History Main / LostCommonKnowledge

* [[https://en.wikipedia.org/wiki/Roman_dodecahedron Metal dodecahedrons]] are commonly found in Roman sites from the 2nd to 4th centuries , but their function is unknown and they aren't found in either contemporary paintings or written sources.

* Not entirely lost, per se, but Lieutenant Huxley in ''Film/DemolitionMan'' is delighted to have obtained a Music/RedHotChiliPeppers {=LP=} (rock music is forbidden in San Angeles) and picks Detective Spartan's brain for information about 20th-century society. The rest of her squad think she's a weirdo for being obsessed with the violent old days.

* In ''Film/TheDarkTower'' Roland and Jake visit some mysterious ruins from the past. Roland says no-one knows what they were. Jake: "It's a theme park."[[/folder]]

** Some version then follow up with a third person asking "What's "sorry"?"

* How [[EenieMeenieMinyMoai moai]] were moved. A lot of theories were proposed, including AncientAstronauts, but experiments have revealed that these huge statues can be "walked" using ropes and the same leverage techniques commonly used to to move a heavy barrel. Rapa Nui oral history always said the statues walked but this was thought to be figurative until the technique was rediscovered.

* "GreekFire" (actually used by the Byzantines, who were Roman) is a fairly well-known incendiary substance that was used as a weapon. Its properties were recorded by contemporary writers, but not its formula. A number of possibilities have been put forward, and weapons with a similar effect are easy to make today, but the actual composition has been lost to history.

* The Spanish wrote that Mississippian culture archers in the southeastern U.S. could perforate two layers of chainmail and shoot down a galloping horse. Archaeologists have also found evidence that the Mississippians used to make wooden or leather armor in earlier periods but abandoned them by the late Middle Ages, which is consistent with an archery revolution making armor obsolete. Nevertheless, no Mississippian arrows or bows have survived, and the tree species in the area have woods too soft to accomplish this. It's been suggested that they hardened the wood with fire and used "cable-backed" bows similar to Inuit bows, but this is just hypothetical.

* The purpose of bâtons de commandement ("rods of command") or pierced rods. Those are palaeolithic artefacts (12-23 thousand years old) made out of a 15-20 cm Y-shaped piece of a deer horn with 1 or more holes drilled. Originally though to be a purely ceremonial sign of an experienced warrior. Current hypotheses include: a tool to straighten arrows or spears (by passing them through the hole), a spear thrower (tested, proven to work), a symbol of fertility, a dress clasp, a calendar (most rods are decorated with patterns), and a leatherworker tool.

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* [[InvokedTrope Invoked]] and PlayedForLaughs in ''ComicBook/{{Asterix}} and the Chieftain's Shield''. [[DatedHistory At the time the volume was first published]], in 1967, the exact location of Vercingetorix's capital and his last stand against Caesar, Alesia, [[RealitySubtext was not known]]. In the comic, Asterix and Obelix travel through Arvernia, the general region where Alesia was in, and the local Arverni, still sore for the defeat, angrily (but obviously falsely) claim to not know where Alesia is and refuse to discuss it any further. A note from the authors then claims that [[HistoricalInJoke this is the reason why]] the location of Alesia was eventually forgotten.

* The page quote is from ''Manga/AttackOnTitan'' which takes place in a world where the last remnants of humanity are holed up in a walled off territory about the size of Texas, hiding in fear of the people-eating giants that have overrun the world. Information about the outside world is not only scarce -- it's ''forbidden'' by the government, and Eren mentions that the book Armin is reading from is illegal to own.

* ''Fanfic/FFSIBelieveInYou'': A large part of the difficulty the heroes face in brewing the magic potion is that its recipe was written shortly after the events of ''Oracle of Ages'', many thousands of years before ''Breath of the Wild'', and thus uses names that have long since fallen out of common use and refers to things that most people have become entirely unfamiliar with. Likewise, when Link is looking through old bestiaries in Gerudo Town, most of the creatures are enemies that were very common in earlier eras but which, having since died out or migrated away, he doesn't even recognize.

[[folder:Fan Fiction]]
* Due to the healing effects of The Zone in ''Fanfic/DeathNeedNotApply'', children who grew up there have little knowledge of things like death, disfigurement, or permanent injury. Izuku unthinkingly asks Shinso about the strange pattern on his skin, not knowing the "pattern" is numerous burn scars.

* As many historians and archaeologists can confirm, this trope is ''very much'' TruthInTelevision. There's a lot we don't know about everyday life and technologies of the past, and what little we can estimate is in large part due to experimental archaeology. This is because, through much of history, people thought that only "important stuff" should be written down, like scholarly works, famous literature, religious texts, and government documents. No one would spend a scribe's value time writing down something everyone and their mother could recite off of memory. It was only around the time of UsefulNotes/TheRenaissance that people realized the error in this, which is why the first article in the first encyclopedia was about ''bread'', of all things.

* As many historians and archaeologists can confirm, there's a lot we don't know about everyday life and technologies of the past. Usually we have something better, but obsolete crafts still interest scientists. This is what experimental archaeology is about.

** President [[UsefulNotes/FranklinDRoosevelt Franklin D.]] [[Music/BonJovi Bon Jovi]], who was involved in UsefulNotes/{{WWI}}.

Compare FutureImperfect, where the knowledge is still there but has been misinterpreted over the years. Compare to AliensNeverInventedTheWheel, which is where aliens don't have something common with humans. Not to be confused with CommonKnowledge.

** When [[BigBad Carnegie]] holds a gun on Solara outside the wreckage of the old couple's house, Eli reveals that he hid the Bible behind their TV. When Carnegie orders one of his young henchmen (born after the nuclear war) to check the TV, he replies with a blank look and a puzzled, "The what?" Carnegie rages, "You're ''[[PrecisionFStrike fuckin' SHITTIN' me]]''!" before telling [[TheDragon Redridge]] (who is old enough to know what a TV is) to check it.

* In the world of ''Film/MadMaxFuryRoad'' this is demonstrated when Nux, one of Immortal Joe's [[ProudWarriorRaceGuy War Boys]] whose entire short lives are dedicated to fighting and dying gloriously for their master, doesn't know what a tree is and refers to it as "that thing" until someone else provides the word. In context it's quite [[TearJerker sad]].

* Little is known about the Philistines outside of what the Bible says about them due to the fact that, for reasons unknown, they left no written record of their history and culture nor did any of their neighboring countries make a detailed account of their society.

* The Pythia, better known as the Oracle of Delphi, was the high priestess of the Temple of Apollo, the most authoritative oracle in Ancient Greece and unarguably the most powerful position a woman could achieve in the classical era. However, despite the Pythia being one of the most well documented religious institutions of the ancient world, the Oracle's actual duties, rituals and how they were selected for the position were never recorded since authors at the time felt little need to explain such universally known facts.

* Due to the healing effects of The Zone in ''[[https://archiveofourown.org/works/16796746/chapters/39424258 Death Need Not Apply]]'', children who grew up there have little knowledge of things like death, disfigurement, or permanent injury. Izuku unthinkingly asks Shinso about the strange pattern on his skin, not knowing the "pattern" is numerous burn scars.