Another possibility is that intelligent life is common but afraid to be noticed. Here's an interesting PBS Space Time video [1], "Dark Forest: Should We NOT Co

Another possibility is that intelligent life is common but afraid to be noticed. Here's an interesting PBS Space Time video [1], "Dark Forest: Should We NOT Contact Aliens?", that goes over some of the game theory that a civilization might want to consider when deciding how visible to allow themselves to be to others. [1] https://www.youtube.com/watch?v=aXYf47euE3U https://www.youtube.com/watch?v=aXYf47euE3U