“Were the chemicals here on Earth at the time when life began unique to us? We used to think so. But the most recent evidence is different. Within the last few years there have been found in the interstellar spaces the spectral traces of molecules which we never thought could be formed out in those frigid regions: hydrogen cyanide, cyano acetylene, formaldehyde. These are molecules which we had not supposed to exist elsewhere than on Earth. It may turn out that life had more varied beginnings and has more varied forms. And it does not at all follow that the evolutionary path which life (if we discover it) took elsewhere must resemble ours. It does not even follow that we shall recognise it as life — or that it will recognise us.”

— Jacob Bronowski, from The Ascent of Man

How accurate do you think we are in projecting what extraterrestrial civilizations might do? The question is prompted by recent speculation on Dyson spheres and the supposition that advanced cultures will invariably build them. After all, a Dyson sphere would seem to be a natural for beings who wanted to extract as much usable power as possible from their sun. Such a civilization, which Nikolai Kardashev thought of as ‘Type II,’ using all the power of its star, would doubtless think breaking up a local gas giant and using it to enclose that star made sense.

Diagram of a Dyson sphere

So let’s assume for a moment that extraterrestrial beings follow a game plan we humans have devised. And let’s take it to the next logical level. Going from Type II to Kardashev’s Type III, cultures that exploit the resources of entire galaxies, we would have to admit the possibility of creating Dyson spheres around every star in a galaxy, an interesting thought when you ask what methods are best for detecting signs of intelligent life elsewhere in the universe.

Image: A Dyson sphere allows a civilization to exploit maximal energy from its star. Excess infrared could conceivably mark its location to SETI-oriented astronomers. Credit: Guillermo A. Lemarchand.

Hunting for Dyson Spheres

For instead of listening for radio broadcasts or looking for optical beacons, finding Dyson spheres, either by themselves or in a wavefront spreading through a galaxy, is an observational SETI that could be successful even if its targets have no interest in trying to contact us. Thus Bruce Dorminey’s recent essay on SETI’s new wave, the idea of searching for distinctive signatures of Dyson spheres and their derivatives. Dorminey, author of the fine Distant Wanderers: The Search for Planets Beyond the Solar System (2001), tracked down people who have begun looking for such objects. People like Dan Wertheimer (UC-Berkeley), who analyzed a thousand solar-type stars (having culled those at least a billion years old), looking for excess infrared. 32 stars made the final cut and were examined for radio or optical transmissions, with no sign of alien intelligence.

Dick Carrigan (retired from Fermilab) has spent five years on 11,124 sources identified by the Infrared Astronomical Satellite (IRAS). It’s all in Dorminey’s essay, how Carrigan went after objects with an infrared temperature of 200-600 K, looking for the radiation of waste heat, again finding no signs of intelligent activity when scanning several contenders for anomalous radio signals. Or consider James Annis (Fermilab), who analyzes not single stars but entire galaxies looking for signs of engineering.

Here’s Annis on the possibilities, looking for a galaxy that might emit only 100th of one percent of the light expected from it, the possible signature of astroengineering at work:

“If you were to see obvious dust clouds around a candidate galaxy in the infrared, then it could be a dusty starburst galaxy where the dust is very clumpy and you can see ongoing star formation. But if you got an infrared galactic image that was completely smooth with no lumpiness, that’s an interesting object.”

Dorminey notes that to achieve this level of dimming on a galactic scale, a Type III civilization would need to have gone to work on just about every star in its galaxy. Which cannot, of course, be ruled out when you’re dealing with technologies at this level. Even here, though, we have to avoid being too doctrinaire. One argument against intelligent life in the nearby cosmos is the lack of Type III engineering, the assumption being that any culture that could harness an entire galaxy’s power would already be blindingly obvious to us. “My guess,” says Dan Wertheimer, “is that just from the astronomical data on file we would have discovered such a civilization by accident.”

Alien Technologies, Human Assumptions

Would we? That would bring us back to Type II as the only kind of advanced civilization to look for, but I disagree with Wertheimer. Here’s one reason why: In trying to understand hypothetical alien cultures, we’re assuming we can extrapolate forward from our own technology to what we would do if we had the necessary tools. Thus Dyson’s sphere, maybe 150 million kilometers in radius, a meters-thick shell rotating around its star. We can see this as a desirable outcome, so we assume aliens would as well. But would they? Perhaps a Type II society would have made breakthroughs in energy management that would render a Dyson sphere a historical curiosity, like some early 19th Century idea of a flying machine powered by flapping wings and a steam engine.

No, I can’t imagine what those breakthroughs would be, but then, that’s the point. How accurate can we be about predicting what science will find down the road? As Brian Wang has recently noted, projecting technology on our own planet out even fifty to a hundred years is all but impossible. For that matter, how can we be sure advanced engineering works would even be detectable, much less understood? My border collies are supremely intelligent dogs (one of them, anyway), but do they understand the difference between artifact and natural object? Do they know what a technology is? Yet the gap between border collie and human could be minor compared to the gap between human and extraterrestrial, especially if the latter has been developing its own technology for millions of years, if not billions.

None of which is to downplay what Wertheimer, Carrigan and Annis have done. Although the odds are daunting, I’m all for keeping our eyes open, and if a search for anomalous stars with excess infrared emission turns up interesting objects, let’s by all means investigate them. If we find galaxies with high infrared and low optical luminosity, let’s subject them to detailed scrutiny. But let’s not make any more assumptions than we have to. A negative result in a search for Dyson spheres or anomalous galaxies may only point to the limitations of our ability to project where technologies go as societies enter higher Kardashev levels.

Anomalous Galaxies and Their Uses

NGC 5907

If you want to find something anomalous about galaxies, consider the case of NGC 5907, a spiral galaxy 39 million light years away. Observations of this galaxy in 1998 by Michael Liu (UC-Berkeley) and an international team of astronomers showed an odd mix of stars. Expecting to see hundreds of bright stars in their field of view, the researchers found only a few. Evidently twenty times more light comes from dwarfs than giant stars in the halo of this galaxy. Liu, lead author of the paper on this work, described the finding this way:

“Our results force us to turn to more esoteric descriptions of the stellar content of NGC 5907’s halo. In particular, our data combined with the measured colors of the halo suggest a very metal-poor stellar population with an enormous excess of faint dwarfs. This is the first direct evidence of a substantial population of stars which is essentially all dwarf stars. Such a population has been invoked in the past as a constituent of the dark matter making up galaxy halos.”

Image: NGC 5907. Can an entire galaxy become the subject of advanced engineering? If so, would we recognize the result? Credit: Brad Ehrhorn, Dan Azari, and Chris Lasley/Kitt Peak Advanced Observing Program.

Larry Klaes recently noted this as an example of anomalies that could be related to engineering on the galactic scale. His point was not that NGC 5907 demonstrates such, but that given the vast number of galaxies we have to observe, our attempts to examine them in the context of SETI are in their infancy. And if I am right that a Type III civilization is going to be extremely difficult to recognize, then hunting for galactic anomalies makes sense in the context of a broader search, rather than one focused on a particular, perhaps overly narrow range of emissions.

There is no question that we are re-examining the nature of the SETI search as we grapple with such issues. In radio frequencies, we are most likely to be able to receive a directed signal, which means that here — or in the optical range as well — our best bet is to find extraterrestrials who already have an interest in communicating with us. Again, we have no reason to assume that alien cultures will feel such a need. Extending SETI into the realm of deep-sky observation (optical SETI is already doing this), using parameters that are both carefully selected yet open to anomalous result, seems a natural and logical development.

LOFAR and the Quest for Synergy

Which brings us to LOFAR, the Low Frequency Array that is now planning to link radio detectors across Britain, France, Holland, Sweden and Germany. LOFAR studies a wide range of frequencies between 20 MHz and 80 MHz, and again between 120 MHz and 240 MHz. Its primary function is scientific, notes Robert Nichol of Portsmouth University in The Guardian:

“We will be looking for all sorts of different things with Lofar,” added Nichol. “We will make surveys of the skies to look for unexpected events; for things that go bump in the night, as it were. We will also be able to study the universe’s childhood years. We know a lot about the Big Bang, when the universe was created 13 billion years ago, and a lot about it now. But its early childhood years, around 500 million years after the Big Bang, remain a mystery.”

But Nichol adds that extraterrestrial broadcasts could potentially be found by LOFAR’s detectors. LOFAR, in other words, is a project dedicated to basic research that could have SETI ramifications on the periphery, and I think that’s about the right mix. Those of us who doubt SETI will produce a confirmed extraterrestrial civilization any time soon would still like to see synergy between ongoing science and the attempt to make such discoveries. And we’d like to be proven wrong in our SETI pessimism. Whichever wavelengths we’re studying, whatever objects in the heavens, let’s keep our minds open and hope to be surprised.