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 utilize directed towards communication. The scale has three designated categories called Type I, II, and III. A Type I civilization – also called planetary civilization – is able to utilize and store energy available from its neighboring star which reaches their planet, Type II is able to harness the energy of the entire star (the most popular hypothetic concept being the Dyson sphere—a device which would encompass the entire star and transfer its energy to the planet), and Type III civilization are in control of energy on the scale of their entire host galaxy. The scale is hypothetical, and regards energy consumption on a cosmic scale. It was first proposed in 1964 by the Soviet astronomer Nikolai Kardashev. Various extensions of the scale have been proposed since, from a wider range of power levels (types 0, IV and V) to the use of metrics other than pure power.