Kardashev scale
What is the Kardashev scale?
What are the three types of civilizations in the Kardashev scale?
How did Carl Sagan modify the Kardashev scale?
What are some criticisms of the Kardashev scale?
What is the Barrow scale?
Kardashev scale, hypothetical measure of an alien civilization’s level of technological advancement, proposed by Soviet astronomer Nikolai Kardashev in his paper “Transmission of Information by Extraterrestrial Civilizations” (1964). It categorizes hypothetical alien civilizations into three categories based on the level of energy they can harness.
Background and definition
Kardashev was part of a team searching for extraterrestrial signals in 1963, and he believed that there could exist alien civilizations far more advanced than humans. He proposed a scale to classify such civilizations based on the amount of energy resources they could use in interstellar communications. American astronomer Carl Sagan later revised the scale and its thresholds.
The Kardashev scale is more qualitative than quantitative and proposes three levels of civilizations:
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- Type I: The civilization is capable of using energy resources on a planetwide scale, or equivalent to the entire power consumption of the planet (about 1016 watts). This would mean harnessing both the energy that reaches the planet from its star, such as solar energy, as well as all energy the planet can produce, such as wind, hydroelectric, and geothermal energy. Such a civilization could also harness the energy of volcanoes and earthquakes.
- Type II: The civilization is capable of using the entire energy output of its star, or about 1026 watts. This would be possible through a theoretical technology called a Dyson sphere that would completely envelop a star to capture all its energy. (Such a sphere in the solar system would have a surface area about 600 million times greater than Earth’s surface area.) The civilization would also be able to transmit information across a galaxy.
- Type III: The civilization is capable of using the entire energy resource of its galaxy, or about 1036 watts. Such a civilization would be able to transmit information between galaxies.
The existence of a Type II civilization was speculated when a star called Tabby’s Star (for American astronomer Tabetha Boyajian, who studied it), about 1,480 light-years from Earth, was seen dimming and brightening in an irregular fashion. One theory suggested that an alien civilization was in the process of building a Dyson sphere around Tabby’s Star, blocking it from view. However, the star dims more in blue light than in red light—a pattern that is inconsistent with a Dyson sphere, which would likely dim the star equally at all wavelengths.
The type of civilization can be determined using the equation:Kp = log10(P/106) / 10where Kp is the type of civilization and P is the nonzero power in watts. For P = 106, 1016, and so on, the equation yields whole numbers 0, 1, and so on.
Variations of the scale
Astronomer Carl Sagan believed that the Kardashev scale was too spread out and that the gaps between the three levels were so large that a finer gradation was needed. He thus proposed decimal additions to the scale, defining a Type 1.1 civilization as one with access to 1017 watts, a Type 2.4 with access to 1030 watts, and so on. He defined human civilization as a Type 0.7 using this scale.
Sagan also attempted to redefine the scale based on civilizations’ level of information mastery, with more advanced civilizations having access to more information. Sagan’s modified scale used the alphabet for classification, with a Type A civilization having access to 106 total bits of information. The scale increases by one letter with every increase by a factor of 10 in the amount of information. Sagan estimated Earth in 1973 as having about 1013 bits of information, which he combined with the Kardashev scale to designate Earth as 0.7H. He guessed that first contact would be with a 1.5J or 1.8K civilization and that a galactic civilization of a million worlds, each with a thousand times the information of Earth, would be a Q civilization. However, in 2024 the estimated amount of data on Earth was 149 zettabytes, or about 1024 bits, making Earth an S civilization.
Further studies established Earth at a level of 0.676 on the Kardashev scale in 1965, rising to 0.728 in 2020. Assuming a linear increase in global energy consumption of 2.3 percent per year, Earth would become a Type I civilization in 2347. More advanced methods have estimated Earth at 0.7276 in 2023, rising to 0.7449 in 2060, and potentially taking millennia to reach 1.0 (Type I), unless new energy technology emerges. Other extensions to the scale have recommended a Type 0 rating for preindustrial civilizations and Types IV and V for civilizations capable of harnessing the energy of an entire universe and a multiverse, respectively.
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The Kardashev scale has been criticized for its assumption that advanced civilizations would expand beyond their home planet and star. English cosmologist John D. Barrow argued that technological prowess would instead focus on increasingly smaller scales. He defined the Barrow scale, which has seven types of civilizations. These civilizations range from Type I-minus, where a civilization can manipulate objects similar in size to its own species, to Type VI-minus, where it can manipulate elementary particles such as quarks and leptons, and eventually to Type Omega-minus, where it can manipulate the basic structure of space-time.
The Kardashev scale has also been criticized for the lack of observable evidence for Type II and Type III civilizations. It has been speculated that interstellar expansion within a galaxy would be impossible, as not all planets would be equally hospitable, thus preventing a civilization from ever reaching Type III. Additionally, with the growing interest in sustainable energy, the Kardashev scale has been criticized for its focus on infinite growth as a measure of progress.