History Main / InvisibleAliens

* In the ''Film/MenInBlack'' [[ComicBook/MenInBlack comics]] and [[WesternAnimation/MenInBlack their adaptations]] (and in the TheMenInBlack urban myth that inspired them), the title organization is expressly dedicated to making sure Earth civilians stay unaware of aliens.

* The ''Franchise/MassEffect'' series explains why humanity wasn't contacted before we opened the [[PortalNetwork Mass Relay]]. In the past, explorers opened an inactive relay where they encountered a hostile insect race called the Rachni. This led to a massive BugWar that threatened all life in the Galaxy before the war was won by wiping out the rachni. As such, in order to prevent a repeat of the Rachni War, the [[FictionalUnitedNations Citadel Council]] made it illegal to open dormant Relays that lead to unknown locations, until extensive research has been done to determine where they go and that there aren't any hostile lifeforms on the other side. The only Relay linking Earth to the rest of the Galaxy is one such example. This Relay was not only dormant, it was covered in so much ice that for centuries humans thought it was a moon, specifically, Charon one of the moons of Pluto. Humans would later discover an alien technology archive on Mars that showed them how to reactivate the relay, which would pave the way for humanity's early period of interstellar expansion and eventually lead to FirstContact with the rest of the Galaxy.

* In ''Franchise/StarTrek'', the [[AlienNonInterferenceClause Prime Directive]] prohibits the Federation from interfering with aliens until they've discovered interstellar travel; according to ''Film/StarTrekFirstContact'', the Vulcans had a similar rule before the Federation was founded, which presumably "explains" why we haven't seen any Vulcans yet in real life.
* In ''Series/DoctorWho'', the Shadow Proclamation, basically a galactic police force, has rules about how alien life forms are not allowed to make contact or interfere with worlds without a minimum amount of technology -- not that most of the aliens seem to care about that, as they really like trying to take over/destroy/control Earth for some reason. It was this rule and groups like UNIT and Torchwood which kept the public from learning about alien existence until around 2008 when [[spoiler:the Daleks invaded and physically teleported the Earth.]]

[[folder:Real Life]]
* Real life you say? But we haven't proven aliens they say! True, however in a sense this trope applies to those meteorite findings, such as in [[https://www.space.com/33690-allen-hills-mars-meteorite-alien-life-20-years.html Antarctica]], that appear to have traces of fossilized germs in it. While not proven, it is possible that some life on Earth is foreign based, and if there is life on other nearby planets and moons, it could be Earth based. This idea is called panspermia and some extremophiles (resilient bacteria that go into "hibernation" when stressed) could be living on other planets such as Mars and moons such as Europa or Enceladus.
** While we can see germs with microscopes, they are invisible to the naked eye so this tropes rings true in a sense.
* Astrophysicist UsefulNotes/NeilDeGrasseTyson claims that we do not have enough of a sample size of the universe to say there is no extraterrestrial life; he compares it to going to the beach, scooping some water into a cup, then looking into the cup and saying "there are no whales in the ocean, because there are no whales in here".
[[/folder]]

* The ''Franchise/MassEffect'' series explains why humanity wasn't contacted before we opened the [[PortalNetwork Mass Relay]]. In the past, explorers opened an inactive relay where they encountered the Rachni, this led to a massive BugWar that threatened all life in the Galaxy before the war was won by wiping out the rachni. As such, in order to prevent a repeat of the Rachni War, the [[FictionalUnitedNations Citadel Council]] made it illegal to open dormant Relays that lead to unknown locations, until extensive research has been done to determine where they go and that there aren't any hostile lifeforms on the other side. The only Relay linking Earth to the rest of the Galaxy is one such example. This Relay was not only dormant, it was covered in so much ice that for centuries humans thought it was a moon, specifically, Charon one of the moons of Pluto. Humans would later discover an alien technology archive on Mars that showed them how to reactivate the relay, which would pave the way for humanity's early period of interstellar expansion and eventually lead to FirstContact with the rest of the Galaxy.

* The [[SufficientlyAdvancedAliens Data Integration Entities]] from ''LightNovel/HaruhiSuzumiya'' are, according to Nagato, undetectable through our normal means. Given that they ''lack physical form altogether'', and seem to exist only as patterns of information, this is perfectly plausible.

* The ''Franchise/MassEffect'' series explains why humanity wasn't contacted before we opened the [[PortalNetwork Mass Relay]]. In the past, explorers opened an inactive relay where they encountered the Rachni, this led to a massive BugWar that threatened all life in the Galaxy before the war was won by [[KillEmAll wiping out the rachni]]. As such, in order to prevent a repeat of the Rachni War, the [[FictionalUnitedNations Citadel Council]] made it illegal to open dormant Relays that lead to unknown locations, until extensive research has been done to determine where they go and that there aren't any hostile lifeforms on the other side. The only Relay linking Earth to the rest of the Galaxy is one such example. This Relay was not only dormant, it was covered in so much ice that for centuries humans thought it was a moon, specifically, Charon one of the moons of Pluto. Humans would later discover an alien technology archive on Mars that showed them how to reactivate the relay, which would pave the way for humanity's early period of interstellar expansion and eventually lead to FirstContact with the rest of the Galaxy.