Kardashev scale

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.

Human civilization is currently somewhere below type I as of this writing, as it is able to harness only a portion of the energy that is available on Earth. A hypothetical type II civilization might employ a Dyson sphere or other similar construct in order to utilize all of the energy output by a star, or perhaps more exotic means such as feeding stellar mass into a black hole to generate usable energy. A type III civilization might use the same techniques employed by a type II civilization, applied to all of the stars of a galaxy individually, or perhaps might use other mechanisms not yet proposed.

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.