Fermi's Paradox - Where The Heck Is Everyone?

The Fermi Paradox is a conundrum proposed by pioneer physicist Enrico Fermi that questions the likelihood of Intelligent Extraterrestrial life. It begins with the Drake Equation or some derivative which guesstimates the possible number of intelligent civilizations in the universe, and then extrapolates expansion rates into the universe from a point location within the cosmos of that species or culture. The paradox concludes that there should have been enough ET's over the last 14 billion years that even if they moved at velocities achievable by human technology today, they could have swarmed over the galaxy, or even the cluster to which our galaxy belongs, many times over.

I think it's fair to say that we humans don't know enough about the universe to draw any firm conclusions from the paradox. Still, it's an interesting thought experiment; The galaxy is over 100,000 light years from rim to rim and contains perhaps 400 billion stars each of which could easily have, on average, a half dozen planets. The galaxy is perhaps 10 billion years old. If there were a single fledgling interstellar civilization in all that space and time, and it expanded away from it's planet or point of origin on average at the measly rate of one light year every ten thousands years, slower than the Voyager Spacecraft are traveling, and grew in all directions, it would take a mere one billion years to get from one end of the galaxy to another and completely fill it up along the way. Humans could begin constructing spacecraft that could move at ten times that rate right now if we put our minds to it. So if we could spread all over the galaxy, why hasn't someone already spread all over us? Once cultures started spreading like this it seems likely a ruthless sort of selection would kick in and favor the culture or the faction within a culture which does so the most aggresively, quickly, and successfully. It's hard to see what would stop it.

Remember, all it takes is a single space faring civilization to develop and survive. It would only have to happen once in all the history of the local group of galaxies and they should be here, or we should at least detect signs of them relatively nearby.

So the question, naturally, is where are they? Where are the ruins? Even if they're not here on Earth right now in any obvious way, where is the interstellar traffic lights or radio chatter or giant interstellar construction projects, some of which would plausibly be grand enough for us to detect from our earthbound and space based observation platforms? Does this mean we, as intelligent beings, are unique or rare beyond imagination? Is it evidence for a Theistic Creator Entity or entities which created human specifically? Why or why not? How would you address the Fermi Paradox?

Possible Solutions: As PZ and others suggested on our sister thread and in comments, intelligence really is very rare, and although there might be more than just one intelligent species in the universe, they're statistically so far apart that there nearest one to us is on the far side of Centaurus A.

As Hank Fox suggested in comments there may be built in physiological or mental factors which are unavoidable or difficult to overcome, and which prevent intelligent species from expanding much. There could be universal consequences

as a result of selection which would be present in any species evolving via ruthless Darwinian processes leaving them prone to self destruction or factional bickering which ultimately leads to their destruction. Based on human experience so far, this sounds quite reasonable to me.

The Prime Directive Solution. There's a peaceful intergalactic wide civilization composed of millions of species working in utopian harmony for the greater good of all and they're so damn concerned that we develop naturally without devastating interference that it's against the rules to intervene in anyw ... buahahaha! OK, DR Sagan, Mr Rodenberry? Please put the bong down now. Moving on then ...

The Zoo Exhibit Solution. We're on display for the amusement or research utility of the ET's and, like in any zoo, there's a rule about not feeding the animals. We're the galactic equivalent of a reality TV show. I include most religious explanations under this category such as Christianity, Islam, or Judaism; where the entire universe and mankind, or at least our local portion, exist solely as a way to keep score in a cosmic pissing contest between rival deities or super aliens. (For some reason that latter scenario with the sociopathic deities comforts some people, although the source of that comfort eludes me)

The Anti-Prime Directive. There is a homogeneous culture throughout the galaxy, but they're paranoid xenophobic motherfuckers who zap any potential competitors as soon as they know about them. Now that's something I can accept based on human behavior! And because they're so paranoid they keep a very low profile in the meantime. In this scenario Beserker Machines or Hiveships are already on their way here with charged photon torpedo banks at the ready thanks to early transmissions of I Love Lucy. (Fortunately, they use windows compatible networks vulnerable to Doom and Gloom viri which we will download into their mainframe and ... )

Periodic Annihilation. Gamma Ray Bursters and/or other things we haven't thought off periodically wipe large regions of the galaxy/cosmos clean of complex organic or replicating structures. The catastrophes could be localized to a few thousands light years and randomly periodic, as in Stephen Baxter's Manifold Space, or cosmic level events such as changes in the vacuum energy level of the entire university.

The Transcendence Solution. Intelligent ET's discover there's much more to the cosmos than we have the faintest inkling of and they reconfigure themselves to live in that realm, create a technology to get them to it, or literally create their own universe or virtual reality. IOW, they leave this universe for something better ... Or they're here right now, we just can't see them because they've evolved or engineered themselves to subsist in a media where they live at speeds and on scales we cannot detect. Maybe they're hanging out right here in this room with me at the quantum level or in an associated higher non Euclidean metric to our humdrum Reimannian cosmos, i.e. Hyperspace. Or maybe they're composed of dark matter and the size of galaxies living in intergalactic voids where it's 'safe'. They're aware of our planet and our culture but they just don't give a shit anymore than you care about bacteria growing on the skin of an apple.

The X-files Solution. They are here in disguise and they're manipulating us to their own dastardly evil ends. Dick Cheney is their leader. Someone should really be checking the White House basement for strange looking pods. (Or conversely maybe the dominant alien race happens to look just like coat hangers and prefers living quietly in closets)

More complex solutions, like any expanding civilization must expand faster and faster to keep resources flowing to the interior of the already settled volume and the process inevitably cannot keep up that race until it crashes, settles into war, or the expanding edges fracture into shards which die out.

Personally my guess would be that PZ or Hank's scenario is the most plausible, but what the hell do I know?