In general, solutions to Fermi’s paradox come down to:
- Life is difficult to start and to evolve to an intelligent and technologically advanced stage and we’re the only one in the galaxy.
- Advanced civilizations destroy themselves on short timescales.
As the revised Drake equation solution (N<<1) shows, it seems that hopefuly, the first solution is the answer.
Here is a list of the various assumptions along with notes pointing to related problems and contradictions.
They are here unobserved
They were here and they left material evidence:
UFO’s, alien artifacts, ancient astronauts. Problem: evidence for aliens is non-existent.
The aliens are here and they are keeping us in a well designed zoo (cut off from all contact) or there is an treaty preventing contact with young races. Problem: this scenario can’t be tested. Only one ET could break the embargo.
They are us:
Humans are the descendents of previous alien civilizations. Problem: where are the original aliens? where are all the other alien civilizations?
They exist but…
They didn’t have enough time to reach us:
The speed of light slows communications and makes space travel too long. Extraterrestrial’s messages may not have reached us yet. Problem: the galaxy exist for billions of years, even if one ET civilization formed a few million years before us, the galaxy would be already filled with Bracewell-Von Neumann probes.
They are sending signals, but we do not know how to listen:
The galaxy is filled with killer robots looking for signals. ET is keeping low. Problem: no evidence of berserkers coming after us.
They have no desire to communicate:
ET has no interest in communicating with lesser intelligences. Problem: with millions of possible civilizations, some of the extraterrestrial ones would be interested in our species.
Civilizations only have a limited lifetime, they are all dead.
Dangerous particle physics
Nanobots -> the gray goo problem
They developed different mathematics:
Mathematics is the universal language, but humans may have a unique system of mathematics that ET cannot understand. Problem: then where are those incomprehensible signals?
They do not exist because…
We are the first in the galaxy:
Life is new to the galaxy and evolution takes time. We are the first intelligent civilization. Problem: the Sun being an average star, if other stars formed a million years ahead of us, then they would be a million years ahead of us technologically speaking.
Planets with the right conditions are rare:
Habitable zones, proper orbit for liquid water are rare
The galaxy is a dangerous place (asteroid impacts, gamma-ray bursters, etc)
The Earth/Moon system is unique (large tides needed for molecular evolution)
Life is rare
Life’s genesis is rare:
Intelligence and tool-making is rare
Language is unique mankind
Technology and science is not inevitable
An answer to the Fermi paradox could be that we haven`t developed the technology to receive messages from other civilizations. The idea that we will detect signals that crawl across space at the speed of light is the issue: a more advanced civilization *might* have a faster than light communication system that we have yet to dream off. Faster than light / warp type drive system seem to be a requirement for meaningful travel between stars. Of course these things are beyond our current understanding. Einstein`s rules preclude FTL- yet we can envisage possible ways around the limits - albeit requiring huge energy and technology beyond our current abilities.