Over at The Economist there's an interesting article about new plans to seek intelligent life in the universe by looking for the signs of what we think an advanced civilization would create. To wit: Vast artificial worlds like the halo worlds in Halo or Ringworld. Or Dyson Spheres, which showed up once on Star Trek. The Allen telescope, an array of dishes being constructed in the California mountains, will be targeting likely Dyson Sphere systems.
The Economist explains:
Freeman Dyson's idea that a truly technologically advanced species would endeavour to capture as much light as possible by building a spherical shell around its central star. Such so-called Dyson spheres would, if they exist, reradiate captured energy (after some of it had been put to good use) as heat-infra-red radiation.
This radiation can be detected although Dyson spheres remain difficult to distinguish from natural astronomical objects that give off similar signatures. The birth and death phases of stars, for example, are associated with heavy dust clouds that give off an infra-red signal which might resemble the swarm of artificial satellites constituting a Dyson sphere.
So far, few astronomers have conducted searches for Dyson spheres-and none has been successful. But [particle physicist] Dr Dick Carrigan still thinks it is worth trying. He has been cataloguing possible candidates from the Infrared Astronomical Satellite, a collaboration between America, Britain and the Netherlands that conducted the first space-based survey of the entire sky at infra-red wavelengths and located hundreds of thousands of sources. On his website he offers tips for amateur cosmic archaeologists who wish to hunt for Dyson spheres. An investigation of SETI signals from the 13 "least implausible Dyson sphere candidates" is planned for the Allen telescope.
You'll want to read the whole article about the Allen telescope - it's really an interesting project that's entirely devoted to seeking out intelligent life beyond Earth.