This is discussion archived from a time before the current discussion method was installed.
Nobodymuch: The Fermi "paradox" was actually intended to examine a specific science fictional premise, the Lensmen/Solar Queen type universe where the universe swarms with tool-using life and interstellar travel is practical. In the scale of the galaxy's lifespan our entire existence as a tool-using species is extremely brief and it is not unreasonable to surmise that we could achieve slower-than-light interstellar travel sometime over the next ten thousand years. Once we do that we could spread over the entire galaxy in a million years or so, precluding by our very existence the natural development of any other oxygen-breathing species capable of space travel. So if we're first, then nobody else will be around and if we aren't first, then we wouldn't be around. The exception of course would be aliens who don't breathe oxygen and consequently won't compete with us for real estate.
- This assumes that once a civilization becomes capable of interstellar travel, it will inevitably colonize the entire Galaxy, which is not necessarily true. Colonies might percolate through the Galaxy up to a point, and then stop when the nearest next potential world to colonize is too far to make it worthwhile. Or, population growth simply won't be enough to create a constant pressure to expand. Or, the expansion will be so slow that the entire species will change long before it colonizes the entire Galaxy, to the point where colonizing a specific kind of planet in the traditional sense is no longer necessary or desirable. And of course, one can imagine a more advanced species taking care not to interfere with the development of new intelligence as it expands. All of these are equally plausible alternatives.
Trimmed as ranty:
- The Fermi Paradox is nonsense. There's no paradox in that there are plenty of reasons why we haven't been contacted by aliens, or other answers to that question: 1: We have (hey, it's simple). 2: No intelligent species in the universe have yet reached a level of communications or travel ability capable of reaching us (depressingly probably with the restrictions of relativity) — i.e. we're simply outside of all the others' light cones. 3: (The one I am constantly amazed is never considered): We're *first* — why not? Someone HAS to be. Even if there are a million sentient species in this galaxy alone, unless by some sort of amazing cosmic co-incidence they ALL started being sentient at the same time, ONE of them must have been first. Did they sit there wondering if there was other sentient life, before there was? It's frustrating that the only two sides to this argument are presented as either "the universe is teeming with life" or "we're all alone". I mean, come on, seriously. There are plenty of possibilities and NO paradox.
The paradox is the very real and not at all speculative contradiction between observations and our best mathematical models. The math says that there should be evidence of aliens, but there's not evidence of aliens - that's the paradox. Those theories are all potential solutions to the paradox, but the paradox itself is clearly defined, and real. The fact that there's a paradox isn't a proof of the non-existence of aliens, but there is a paradox.
Nornagest: The universe has been cool enough for sentient life to evolve for as long as galaxies have existed, which is most of those 15 billion years. However, "metals" (which in astronomy parlance means any elements heavier than helium) were rare until the Population 1 stars (the set of stars including our sun) formed; that's a reasonable barrier to the formation of life. There are, potentially, others, but most of them are somewhat speculative.
Also, the Fermi paradox as a paradox depends very heavily on the values you put into the Fermi equation; a lot of them (like the probability of evolving life at all, the probability of evolving complex life given the existence of life, or the probability of evolving sentient life given complexity) aren't even known well enough to make an informed guess. I've seen plausible-sounding solutions for the Fermi equation giving values of everything from thousands of interstellar civilizations to low fractions of one.
Madrugada: Here's the entire section that was labelled "Real Life". This is general discussion not a trope example, so keep it on the Discussion Page.
- Real-world example: Well, reality. While some people might object that we haven't even thoroughly explored the solar system, many of the serious minds
devoted to the search for extraterrestrial life view the fact that we haven't found any trace of it to be a serious problem for a variety of reasons (particularly the complete lack of any indication that anyone has made even the slightest effort to colonize the galaxy over the past hundreds of billions of years that, realistically, you would expect many many other species to have had to do so); this is a paradox with possibly nasty implications for us personally. Of course, it's hardly impossible that there's intelligent life out there despite all this; but even the fact that we haven't seen any trace of it from our own small vantage point would rapidly require some sort of increasingly odd justification (such as [1]); compared to these, the existence of Great Filter seems frighteningly probable.
- It's actually only been about 15 billion years since the Beginning, as I recall, and a large chunk of that time was hostile to our type of life (not enough heavier elements, in particular) This troper believes that what's really happening is that we are among the first species out of the sentience gate.
- To quote Hobbes: "It's a big universe."
- It's a massive universe, and that's the reason this troper is convinced that there must be life out there. There were millions-to-one chances of life developing on Earth, and the universe - indeed, the galaxy - is definitely capable of replicating those odds more than once.
- We're one star in one hundred billion in our galaxy alone, and we have enough trouble seeing what's happening in our own solar system. We can only just detect the presence (we can't actually see them yet) of Jupiter-sized planets around other stars. It's a little early to make judgement calls on whether there's anyone out there, methinks.
- This is actually the problem with attempts to decide how "likely" intelligent life is (see also, the Drake Equation). Namely, it is literally impossible for us to ever calculate the precise odds of life as we know it evolving on any given planet under the proper circumstances. So while there may be 17 quadrillion "habitable" planets capable of supporting life in the universe, if the odds of life ever evolving on any given habitable planet are something like 1-in-17 quadrillion, then we might indeed be the only planet in the universe that has managed to produce life. This doesn't even take into account whether "habitable" planets are even sufficient to generate life in the first place (the process may require unique aspects that only SOME habitable planets possess, and possibly very few habitable planets possess), what the odds are that life could evolve along lines completely alien to our own (and if we could even RECOGNIZE it if we found it!), and so on. The sheer size of the universe and the number of stars/planets IN it are meaningless numbers until we can actually figure out what the dozen other variables in the equation are.
- Or maybe FTL Travel isn't just hard, it's simply impossible. Perhaps the speed of light isn't some obstacle that any sapient race could work its way around given enough time. It could very well be that the speed of light is an absolutely impenetrable wall of physics that nothing of any significance can go faster than. Also, nobody wants to waste their life travelling the stars slower than light, as this is very impractical. Therefore, no colonization.
- Even if FTL Travel is impossible, and even if no-one bothered to colonize the galaxy, it would only take one civilization building a single self-replicating robotic spacecraft to seed our entire Milky Way with alien robots in a very short time - only five hundred thousand years, in fact, even if they all moved at sub-light speeds. And given that building such machines seems almost (though not quite yet) possible even at our present technological level, if alien civilizations were out there, you'd expect that there would already be at least one Von Neumann probe somewhere in our own solar system. Of course, maybe there is an alien probe somewhere nearby - it probably wouldn't be easy to find, given that even within a single solar system, space is a big place.
- Why the hell would they seed a bunch of planets with robots they couldn't access?
- The novelty of a race of space-faring self-replicating robots, of course!
- Novelty?
- They would do it For Science!! The robots would send information back to their world of origin (possibly using each other as relays) so that, over the millennia (and tens and hundreds of millennia), the civilization that built them would gradually learn more and more about the Galaxy. And eventually, they would find other life. It's certainly a long-term goal, but given that you only need to build one robot to get it started, and the reward would be a truly astronomical amount of scientific knowledge, it could be seen as an investment well worth making. So... why does it seem that no-one has bothered?
- Prime Directive?
- That's really the question, because Von Neumann Probes, as they are called, are considered one of the very few feasible ways of mapping out the galaxy. It has been calculated that it should take less than 5 million years for a swarm of Probes to spread through the galaxy. So if there was ever any civilisation potentially able to do so (like us) and willing to do so (like us) they would already have done it.
- You're assuming humans are willing to do so. We are not, as a whole, willing to risk exposing the universe to a plague of semi-autonomous roach robots simply to satisfy our own curiosity.
- History strongly suggests humans do not have the foresight you describe. It is more a matter of economics: engineering and building such a probe would be astronomically expensive. As for potentially wiser alien races willing to spend the resources on such probes - I'd like to point out that the "plague of robots" scenario is more of a science fiction trope than something likely to be realistic. It would be fairly simple to keep the robots from overpopulating (simply include a record of every solar system already visited by other robots in the memory of each new unit so they avoid those systems, and have them send out signals to ensure no other robots are in the same solar system before they replicate.) Also, replication is likely to be a long, difficult, and expensive process, placing a natural limit to the likelihood of the robots becoming a plague, and making it very probable that they would be designed not to let the arduous process of replication go to waste by over-populating. Further, they wouldn't be able to "eat" everything they come across in some sort of "grey goo" scenario - it is likely resource extraction will also be difficult, and only possible in a few specific settings. I suggest it's likely Von Neumann probes do exist, and we haven't detected one in our system yet because there would only be one or two within each system, and finding them would be like looking for a needle in a haystack.
- Even if FTL Travel is impossible, and even if no-one bothered to colonize the galaxy, it would only take one civilization building a single self-replicating robotic spacecraft
Peteman: I can't remember if The Stainless Steel Rat uses this trope. I remember reading one of the books where they find a seemingly alien artifact, but by the end of the book, it was revealed to be the work of time travelling humans.
Incompleteness In Space Above And Beyond there are no known aliens at the start of the series. Then they pop out and declare war with the humans, who have maintained an impressive space armada due to healthy paranoia. quote: "We thought we were alone in the universe. We were so terribely wrong." Does anyone else know of fiction where aliens are only absent so they can launch a surprise attack? Should we add it to the reasons writers use this trope?
I just removed two recently added examples: Under Live-Action TV:
- Several pop up in Star Wars, among them the Taung, Rakatan, Architects, and to some degree the Killiks.
- The Xel'naga in Starcraft fit here, they created the Protoss and Zerg (and an unspecified number of 'failures' before that) and were later killed by the latter.
