classification of possible civilizations after energy
usage. Type I civilizations control all available energy
on a single planet. Type II civilizations control all available energy in a solar system
(for example, using Dyson
spheres). Type III civilizations control use all available energy in an entire galaxy. (Mitch Porter suggested
that a Type IV civilization controls all available energy
in the entire universe) We are currently moving towards a Type I
civilization. [Nikolai Kardaschev, 1964].