1. The Fermi Paradox

2. Where Is Everybody?
If there are an abundance of societies in the Universe, at least a couple should’ve reached galactic colonization…. So where is everybody?
Proposed by Enrico Fermi.
Based on Earth not being special. (so someone should’ve colonized by now and we should have evidence!)

3. How likely are other civilizations?
The Universe is old.. Much older than our species.
If our whole Universal history was scaled to 1 year, our civilization only takes up the last 30 seconds. (a small amount of time)
If it takes 4.5 billion years from birth of planet to an advanced civilization, the Universe has had time for a lot of them.

4. The Cosmic Calendar 1 second = 390 years 1 min. = 23,000 years
New Year’s Day: The Big Bang
The Milky Way forms
Sun and planets form
Oldest known life forms
First multi-cellular life
1 second = 390 years
1 min. = 23,000 years
1 day = 33 million yrs

5. How likely are other civilizations? (2)
If planets started forming early on in the universe, civilizations that took 4.5 billion years would have started popping up over 6 billion years ago!
With 100 billion stars in our galaxy, if 1 in a million gets a civilization, that’s 100,000 civilizations!
Starting 6 billion years ago, and evenly spread, that’s one every 60,000 years! (every 3 minutes on the cosmic calendar)
If you start more recently (not enough heavy elements), you still get a 0.5 billion year head start and one civilization every 100,000 years! (every 5 minutes on the cosmic calendar) (So the last one was 100,000 years ago… they should’ve figured out colonization by now!)
So, if civilizations are common, there should be lots of them!

6. Could they colonize? Are they technologically capable?
Even at slow speeds (10% c), the trip to the next nearest star would be within a human lifetime.
They could then leapfrog to the next star, expanding the colonies at the edges (the coral model).
Would take a few million years to colonize the galaxy.
(100 million years for 1% c)

7. Would they colonize? Do they want to? Motives for colonization:
predisposition
Resources
war or persecution
“extinction proof”
end of their star’s life.
Non-motives
Population pressure – colonization is not an answer. To deal with our current population growth (keep it stable on Earth), we’d need to move 100 million people off Earth every year. We can’t do that. Cost prohibitive, not enough transport, not enough resources, no place to put them to easily colonize.
Conquest: we are likely behind any other species we encounter, so we aren’t likely to prevail.

8. The Paradox Someone should’ve colonized No evidence of colonization
Solutions?
We are special! The first civilization to attain this level. (so SETI should stop looking)
Civilizations are common, but no one colonizes.
There is a galactic civilization, but it hides from us.
We are alone – philosophically unappealing. Goes against our not-special belief, but can’t be ruled out. Maybe civilizations have been impossible until now for some unknown reason
No colonization –
Technological difficulties - (as discussed in the last chapter) for interstellar travel, biological/physical barriers for interstellar travel
Sociological concerns – content to stay home, can’t maintain enthusiasm for colonization for millions of years, become less aggressive (curb their invention of weapons of mass destruction and therefore maybe rocketry as well)
Self-destruction – society self-destructs before colonization is begun or completed.
The hiding civilization –
No interest in us (too young, too simple)
Watch us (zoo hypothesis), set aside and left to ourselves to thrive in a natural environment
Reveal themselves after we reach a certain level of intelligence/technology
They wait and watch (sentinel hypothesis)

9. Implications of the paradox
We are alone
We are remarkable, we alone are self-aware, humanity is precious
No colonization
Everyone else failed, what hope do we have? If everyone failed due to lack of interest or self-destruction we are in trouble.
Hidden civilization
We are newcomers that may be in store for an amazing journey