Introduction:

Plan today is to try and solve the paradox from Living Universe E1. If life should be everywhere and we don’t see it, then what happened?
The Fermi paradox: Why don’t we see life everywhere?
Simple Solutions:

The “Rare Earth” solution just means that in some way, Earth-like planets are very rare. Maybe there is some mechanism that stops rocky planets from forming in the habitable zone.
The “Rare Chemistry” solution means that maybe Earth got lucky in having just the right mix of chemicals to support life.
The “Rare Intelligence” solution means that there is some factor which limits the development of intelligent life.
Finally, the “Rare Technology” solution means that intelligent life develops but rarely in a way that develops tools/technology.
Other Mechanism for restricting life:

“Shielded Earth” Hypothesis in which our Earth is protected by our special solar system. We know that Jupiter has absorbed many asteroids/comets that could have instead hit us and wiped out life on the planet.
“Early self-limiting life” where an early stage of life does something that inhibits growth or kills life all together.
Another possible limit on life is “late annihilation” where a civilization becomes technologically advanced but destroys itself with nuclear weapons.
Fermi paradox with life:

First, there is the “Firstborn” hypothesis. The idea is that life is as common as we think it is, we are just the first.
Another possibility is the “zoo world” hypothesis. Where Earth is an experiment by aliens to observe how life evolves.
A similar possibility is the “prime directive” hypothesis. This is popularized in star trek, where there is a collaboration of advanced civilizations that hide themselves from new civilizations until they reach a certain technology level.
A more sinister version is the “Dark forest” hypothesis. This is the idea that there are indeed many civilizations that are technologically advanced, but they are all hiding from each other.
A less sinister version is the “Secluded world” hypothesis. Where a civilization just isn’t interested in exploring, they develop really good virtual reality technology and end up just playing games and simulations instead of exploring.
Finally, the least sinister is the “Transcension hypothesis”. Where some technology vastly beyond our understanding allows a civilization to leave our universe altogether and venture into some different plane of existence.

Special thanks to Colin Vendromin for the music, also thanks to Zac Kenny for the logo!