There are many ideas of how astronomers could detect extraterrestrial civilizations. And in some way or another they are related to the different types of civilizations that we might look for. A Soviet astronomer Nikolai Kardashev came up with a certain scale for measuring a civilization’s level of technological advancement, based on the amount of energy a civilization is able to utilize. According to this scale, there are 3 types of civilizations — types 1, 2 and 3. Type 1 civilization is capable of harnessing energies, which are equivalent to the solar insolation on Earth. Type 2 civilization would completely control the host star by harnessing most of it energy using such devices as the Dyson sphere. Finally, the type 3 civilization would possess energy on the scale of its host galaxy.
Interestingly, the heat emitted by the type 3 civilization would surpass the radiation from its host star or even the galaxy, which would theoretically make the job of those hunting for ET a lot easier. In this recent SETI talk, Jason T. Wright will discuss how the WISE all-sky mid-infrared survey has improved our chances of finding ET. For more videos, visit SETI channel on YouTube.