When Are the Intelligent Aliens?

Obligatory talking points associated with the Fermi Paradox:

- It takes a very short time in comparison to the age of the galaxy for a single self-replicating probe to result in a descendant probe visit to every star. A few million years. This means that you cannot really argue plausibly that all civilizations fail to do this - it would take trivial effort for just one faction within just one advanced civilization to set this underway. It's quite clearly the case that we will do it when we can.

- There is a proposal I recall reading that suggests all colonization/self-replicated expansion is patchy in a sort of fractal way. You're always going to get sparse frontiers and empty real estate.

- The Great Filter. http://en.wikipedia.org/wiki/Great_Filter

- The Simulation Argument (Bostrom variant). http://en.wikipedia.org/wiki/Simulation_hypothesis

- The Drake Equation http://en.wikipedia.org/wiki/Drake_equation

- Where are the macrostructures? We don't see Dyson spheres or other evident macroscale engineering. Everything we can see so far looks natural. This is more troubling than an absence of detectable communications. There are any number of ways we can think of for interstellar communication networks to exist and yet be undetectable by us at the moment, and then there are no doubt all the ways that we can't think of.

- Agents responsible for the Fermi Paradox through suppression of nascent intelligence are a popular science fiction trope. First one to the top kills off the rest as they turn up. (Berzerkers, Wolves, etc). It makes for good plotting, but in reality this suffers from all the same issues as economic monopolies and monocultures - i.e. without some sustaining outside influence they are fragile and short-lived, prone to defection, being undercut, and out-innovated from a blind spot. So it's not plausible to suppose that we are randomly in a period of suppressive monopoly.

The other great apes are quite intelligent and occupy the top spots in their ecological niches. Bottlenose dolphins pass the mirror test for self-awareness and appear to have individual names [1], and are at the top of their ecological niche. Elephants pass the mirror test and are at the top of their ecological niche. Octopuses are surprisingly intelligent for invertebrates, and are among the top predators in their niches. In the blink of an ecological eye, intelligence has started showing up at the top spots of the food chain across a diversity of different niches. Just because we haven't seen it before (e.g., the top dinosaur intelligence, the genus Troodon, only had a brain-to-body mass ratio comparable to modern birds [2]), doesn't mean it isn't adaptive - only that it took a while to evolve. Life existed for a pretty long time on Earth before it started running around on the land, too. Doesn't mean running around on the land is maladaptive.

[1] http://www.wired.com/wiredscience/2013/02/dolphin-names/ [2] http://en.wikipedia.org/wiki/Troodon

I would guess that most civilizations don't use detectible radio communications for very long. Look at us now. Everything is going over the internet. I doubt that these signals travel much from Earth before dissipating to the point of being undetectable.

Considering the vast time scales and the vastness of the galaxy, the most plausible explanation for me is still that we happen to live in a historical dark zone.

But it's fun to speculate since any number or combination of events might be responsible for the absence of fellow civilizations.

There is a Great Filter argument that tries to say that we're really, really, really special or that our civilization-ending event might still be in the future. Since we're speculating, I don't think the biological filter argument is very plausible. Historically, we have always been proven utterly wrong after presuppositions of specialness. On the other hand if the Filter is ahead of us, it would have to happen very soon - good candidates for this remain AI, nano tech, or plain apathy. But then again assuming these would be an issue for every advanced civilization seems a stretch.

The simulation argument only makes a difference if the simulation is specifically targeted and limited to simulating us humans. If it's just a universe in a box, it wouldn't tip the scales either way.

The Drake equation and its cousins are nice, but they contain a lot of unknowns. Still, it's a good tool that shows how easy it would be to have statistical fluctuations resulting in a dark epoch.

I personally like the Agents of Suppression theory as well. It wouldn't even have to be another civilization suppressing everything directly - it could just as well be a completely automated armada of leftover killer robots. In my opinion it's one of the more plausible hostile alien invasion-stories as well: one day, we'll fulfill a set of unknown criteria and are simply tagged for extermination. But again, they would have to come our way pretty soon, like in the next 1000 years (which is not a lot of time). This would require a pangalactic drone network for observation and a fast local strike capability. Not completely unfeasible, but not exactly obvious either.

The absence of large-scale artifacts is also interesting, but we have to ask ourselves if we could even detect, say, a ring world or a Dyson sphere if it was in our direct neighborhood (and chances are, it wouldn't be that close). Also, intelligent civilizations would not necessarily produce them. However it would be enough if a few did build huge structures. Again, I don't think we're advanced enough to detect them (or their absence) with any confidence.

> the most plausible explanation for me is still that we happen to live in a historical dark zone.

I am no expert, but I remember reading somewhere that our Sun is among the first generation of solar systems that were born with enough heavy elements to make life based on carbon, oxygen, nitrogen, occasional iron etc. possible.

That there first needs to be some generations of starts going nova so that the stars have generated the heavier elements, and then the supernova explosions have to spread these around to that then the new interstellar clouds have enough of these element when they collapse to next generation stars and solar systems.