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πŸ’‘ Today You Should Know

Learn something new every Friday. Join 2,000+ nerds and satisfy your curiosity one question at a time with topics including science, technology, history, and more.

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Featured Post

What makes you feel full when you're eating?

What makes you feel full when you're eating? This question came from a reader submission (thanks Rodrigo!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Feelings of fullness are triggered when your stomach physically stretches and hormones signal to your brain that you’ve eaten enough. The food's nutritional content, your body fat and gut bacteria, as well as the variety of food on your plate all affect how...

yellowed plastic

Why does plastic turn yellow? πŸ““ The short answer Plastics typically turn yellow due to photo-oxidation, a process where UV light and oxygen triggers a chain reaction that breaks down the material's chemical bonds. Over time, new molecular arrangements start to absorb more blue and violet light, making the plastic appear yellow. πŸ“š The long answer Once upon a time, your retro gaming device, lawn chair, or other favorite older plastic object was brilliantly white. Now? It's yellow and brittle....

brown bread with hotdog on top

Why are hot dogs called hot dogs? This question came from a reader submission (thanks Zuzu!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Two main theories explain how hot dogs got their name. The sausages were once called "dachshunds" due to their resemblance to the dog breed, making "hot dog" a natural evolution. Another theory links the name to 19th-century rumors that German sausages contained dog meat. πŸ“š...

woman in black long sleeve shirt using black laptop computer

Why does your voice sound different on a recording? This question came from a reader submission (thanks, Aastha!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer When you speak, you hear yourself through both air and bone conduction, which makes your voice sound deeper. A recording captures only air conduction, losing the lower tonesβ€”so your voice sounds higher and unfamiliar. πŸ“š The long answer One of the reasons...

flock of white and red rooster on green grass field during daytime

Why can't chickens fly? This question came from a reader submission (thanks, Sonja!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Chickens actually can fly, but their body structure and selective breeding limit them to short bursts rather than sustained flight. Certain farming practices also intentionally or unintentionally hamper their flying capabilities. πŸ“š The long answer Let me stop you right there:...

unknown person lying on brown bench indoors

Why does traveling make you tired? This question came from a reader submission (thanks Renee!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Traveling makes you tired because your body is constantly working behind the scenes. Stress keeps your brain on high alert, motion forces your muscles to stabilize, and prolonged sitting reduces circulation. On planes and long car rides, dehydration and lower oxygen levels...

purple butterflies

What causes the "butterflies in your stomach" feeling? This question came from a reader submission (thanks Saurav ❀️). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer The "butterflies in your stomach" feeling happens when your brain activates the fight-or-flight response, releasing adrenaline and redirecting blood away from your digestive system. This reduces oxygen flow to the stomach, causing a fluttery...

person with band aid on middle finger

Why do paper cuts hurt so much? This question came from a reader submission (thanks Rodrigo!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Paper cuts hurt so much because they cause jagged wounds, hit densely packed nerve endings in your fingertips, and are shallow enough to stay exposed without quick healing. πŸ“š The long answer While much of our daily lives has gone digital, we're still at risk of getting the...

brown and white border collie mix

How does the birthday paradox work? πŸ““ The short answer The birthday paradox shows that in a group of 23 people, there’s over a 50% chance of a shared birthday. Only 23 people seems counterintuitively low, but with 253 possible pairings, a match becomes far more likely than it seems at first glance. πŸ“š The long answer How many people must be in a group for there to be a greater than 50% chance that two share a birthday? The answer? Just 23 people. Fill the room with 75 people and the likelihood...

super glue

How does superglue work? πŸ““ The short answer Unlike water-based glues that bond through evaporation, superglue works because of a chemical reaction triggered by the tiny amounts of moisture in the air. Its cyanoacrylate molecules rapidly link together into a strong, plastic-like material that bonds surfaces almost instantly. πŸ“š The long answer Superglue? More like super-duper-glue. A one square-inch bond using superglue can hold more than a ton of weight. In fact, the Guinness World Record tops...