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!
#2

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.
Don't talk on speakerphone in public.
Don't FaceTime on speakerphone in public.
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133points
#3

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."
anamorphic_cat:
Dozens of poisonous plants and lethal gases illustrate your point.
allthecats:
And "chemicals" doesn't mean "bad."
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100points
#4

That tariffs are paid by the end user. They are initially paid by the importer but are passed along to the consumer.
98points
#5

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.
Also affect vs effect.
94points
#6

DON'T DRIVE FAST IN BAD WEATHER. I CAN'T BELIEVE PEOPLE NEED THIS EXPLAINED TO THEM.
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90points
#7
There's a stick on the steering column of your car that indicates in which direction you want to turn.
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87points
#8
That you do not have to talk. Sometimes it's possible for you to shut up.
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86points
#9

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.
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.
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82points
#10

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.
Giving_Cat:
Or Subway or bus or…
Marlsfarp:
Generalize to: people exiting the more confined space have the right of way.
81points
#11
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.
Be greatfull that you can stand. One day you may wish someone would be kinder to you than you have others in the past.
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78points
#12

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.
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.
76points
#13
It’s genuinely not a judgement, but I find it alarming how many adults I know have poor grammar or spelling capabilities.
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72points
#15

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.
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66points
#16

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.
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.
64points
#17

Tax brackets! No, Bob, taxes won’t wipe out the raise you just turned down. You’re just an idiot.
64points
#18
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.
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.
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64points
#19

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.
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.
63points
#20

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.
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61points




