For several decades, astronomers, when thinking about technologically advanced extraterrestrial civilizations, have been using the classification of civilizations proposed in 1964 by the Soviet scientist Nikolai Kardashev. According to this classification, which is based on the ability of a civilization to control certain amounts of energy, all extraterrestrial civilizations can be divided into three types.
According to Kardashev, a type 1 civilization can control energy only within its planet, a type 2 civilization controls energy within the planetary system, and a type 3 civilization can control energy on the scale of an entire galaxy.
In the new study, a team of scientists led by Adam Frank of the University of Rochester, USA, proposes a new classification of hypothetical extraterrestrial civilizations based on "nonequilibrium thermodynamics" - the power of nonequilibrium energy flows caused by the activity of life forms.
According to this new scheme, the planets should be divided into five categories:
Class 1 - planets (or satellites of planets) without atmosphere, such as Mercury and the Moon;
Class 2 - planets with a thin atmosphere containing greenhouse gases, on which there is no life (Mars, Venus);
Class 3 - planets with a thin biosphere and relatively low biological activity, however, too low to "influence the evolution of the planet as a whole." There are no examples of such planets at the present time, in the past it is the early Earth;
Class 4 - planets with thick biospheres, supported by photosynthesis, on which life has a significant impact on the energy flows associated with the planet.
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The Earth is currently, according to Frank and his colleagues, a "hybrid" planet, making the transition to the final, 5th class of planets, for which a technologically advanced civilization has a decisive influence on the free energy flows associated with the planet.
The research is published in the journal Anthropocene.
