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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.

leaves vs. snow on lawn
Featured Post

Why do leaves kill grass but snow does not?

Why do leaves kill grass but snow does not? This question came from a reader submission (thanks Omar!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Leaves can kill grass if they pile up thickly, blocking light and airflow, but a light layer can fertilize and support soil health. Snow usually doesn’t hurt grass and may help it survive winter by insulating it and adding moisture and nutrients, though problems...

sprouting potato

Why do potatoes sprout? This question and the bonus question came from reader submissions (thanks to Sherry and Sean, respectively). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Potatoes sprout from small stem nodes called eyes when they are kept in warm, humid, and light conditions, using stored starch to fuel asexual reproduction and grow new plants. πŸ“š The long answer If you leave a bag of potatoes sitting...

speed limit 25 sign

How are speed limits determined? This question came from a reader submission (thanks Arushi!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Speed limits are set using a combination of engineering calculations, real-world driving behavior, and crash data. The goal is to balance safety and mobility based on how roads are designed and how drivers actually use them. πŸ“š The long answer We've been trying to slow down...

a person holding a chip in their hand

Why does stress cause people to overeat? This question came from a reader submission (thanks M Meg!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Stress fuels overeating because it triggers the release of cortisol, a hormone that ramps up appetite and urges your body to stockpile energy for future threats, particularly with calorie-dense food. πŸ“š The long answer Overeating is a very common response to feeling...

a large crane with a flag hanging off of its side

Why do cranes have flags on them? This question came from a reader submission (thanks Natalie!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Cranes fly flags to indicate wind conditions, display patriotism or remembrance, and comply with airport safety rules. πŸ“š The long answer Whether you're considered an umarell or not, you may have noticed before that flags are often flown on construction cranes. Wikipedia...

Young woman sneezing with hand over mouth.

Why do we say "achoo" when we sneeze? 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 πŸ““ The short answer "Achoo" mimics the sound of the sneeze itself, shaped by how we breathe and move our mouth. But not everyone says "achoo" since different languages have their own versions, and making a sound at all is a cultural habit, not a biological need. πŸ“š The long answer We've all...

view of Earth and satellite

What happens to the temperature of the atmosphere the higher you go? This question came from a reader submission (thanks Omar!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer The higher you go in the atmosphere, the temperature either rises or falls depending on the layer. These changes are caused by how different parts of the atmosphere absorb energy from the Sun and how air pressure affects heat. πŸ“š The long...

a man holding a baby

Why do men have nipples if they can't breastfeed? This question came from a reader submission (thanks Pedro's daughter!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Men have nipples because all embryos start developing the same way, and nipples form before sex-specific genes activate. They likely remain simply because there’s no evolutionary pressure to remove a harmless trait. πŸ“š The long answer Great thinkers...

Denver Broncos

Do sports teams that train in high altitudes have a home advantage? This question came from a reader submission (thanks Jacqui!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer There is strong statistical evidence that high-altitude teams have a home advantage, largely because visiting players experience reduced oxygen intake and quicker fatigue at elevation. πŸ“š The long answer It's high time we level up our...

brown bread on brown wicker basket

How was bread invented? 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 Bread originated over 14,000 years ago with early humans baking ground wild grains on hot stones. Over time, developments in agriculture, fermentation, and oven construction led to increasingly specialized and widespread bread production across ancient civilizations. This week's...