Astronomers have theorized that there could be three types of civilizations. what are they? how would they be recognized? which one has been ruled out so far?

The astronomer Nikolai Kardashev introduced the Kardashev scale which classifies the different civilizations based on the energy consumed by them. The three types of civilizations as described by Kardashev are as follows:

Type I - This type of civilization is completely capable of utilizing the energy from their planets, including all the natural resources, volcanoes, sea etc. They can extract and then store the energy of the star.

Type II - This type of civilization is capable of harnessing the energy of their star by the means of a Dyson sphere around it. This civilization is capable of occupying multiple planets.

Type III - This type of civilization is galatic travelers who move from planet to planet, and colonize each planet they visit to.

The three types of the civilizations are recognized based on their ability to extract and utilize energy and how technologically advanced they are. Further types of civilizations with far more advanced means of energy utilization from the black holes, and other galaxies are ruled out. Because no whole galaxy is seemed to be losing it energy.

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