Nikolai Kardashev

**Nikolai Semenovich Kardashev** (1932 - 2019) was a Russian astrophysicist, Doctor of Physical and Mathematical Sciences, and deputy director of the Astro Space Center (Russia) of PN Lebedev Physical Institute of the Russian Academy of Sciences in Moscow.

In 1963 Kardashev examined quasar CTA-102, the first Soviet effort in the search for extraterrestrial intelligence (SETI). In this work he came up with the idea that some galactic civilizations would be perhaps millions or billions of years ahead of us, and created the Kardashev Scale to rank such civilizations.

In his 1964 publication *Transmission of Information by Extraterrestrial Civilizations,* Kardashev defined three levels of civilizations, based on energy consumption:

* Type I, "able to collect and use all the available energy on its planet, that is, the theoretical equivalent of 1017 watts."
* Type II, "able to surpass the first by a factor of 10 billion, reaching a consumption of 1026 watts, this time using all the power emitted by its star."
* Type III, "able to collect and consume all the energy emitted by its galaxy, which is equivalent to 1037 watts."

Various extensions of the scale have since been proposed, including a wider range of power levels, and the use of metrics other than pure power. The most popular is Carl Sagan's interpolated scale.

In later publications, Kardashev discussed searching for extraterrestrial intelligence and supercivilizations, similar to the questions posed in the Fermi paradox:

* Our civilization would be too young to be able to contact another civilization that would certainly be more advanced than us. The solar system is too young at five billion years. The first ancestors of today's man appeared only 6 million years ago at the earliest. The oldest celestial objects are between 10 and 14 billion years old. Therefore the knowledge of incomparably older civilizations must be greater than ours, and they must surely be aware of what we are doing.
* Since our present development covers only a negligible fraction of eventual interstellar communication, Kardashev hypothesizes the high improbability that we will meet "brothers in intelligence" who are at the same stage of evolution as we are. After all, highly advanced civilizations know and use the laws of physics to a degree that we have yet to suspect, and our present state is only one of the stages through which every civilization passes during its evolution.
* In 1977 Iosif Shklovsky found it strange that the "shock wave of intelligence" of a supercivilization had not yet reached the limits of the whole universe. Kardashev tried to explain that it would not be really useful for a supercivilization to expand the space it occupies in order to maintain its activity, and that such a civilization would rather continue its activities of information analysis in order to discover new fundamental laws (such as the exploration of the microcosm, or black holes for example).
* He also discussed how to search for such a supercivilization whose activities would require the use of abundant energy, which in turn requires a large amount of solid matter for stellar engineering activities, all of which would emit electromagnetic radiation. They could be found by SETI observing sources of radiation in space, or searching for new and powerful sources of radiation such as signals from the galactic center, or from quasars and other exotic cosmic objects. According to Kardashev, in order to capture the significant radiation of an advanced civilization emitted by a megastructure (such as a Dyson sphere), a radio telescope with a diameter larger than the diameter of the Earth would have to be placed in orbital space.
* In 1985, Kardashev discussed the detection of hypothetical extraterrestrial supercivilizations. The range of supercivilization activities that obey the laws of physics is limited only by natural and scientific constraints, and the evolution of supercivilization activities cannot self-destruct or retrogress. Therefore must exist in space megastructures of cosmic dimensions, emitting a lot of energy and information, and existing for billions of years, while being compact enough to rapidly exchange large amounts of data between them, such as the Dyson sphere. Other phenomena may indicate highly technological activities, such as artificially exploding stars, or the changing of stellar orbits to store mass and energy, or giant molecular clouds indicating astroengineering. There could also exist a megastructure in the form of a disk rotating on itself at a constant angular velocity, reflecting the surrounding radiation.
* In 1997 Kardashev listed six possible scenarios for the evolution of supercivilizations:
	1. A large unification of civilizations over an extent of one to ten billion light-years with concentration in a certain region has a probability of 60%. These civilizations and their megastructures are to be searched for in the most powerful quasars and in the galactic bulge, at a radiation level higher than 1038 watts, in the wavelengths from 10 µm to 1 cm. In the event of contact, humanity would need to progress in all areas of society in order to join this supercivilization.
	2. A unification on the scale of the galactic cluster has only a 20% probability of realization. Kardashev advises to observe the Virgo cluster, especially M87.
	3. A unification on the scale of galaxies has only a 10% probability. We must study the galactic centers, both of the Milky Way and of neighboring galaxies.
	4. A complete colonization of space has no probability of being realized according to Kardashev because if it were realizable then "they" would already be on Earth.
	5. All civilizations would have destroyed themselves before any contact. Kardashev estimates the probability of this to be 10%. Humanity should be able to detect ancient megastructures in the vicinity of the nearest stars.
	6. We are the first or the only ones in the Universe. Kardashev estimates its probability at 10%. Only exobiology can confirm or falsify such a scenario.
* Kardashev talked more about detecting supercivilizations. Assuming the rate of evolution of life on Earth and considering the age of the Universe, it is reasonable to assume that a civilization could have reached our level of technological development in 6 × 109 years, and that such civilizations dating from 6 to 8 billion years ago may exist in our galaxy. It is likely that they have long since discovered our own civilization. He goes on to discuss hypotheses that pose more questions or attempt to answer questions in the Fermi paradox. Kardashev concludes by saying that since the expansion of the Universe is infinite, the number and lifetime of such supercivilizations are also infinite.

See also:

A white paper discussion