Kardashev scale

The Kardashev scale is a way of classifying a civilization by the rate at which it uses energy. The Soviet astronomer Nikolai Kardashev proposed it in 1964 with three types: a civilization of type I uses about as much power as Earth did at the time, type II uses the output of its star, and type III uses the output of its galaxy. It appeared in a paper titled "Transmission of information by extraterrestrial civilizations".^[1]

Nikolai Kardashev (1932 to 2019) was a radio astronomer in Moscow. He founded the Astro Space Center of the Lebedev Physical Institute in 1990, led the RadioAstron space interferometry mission, and had proposed very-long-baseline interferometry in the early 1960s.^[2] He presented the scale at a conference at Byurakan, Armenia, in 1964, and the paper appeared the same year in Astronomicheskii Zhurnal and, in English, in Soviet Astronomy.^[1]

The paper asked how much power a transmitter could command, since that decides how far away its signal could be detected. It gave three round numbers and cited two radio sources, CTA-102 and CTA-21, as having characteristics close to those of an artificial source. CTA-102 is now known to be the nucleus of a distant active galaxy.

Kardashev gave his values in ergs per second: 4 × 10¹⁹, 4 × 10³³ and 4 × 10⁴⁴. Carl Sagan, in The Cosmic Connection of 1973, added a formula that gives a civilization any fractional rating, and that assigns ratings 1, 2 and 3 to 10¹⁶, 10²⁶ and 10³⁶ W,

where P is the power in watts.^[3] Kardashev's steps are 10¹⁴ from type I to type II and 10¹¹ from II to III. Sagan's are 10¹⁰ each. By his formula Kardashev's own type I has a rating of 0.66.

The Energy Institute reported that world energy supply exceeded 600 exajoules in 2025. That averages about 19 terawatts, a rating of 0.73, and 4.7 times Kardashev's type I.^[4] Sagan's type I, at 10¹⁶ W, is about 6% of the 1.7 × 10¹⁷ W of sunlight that Earth intercepts, and a type II civilization at 10²⁶ W uses a quarter of the Sun's 3.8 × 10²⁶ W.^[a]

Extrapolation is arithmetic. A civilization that used 19 TW and grew by 2% a year would take 461 years to use all the sunlight that Earth intercepts and 1,547 years to use the Sun's whole output. At 4% a year the times are 233 and 781 years, and at 1% they are 917 and 3,079.^[b] Newman and Sagan modeled the spread of galactic civilizations by their population dynamics and interstellar diffusion.^[5]

Type II implies a way of collecting a star's output. In 1960 Freeman Dyson had suggested that a civilization might surround its star with a shell or swarm of matter to capture the light, and that such structures would shine in the infrared and could be searched for.^[6] Whatever power a civilization uses must in the end be radiated away as heat, and that heat is the signal. The structure is called a Dyson sphere, and it is the standard illustration of the scale. See Freeman Dyson.

Sagan also proposed rating a civilization by the information it holds, in classes lettered from A, at 10⁶ bits, upward by factors of ten, and put humanity in 1973 at about 0.7 H.^[3]

John Barrow, in Impossibility of 1998, proposed a scale that runs inward. On it a civilization of type I-minus manipulates objects of its own size, type II-minus manipulates genes, type III-minus molecules, type IV-minus individual atoms, and types V-minus and VI-minus nuclei and elementary particles.^[7]

In February 2026 the website of Molecular Reality Corporation described the volunteer network it calls the Molecular Streaming Corps as a "Global Hyper-Instrument", "a virtual machine that we could not build monolithically at our Kardashev level".^[8] The company's About page calls the Corps a virtual "ultra-instrument" (see Ultra-Device).^[9] The company's glossary lists a "Kardashev level" among its terms (see Glossary of Molecular Reality jargon and List of unusual units used at Molecular Reality).

• Utility-scale molecular sensing
• Molecular Streaming Corps