Aliens 101: The Kardashev Scale & Fermi Paradox

Think about how far humanity has progressed in its short 200,000 years of existence. Now consider that our galaxy is roughly 10 billion years old.

If we can go from cave-dwelling hominids to an internet-using and robot-building society in 200,000 years, what could an alien race achieve in 10 billion years?

That's more than enough time for a civilization to develop sophisticated rockets — possibly faster-than-light travel, wormhole technology, or some other kind of cosmic shortcut that would allow them to rapidly colonize the galaxy and beyond.

The Kardashev Scale, created by astrophysicist Nikolai Kardashev, is helpful when considering such technological advancement by a developing civilization. It has three types:

1. A Type-I civilization has figured out how to harness all the energy on its planet. Humans are getting close to achieving this, but that's just the first tier.
2. Type-II civilizations are so intelligent they've figured out how to harness all the energy of their own star — an incomprehensibly larger amount of energy than what's available on one puny planet.
3. That's nothing compared to the Type-III civilizations, though. Those have harnessed all the energy available in their galaxy.

Any type of civilization on the Kardashev Scale would be more than capable of colonizing the universe. But we haven't detected any of these civilizations — and that's the heart of the Fermi Paradox.

You can group the best explanations for the paradox into two distinct categories: one in which aliens don't exist, and we're completely alone in the universe, and one in which aliens do exist, but for some reason we haven't made contact.

Let's start with leading ideas in the former category.