Facts That Should Be Common Knowledge But Aren't

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01-06-2025

There are plenty of common knowledge facts we don't realize we don't know until someone points them out. For instance, ask most people which planet is closest to Earth, and they'll probably say Mars. But in reality, it's actually Venus on average, followed by Mercury!
Recently, Reddit user Shag_Dawg was curious about those type of facts when they asked: "What's your biggest 'how do people NOT know this?' fact?"
The thread got thousands of responses, from misconceptions because of myths to misunderstandings of common science concepts. Below are some of the the top and most often repeated comments:
"The Underground Railroad was not a literal subterranean locomotive."
—George_W_Bushdiver
"Green peppers are just immature red peppers that were harvested before they were ripe."
—FigBug
"Percentages are reversible. Like, 8% of 25 is the same as 25% of 8, and one of them is much easier to do in your head."
—MirSydney
"Copy and pasting: Ctrl+C and Ctrl+V. The number of people who go through life working in a corporate office and have no idea about this is astounding. Truly worrying."
—toby_gray
"Jalapenos and chipotles are the same peppers, chipotles are just smoked."
—UnsorryCanadian
"Butterflies have four wings, not two."
—heralies
"The Better Business Bureau is not a government agency. They don't hold any legal power."
—LizardPossum
"There are 4 quarts in a gallon because they are quarter gallons."
—Vivid_Obscurity
"All Visa credit cards start with a 4. All Mastercard credit cards start with a 5. All Amex credit cards start with a 3. And Discover starts with 6."
—No-Chapter1389
"Cows have to get pregnant to make milk — they don't just make milk."
—flavouredicecubes
"Don't center your plates or bowls in the microwave. It heats better off-center. There's like a dead spot in the middle. That's why the bowls get hot but the food stays cold."
—shroomie19
"Flammable and inflammable mean the same thing."
—white_hart_2
"Plants can emit 'screams' at certain frequencies when in danger."
—Vivid-restaurant99
"I'm sad to say that I know people who only use Excel for its razor-sharp rows and columns, with no idea that Excel can calculate the numbers that go into their razor-sharp rows and columns."
—hymie0
"That the ancestors of whales lived on land and had legs. It's shocking how many people don't know that."
—GraphicDesignMonkey
"That you can't actually see the Great Wall of China from space with the naked eye. Still blows my mind how many people believe this."
—Kaerevek
"When you're using a spray product to disinfect or clean a surface, you have to let it sit for a few minutes. It will tell you how long you have to wait for the bottle. If you just spray something and immediately wipe it up, it's not getting the job done right."
—HamHockShortDock
"Peanuts are not nuts, they are legumes. So approximately 20% of people with a peanut allergy are also allergic to lentils, etc."
—Kamic1980
"Blood is not blue in your veins. It is always red. A darker red, but still red. Your veins look blue because of the way your skin and tissue interact with light."
—The_Queen_Zsofia
"The moon is out during the day just as much as it is out at night."
—ryan1987mn
"An undercover cop doesn't have to tell you they're a cop. Cops can lie to you, but you can't lie to cops. Even if you're innocent, don't talk to the police without a lawyer present."
—sc0n3z
"Not everyone has an internal monologue. For some people, thoughts are purely conceptual. They do not have a narrative voice in their head."
—NotoriusPCP
And lastly, "The yolk is not the part of the egg that turns into a chicken."
—quartzgirl71
You can read the original thread on Reddit.