What does the Kardashev scale measure?

The Kardashev scale is a way of measuring the technological advancement of a civilization based on the amount of energy the civilization is able to harness. The original scale had three levels, I, II and III, but in later years levels 0, IV and V were added. Currently, humanity has not even reached the first level (0,73).

Nikolai Semyonovich Kardashev (25 April 1932 – 3 August 2019) was a Soviet and Russian astrophysicist, Doctor of Physical and Mathematical Sciences, and the deputy director of the Astro Space Center of PN Lebedev Physical Institute of the Russian Academy of Sciences in Moscow.

In his paper published in 1964, "Transmission of Information by Extraterrestrial Civilizations", he proposed a three-tier system for the classification of a civilization based on their ability to harness energy.

Type 0: These are civilization that extracts its energy from crude organic-based sources.

Type I: These are civilization that extracts its energy from fusion power, hydrogen, and other "high-density" renewable-resources.

Type II: These are civilizations that have evolved to the point where they could harvest all the energy emitted by their star.

Type III: These are civilizations that would be able to harness the energy of an entire galaxy.

Type IV: These are civilizations that would be able to harness the energy of the entire Universe.

Type V: These are civilizations that would be able to harness the energy from all universes and in all time-lines.