The Kardashev scale is a general method of classifying the magnitude of a civilization, first proposed in the 1960s by the Russian astronomer Nikolai Kardashev. It has three categories, based on the amount of usable energy a civilization has at its disposal and increasing logarithmically:
- Type I - A civilization that is able to harness all of the power available on a single planet.
- Type II - A civilization that is able to harness all of the power available from a single star.
- Type III - A civilization that is able to harness all of the power available from a single galaxy.
All such civilizations are purely hypothetical at this point. However, the Kardashev scale is of use to SETI researchers, science fiction authors, and futurists as a theoretical framework.