The search for signs of intelligent life elsewhere in the universe should not only focus on detection of electromagnetic signals, but should also seek evidence of the physical artifacts that an intelligence life form might produce, a scientist at the Fermi National Accelerator Laboratory suggested in a paper (pdf) last month.
“Searching for signatures of cosmic-scale archaeological artifacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI [Search for Extraterrestrial Intelligence, which searches for radio waves]. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology.”
All of this of course is quite speculative, not to say whimsical. “With few exceptions interstellar archaeological signatures are clouded and beyond current technological capabilities,” the author notes.
But the concept and the logic behind it are explained with pleasant clarity in “Starry Messages: Searching for Signatures of Interstellar Archaeology” by Richard A. Carrigan, Jr., Fermi National Accelerator Laboratory, December 1, 2009.