%% Please note: this is a Useful Notes page, not a trope. Examples should be limited to works that explicitly discuss or reference the paradox itself. Examples which merely provide a particular solution should be listed on one of the trope pages; either AbsentAliens or InivisibleAliens.

->''Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.''
-->-- '''Arthur C. Clarke'''

The Fermi Paradox is an observation/question by physicist Enrico Fermi: The universe is very old. Life (from a scientific viewpoint) seems to be relatively simple--simple enough that, given the unimaginable size of the universe, there should be millions of planets with life scattered out there, and surely thousands at least in our own galaxy. And even without Faster-than-Light Travel, an intelligent spacefaring species should be able to spread across the galaxy in a relatively short amount of time.

So where is everybody?

We should be able to see all kinds of signs of intelligent alien life when we look at the stars, or possibly even evidence of alien life visiting Earth. But we don't.

There are numerous proposed solutions to this question, which break down into two broad categories:

* AbsentAliens is [[OccamsRazor the simple solution]], and makes for a fairly straightforward story: the entire universe is essentially uninhabited, and out there for us to settle freely.
* InvisibleAliens is more tricky, as there may be all kinds of reasons we might not see the aliens that are out there. Even if life is common, ''intelligent'' life might be rare for any of a number of reasons. And even if intelligent life is common, it might be hiding, or it might not last very long. If they're bizarre StarfishAliens, we may simply not recognize what we're looking at. If they're SufficientlyAdvancedAliens, we may not even have discovered the technologies required to detect them.[[note]]Currently the primary method of searching for aliens is to listen for possible extraterrestrial radio transmissions. But if alien civilizations tend to only use radio for a brief time before moving on to some other technology we haven't conceived of yet, there would be only a be a brief window to detect any given planet's transmissions.[[/note]] And if they're more than sufficiently advanced, their intelligence might have led to some sort of [[AscendedToAHigherPlaneOfExistence transcendence]] that we can't detect, even in theory. Alternatively, they may be perfectly visible already, but TheMenInBlack are making sure the general public doesn't realize it.

The Fermi paradox has also been presented as one of the arguments against the [[https://en.wikipedia.org/wiki/Steady_State_theory Steady state theory]], that states the Universe has existed forever as we know it. With an infinite amount of time behind it -- no matter how rare truly advanced space-faring species were -- sooner or later, not one but many would appear and we'd see evidence of their existence.

Related to the paradox is the [[http://en.wikipedia.org/wiki/Drake_equation Drake equation]], one attempt to quantify the elements required to actually discover other intelligent life forms out there. The Drake Equation has been criticized because most of its terms are unknown, leaving it to the discretion of individuals. Depending on the numbers you put in, the number of intelligent species per-galaxy as predicted by the Drake Equation can be anywhere from millions to less than one. In the end, these terms can never be known for sure until after we resolve the Fermi Paradox one way or the other: either by finally contacting an alien civilization, or by exploring enough of the universe to say convincingly that they don't exist.

Wiki/TheOtherWiki has [[http://en.wikipedia.org/wiki/Fermi%27s_paradox more details.]]

Note that technically, Fermi was [[http://blogs.scientificamerican.com/guest-blog/the-fermi-paradox-is-not-fermi-s-and-it-is-not-a-paradox/ actually pessimistic about interstellar travel, and it isn't a paradox.]]
!! Works that mention or discuss the paradox:


[[folder:Comic Books]]
* The Comicbook/FantasticFour: Reed Richards attributes this to ComicBook/{{Galactus}} in the regular and ''ComicBook/UltimateMarvel'' universes.

* Creator/StephenBaxter's three ''Manifold'' novels investigate three different solutions (using the same characters in each novel):
** ''Literature/ManifoldTime'' assumes AbsentAliens.
** ''Literature/ManifoldSpace'' assumes intelligent races don't last long.
** ''Literature/ManifoldOrigin'' assumes each universe in a multiverse has its own unique intelligent race.
* A favorite subject of Creator/DavidBrin's:
** [[http://www.davidbrin.com/xenology2.htm Xenology: The Science of Asking Who's Out There]] is an essay on the subject.
** ''Literature/{{Existence}}'' discusses the paradox at length, especially in the chapter headers.
** He has mentioned that it was part of the inspiration for the ''Literature/{{Uplift}}'' series. Where every space-faring race is governed by a bureaucracy that tightly controls colonization rights and which declared Earth's sector off-limits millions of years ago.
* "The Fermi Paradox is Our Business Model" is the name of a short story by Charlie Jane Anders.
* Discussed by an astronomer and a possible answer provided in ''Literature/VariableStar''. [[spoiler: As a GenerationShip leaves Earth, the astronomer on the ship sees something odd about the sun. A quarter of the way through their trip, the sun explodes, destroying the entire solar system. The inhabitants of the ship conclude that this was done on purpose by an alien race, resolving the paradox AbusivePrecursors style.]]
* ''Literature/MoreInformationThanYouRequire'' proposes a solution: that the aliens are merely very far away. Possibly even... ''on other planets''. It's also implied that [[BeethovenWasAnAlienSpy Fermi himself was an alien.]]
* Creator/AlastairReynolds' Literature/RevelationSpace universe at first appears to be a case of AbsentAliens as humanity finds many worlds with life, and the ruins and relics of numerous advanced interstellar civilizations, but only a few rarely encountered, sparsely distributed interstellar species. As the series progresses, however, it turns out there's a very good reason for this...
* In Creator/CharlesStross's ''A Colder War'' short story, some characters discuss the fact that they're pretty sure they've solved why the paradox exists. [[CosmicHorrorStory It's not very pleasant.]]

* The band Music/TubRing has albums named ''Fermi Paradox'' and ''Drake's Equation''.

[[folder:Video Games]]
* ''Franchise/MassEffect'' has aliens plentiful and perfectly understandable to humans; they are simply not encouraged [[AlienNonInterferenceClause to interfere with intelligent races that have yet to develop spaceflight]]. (Some of them do so anyway for various reasons, but not with humans.) Another potential answer is offered why none have yet completely conquered the galaxy: every fifty thousand years, an unthinkably ancient and powerful machine race marches in, exterminates all spacefaring species along with most signs they existed, then leaves again.
* ''VideoGame/Prey2017'' namechecks the Fermi Paradox, and offers an existentially terrifying resolution: no intelligent life has yet been encountered because the Typhon species evolved to detect and consume all advanced consciousness they come into contact with. Rather than flesh, they eat ''minds''.
* ''Videogame/DeadSpace'' resolves the paradox in the name. No advanced life has been found because... well, it's dead. Every advanced civilization has found Markers, been overwhelmed by the Necromorphs, and had their combined biomass formed into a new Brother Moon, the largest form of Necromorph.

[[folder:Web Animation]]
* ''WebAnimation/ExtraCredits'' devotes [[MultiPartEpisode a two-parter]] to this subject and the Drake Equation. Available [[http://www.penny-arcade.com/patv/episode/funding-xcom-part-1 here]] and [[http://www.penny-arcade.com/patv/episode/funding-xcom-part-2 here.]]

[[folder:Web Comics]]
* In ''Webcomic/AMiracleOfScience'' Mars re-established contact with the rest of humanity after going out into the universe and finding no aliens. [[spoiler:They were all dead.]]
* One strip of ''Webcomic/{{xkcd}}'' suggests that the solution to the paradox is that [[http://xkcd.com/962/ fun trumps survival]].
** [[http://xkcd.com/1377/ Another]] offers an alternative solution, [[spoiler: they're all hiding]].
* The paradox is brought up in ''Webcomic/SchlockMercenary'' as a concept that has been largely disregarded in the thousand years since FirstContact, but, after hearing evidence that [[spoiler: galaxy-spanning civilizations have risen and fallen many times over millions of years]], the idea is revisited.
* The paradox is lampooned in ''Webcomic/FreeFall'': an alien squid (Sqid, if you would) who just so happens to be very tasty to virtually any sort of Terran animal points out that humanity's resilience is, in large part, due to asteroids smacking into Earth and giving more time to evolve: those who got it on the first try have simpler cellular structures. So...
-->'''Sam:''' There is no Fermi Paradox! Every time the aliens make it to Earth, the cows get them!

[[folder:Web Original]]
* In ''Literature/VeilOfMadness'', the reason humanity hasn't found any aliens is because Earth is smack in the middle of the titular "Veil of Madness", which causes violent insanity in any intelligent life that lives there, usually driving them to extinction. Humanity is the only race to have avoided this (well, one other race hasn't destroyed themselves quite yet, but they're definitely affected and they haven't got out of the Stone Age).

* Creator/GeorgeCarlin half-jokingly suggested that we haven't discovered aliens because they know exactly [[HumansAreTheRealMonsters how bad we are]] [[HumansAreMorons as a species]] and are actively avoiding us.
* ''ComicStrip/CalvinAndHobbes'' suggested the same thing:
-->'''Calvin:''' I think the surest sign of intelligent life in the universe is that none of it has ever tried to contact us.
* As did Eric Idle's "Galaxy Song" Film/MontyPythonsTheMeaningOfLife'''
-->''And pray that there's intelligent life somewhere up in space...\\
...[[NoIntelligentLifeHere 'cos there's bugger-all down here on Earth]]''