An enumeration of possible solutions to fermi’s paradox.

• Aliens exist, but we see no evidence
  • Human limitations
    • Human beings have not been searching long enough (Freitas Jr 1983; Freitas Jr. 1985)
    • Human beings are not listening properly
  • Practical limitations
    • Communication is impossible due to problems of scale
    • Intelligent civilizations are too far apart in space or time (Wesson 1990)
    • Communication is impossible for technical reasons
    • They only recently emerged and have not yet had the time to become visible. This could for example be due to synchronization due to a declining rate of gamma ray bursts that sterilize much of the galaxy (Annis 1999; Cirkovic 2004).
    • Civilizations only broadcast detectable radio signals for a brief period of time before moving on to other media.
    • It is too expensive to spread physically throughout the galaxy (Landis 1998)
  • Alien nature
    • They are too alien to be recognized
    • They are non-technological and cannot be detected except by visiting them.
    • They tend to experience a technological singularity becoming unfathomable and invisible.
    • They develop into very fast, information-dense states that have no reason to interact with humans (Smart 2002; Cirkovic and Bradbury 2006)
    • They migrate away from the galactic disk for cooling reasons (Cirkovic and Bradbury 2006)
    • They tend to (d)evolve to a post-intelligent state (Schroeder 2002)
    • They choose not to interact with us
  • They are here unobserved
    • Earth is purposely isolated (The Zoo or “Interdict” hypothesis) (Ball 1973; Fogg 1987)
    • Earth (and nearby parts of space) are simulated (Baxter 2001; Bostrom 2003).
    • They secretly deal with the government or other groups.
• No other civilizations currently exist
  • We are the lucky first civilization
  • Intelligent, technological life is exceedingly rare
    • Rare earth hypothesis
    • Life is very rare (Wesson 1990)
    • Intelligence is very rare
  • Intelligent, technological life is very short-lived
    • Intelligent life is wiped out by external disasters at a high rate
    • Technological intelligent life exhaust its resources and dies out or becomes nontechnological
    • It is the nature of intelligent life to destroy itself.
    • It is the nature of intelligent life to destroy others.

• Uncategorized