The idea of the multiverse — an infinite number of universes co-existing with our own — has a philosophical and mathematical appeal, at least if you’re a follower of string theory. Indeed, there are those who would argue there could be as many as 10500 universes, each with its own particular characteristics, most probably inimical to the development of life. But I have to say that I’m far more interested in the universe that is demonstrably here, our own, and thus the news that Geoff Marcy has received a grant to look for Dyson spheres catches my eye more than news of a similar grant to physicist Raphael Bousso to probe multiverse theory.

Not that I have anything against Dr. Bousso (UC-Berkeley) and his work, and if he eventually does find a way to make predictions of multiverse theory that can be tested, I’m all for it. But I think the new grants, given to the researchers in a series called New Frontiers in Astronomy & Cosmology International Grants (funded through the UK’s Templeton Foundation), were wisely balanced between the practical (observational astronomy) and the highly theoretical. Marcy will use his to probe the continually swelling Kepler datastream looking for distinctive signatures.

Instead of planets, though, Marcy has more unusual targets, the vast structures Freeman Dyson hypothesized over fifty years ago that could ring or completely enclose their parent star. Such structures, the work of a Kardashev Type II civilization — one capable of drawing on the entire energy output of its star — would power the most power-hungry society and offer up reserves of energy that would support its continuing expansion into the cosmos, if it so chose. Marcy’s plan is to look at a thousand Kepler systems for telltale evidence of such structures by examining changes in light levels around the parent star.

Image: A Dyson sphere under construction. Credit: Steve Bowers.

Interestingly, the grant of $200,000 goes beyond the Dyson sphere search to look into possible laser traffic among extraterrestrial civilizations. Says Marcy:

“Technological civilizations may communicate with their space probes located throughout the galaxy by using laser beams, either in visible light or infrared light. Laser light is detectable from other civilizations because the power is concentrated into a narrow beam and the light is all at one specific color or frequency. The lasers outshine the host star at the color of the laser.”

The topic of Dyson spheres calls Richard Carrigan to mind. The retired Fermilab physicist has studied data from the Infrared Astronomical Satellite (IRAS) to identify objects that radiate waste heat in ways that imply a star completely enclosed by a Dyson sphere. This is unconventional SETI in that it presumes no beacons deliberately announcing themselves to the cosmos, but instead looks for signs of civilization that are the natural consequences of physics.

Carrigan has estimated that a star like the Sun, if enclosed with a shell at the radius of the Earth, would re-radiate its energies at approximately 300 Kelvin. Marcy will turn some of the thinking behind what Carrigan calls ‘cosmic archaeology’ toward stellar systems we now know to have planets, thanks to the work of Kepler. Ultimately, Carrigan’s ‘archaeology’ could extend to planetary atmospheres possibly marked by industrial activity, or perhaps forms of large-scale engineering other than Dyson spheres that may be acquired through astronomical surveys and remain waiting in our data to be discovered. All this reminds us once again how the model for SETI is changing.

For more, see two Richard Carrigan papers, the first being “IRAS-based Whole-Sky Upper Limit on Dyson Spheres,” Journal of Astrophysics 698 (2009), pp. 2075-2086 (preprint), and “Starry Messages: Searching for Signatures of Interstellar Archaeology,” JBIS 63 (2010), p. 90 (preprint). Also see James Annis, “Placing a limit on star-fed Kardashev type III civilisations,” JBIS 52, pp.33-36 (1999). A recent Centauri Dreams story on all this is Interstellar Archaeology on the Galactic Scale but see also Searching for Dyson Spheres and Toward an Interstellar Archaeology.