Back in the 1960s, the Soviet scientist Nikolai Kardashev proposed a scale to measure the technological level of extraterrestrial civilizations. I was reminded of his work by this paper, which appeared today. Here is an explanation of the Kardashev scale, with some minor additions of my own:
Kardashev Type I: This is a civilization capable of harnessing all of the energy that strikes their own planet. Our own civilization is Type I.
Kardashev Type II: A civilization capable of harnessing all of the energy emitted by their sun. This would require, for instance, the construction of a Dyson sphere to trap the sun's energy.
Kardashev Type III: A civilization capable of harnessing the energy output of an entire galaxy.
Kardashev Type IV: A civilization of almost unimaginable power. When their internet service isn't working, they are capable of compelling Time-Warner or Comcast to fix it. They have the technology to untangle that ball of cell phone chargers in the kitchen cabinet. When they call their credit-card company, a real person comes on the line right away.
The first three Kardashev levels are legitimate -- the fourth, of course, is science fiction.