Editing Kardashev scale (section)

=== First publication (1964) ===
[[File:KScale.svg|alt=A red dotted line that goes up from left to right.|thumb|upright=1.4|A projection of the Kardashev scale to 2040 based on data from the International Energy Agency World Energy Outlook]]
Kardashev presented for the first time a classification of civilizations according to the level of the rate of their energy consumption, or ability to harness power, in an article entitled ''Transmission of Information by Extraterrestrial Civilizations'', published in 1964 first in Russian in the March–April issue of the [[Astronomy Reports|Astronomicheskii Zhurnal]],<ref name=Kardashev-1964 /> then in English in the September–October 1964 issue of the Soviet Astronomical Journal.<ref name="Kardashev-1964"/> In this article, the scientist presents a calculation of the evolution of the power needs of humanity. Assuming that overall human power use will continue to increase, he calculated that the rate of energy consumption will cross specific mileposts. Kardashev proposed a typology of technological civilizations based on the evolutive attainment of the three power harnessing mileposts he described.<ref name=Kardashev-1964 /><ref>{{Cite book |last=Basalla |first=George |title=Civilized Life in the Universe: Scientists on Intelligent Extraterrestrials |year=2006 |publisher=Oxford University Press |isbn=978-0195171815 |pages=148–149 |language=en |chapter=Life in an Expanding Universe}}</ref>

A [[civilization]] known as "Type&nbsp;I" has achieved a technological level close to the one attained on earth at the time Kardashev’s article was submitted (December 1963), with a rate of energy consumption evaluated at about 4 x 10<sup>12</sup> [[watt]]s (W). A civilization known as "Type&nbsp;II" would surpass the first by fourteen orders of magnitude, matching the entire power emitted by the Sun in about 3,200 years, i.e, our home [[star]]’s “output“ at that time, predicted at 4 × 10<sup>26</sup> W. Finally, a civilization known as "Type&nbsp;III" reaches the milepost set in 5,800 years when humanity’s rate of energy consumption is predicted by the author to match the power emitted by the approximated 10<sup>11</sup> stars in our home [[galaxy]], the Milky Way, which involves harnessing power of up to an estimated 4 x 10<sup>37</sup> W.<ref name=Kardashev-1964/> 

Assuming the development of [[radio]], Kardashev predicted that in the following two decades (i.e. in the 1980s) it would be possible to build antennas of 100,000 m<sup>2</sup> capable of detecting Type&nbsp;II and III civilizations. A Type&nbsp;I civilization like that of earth would be able to receive the extraordinary energetic emissions of the other types of civilizations, which would supposedly be able to emit continuously.<ref name=Kardashev-1964/><ref name="Galántai-2003">{{Cite journal |last=Galántai |first=Zoltan |date=2003-09-07 |title=Long Futures and Type IV Civilizations |url=http://mono.eik.bme.hu/~galantai/longfuture/long_futures_article1.pdf |url-status=live |journal=Periodica Polytechnica, Social and Management Sciences |volume=12 |issue=1 |pages=83–89 |archive-url=https://web.archive.org/web/20230307020046/http://mono.eik.bme.hu/~galantai/longfuture/long_futures_article1.pdf |archive-date=2023-03-07}}</ref>

Kardashev then examined the characteristics of a transmission from an artificial source. He mentioned the two cosmic radio sources discovered in 1963 by the [[California Institute of Technology]], CTA-21 and [[CTA-102]] in particular, which would have characteristics close to those of a presumed artificial source. The most suitable region of the galaxy for observing Type&nbsp;II and III civilizations would then be the [[Galactic Center]], due to the high density of the stellar population it harbors. He then recommended that the search programs for such artificial sources should focus on other nearby galaxies, such as the [[Andromeda Galaxy]], the [[Magellanic Clouds]], [[Messier 87|M87]], or [[Centaurus A]]. Kardashev concluded his paper by noting that the possible discovery of even the simplest organisms on [[Mars]] would increase the likelihood that Type&nbsp;II civilizations exist in the galaxy.<ref name=Kardashev-1964/>[[File:Consommations énergétiques des trois types de l'échelle de Kardashev.svg|thumb|upright=2|alt=Three schematic representations: Earth, Solar System and Milky Way|Energy consumption in three types of civilization as defined by Sagan's extended Kardashev scale|center]]