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💡 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

Why does the mouth heal so fast​?

Why does the mouth heal so fast? 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 📓 The short answer The mouth heals quickly because oral tissue is already primed for repair, has a calmer immune response that reduces scarring, and stays bathed in saliva full of wound-healing molecules. SPONSORED BY TINGGLY One Gift. A World of Experiences. Give experiences to your loved...

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Why do we feel secondhand embarrassment? 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 📓 The short answer Secondhand embarrassment happens because our brains are built for empathy: we can imagine another person’s awkwardness so vividly that we feel some of it ourselves. 📚 The long answer Secondhand embarrassment, or vicarious embarrassment, is the feeling of being...

a black and white dog laying on top of a couch

Why do dogs tilt their heads when you talk to them? This question came from a reader submission (thanks Kim!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer Dogs probably tilt their heads when we talk to them for a mix of reasons: to hear you better, to see you better, to signal that they're paying attention, and to receive praise. 📚 The long answer For at least 15,000 years, dogs have lived alongside humans....

person pouring a mug

How does a thermos work? This question came from a reader submission (thanks Duncan!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer A thermos keeps hot drinks hot and cold drinks cold by blocking all three types of heat transfer: conduction, convection, and radiation. It does this with a vacuum between its double walls (which eliminates conduction and convection) and a silvered inner surface (which reflects...

long-coated white puppy litter

Why do we feel the urge to squish cute things? 📓 The short answer Cute aggression is thought to be your brain's way of balancing out an emotional overload so you stay functional enough to actually care for the thing you're fawning over. 📚 The long answer Have you ever spotted a baby with those adorable chubby cheeks and felt the urge to…squish them? Well, you’re not alone. Source This phenomenon, known as “cute aggression,” is the paradoxical pairing of intense adoration with aggressive...

Old hands

Why do we feel colder as we age? This question came from a reader submission (thanks Gary!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer Aging causes your body to produce less heat, lose it more easily through thinner skin, and be slower to trigger warming responses, so we feel colder than we did when we were younger. 📚 The long answer Aging — if we're lucky — comes for us all. One day you're a reckless...

A badminton racket and a ball on a table

Why does a shuttlecock turn when you hit it? This question came from a reader submission (thanks anonymous!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer A shuttlecock turns when you hit it because most of the mass sits near the compact cork, while the wide skirt catches most of the aerodynamic resistance. That offset creates a torque that flips it cork-forward within about 20 milliseconds of impact. 📚 The long...

total lunar eclipse

Are humans affected by the Moon? This question came from a reader submission (thanks Soju!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer While science hasn't found convincing evidence linking the lunar cycle to mental health or menstruation, there is evidence that moonlight disrupts sleep around a full moon, possibly through an innate circalunar rhythm. 📚 The long answer The Moon: Earth's little sidekick, the...

person holding balloons

Longtime readers of Today You Should Know may recognize this question – it's a repeat! Life has been very full lately (in good ways, fortunately!), and I'm trying to be better at taking rest when I need it. So please enjoy this re-run of a newsletter all about ʰᶦᵍʰ⁻ᵖᶦᵗᶜʰᵉᵈ voices. All my best, 👋 Caitlin Why does helium make your voice higher? 📓 The short answer When you inhale helium, the gas's lower density speeds up sound waves, amplifying higher frequencies in your voice while dampening...

couple wearing silver-colored rings

Why is the "ring finger" the ring finger? This question came from a reader submission (thanks Rayvan!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer We typically wear rings on the “ring finger” because the ancient Egyptians believed a special vein ran from the fourth finger on the left hand straight to the heart. The Romans later gave this idea a romantic name: the “vein of love.” 📚 The long answer Humans (and...