The Fermi paradox is a conflict between an argument of scale and probability and a lack of evidence.
The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist.
However, this hypothesis seems inconsistent with the lack of observational evidence to support it.
If technology continues to improve, we can easily conceive of colonizing the entire galaxy in less then 100 million years. For example, one can conceive of many man made probes sent to a host of other stars. Some will find environments suitable for human life and could clone humans (and other animals and plants) from onboard DNA samples.
Another possibility is that artificial intelligence will develop an exploratory desire and produce machines that can replicate themselves. These machines could travel to neighbouring stars. Those that find solar systems with enough raw materials could go about manufacturing replicas of themselves (or improvements thereof). These daughter probes could then be sent to further multitudes of stars and in a short time the entire galaxy would be completely colonized by these so called Von Neumann probes.
Most of the stars in the galaxy are more than a billion years older than the Sun. If life and civilizations are common throughout the galaxy then they should have colonized the galaxy long ago. Where are they? This is known as Fermi's paradox. Fermi's paradox relies on the assumption that civilizations (as we know them) have a desire to colonize (or at least explore) the Galaxy.
- Team 1 resolves Fermi's paradox by arguing that we don't see evidence for aliens because other technological civilizations have no desire to colonize or explore the Galaxy (do we have such a desire?) or that the physical limitations behind space travel have made colonization impossible.
- Team 2 argues that other technological civilizations will have a desire to colonize or explore the galaxy. They resolve Fermi's paradox with plausible speculations such as we have been colonized but we just don't know it; for example, the alien civilization is into nanotechnology so small that we haven't detected it yet or we have been quarantined in a galactic zoo.
