two molecules (e.g. CH3 and O2) that ought to react like gangbusters, together, and if you observe them in the same abundance over an extended period of time, life is a plausible explanation.
I do have a question related to one of my points above, though, as it perhaps relies on too many assumptions, now that I think about it: Is it too prejudiced to assume that any civilization capable of producing a signal that we can detect over interstellar distances with current technologies would utilize something approaching maximal compression in its telecommunications? To the extent that I understand the arguments pro this assumption, I tend to find it pretty compelling, but I’m interested in opposing points of view. This excludes, of course, deliberate attempts at communicating with aliens like us, which, presumably, wouldn’t be compressed at all so as to maximize apparent signal:noise.
Bah, CH4. Damn fingers.
One of the better science fiction writers was Stanislaw Lem, and he made a point that intelligent life elsewhere in the universe might operate in ways that we can’t understand at all, maybe not even recognize as intelligent. How an intelligent life elsewhere would encode their thoughts into symbolic structures, if they do that at all, might be unfathomable to us. The converse might be the case as well. Some species of cephalopods here on Earth exhibit intelligence, or at least high levels of adaptive learning, where some species of octopi have brains the size of basketballs. They communicate by colour changes and patterns on their skin. A lot of neural processing goes on with those guys, and we understand little of it.
One problem with the whole SETI program is that interstellar space is filled with a very diffuse plasma. It has a Debye length and acts to attenuate signals. I doubt much of our radio transmission go much further out that a few light years. A source to radiate far out into space has to be pretty powerful, such as pulsars and further out radio galaxies. Also our communications are much more highly directed, and we use cable and fiber optic a lot. It is as if our planet is going radio silent.
I would imagine if some ETs want to send signals to other planets they would do so with a minimum of encryption or compression. After all the intention is to make an announcement instead of stealtily slipping a message past unnoticed.
Lawrence B. Crowell
The really cool thing about this is that we now have the capability to detect this kind of stuff. As for the argument that a civilization that can make one dyson sphere can travel the galaxy and make more, that just needs a slight change to the search process. You just look for galaxies with an underabundance of low mass main sequence stars, and an anomalous emission in the 100-400K region.
” I guess I should go ahead and submit my DOE grant proposal to look for photon torpedo signatures in the CMB.”
*snicker*
I would have thought a civilization advanced enough to build such a thing, would be able to make some pretty decent insulation, or not waste energy through heat radiation. So even if the spheres do exist, maybe we couldn’t detect them.
Besides I tend to think that there would be alot more ring-worlds rather than spheres.
Serge,
See http://arxiv.org/abs/astro-ph/9901322
which is based exactly on the point you raise.
Lab Lemming: That is what is interesting about this. This gives some lower bound on some of these exotic ideas. It might appear to be like searching for photon torpedos in the CMB, but this data mining is a curious endevour that supports our suspicions about these things.
Lawrence B. Crowell
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We assume that truly intelligent beings would WANT to talk to the momkeys with car keys on this lowly rock.
Now that is absurd, far more than building a Dyson Swarm. In fact, I contend that this lack of imagination on the part of certain people in this thread and beyond shows just how unworthy we are of contacting alien beings at this time.