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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.

fly rubbing hands together
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Why do flies rub their legs together?

Why do flies rub their legs together? πŸ““ The short answer Flies rub their legs together to clean off dust, dirt, moisture, and pollen that can interfere with their senses. Staying clean helps them fly, avoid infections, an taste with their feet. πŸ“š The long answer You've probably spotted a fly rubbing its little legs together and wondered what that's all about. The options run through your head (memes linked for illustrative effect): (A) Plotting world domination (B) Gearing up for a delicious...

U.S. Capitol

Longtime readers of Today You Should Know may recognize this question – it's a repeat! I just returned from a fantastic trip seeing lovely people and climbing beautiful mountains. Not one word was written as I focused on being present. Hope you enjoy (re)learning about why the U.S. eats quarter pounders and not ... 113 grammers πŸ”. Back next week with a new curious question. πŸ‘‹ Caitlin Why doesn't the U.S. use the metric system? πŸ““ The short answer Pirates are a big reason why the United States...

man shaving himself

What does shaving cream do? This question came from a reader submission (thanks Saurav πŸ’˜!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer Shaving cream is a specially designed soap that forms a dense, long-lasting foam. It lifts hairs for a smoother, closer shave, hydrates and protects your skin, and cleans away oils and debris as you go. πŸ“š The long answer Humans have been shaving for thousands of years, but the...

person putting hand outside of window

What causes the weird throbbing sound when you drive with only one window down? This question came from a reader submission (thanks Roger!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer When wind blows over just one open window, it pushes air into and out of the cabin in a rhythmic pattern, which produces a super low frequency sound. It's the same principle that produces a sound when you blow across the top of a...

white tissue paper in blue box

What happens in your body when you sneeze? This question came from a reader submission (thanks Meg!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer A sneeze begins when irritants in your nose trigger immune cells to release histamine, which stimulates nerve endings that send a signal to the brainstem’s β€œsneeze center.” In response, you take a deep breath, tense your chest and abdominal muscles with your vocal...

map of Frisian languages

Where does "hunky-dory" come from? This question came from a reader submission (thanks Miguel!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer β€œHunky-dory” likely stems from Frisian honcke (β€œhome”), later paired with a playful β€œ-dory” suffix, and it entered everyday speech with the rise of 19th-century blackface minstrel shows. πŸ“š The long answer If you're not familiar with the Americanism, to say something is...

a broken glass window with a field in the background

Why does glass break so easily? 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 Glass breaks easily because its atoms form a rigid, disordered network rather than an ordered crystal lattice. When under stress, there's no way for planes of atoms to slip past each other, so its molecular bonds break easily and form cracks. πŸ“š The long answer Glass is...

person in green shirt washing stainless steel sink

Do you need to wash dishes with hot water? 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 Cold water with soap and scrubbing removes most grease and germs, but hot water makes cleaning easier by better dissolving oils. You would need to use water hotter than your hands can comfortably tolerate to kill germs, which is one reason why dishwashers are so...

Lego house

Can we build full-size buildings using LEGO-like bricks? This question came from a reader submission (thanks Stephen's daughter!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question πŸ““ The short answer While actual LEGO bricks are too precise, weak, and expensive for real buildings, several modern construction methods use interlocking, LEGO-like blocks made from earth, foam, or composites to build strong, efficient structures faster and...

a plaque on a wall that says michelin

Why does a tire company rate restaurants? πŸ““ The short answer The Michelin tire company started rating restaurants to encourage more people to drive (and buy car tires). Today, the Michelin Guide lives on as a powerful branding tool that keeps Michelin top of mind for premium customers. πŸ“š The long answer Fine-dining chefs push themselves to the limits of culinary excellence β€” in the hopes of impressing a tire company. I still can't believe this parody image of The Last Supper exists. It's not...