35: The Fermi Paradox ("where are they?")
Fermi Paradox: What is an alternative to the Fermi Paradox?
"The Great Silence" • advanced civilizations may rise & fall, but are so rare that the chances of two or more sharing the galaxy at the same time are very small • alternatively, some have suggested that the Great Silence is a respectful silence kept by older species to not disturb those younger species just emerging into maturity
What are the 3 explanations for the Fermi Paradox?
#1: Advanced civilizations are intrinsically rare. #2: Advanced civilizations are common, but they cannot do interstellar travel. #3: Advanced civilizations are common, but we don't know they exist because we're not advanced enough to pick up any signal of their communication.
Fermi Paradox: What are the 3 basic types of solutions that have been proposed to resolve the Fermi Paradox?
1) Advanced civilizations are very rare. There is at most one per galaxy (and we're in it!) 2) Civilizations are common, but they have not colonized the galaxy 3) Civilizations have colonized the galaxy, but we remain unaware of them.
Fermi Paradox: Solution 3a: the Zoo Hypothesis...
Earth is protected from dangerous outside contact until we are ready (i.e. a wild species that is "protected" by other civilizations). *there are many examples of this in human history
Fermi Paradox: Solution 3d: the Late-to-the-party Hypothesis...
Earth was visited in the distant past long before humans (Earth's history is 99.95% human-free)
Fermi Paradox: Solution 1c: the Inhospitable Universe Hypothesis...
Earth's geological past records multiple mass-extinction events...perhaps Earth life has survived them by good luck • asteroid or comet impacts • super-volcanism (Deccan Flood) • deep ice age (Snowball Earth) • supernova or gamma-ray burst sterilizes the planet
Who asked "where are they?"
Enrico Fermi
Fermi Paradox: Solution 3a: "Prime Directive" Hypothesis
Ethics of contact with less advanced civilizations (i.e. maybe other civilizations have the morales Columbus didn't have when he came to America...don't want to bring diseases, etc.). *there are many examples of "fatal impacts" between peoples in human history, even when well-intentioned
Who was Enrico Fermi (1901-1954)?
Italian physicist best known for fundamental contributions to quantum mechanics and nuclear physics; built the first nuclear reactor at the University of Chicago; worked at Los Alamos Lab on the Manhattan Project to build the first atomic bombs
Fermi Paradox: Solution 3d: the Low-Rent Hypothesis...
Our part of the galaxy is out of the way and boring and not worth the resources to visit
Fermi Paradox: T/F? The Drake Equation is basically a static version of the Fermi Paradox.
T: one of the critiques of the Drake equation is that it doesn't allow for interstellar travel because it assumes every civilization is stationary
Fermi Paradox: Solution 3b: Civilizations have colonized the galaxy, but...
The government is covering it up (conspiracy). • fuzzy photographs and anecdotal accounts are not strong proof • claims of government conspiracy to hide definitive evidence • congress can't pass a budget much less keep secrets for years... *there are unexplained sightings, but failure to explain them does not justify wild leaps of the imagination.
Fermi Paradox: Solution 3d: the Predator Hypothesis...
There are a few nasty predator civilizations in the galaxy, and sensible civilizations keep a low profile
Fermi Paradox: Solution 3d: Civilizations have colonized the galaxy, but...
Variations on a theme (e.g., the Late-to-the-Party hypothesis, the Low-Rent hypothesis, the Predator hypothesis)
Fermi Paradox: Solution 3c: Civilizations have colonized the galaxy, but...
We haven't noticed yet. • perhaps aliens live among us covertly monitoring our culture • maybe they've been guiding our cultural evolution all along • perhaps aliens use a form of communication that we haven't developed yet *^this would make our radio and microwave eavesdropping useless.
Fermi Paradox: Solution 1b: the Doomsday Hypothesis...
advanced technology is dangerous because of deliberate aggression & inadvertent mistakes • nuclear war • biological war • environmental catastrophe • nanotechnology catastrophe • zombie apocalypse
Fermi Paradox: Solution 2a: Civilizations have not colonized the galaxy because...
it is too difficult: • sending generation ships ("arks") between the stars is an enormous investment of resources • however, sending robotic probes is a lot cheaper • why have't we encountered alien robotic probes?
Fermi Paradox: If life and intelligence are common, but civilizations are short-lived, there could be a very large number...
look in photos for explanation (= 3.2 civilizations)
Fermi Paradox: If life and intelligence are very rare, but civilizations are long-lived, you should at least get a few...
look in photos for explanation (= 4 civilizations)
Fermi Paradox: Solution 1c: Advanced civilizations are rare because...
natural disasters destroy them (e.g., inhospitable universe hypothesis)
Fermi Paradox: Solution 1a: the Rare Earth Hypothesis...
perhaps we result from a series of unlikely circumstances... • we live inside a narrow "galactic habitable zone" • we orbit around the right kind of star • Earth has a moon that stabilizes its rotation IMPLICATION: we are the only intelligent species in our galaxy.
Fermi Paradox: Solution 3a: Civilizations have colonized the galaxy, but...
they aren't telling us (e.g., Zoo Hypothesis, "Prime Directive" Hypothesis)
Fermi Paradox: Solution 1b: Advanced civilizations are rare because...
they destroy themselves (e.g. The Doomsday Hypothesis)
Fermi Paradox: Solution 2b: Civilizations have not colonized the galaxy because...
they don't want to: • no precedent in human history for whole peoples staying in one place • while individuals and some communities adopt monastic lifestyles, would an entire species do this? • a counterargument: we are young-is exploration a "phase" that an advanced species eventually grows out of?
Fermi Paradox: Solution 1a: Advanced civilizations are rare because...
they seldom develop (e.g. The Rare Earth Hypothesis)
What is the Fermi Paradox?
• Reasonable assumptions predict that a galactic civilization should have already arisen in the Milky Way. Yet, we have absolutely no evidence for it. • The paradox is why this hasn't happened already • It's a statement about the rapidity of colonization-not about how often civilizations arise. - galaxies are ~10 billion yrs old - a long-lived, star-faring civilization could colonize an entire galaxy 100s or 1000s of times over - but, it only has to happen once or twice
Fermi Paradox: Solution 3d: the Predator Hypothesis: a recent variation of the predator hypothesis is called the "Dark Forest Hypothesis"...
• the fact that there is a Fermi Paradox is a sign that we should avoid making contact with other civilizations • civilizations that speak up risk fatal problems after first contact • it is too dangerous to transmit, so everyone is just listening silently
