Where is everybody? Welcome to the Fermi Paradox, the idea that given that our solar system is quite young compared to the rest of the universe — roughly 4.5 billion years old, compared to 13.8 billion — and that interstellar travel might be fairly easy to achieve given enough time, Earth should have been visited by aliens already, the idea goes. This is a blogpost from WaitButWhy explaining and exploring all the possible explanations to the Fermi Paradox.