IntroductionThere are a number of possibilities for cosmic archaeological signals. One of the more interesting perspectives on this has been a classification scheme suggested by Kardashev. He divided civilizations into those harvesting all the energy of a planet, of a star, and of a galaxy.
I planet (1016 W)
exosolar planetary atmospheres.
II star (4*1026 W Sun)
III galaxy (1036 W)
|Radio SETI falls below this classification so it might be type 0. A type I civilization would utilize the energy available from a planet. Signals from exosolar planetary atmospheres fall roughly in this category. A Dyson Sphere, a star cloaked in broken up planetary material, would be an example of type II. Another example would be some sort of engineering of the stellar burning process suggested b Martin Beech. A civilization using all of the energy of a galaxy would be type III. Jim Annis, an astronomer at Fermilab, has looked for type III Kardashev civilizations by plotting a surrogate for the galaxy brightness versus the size of the galaxy for 106 elliptical galaxies.|