No Dyson Spheres Found Yet

By Sean Carroll | December 2, 2008 12:20 am

dyson sphere 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 Jr

Abstract: 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.

CATEGORIZED UNDER: arxiv, Science
  • Chris Leonard

    I thought this was goint to be about the new Dyson vacuum cleaners that pivot on a ball. The shame!

  • http://onionesquereality.wordpress.com Shubhendu Trivedi

    Sean,
    I was just about to ask, after reading this line: The solution is then obvious: a sphere of matter that encircles the entire star.
    Isn’t it a swarm? “Sphere” though popularized by trekkers is nothing like a sphere in the sense we know it.

    And then I just read the line by Richard A. Carrigan, 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. So that clears it. :)

    Your article that points out that there is ACTUALLY a program dedicated to finding Dyson Spheres was very interesting. In the meanwhile, there are some interesting variations to the Dyson Sphere idea like the Matrioshka Brains, now if something like a matrioshka brain existed finding it would be very difficult than a Dyson sphere as you described it.

    This is what I like about Dyson, no fear in proposing something that mainstream physicists would smirk at at best, basically for the sheer “less likely coefficient” of the ideas. :)

  • http://diracseashore.wordpress.com/ Moshe

    Took me a while to understand the logic, but it really is beautiful: a search strategy for extraterrestrial intelligence that explicitly, almost deliberately, excludes us. I suppose we cannot hold our own as respectable species until we build this contraption, now it’s a matter of pride.

  • http://jollybloger.blogspot.com Jolly Bloger

    What with the recent “invisibility cloak” research going on, where some sort of nano-meta-material is able to do very strange things with light, it seems likely that a civilization twelve orders of magnitude beyond ours would have some way of redirecting the used energy to some other goal – perhaps focusing it into a long-range communication system with other advanced civilizations.

    Yes, I know, thermodynamics and all, but if we’re talking about Dyson spheres we can think outside the box a little.

  • http://radoslav-harman.blogspot.com Radoslav Harman

    Perhaps the universe is densely populated by Matrioshka brains that are almost impossible to detect … and we have an explanation for the dark matter. (Just joking :-)

  • http://onionesquereality.wordpress.com Shubhendu Trivedi

    Actually Radoslav,
    Robert Bradbury (the originator of the idea of Matrioshka Brains) once told me over e-mail exactly the same thing as you said. And he was not joking. He said that a small “component” COULD be matrioshka brains or similar structures.

  • http://onionesquereality.wordpress.com Shubhendu Trivedi

    But these are speculations. The universe is so HUGE, we can’t say what to expect.
    and thus:
    We should not be afraid to speculate but we should be careful to separate speculation from fact.

  • Alan Haggard

    The irony.. I was just reading about this project a few weeks ago. In my opinion, it seems to be one of the least likely projects to find evidence of intelligent non-terrestrial life, almost as unlikely as SETI, primarily because of the monumental amount of time & resources it would (seemingly) take to construct such a device (a Dyson sphere) when there would likely be other alternatives, likely more efficient an powerful to be invented or discovered (i.e. exotic matter or negative mass propulsion/powerplant technology, anti-matter reactors, etc.) . Optical SETI would appear more promising of the three (to me, at least), considering the time-frame in which laser technology would be used is more likely to be greater than that of radio communication, but I could be wrong. Regardless, it can’t hurt to look, whether it be for traces of Dyson spheres (even if they’re relics of a long-dead civilization) or extra-terrestrial radio signals of some sort.

  • physics groupie

    nice article about DS observation programme here:
    http://physicsworld.com/cws/article/print/33579

  • http://blogs.uslhc.us/?author=9 Seth Zenz

    This is a fascinating project, and worth a look given that how much easier the search is than when Dyson first proposed it. However, it doesn’t seem too likely to bear fruit, at least not in its simplest form; even of aliens built such a structure, it’s not at all clear what temperature they would radiate at. For one thing, it’s hard to guess what ambient temperature they prefer. For another, they would probably have the technical capability, and very possibly the motivation, to hide themselves a bit better.

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  • Metre

    Repost – there were posting errors in teh first post:

    Personally, I’m in the camp that while life may be common, intelligent life is not. On our own planet, intelligent life capable of space travel and radio communications has been around for only one million of the 4 billion years that life has existed – that’s 0.025% of the history of life on earth. And of that million years, only in the last 100 years have we developed the requisite technology – that’s 0.0000025% of the history of life. In terms of the Drake equation (http://en.wikipedia.org/wiki/Drake_equation), the probability that intelligent life exists on a planet is given by fi and the probability that it has developed sufficiently advamced technology is given by fc.
    The current estimate for the product fi*fc is .01%. But I think the value that I derived above is a better estimate given our one data point (Earth); that is, fi*fc = 0.0000025%. In evolutionary terms, intelligence requires time to develop and is only one strategy for survival. Other factors such as big teeth, sharp claws, and size are simpler to evolve and have been shown to be very effective in helping a species survive. The rarity of intelligent life would explain the negative result of SETI and the Fermi paradox and the search for Dyson spheres.

  • Thomas

    Any civilization with the capability and interest in redesigning an entire solar system also ought to be interested in interstellar travel, which at this level of technology becomes almost trivial (although still slow). We should therefore not be surprised that we don’t find one in our neighborhood, if one existed it would most likely have absorbed our solar system too. Maybe, if they were very ethical, they’d have left Earth alone as already inhabited, but Jupiter would be way too tempting.

  • gopher65

    Metre: I agree.

  • http://mirror2image.wordpress.com Serge

    It could be just too early. The age of the universe is about 14 billion years, the age of the solar system is about 8 billion year and it took about 4 billions years to develop intelligent life on the Earth. The age of the galaxy seems about the same as the age of the sun. So we could be just early arrivals in our galaxy, and not far behind other galaxies too. We also have no idea how fast intelligence can evolve, with or without technological singularity. The developing tech for dismantling gas giants can take another billion years of sentient evolution.

  • Elliot Tarabour

    “In the emerging spirit of science and entertainment exchanges, there will be a panel discussion at Caltech’s Beckman Auditorium this Friday (the 6th) with Derrickson and Reeves”

    ————————————————————————————————————————————–

    and of course Sean will be pitching the winning idea(s) from the elevator pitch contest to both of these gentlemen…….

    e.

  • A-Tom-IC

    I see no mention of the event on any of Caltech’s websites, and Friday is the fifth, not the sixth.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    Caltech does not yet have its act together, but hopefully information will be up soon. I personally got my act together by fixing the typo.

  • http://tyrannogenius.blogspot.com Neil B

    Sure, no Dyson spheres – but an entire sphere around a star is a rather ambitious and perhaps physically unstable project (well, I suppose the proper rotation rate might average out stresses OK, I wouldn’t know.) The Larry Niven Ringworld type idea – just a band all around in the equatorial plane of the star, same as a solar system (more or less) is much more credible and likely to be out there. Even more cool, you can stack them up since at a distance, a narrow enough ring recedes in angular width relative to the disk of the star. That might actually be out there – are our methods capable of finding them? After all, few thought we’d have real pictures of planets around other stars so soon.

    http://en.wikipedia.org/wiki/Ringworld

  • http://albatross.org Albatross

    A ringworld around a star is a logical precursor to a full-on Dyson sphere, and ought to be detectable as it occults the star and makes it “blink” (assuming we’re lucky enough to be close to edge-on to the ring).

    A ringworld that is simply a kind of large open-topped space station – in other words, one that does not necessarily encircle a star – is another logical step towards a star-encircling ringworld. Anyone who has seen the “Halo” video games has seen a representation of this smaller kind of ringworld. I don’t know that they would be particularly detectable.

  • mandeep gill

    Sean- Did you mean 1 AU in *radius*, not diameter, for the reradiating sphere, or did you really mean a sphere that had a radius half of the Earth’s orbit when saying it would reradiate in the far IR..? Intriguing post! -M

  • Karl

    What about other celestial bodies like asteroids, meteors, and the like. Even if the sphere is strong enough to withstand the constant bombardment how will it stay in one place? Its an accident waiting to happen. What about when our star dies? Seems like a bad idea to me.

  • http://blogs.discovermagazine.com/cosmicvariance/sean/ Sean

    I meant “radius,” of course. That’s what I get for late-night posting.

  • Metre

    Serge,

    I concur. It may turn out that we among the first generation of intelligent life to emerge in the cosmos. It took 4 billion years for intelligence to develop on earth, and earth has a number of special features (beside liquid water) that have allowed life not just to exist here, but to fluorish: a protective atmoshere, a protective magnetic field, and a large moon. Take away any one of these and life would still exist on earth but only in limited, protected niches. Big brains are complex devices that take a lot of evolutionary time and trial and error to develop. If life is constrained to a few limited areas on a planet, the chances of intelligence developing become nil. Only on a planet where life flourishes virtually everywhere and for much of the planet’s history will intelligence have a chance to develop. So if we include all of the earth-like features (atmosphere, mag field, moon), I believe the number of earth-like planets is over-estimated in the Drake equation as well.

  • Odani of the Aliens

    C’mon guys–we use dark energy for our “civilizations”, ’cause there’s a lot more of it. Once y’all figure out how to measure it, and start lookin’ around, we’ll be out of the closet. Current Milky Way betting is that some sort of Prop 8 will keep you from ever gettin’ to that point–I’ve got a sizable bet that way myself.

  • Lawrence Crowell

    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

  • http://tyrannogenius.blogspot.com Neil B

    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?

  • Lawrence Crowell

    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

  • http://teoriasdomiguel.blogspot.com/ miguel
  • http://mirror2image.wordpress.com Serge

    @ 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?

  • Kenneth

    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.”

  • Lawrence Crowell

    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

  • Lawrence 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

  • Elliot Tarabour

    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.

  • Lawrence Crowell

    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.

  • changcho

    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!

  • http://www.pipelin.com/~lenornst/index.html Leonard Ornstein

    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

  • Jeff

    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.

  • Low Math, Meekly Interacting

    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.

  • Lawrence Crowell

    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

  • Low Math, Meekly Interacting

    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.

  • Low Math, Meekly Interacting

    Bah, CH4. Damn fingers.

  • Lawrence Crowell

    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

  • http://lablemminglounge.blogspot.com Lab Lemming

    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.

  • Joseph Brant

    ” I guess I should go ahead and submit my DOE grant proposal to look for photon torpedo signatures in the CMB.”

    *snicker*

  • Jonny

    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.

  • Fermi-Walker Public Transport

    Serge,

    See http://arxiv.org/abs/astro-ph/9901322
    which is based exactly on the point you raise.

  • Lawrence Crowell

    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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  • My-Name-is-Kenneth

    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.

  • amphiox

    How would we distinguish a ringworld type structure from something natural, like a particularly dense asteroid belt?

    While we have been “intelligent” here on earth for more than a million years, I doubt that we could credibly argue that we have been intelligent enough for space travel for that entire period of time. I don’t think H. erectus and H. habilis would have been capable of a space program, no matter how much time we allow for cultural evolution, though both would certainly qualify as intelligent species.

  • Lawrence Crowell

    Kenneth above provided the following link

    http://arxiv.org/abs/astro-ph/0503580

    which does address the question of how to distingish between an asteroid ring and an ET artifact.

    Lawrence B. Crowell

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  • http://impearls.blogspot.com/ Michael McNeil

    How about somebody taking a look for some of these Dyson-predicted objects?

  • Lawrence Crowell

    Maybe they exist, or for that matter we humans might release self-replicating nano-bot/AI systems into the solar system. However, if some other solar system is inhabited by such things they would need to make some sort of measurable impact on the stellar system. We appear to be on the cusp of being able to observe fine details of extrasolar systems. I think we can expect lots of scientifically interesting developments, but I suspect we will probably not find anything like ring worlds, Dyson spheres or any massive ET engineering of these systems.

    Lawrence B. Crowell

  • Count Iblis

    The total power available is much larger. In theory, you could compress an object, say an asteroid, into a black hole. Such a black hole would emit Hawking radiation at huge powers. You can then feed it using the matter from the star. This then converts matter into energy much more efficienctly than fusion processes in the star.

  • Count Iblis

    Actually, thinking about this a bit more, I think that you wouldn’t expect that advanced civilizations would bother to make Dyson spheres because the energy that is leaking away is insignificant to the energy they can generate themselves. They can do that using black holes as I explained above. It is then practical to use a big mass of cold matter instread of a hot star. So, they may use brown dwarfs for this purpose.

    So, perhaps the signature of an advanced civilization would be high energy neutrino emissions from cold dark objects like brown dwarf stars. If the civilization captures all the gamma rays emitted from their micro black holes, then the high energy neutrinos will still escape.

  • Lawrence Crowell

    A dyson-like sphere or ring around a large Kerr type black hole would be set up to extract the rotational eneryg of the black hole according to the second laws of BH thermodynamics. It would have to be a big thing, and it could extract a significant portion of the BH’s mass-energy.

    If atom sized black holes exist or can be manufactured in some ways a confinement system could keep feeding matter in at the same rate energy in the form of radiation comes out. Of course black holes that size probably quantum produce a lot of neutrinos. Of course this thing would require some tricky balancing to make work. An interruption in the matter feed could cause it to explode.

    Lawrence B. Crowell

  • Amenhotep IV

    I’d like to point out that the “Dyson Sphere” is a conjecture about what an advanced spacefaring civilization might come to look look like overall, and not necessarily some sort of colossal “public works project” that such a society would build on a whim. I.e. they would begin with only a modest array of orbiting collectors, and after a few aeons of slow geometric growth (assuming availability of building materials), the collectors might attain such an enormous multitude as to noticeably occlude the star itself.

  • John R Ramsden

    I can’t see aliens hanging around in one solar system long enough to bother with Dyson spheres.

    Once they’ve discovered all the laws of physics they can verify, and catalogued everything in nature on their planet, and written every tune and told every joke in a hundred ways (all preserved in some super-duper Wikipedia-like repository, perhaps plugged straight into their minds) the only thing left to save a remorseless decline is to head off for pastures new and see more of nature’s variety.

    We’ve all heard about lone astronauts zooming off at close to the speed of light, and returning in a few of their years to find centuries or eons have passed back home, and this gloomy scenario is seen as proof that star travel is impractical.

    But suppose *everyone* heads off at the same time, and coordinates their arrival elsewhere to compare notes. This isn’t so far-fetched when you consider that populations will probably decline once robots become ubiquitous, and when you take into account the likelihood of civilizations going stale or even turning ugly in some sense if they hang around together in the same place for too long.

    I pursued this idea further in the final comment on Jennifer Ouellette’s recent blog article on Little Green Men.

    In summary, I believe the reason we’re unlikely to see Dyson spheres, or intercept alien signals, is that from our standpoint all the aliens spend decades or centuries travelling at 0.99c and have no reason to be even awake during their journey let alone chattering via radio.

    Of course, that’s not to say they’d be so quiet when they meet at their rendezvous, and recharge their batteries (perhaps literally).

  • Lawrence Crowell

    I wrote a book which discusses the physics of interstellar exploration. I consider the prospect of sending robotic probes more than any actual star travel. The little book is more as a way of discussing classical mechanics and relativity than any serious proposal. However, I do think it is possible to explore nearby extrasolar systems. The big limitation is energy. A low gamma probe gamma < 2 or so has velocity < .86c, or half or less of the the mass-energy on the craft be in its relativistic kinetic energy. It is not impossible of course, but it is difficult. There are various approaches which might work, where some form of solar concentrated light or radiation on a large sail might be feasible. I also discuss elecromagnetically propelled nano-probes as well.

    If we were to find a rocky planet around a star within 25 to 50 light years of Earth that has biological signatures a considerable scientific premium would be placed on plopping a probe down there to look at things close up.

    Sending a crew to other stars does what we see with more parochial space exploration now, it magmifies the costs and energy requirements enormously. Any form of intelligent life is probably faced with the same resource/energy/cost limitations. I suspect that ET is a very rare occurrence in the universe (one per so many galaxies), and far rarer will be cases where they manage to control the external world in space on magnitudes seen in science fiction stories of star travel or with thinks such as ring worlds or Dyson spheres.

    Lawrence B. Crowell

  • John R Ramsden

    Lawrence, your book sounds fascinating and I must buy a copy. However, in the long run the inexorable social progression (or decline) of advanced civilizations are probably the best determinants of how interstellar travel will pan out, or the overriding motive to start it, and maybe psychologists or even historians are better placed to provide insights on that.

    You mention cost as a limiting factor. But in the twinkling of an eye, as we can anticipate even today, there will be armies of robots waiting on us hand and foot. Few now dispute that, except for the timing (which admittedly has always seemed to be “in about 20 years” ever since I can remember!).

    As well as removing any advantages of having hordes of humans, as now (the point in my preceding post about populations declining), robots with their replication and self-repair abilities also obviously allow engineering projects of a qualitatively higher scale but at a similar “start up” cost, just as today’s PCs calculate PI to billions of d.p.s at the push of a button, in contrast to 19th century human calculators who struggled for years to find a mere 100 d.p.s or so.

    Global warming? No problem – program an army of robots to excavate rock from under the antarctic ice sheets and build a vast 10,000 mile long perimeter wall round that continent to contain a repository of ice there twice as thick as it is today. (Actually the weight of all that extra ice would probably depress the crust, which might cause problems. But that’s an example of the kind of project which couldn’t be contemplated in practice today.)

    The same applies in space. I imagine the first thing an alien (or future human) team will do on arriving in a new unoccupied solar system is to instruct robots to start mining asteriods and building tremendously long rail guns, or a relay of dozens of these, all to be aligned ready for their departure. In due course they would have the means to literally shoot out of that solar system at a large percent of light speed, after which the robots would dismantle it all including finally themselves, and leave everything as it was found.

    You may be right about ET being a very rare occurrence, but the sheer number stars even in one galaxy (the number of grains in a large barrel full of sand) must increase the odds. Also, of course once one star-hopping ET civilization emerges perhaps one of their goals will be to nudge life in a direction favourable to the emergence of intelligent life, or even resculpt whole solar systems for that purpose if the fancy takes them. So it may not be solely a matter of blind chance.

    In parting I’ll return to my first theme, the decline of population. With the knowledge of past multitudes that occupied the Earth, the few people living in that time will feel that in a sense the party’s over at least in its current form. As the Good Book says (Lamentations v1 ch1) “How doth the city sit solitary, that was full of people!”. I’m certain there will be a feeling that it’s time to move on to pastures new, reinforced by a growing belief (perhaps of a cult) that our solar sytem is only a stepping stone or “cradle” and our destiny lies in further travel. After all travel, or a change of scenery, is a human instinct, from our nomadic ancestors.

  • Count Iblis

    I think that these robots will simply take over from us. We will make faster and larger computers until we become obsolete outdated technology ourselves.

    If you are a robot then you can travel at the speed of light from one civilization to another by uploading your brain to a machine located at the other civilization via radio communications or perhaps using lasers.

    A civilization can spread itself to other uninhabited solar systems by sending nanotech machines that build up some infrastructure there. Then they can upload themselves to the new location.

  • Pingback: Timeblog.de » Noch keine Dyson-Sphäre gefunden()

  • Pingback: David Galbraith’s Blog » Blog Archive » No Dyson Spheres Found Yet()

  • Lawrence Crowell

    The Ramsden/Iblis ideas here are a bit “far out.” I will say right off that the best way to reduce global warming problems is to stop doing what we are doing! If we have to engage in heroic technological programs or space activities to hedge global warmings I imagine we could build large panels woven with carbon nanotubes which Mie scatter sun light to reduce the illumination of Earth. These could be placed at the L1 Lagrange libration point, and if we are ambitious enough we might reduce the illumination or irradiance of the Earth’s surface by .5 watts/m^2 and counter the effects of CO_2 warming.

    I do disucss the prospect of nanoprobes sent to other stars. I discuss using railgun type of technology to send the little buggers out to other stars. The fly in the ointment is how to stop them once they get there? But a small number of these might find their way to an asteroid on another solar system and once there they replicate to build a network which acts as an exploration-teleresponding system that sends data back to us.

    We might end up unleashing self-relicating AI systems or nano-bots into the solar system or other solar systems. This might prove to be another uncontrolled experiment we humans are so good at setting up, where a case of this is global warming.

    Lawrence B. Crowell

  • http://gamesrevue.com Nestor

    Even if they find nothing, negative findings are data too… Though personally I dislike the Dyson sphere as a concept on aesthetics alone. You’d get all the energy sure, but your solar system would end up looking like shit…

  • Lawrence Crowell

    Nestor: That is an excellent point. What we have seen and probed of the solar system has a beauty to it. Stark maybe, but there is a beauty to it. The rover-robots moving around Mars have shown a landscape that is devoid of life, but it is artfully sculped by nature. This is also why I am generally opposed to grand schemes on Earth to dam up rivers or change the landscape. The current mountain topping coal mining in the Appalachian mountains I think is an abomination.

    Lawrence B. Crowell

  • Russell Bushby

    I have one major concern about the issue of building a dyson sphere, or even a Niven type ring….. Where would we get planning prmission from?

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .

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