It's actually significantly less probable than that by many orders of magnitude but it's hard for humans to grasp just how isolated everything in the universe is from everything else.
That fact that we dont find drones suggests one of only a few things
* life is rare
* we're first
* they all kill themselves before they get the drones built
Or, that there is something fundamentally flawed with the concept of self-replicating drones covering the entire galaxy that would make it infeasible in practice, despite it seeming perfectly rational on paper.
The decision to use resources to pollute the wilderness with arbitrary technology is a leadership decision, relying on the personality characteristics of an entity or social chain of command.
This business about "drones" is an anachronistic paraphrasing of the original concept. People didn't speak in terms of the "drone" fad in the 20th century, like we do now. Drones were usually just target practice for the Air Force and Navy.
The original concept just specified range of influence, and a demonstration of presence. It did not impose a manner of activity, be it drone replication or direct colonization with regimented staff, and divisions of duty among personel. [0] The Fermi paradox remained agnostic, simply implying possible speed of travel given geological time scales.
Carl Sagan's Cosmos mentioned unmanned satellites (or unaliened? unoccupied...) as the most likely hypothetical form of first contact. Before we bump into any living thing, will probably notice a few remote control devices fanned out in front of their main corpus of civilization or colonization. That TV show also hypothesized about the possibility of dying civilizations leaving behind self-perpetuating remnants of technology, the likes of which might or might not be sentient. All of it was TV speculation though, not presented as surely factual.
If you read between the lines, the premise of a "dying" civilization hints at the lack of self control present in a runaway factory neglected and left to churn out garbage. That idea does not assume that a collective of entities would always wish to tamper with and contaminate their surrounding domain presumptiously.
It's pretty clear that the "drones" the GGP is referring to are self-replicating autonomous machines, which could, with a relatively extremely small initial mass-energy investment, visit every solar system in the galaxy in a matter of megayears. It doesn't require leadership or social approval or whatever you're talking about; anyone with technology marginally more advanced than what we have could do it with the equivalent of a few tens of billion dollars of machinery. The more advanced you are, the cheaper it gets. It's very odd that we haven't seen anything like that yet.
It's like Kurzweil describing the exponential curve of self-replicating AI leading to the Singularity and infinite machine intelligence... it's an elegant, mathematically self-evident solution that just happens not to correlate with reality.
It has literally nothing to do with the nature of whatever aliens might build these hypothetical machines. The only requirement is that some group with modest resources and marginally better technology than us wants to do it.
> It's like Kurzweil describing the exponential curve of self-replicating AI
A little early to try and refute that, don't you think? We're still on an exponential production trend.
That's not "modest resources and marginally better technology than us", that's perilously close to being magic. Not even viruses, the most aggressive and efficient self-replicators we know of, have managed to consume all the biomass on the planet, or could reasonably be expected to do so.
This is a false premise. It doesn't have to do anything this fancy.
You can expect that any given asteroid is likely to have a certain amount of iron, carbon, silicon, nickel, etc.
In almost any solar system, you can mine the materials needed for construction very easily. Solar gives you enough energy to do (slow, deliberate) resource extraction from asteroids.
As for propellant and reaction mass, we already know nuclear explosions work excellently. Unfortunately, based on analysis of meteors we don't expect asteroids to have great heavy-metal concentrations; on the order of 10ppb for Uranium. This presents a challenge, but not an insurmountable one; it just means that you'll probably want to get explosive materials closer to the center of the system.
> Not even viruses, the most aggressive and efficient self-replicators we know of, have managed to consume all the biomass on the planet, or could reasonably be expected to do so.
This is true, but 100% irrelevant to the challenges of creating space-based manufacturing capable of reproducing all its own components.
It doesn't have to be "self replicating drones." It could be inert bullets, arrow heads, sharp sticks, carefully arranged electromagnetic retro-reflectors.
Drones are a fad. The paradox doesn't require an alien implementation of drone technology, self replicating, autonomous, or what have you.
The concept of autonomous machines is a fad?
As technology advances, autonomous machines may very likely grow beyond the definition/parlance of a "drone" (machinery designed and dedicated only to perform specific tasks) into more powerful forms of intelligence.
At that point, such machinery graduates beyond the definition of an artifact (a possession held in the ownership of higher-order life), and one might speculate whether it represents a form of life unto itself, or where one might draw such a boundary.
Either way, such sentient machinery (read: not drones) might not be bound by geological/astronomical timescales, outlasting its inventors possibly permanently, but still represents a component of the Fermi Paradox. If such things are possible, where are they?
Yeah, you're just making shit up. The first machine intelligence in pop culture can be found in https://en.m.wikipedia.org/wiki/R.U.R. (the origin of the phrase "robot"). Non-sentient autonomous machines are even older. https://en.m.wikipedia.org/wiki/Golem Sci-fi authors have been talking about modern-looking self-replicating machines for decades.
Maybe you have some weird definition of a drone? Drones in common parlance have come to be associated with any robotic vehicle, and are used in technical parlance to refer to a huge variety of autonomous or semi-autonomous machines.
https://en.wikipedia.org/wiki/Great_Filter
Another option is something like the outcome of the novel Blood Music, where engineering efforts become smaller and smaller and the outside universe is ignored completely in favor of microscopic exploration and engineering efforts.
might just as well be: they manage to build the drones, but the drones don't go on or the power gets turned off.
I think we get caught-up in the physical nature of the universe. I mean, anyone who can efficiently traverse the galaxy would have completely understood the laws of the universe and be able to somehow travel as fast/faster than the speed of light, meaning that they would have to somehow violate the physical mass=infinite, length=0, time=0 constraints of the speed of light. There's no way that you would be able to travel efficiently under those physical constraints. It would have to be some dimensional non-physical method of travel. And if they can do that, then physical drones would be unneeded.
The concern isn't little green men in flying saucers; it's if, for example, someone makes an exponentially replicating terraforming system. It wouldn't take very long to swamp the galaxy.