Britannica
Sources used in this answer
How does the Kardashev scale classify advanced civilizations?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
extraterrestrial intelligence
An artist's conception depicts Kepler-186f, the first Earth-sized extrasolar planet found in its star's habitable zone.
The Kardashev scale is a hypothetical measure of an alien civilization’s technological advancement, based on the amount of energy it can harness. Proposed by Soviet astronomer Nikolai Kardashev in 1964, the scale classifies civilizations into three primary categories:1
- Type I: Capable of utilizing energy on a planetwide scale (approximately watts), including all available solar energy, wind, hydroelectric, and geothermal energy.1
- Type II: Capable of harnessing the entire energy output of its star (approximately watts), potentially through structures like a Dyson sphere.1
- Type III: Capable of utilizing the energy resources of its entire galaxy (approximately watts).21
While Carl Sagan later refined the scale with decimal gradations and information-based metrics, the original framework remains a foundational concept in the study of potential extraterrestrial intelligence. Some critics argue the scale’s focus on infinite energy growth overlooks sustainable development or alternative technological trajectories, such as those proposed by the Barrow scale.1