Kardashev scale
The Kardashev scale is a method of measuring a civilization's level of technological advancement, based on the amount of energy a civilization is able to use for communication. The scale has three designated categories:
The scale is hypothetical, and regards energy consumption on a cosmic scale. It was proposed in 1964 by the Soviet astronomer Nikolai Kardashev. Various extensions of the scale have since been proposed, including a wider range of power levels (types 0, IV and V) and the use of metrics other than pure power.
In 1964, Kardashev defined three levels of civilizations, based on the order of magnitude of power available to them:
Michio Kaku suggested that humans may attain Type I status in 100–200 years, Type II status in a few thousand years, and Type III status in 100,000 to a million years.
Carl Sagan suggested defining intermediate values (not considered in Kardashev's original scale) by interpolating and extrapolating the values given above for types I (1016 W), II (1026 W) and III (1036 W), which would produce the formula
where value K is a civilization's Kardashev rating and P is the power it uses, in watts. Using this extrapolation, a "Type 0" civilization, not defined by Kardashev, would control about 1 MW of power, and humanity's civilization type as of 1973 was about 0.7 (apparently using 10 terawatt (TW) as the value for 1970s humanity).
In 2012, total world energy consumption was 553 exajoules (553×1018 J=153,611 TWh), equivalent to an average power consumption of 17.54 TW (or 0.724 on Sagan's Kardashev scale).
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