Editing Kardashev scale (section)

==== Discovering supercivilizations ====
In the article ''On the Inevitability and the Possible Structure of Supercivilizations'' published in 1985, Kardashev evokes the possible scenarios and the means of investigation available to humanity for the detection of [[Extraterrestrial hypothesis|hypothetical extraterrestrial supercivilizations]]. The Soviet astronomer reminds us that we search for these supercivilizations on the basis of our own development criteria, and that predictions are possible only for extraterrestrial worlds close to our technological level, the others being beyond our intellectual representation. Nevertheless, it seems useful to him to conceive models of supercivilizations based at the same time on imagination and on our present scientific knowledge. Since the [[Scientific law|laws of physics]] are immutable, even if new laws are discovered in the future, they will not abolish those already known.<ref name=Kardashev1985/>

According to Kardashev, theoretical models of supercivilizations must meet two basic assumptions. The first is that the range of supercivilization activities that obey the laws of physics is limited only by natural and scientific constraints, while the second is that the evolution of supercivilization activities cannot be interrupted or limited by intrinsic, inherent contingencies, such as large-scale social conflicts. For Kardashev, unlike other scientists, supercivilizations cannot self-destruct or retrogress. According to these principles, there must exist in space [[megastructure]]s of great size, 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.<ref name=Kardashev1985 /><ref name="Kardashev-1997"/>

A supercivilization would thus create a technological structure of cosmic dimensions. As an example, Kardashev cites [[Freeman Dyson]]'s megastructure, in the form of a [[Dyson sphere|sphere]] of several [[astronomical unit]]s in diameter. Other phenomena may indicate highly technological activities, such as artificially exploding stars or the changing of stellar [[orbit]]s to store mass and energy. [[Molecular cloud|Giant molecular clouds]] also hold great potential for [[Astronomical engineering|astroengineering]]. Kardashev even raises the possibility of a supercivilization reshaping the entire galaxy.<ref name=Kardashev1985 /><ref name="Kardashev-1997"/>

Then he evokes the theoretical and mathematical possibility of the existence of a megastructure in the form of a disk rotating on itself at a constant [[Angular frequency|angular velocity]]. According to him, the search for intelligent signals should be directed to the detection of such megastructures at the characteristic radiation (20 μm). [[Quasar]]s or galactic centers can be excellent candidates to testify to the existence of a supercivilization since they emit strong [[infrared]] radiation, which indicates a solid structure. The astronomer advises to look for these objects in a [[wavelength]] range from a few microns to a few millimeters. Large intelligent structures can also be detected by the fact that they screen or reflect the surrounding radiation.<ref name=Kardashev1985 />