We grow up in different circumstances, and it’s impossible for everyone to develop the same worldview. Still, for society to function, we expect certain stuff to be universally understood — fundamental facts that people can agree on and rely on. But that isn’t always the case.
Reddit user JustBeingElara recently asked the platform what common knowledge they realized wasn’t so common.
Thousands replied, sharing etiquette rules, marketing tricks, basic biology, and much more, teaching each other all sorts of useful things. So we decided to collect the most interesting ones for those who love to learn!
#1
Wait for the people to get off the elevator before trying to enter.
Giving_Cat:
Or Subway or bus or…
Marlsfarp:
Generalize to: people exiting the more confined space have the right of way.
Image source: No_Lies_Detected, Liliana Drew/Pexels
#2
That “natural” doesn’t mean “healthy”.
anamorphic_cat:
Dozens of poisonous plants and lethal gases illustrate your point.
allthecats:
And “chemicals” doesn’t mean “bad.”
Image source: TaintM3, AS Photography/Pexels
#3
DON’T DRIVE FAST IN BAD WEATHER. I CAN’T BELIEVE PEOPLE NEED THIS EXPLAINED TO THEM.
Image source: Ohaibaipolar, Chris Peeters/Pexels
#4
That tariffs are paid by the end user. They are initially paid by the importer but are passed along to the consumer.
Image source: DoTheRightThing1953, Julius Silver/Pexels
#5
Ponies are not baby horses, just like how chihuahua and pugs are not baby dogs. Ponies are a type of horse that stay small even as adults.
Image source: Spoonula, David Jia/Pexels
#6
That being out in the cold does not give you a cold.
Tomschewies:
Soooo many people believe this. I think it confuses people that cold weather can cause a leaky nose but that doesn’t mean it’s a cold.
Image source: Brikish, Kristin Vogt/Pexels
#7
That cows have to be kept repeatedly pregnant to continue producing milk- too many people think that cows are just always making milk and it somehow “needs to be relieved” when their udders are full.
Image source: MetamorphicMermaid, Matthias Zomer/Pexels
#8
When I became a wheelchair user, I thought “wheelchairs don’t do stairs” was common knowledge. So imagine my shock when I started coming across people who thought 3-5 steps would still be considered “wheelchair accessible.”
This is why we need to be super specific when asking if a place is wheelchair accessible. We need to ask if there is step-free access. “Oh yeah, we are wheelchair accessible, there are just one or two steps” isn’t an acceptable answer.
Image source: buckyhermit, Marcus Aurelius/Pexels
#9
That the seasons are reversed in the northern and southern hemispheres.
As an Australian, this is a fact we all know from a very young age. When I first went overseas at age 16, I quickly learnt that many, many people (including full grown adults) in the northern hemisphere have no idea about this.
Image source: Lost_in_the_Library, Pixabay/Pexels
#10
When you’re in a touristy part of a city, overly friendly strangers that come up and talk to you unprovoked are not looking for new friends.
Image source: mechy84, George Pak/Pexels
#11
This may sound like common sense, but you’d be SHOCKED. Chickens will lay eggs nearly every day regardless of the presence of a rooster. It’s the equivalent of a period not a baby.
Image source: Immediate_Ad_7993
#12
Low(er) in calories does not mean it’s healthy or better for you.
Image source: drinking_varnish, Karola G/Pexels
#13
Tax brackets! No, Bob, taxes won’t wipe out the raise you just turned down. You’re just an idiot.
Image source: Damn_Dog_Inappropes, Nataliya Vaitkevich/Pexels
#14
The fact that deer do in fact drop their antlers, usually after mating season is over & then grow a new set every year 🤷🏻♀️.
Image source: Natural-Seaweed-5070, Hobi Photography/Pexels
#15
That the UK has not left the European continent, just the European Union. The amount of people who genuinely think we’re not part of Europe anymore shocks me.
Image source: 247mumbles, Anthony Beck/Pexels
#16
The President doesn’t have unlimited authority and cannot rule by decree.
I’ve met so many people on all sides of the political spectrum that don’t know civics.
They keep saying “why doesn’t the president just ban/enact X?”
They are all surprised when i point out the president doesn’t have such authority.
Image source: Sea_Advertising8304, Aaron Kittredge/Pexels
#17
As a kid, I once argued with someone about penguins. They didn’t know penguins are birds so we placed a bet, googled to confirm that they are in fact birds, and then I took the money to buy lunch in the canteen the next day. I told the canteen lady that I won my lunch money by placing a bet on penguins being birds. To my surprise she also denied them being birds. So I made another bet – if google says they are birds, I get my lunch for free.
At that time I’ve only discussed penguins being birds with two people. So what I thought was common knowledge appeared not to be.
Sometimes I wonder how many people out there doesn’t know that penguins are birds. And if I can meet them to place bets or get free food.
Image source: HeisenbergsIntern, Pixabay/Pexels
#18
Don’t watch videos on speakerphone when you’re in public.
Don’t talk on speakerphone in public.
Don’t FaceTime on speakerphone in public.
Image source: PeonyM, benzoix/Freepik
#19
Local bird species. I grew up in a family that loved birdwatching, whenever we saw a bird they would refer to it by its name. For example, we wouldn’t just say there were birds on the feeder, we would say that there were goldfinches and grosbeaks on the feeder, etc. I am no expert, but I thought that knowing some common species was as normal as knowing some common dog breeds. Hearing that someone doesn’t know what a junco looks like, for me feels like someone saying they don’t know what a husky looks like.
Image source: ooooooooono, Patrick Droog/Pexels
#20
Europe is a continent, not a country.
Image source: GHAAITE, Suzy Hazelwood/Pexels
#21
The little arrow by the gas icon on a dashboard indicates what side of the car the gas cap is on.
Image source: Crickson1, Erik Mclean/Pexels
#22
That plastic is created from oil.
Image source: Fast_Code_9212, Magda Ehlers/Pexels
#23
That in English, apostrophes are generally used for contractions (cannot=can’t) or to show possession (the bone belongs to the dog. The dog’s bone). It is NOT SUPPOSED TO BE USED FOR PLURALS. 1 dog, 2 dogs. 1 ex, 2 exes.
Image source: AMugOfPeppermintTea, Mary Taylor/Pexels
#24
Getting an IV does not mean a needle is left inside you while that IV is in place.
While I don’t expect everyone to know this, I continue to be surprised that people who actively have IVs in place do not know this.
hotdiggity75:
I didn’t know this and now I feel stupid.
LegCompetitive6636:
The needle has a plastic tube, a catheter, on it which is left inside the vein when the needle itself is removed
Edit: just to clarify more, the needle pierces the vein then the catheter is advanced further into the vein and the needle is removed, that long needle isn’t going all the way in your vein.
Image source: Hoppypoppy21, Anna Shvets/Pexels
#25
That not everything on the internet is real.
Image source: pookapotomus2
#26
Thunder is the sound of lightning. I’ve met people with Bachelors degrees in Science that didn’t know this!
Image source: monty_mcleod, Philippe Donn/Pexels
#27
Thin doesn’t mean healthy. You could be what the BMI chart considers to be a healthy weight, but that’s just weight. You still need to eat healthy and live a healthy lifestyle; weight isn’t the only indicator of health, but the number of thin/average weight people who eat [badly] but don’t understand why they feel bad is alarming.
Image source: MaryDoogan91, Engin Akyurt/Pexels
#28
That alcohol is a class one carcinogen. Just like asbestos and smoking cigarettes.
Image source: Astuary-Queen, Chris F/Pexels
#29
No, you cant use US $ to pay for things in an European country!
Image source: Affectionate_Staff46, Lukas/Pexels
#30
The size of the Great Lakes. The number of people who just don’t believe that you can’t see across most of Lake Michigan. Or that the lakes can produce any kind of waves at all, let alone of ship-sinking size. A friend was going to a wedding in the Upper Peninsula and told me they were also going to spend a day kayaking around Lake Superior. I said “Cool! What part?” And they looked at me like I was an idiot and said “All the way around? I’ve got a whole day.” I wish I were kidding.
Image source: Schoonicorn, Todd Trapani/Pexels
#31
That percentages are reciprocal. If someone is struggling to figure out 8% of 25, just tell them it’s the same as 25% of 8. It seems to blow people’s minds.
Image source: Hot_Sea_7676
#32
As an Aussie: the size of Aus and the distance/travel time between places in Aus. You can start in one state, drive for three days, and still be in the same state.
We’re basically the size of the US with nowhere near the population or inhabitable landscape.
Image source: Scritches98
#33
That green bell peppers are the unripe versions of yellow, orange, red and purple peppers
(ETA I didn’t say those colors were stages of ripeness. Orange bell plants will grow orange peppers. Red bell plants will grow red peppers. But they start green and you have to let them ripen).
Image source: BitterDeep78
#34
The lack of knowledge religious people have about their religion tends to surprise me.
Surullian:
American churches don’t tech the bible. The ministers make speeches about what they believe, then cherry pick parts of the bible to quote that seem to back them up.
What I remember most from the times I’ve had to go to church in life was how most of the sermons I heard were actually quoting the bible.
Image source: Max_Danage
#35
You are allowed to not have an opinion on a subject.
Image source: WerewolfBe84
#36
You don’t need religion to have morality.
Image source: redomisia
#37
An awful lot of people I talk to don’t realize their tax refund is their money anyway.
Image source: Stonegen70
#38
That ‘German Chocolate Cake’ has nothing to do with Germany.
It’s named after an American guy named Sam German, who invented the specific baking chocolate for it. I mentioned this at a party and people looked at me like I’d just told them the sky was green.
Image source: Used-Dealer7924
#39
Yellow dandelions transform into white puffs. They are not separate plants.
Image source: Vertigobee
#40
There’s a stick on the steering column of your car that indicates in which direction you want to turn.
Image source: yeehah
#41
Sharks are older than trees.
Image source: Classic-Green9530
#42
That disabilities don’t check for proof of age before affecting someone – you can be any age and disabled, and that not all disabilities are immediately externally visible.
Also affect vs effect.
Image source: arachnia42
#43
The US Interstate system is numbered so that even numbers run East- West, and odd numbers North-South.
I’ve met an incredible number of grown assed adults that had no idea about this.
Image source: curtman512
#44
That’s it’s not up for debate whether we landed on the moon. Now you might debate whether the first landing was faked. But we went 5 more times (manned landings). There is a lot of equipment left there that can be seen from earth. Even a mirror you can hit with a laser.
Image source: longhornmike2
#45
Grapes, onions, garlic, chocolate, corn cobs, xylitol are all harmful for dogs to consume. I hate seeing people giving their dog a protein of whatever they cooked for dinner knowing that there’s onion in it. Yeah, a lot of dogs won’t get seriously sick, but I will hurt their stomach. And some do get very sick. Don’t give your pets human food.
Image source: _-Cuttlefish-_
#46
That human bodily fluids contain germs and other disgusting gunk, which can in turn linger on public surfaces.
This after a co-worker touched an elevator button and proceeded to immediately dig the insides of his nose. I told him, you never know where the hands of the previous person could’ve been – up scratching his armpits, picking up some slimy [stuff], etc – before touching that same button.
And it’s just ewwww that he would touch the same surfaces before putting it inside his nose.
His response – “*That can’t be. If we can’t see those germs then there’s probably nothing there*.”
Even before Covid, I’ve always avoided touching elevator buttons, door handles, etc with my fingers and used my elbows instead. If I had no choice, I would at least remember to avoid putting it in my mouth, nose or eyes before washing my hands.
Image source: Lightning_Reverie
#47
It’s genuinely not a judgement, but I find it alarming how many adults I know have poor grammar or spelling capabilities.
Image source: Aquarius1992
#48
On Highway signs announcing upcoming exits, the smaller sign with the exit number on it which is above the larger sign will be aligned to the edge of the sign corresponding to which side of the road that exit will be on.
Image source: Anishinaapunk
#49
As a former paramedic and child of law enforcement and firefighters … FOR THE LOVE OF GOD PEOPLE FORGET WHAT TO DO WITH EMERGENCY VEHICLES COMING TOWARDS/AROUND THEM!!
STOP. Dont stop in the middle of an intersection, dont jerk your vehicle to try and get outta the way subsequently causing another accident, dont try to beat the EMS vehicle, dont follow the vehicle, just pull over safely (or, if all you can do is stop where you are, STOP). Seriously, the amount of accidents that happen with EMS vehicles to and from calls because of people who just panic or are so wrapped up in their phones, vlogs, conversations etc that they dont see big wee-woo’s is insane.
Image source: Spooky_Kitty8731
#50
My parents were public defenders. I thought everybody knew you weren’t supposed to talk to the police, and that they police are allowed to lie.
Image source: Icy-Builder5892
#51
How to properly train and own a dog. The amount of people who know nothing about dogs is baffling to me. The belief of alpha hierarchy has been proven false in both dogs and wolves for over 20 years by researchers. Yet, people still use it and recommend it as a form of training. It’s proven harmful. This leads to fearful and aggressive dogs.
There is a TON of ignorant dog owners. Not only do they spread false information, they don’t even bother fact checking themselves.
The reason why dogs end up in shelters is because of BOTH irresponsible breeding and irresponsible/uneducated owners.
Image source: Astro_The_SpaceDog
#52
How to use computers in general, it’s funny cause there are at least 2 generations alive right now who don’t truly know how to work one and both are completely different in terms of age.
Image source: LoraBerryy
#53
All calico cats are female or sterile males. To get both orange and black, a cat needs to have two X chromosomes. Any male calico cat has an extra X chromosome (XXY) and is therefore sterile.
Image source: IDCouch
#54
I was an anatomy teacher and I had a student that didn’t know the meat we eat is muscle from animals until I was using a steak to demonstrate connective and muscle tissues.
Image source: ElbowsMcDeep
#55
People don’t know that you should not swaddle a child with a fever ! TAKE THEM CLOTHES OFF ! you’re trapping in body heat and making the fever elevate.
Image source: InvestigatorThis4581
#56
Pickles are pickled cucumbers.
i was amazed by the amount of people who argued with me when i told them.
Image source: PleaseGiveMeSnacc
#57
I don’t know about most, but a lot of people near me:
That the ACA (Affordable Care Act) and “Obamacare” are the same piece of legislation.
Image source: No-Beautiful8039
#58
I’m always surprised that the random medical knowledge in my head is not actually common knowledge.
Image source: ChoiceRevolution9308
#59
You COULDN’T care less.
This is something I *could* care less about and really should.
CoolhandLW:
Dang that’s a huge pet peeve of mine. I don’t know why it bothers me so much.
Image source: _Monsterguy_
#60
Laying on your left side for digestion.
Lol the middle school nurse told me that and I walked around in life thinking everyone knew that because of their school nurses until someone else was like omg! I just found out this fact and told me. I was like duh and they said how would you know that and I said that the nurse tells you and they looked at me like that was just you haha.
Image source: gold_dust_woman13
#61
Growing up I thought every household had constant yelling, walking on eggshells, and random silent treatments. Took me way too long to realize a lot of people actually grew up in calm, supportive homes and that mine wasn’t “normal conflict,” it was just unhealthy.
Image source: Mother-Ad-6360
#62
That caffeine stays in your body for 10 hours. A lot of people I know complain about not being able to sleep and I see them having coffee, tea or caffeinated soda at 4pm… I’m like, that’s why….
Image source: oh_jeez_smh
#63
How to read.
Nowadays 20% of kids are functionally illiterate after school according to PISA results (added: in Finland).
Image source: KofFinland
#64
Common knowledge isn’t that common.
Image source: Slow-Power2713
#65
How to spell ‘definitely’. There are a finite number of ways to spell de-FINITE-ly.
Image source: AngryWizard
#66
How sound works. Now, I’m a highly trained audio engineer, so I’m biased, but I’m not talking the fancy tone pitch and frequent stuff. Just the simple fact that sound is often directional and gets soft rapidly.
My church’s sanctuary had 4 speakers installed when I started attending. They were sideways, under a soffit, and pointed up to the vaulted ceiling. And they sounded [bad]. I got then rotated upright and pointed at the seating area, and it was night and day.
Image source: OliverCaneStaff
#67
“Earthquake weather” is nonsense. Earthquakes originate many miles underground and most weather won’t affect ground soil more than a foot or two deep, if that.
Image source: gladeye
#68
Apart and a part are opposites.
Image source: Jonathon_G
#69
I (a Canadian) had to tell a grown woman (an American) that no I am not jet lagged from my flight because Vancouver and LA are in the same time zone. And then yes the entirety of Canada shares time zones with America.
Image source: sydann6
#70
Try listing these in order of (average) size from smallest to largest or I guess in order of orbit. I’ll put them in a random order, you reorder them.
* Galaxies
* Moons
* Stars
* Solar Systems
* Planets
I was surprised how few people can do this.
Image source: handtoglandwombat
#71
How seasons work and that they *are not* caused by daylight saving time.
How banks work. Too many people think a regular checking/savings account means they keep cash in a vault specifically for you.
Image source: Hefty_Pangolin3273
#72
Pools of still water are the perfect breeding environment for mosquitos. Pour out your garden buckets and containers after it rains.
Image source: Realistic_Food_7823
#73
Surprised at how little knowledge of civics most people have……..
* That the First Amendment applies only to the government and not individuals and businesses.
* That a presidential executive order applies only to the Executive branch of the federal government and is not a law.
* That a presidential pardon can apply only to someone convicted on federal charges and does not apply to someone convicted on state or local charges.
* That a person born in a foreign country to a parent with US citizenship is automatically a US citizen.
Image source: tunghoy
#74
That the Moon doesn’t actually Glow In The Dark! 🤔.
Image source: Ryan_Petrovich8769
#75
Simple financial self disipline. I don’t understand why so many people spend money they don’t have to buy things they don’t need to impress people who don’t care.
Image source: moccasinsfan
#76
That you give your seat up on the bus/subway etc for the elderly, humans with small children, humans with crutches/walkers/canes and humans with a lot of heavy looking bags (to name a few).
Be greatfull that you can stand. One day you may wish someone would be kinder to you than you have others in the past.
Image source: Macabracadabra
#77
The only things you should flush down the toilet is TP and human waste. It doesn’t matter if the wipes or the cat litter says it’s flushable. It’s not!
Image source: caitlowcat
#78
The number of people who don’t know that water boils faster if you put a lid on the pot is genuinely concerning.
Image source: okpatient123
#79
The basics of the solar system and how things like eclipses work. It’s not genius level stuff, but I’ve heard incredibly ignorant explanations of solar system phenomena from many adults.
Image source: gladeye
#80
We are losing our effective antibiotics at a shocking rate that far outpaces the rate at which we discover new antibiotics. We will return to the days of people dying of simple infections within most living people’s lifetimes. If you are younger than 45 today and live until you’re 70, this will likely be what [ends] you.
Image source: ArmpitPutty
#81
“Tucking in” the string when you put in a tampon. My mom advised me to do that the very first time I wore one, so that 1) it would be possible to go to the bathroom without having to take the tampon out, and 2) there’s no risk of the string sticking out in a bathing suit.
Fast-forward to now, when I’ve heard way too many times to count from other women how they hate having to take the tampon out every time they [go to the bathroom], or how it’s a miracle that the string is staying in their bathing suit, etc etc. Come to find out, mainly from reading internet discussions, that almost NOBODY knows about tucking in the string?!?
Image source: refrigehimratehim
#82
I still see folks on reddit talking about the “alpha dog” theory.
there’s no such thing as an “alpha” dog, even in wolf packs the hierarchy goes to the breeding pair of a family unit. the breeding pair keeps the pack cohesive.
in domesticated dogs, the social hierarchy is fluid based on immediate needs and opportunity, and is constantly being reevaluated and adjusted to. what people assume is “alpha dominance” in a group of dogs is just a dog atm displaying more confidence in its surroundings and prioritizing its needs, be it resources or instincts. humans are the “pack leader” because they are the ones in control or in possession of the dog’s priorities. this is how we domesticated them to begin with…and are able to teach them silly tricks.
Image source: ms_directed
#83
That the left lane is for passing.
Image source: ToneThugsNHarmony
#84
The rules of Monopoly. The game goes on so long because no one plays by the rules. If a person lands on a property and decides not to buy it than the banker must hold an auction for that property right away and all players can bid on it including the person who declined the purchase in the first place.
Image source: Tasty-Run8895
#85
Gravity at the International Space Station is about 90% of the earth’s gravity. People think that the astronauts appear floating because of lack of gravity.
It’s actually because they are in a continuous free fall as they orbit the earth. Kind of like you would look if you were inside an elevator that was free falling towards the ground floor.
Image source: weasel_face
#86
That the best way to store cake is to put it on the lid of a container and put the container over it, rather than put the cake in the container.
Image source: PaperHatPrincess
#87
I once jokingly said “it’s like herding cats”
People looked confused, “why would you hurt a cat?”
“No, *herding* cats.”
“Wouldn’t that be really hard?”
I said it cause we were talking about something difficult.
Image source: Fianna9
#88
Lots of people have no idea who Amerigo Vespucci was, even though he’s widely known in my country. If you’re wondering, he’s the one who realized that Christopher Columbus had actually reached a new continent rather than India. That’s where the name “America” comes from.
Image source: Rexam14
#89
That you have to take the corn husk off of a tamale before eating it. My wife made tamales for her coworkers and many of them didnt know to do that.
Image source: FalconDCW
#90
Organic farming adopted 100% on a global scale would lead to major price shocks, crop failure and famine. Organic production also blows conventional production away when it comes to CO2 emissions, producing more carbon per pound of food produced . And last, the rules for organic certification are often arbitrary and meaningless, meant only to virtue signal to end consumers.
Image source: ApostateFarmer
#91
The separation of powers in the United States.
The Legislature creates or changes laws, and the branch that controls funding.
The Executive or President is final approval of law and who then enforces the laws, and also the branch that runs the Government.
The Judicial Branch with our Legal system is the ones who determine if a law should stay or should be removed from the books. They also able to overrule the Executive if they feel a law is not being enforced.
They all have roles, ALL of them, not just the President. That is why he is not and cannot be an absolute ruler or King. 🙈🤷♂️
… and this IS as good thing, regardless of who the president might be.
Image source: BranSh81
#92
“Lead” pencils do not contain lead, they contain graphite.
Image source: Dizzy-muse2258
#93
That Alaska is not an island and it is not smaller than Texas.
If you laid Alaska over the lower 48 you wouldn’t have a lot of land left over.
Image source: Pettsareme
#94
That modern physics is real. I’ve spent my entire adult life reading books about physics. Some things that I just take for granted, I find a lot of people have trouble wrapping their minds around. Things like time being relative or the concept of superposition are just intuitive for me. We’ve proven time is relative. We’ve measured it. It’s not a fringe idea. Superposition is fundamental to quantum computing.
Image source: Agitated_Quail_1430
#95
That you do not have to talk. Sometimes it’s possible for you to shut up.
Image source: HVAC_instructor
#96
That front-loader washing machines are best left with the door open when not in use.
Image source: stnapstnap
#97
Two children can have the same parents and have two different attachment styles and relationships with this person.
Image source: jupiteegonewild
#98
There is an arrow in the middle of the E and the x in FedEx logo.
Image source: Interesting_Gift4953
#99
People treat you better when you invest in your appearance and take care of yourself.
Image source: jupiteegonewild
#100
A light year is a measure of distance, not time.
Image source: DetectiveBulky7850
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