On the Fermi paradox

Humans have been fascinated by the possibility of extraterrestrial life for millennia. Our discussions about aliens range from outlandish conspiracy theories to genuinely thought-provoking puzzles like the Fermi Paradox.

The Fermi paradox is a contradiction between the high probability of advanced extraterrestrial life existing and the lack of any definitive proof of its existence.

It’s a close cousin of the Drake equation, which attempts to calculate the probability of the existence of extraterrestrial civilizations in the Milky Way Galaxy. While there’s significant debate and disagreement about the values that go into the equation, the “conservative” reasoning goes something like this:

  • 1 star formed every year on average over the lifespan of the galaxy
  • 1 in 5 of all formed stars will have planets
  • 1 planet that can support life for every star that has planets
  • 100% of those planets will develop life
  • 100% of the planets that develop life will develop intelligent life
  • 10% of these planets will be able to communicate
  • And release detectable signals over 1,000 years

A lot of this is (intelligent) guesswork, so you can see why it’s controversial. But if you take it at face value, you’d reach the conclusion that there are at least 20 planets with civilizations in the Milky Way Galaxy.

Here’s another way to think about it. Estimates suggest that there are 100 billion billion Earth-like planets in the universe i.e. there are 100 Earth-like planets for every grain of sand in the world. If even a tiny percentage of them were to develop intelligent life, then it seems likely that we would have seen signs of intelligent life from somewhere else. So the natural thing to ask is:

But where is everybody? - Enrico Fermi, in conversation with fellow physicists

The Fermi paradox is contentious and this question has both puzzled and annoyed scientists for decades. But it’s still an intriguing topic for us normies to ponder.

In the next post, I’ll talk about some of the most interesting theories that attempt to solve the Fermi paradox. Until then, try to come up with your own theories, or check out this great video: