I know that it can vary A LOT if you are using the Drake Equation but using realistic figures, how likely is it to discover a civilisation that is at least semi-intelligent (stone age - medieval era, comparing to human history).

Also I heard that there are various classes of civilization:

  1. Us (Humans), doesn't reach the energy milestones in the classes. (Level 0)
  2. Controls 100% of the energy from their home planet (1,000 - 10,000 yrs away). (Level 1)
  3. Controls 100% of the energy from their home star (5,000 - 20,000 yrs away). (Level 2)
  4. Controls 100% of the energy from their local group of stars (never or 10,000 - 30,000 yrs away). (Level 3)
  5. Controls 100% of the energy from their home galaxy (NEVER! just deal with it). (Level 4)

The last paragraph is NOT PART of the question; it is just for your knowledge!

  • 4
    $\begingroup$ "What are the odds of (Semi) Intelligent Life in the Milky Way?" Pretty good, I should think considering we know ourselves to be in it! (Assuming we count as intelligent) $\endgroup$ Dec 30, 2014 at 3:34
  • 2
    $\begingroup$ Any answer will be speculation (other than the one given by @MitchGoshorn ). $\endgroup$
    – ProfRob
    Dec 30, 2014 at 16:33

1 Answer 1


The odds of detecting a civilization at the technology level you describe are exceedingly remote. The reason is suggested by your mention of the Kardashev scale.

The search for extraterrestrial intelligence (SETI) generally involves looking for various electromagnetic signatures, such as radio waves, etc. At the level of stone age through medieval era, about the best one might hope for is to see fires on the night side of a planet. This seems hardly likely at interstellar distances (though such signatures could certainly be able to be picked up within a particular stellar system).


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