A method for classifying civilization types was introduced by Russian astronomer Nikolai Kardashev in 1964. Known as the Kardashev scale, classifications are assigned based on the amount of usable energy a civilization has at its disposal and increasing logarithmically:
Type I - A civilization that is able to harness all of the power available on a single planet, approximately 10^16W.
Type II - A civilization that is able to harness all of the power available from a single star, approximately 10^26W.
Type III - A civilization that is able to harness all of the power available from a single galaxy, approximately 10^36W.
Human civilization has yet to achieve full Type I status, as it is able to harness only a portion of the energy that is available on Earth. Carl Sagan speculated that humanity's current civilization type is around 0.7.
A major criticism directed at the Kardashev scale is that the difference between a Type II and Type III civilization is ten orders of magnitude and that significant civilization types likely reside within that range. Moreover, given the seemingly extreme energy sources available to Type II and III civilizations, the question as to why we haven't seen evidence of these advanced societies remains unanswered, a possible indication that no such civilizations exist.
Between this and the Drake Equation, I wonder whether we'll ever see anything interesting before we sputter and extinguish like a candle in the dark.
I mean, I envision a future where we eventually leave our cradle, and go on to seed other places; in order to get to a point where that is viable, we'll need to be past Level I anyway. If we manage to make it that far, chances are that we won't be anything like we are now-certainly we'll be the same physically- but the very nature of the type of space exploration I'm talking about necessitates a wholly different type of social management, government, and psychological outlook.
I'm dying to know whats out there.
I wonder whether we'll ever make it far enough to find out...