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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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How do contact lenses work?

How do contact lenses work? 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 πŸ““ The short answer Contact lenses correct refractive errors, like nearsightedness, farsightedness, and astigmatism, by using precisely shaped lenses to bend incoming light so it lands on the retina instead of in front of or behind it. πŸ“š The long answer As someone with a mild aversion to putting...

a bird on a tree

Why do nuthatch birds walk upside down? This question came from a reader submission (thanks Nancy!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Nuthatches climb down trees headfirst to forage more efficiently. By approaching the bark from above, they can spot hidden food that upward-climbing birds may miss. πŸ“š The long answer Say hello to the nuthatch. πŸ™ƒπŸ‘‹ "Sitta-carolinensis-001" by Mdf is licensed under CC...

brown brain decor in selective-focus photography

Can the brain heal itself after a stroke? This question came from a reader submission (thanks Aunt Genie!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer After a stroke, the brain can reorganize its neural pathways to recover lost functions through neuroplasticity. The best way to promote healing is consistent practice of the affected functions, like deliberately using the weaker side of the body for everyday...

coconut water

Why do coconuts have water? This question came from a reader submission (thanks Akaal!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Coconuts carry water because they’re designed to launch a seed with an immediately usable food reserve. This liquid endosperm supports early growth, while the meat provides sustained fuel as the seedling develops. πŸ“š The long answer Coconuts are an unusual fruit (yes, they are a...

liquor pouring on clear shot glass

Why does alcohol make you feel warm? πŸ““ The short answer Alcohol feels warming because ethanol lowers the activation threshold of heat-sensitive receptors, fooling your nervous system into thinking you’re overheating. Your body then attempts to cool itself by dilating blood vessels and sending warm blood to the skin’s surface. πŸ“š The long answer Normally, a beverage needs to be warm to make you feel warm β€” but not alcohol. Whether it's a burning sensation from taking a shot or a more gentle...

left: person on cold day | right: person on hot day

What does "feels like" temperature mean? This question came from a reader submission (thanks Nikilah!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer β€œFeels like” temperature reflects how wind and humidity change how cold or hot the air feels to the human body. Wind chill increases heat loss in cold conditions, while the heat index reflects how humidity interferes with sweating in hot weather. πŸ“š The long answer...

round black vinyl disc on vinyl player

How do record players work? This question came from a reader submission (thanks Leah!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Record players work by dragging a needle through grooves in a spinning vinyl record, where tiny vibrations are converted into electrical signals, amplified, and turned back into sound by speakers. πŸ“š The long answer In high school, I decided to buy an old record player at a garage...

red hair person next to color blocks of red and orange

Why is orange hair called red? 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 πŸ““ The short answer Orange hair is called red because the word orange didn’t enter English until the fruit did, which was after the term redhead was already established. πŸ“š The long answer About 2% of the world's population has red hair, which means that ~40 people subscribed to this newsletter...

duck on pond

How does the Doppler effect work? 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 The Doppler effect is when waves like sound or light seem to change frequency because the source or observer is moving. As the source of a wave (e.g. an ambulance siren) moves closer, its waves compress and create a higher frequency; as it moves away, the waves stretch...

doctor and nurses inside operating room

How does general anesthesia work? This question came from a reader submission (thanks Ana!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer General anesthesia works by disrupting how brain cells communicate, leading to unconsciousness, immobility, and pain relief. While the exact mechanism is still unclear, anesthetics appear to either flood neurons with charged molecules or block them entirely, breaking down...