Not recently, but when I was in High School, we were taught that Shakespeare's plays weren't written down until later. They were cobbled together from people who could remember the lines and wrote them down later.

When I went to college I learned a) not even remotely true and b) High School is basically bullshit to keep you busy until you go to college.

I used to believe that common sense existed. You know, the usual stuff, like water is hot and fire is wet...

But then it occurred to me a few years ago, that what people believe to be 'common sense' are actually the things that nobody bothers to teach the next generation.

Meaning that common sense is only as common as one's elders teach you. So when the elders assume that you automatically know certain things, they won't bother teaching you.

Hence, common sense does not exist.

Mosquito hawks don't eat mosquitos or larvae or do anything against mosquitos.

It always seemed odd since they fly like they're drunk but I figured mosquitos aren't much stronger fliers so maybe they're just 'good enough' to catch mosquitos. Nope- it's just a dumb name for a crane fly. I always gave them room even when they bothered me because I figured they're doing good work eating the enemy, but now I know they're not allies I swat them like any other pest.

I always thought peanuts were nuts and grew on trees. Oh how utterly, devastatingly naive I've been...

I used to believe narwhals were a fake internet cryptid, but no, real ass aquatic mammal.

I was always told that the reason you used to see an Olive Garden next to every Red Lobster is because a husband/wife couple owned both chains and wanted the restaurants placed next to each other. Then a decade ago when they kinda stopped doing that it was because they divorced.

I can’t find a single piece of evidence that supports this claim online. The two restaurants were just owned by the same parent company and Red Lobster got sold off in 2014.

Oh there's a lot.

• When I was a kid, parents and teachers used to teach, if you have sore muscles a day after an extensive workout, you need to work out even more in order to reduce the soreness. In fact, however, you need to rest those muscles.
• I thought, pepperoni was pepper. (Like bell pepper, just smaller; similar to chilli). Then my girlfriend enlightened me after a confusing conversation, that pepperoni was a kind of salami. And then recently, at a company event before ordering pizza and after a very confusing discussion of what toppings we order, it turned out pepperoni was actually a kind of a salami, but not everyone agreed. So by now I've learned that pepperoni is neither of them. It doesn't exist. It's listed on pizza menus, and when you order it, you'll get something for sure, but you won't know in advance what it would be.
• This isn't new, the realization was several years ago, but fits this list nicely: I thought, perfume was something for women. It turned out, there was perfume for men too.
• Parents used to teach, if you read in the dark (on paper, not on a screen, I must add), you're ruining your eyes. But if you think about it: wtf does low light do to your eyes? By that logic, you're constantly ruining your eyes while sleeping.
• For some reason I used to think, you could simply delete related entities bound by foreign key constraints in postgres, if you ran the query in a transaction. Once when I finally needed to do this, I learned the hard way I was wrong.

There's a lot more than this, probably I'll update this comment in the future. Or not.

That vapes cause popcorn lung. Only specific vape juice that isn't sold anymore or hard cbd oil in a vape caused popcorn lung.

That isn't to say vaping is good for you. It just doesn't cause popcorn lung

I used to believe business could claim tax breaks for the money we contribute when they ask "Do you want to donate to XYZ cause?"

I learned today about how businesses can't actually claim point-of-sale charitable donations that show on a receipt for a tax write-off. Also, I learned about how no one can claim tax write-off for cash donations into a charity jar.

NaN == NaN

Not every Corner Bakery is, in fact, located at a corner

That I was the only idiot around. My, how wrong I was!

Allowing a Pokémon to evolve earlier results in a stronger 'mon at the end.

I thought that was to balance the faster level gain and learning of moves, but no. The only consideration to letting a Pokémon evolve is "will it learn the move I want". I was corrected yesterday.