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๐Ÿ’ก 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.

man shaving himself
Featured Post

What does shaving cream do?

What does shaving cream do? This question came from a reader submission (thanks Saurav ๐Ÿ’˜!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question ๐Ÿ““ 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. ๐Ÿ“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 ๐Ÿ““ 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 ๐Ÿ““ 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 brainstemโ€™s โ€œsneeze center.โ€ 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 ๐Ÿ““ The short answer โ€œHunky-doryโ€ likely stems from Frisian honcke (โ€œhomeโ€), later paired with a playful โ€œ-doryโ€ suffix, and it entered everyday speech with the rise of 19th-century blackface minstrel shows. ๐Ÿ“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 ๐Ÿ““ 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. ๐Ÿ“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 ๐Ÿ““ 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 ๐Ÿ““ 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? ๐Ÿ““ 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. ๐Ÿ“š The long answer Fine-dining chefs push themselves to the limits of culinary excellence โ€” in the hopes of impressing a tire company. I still can't believe this parody image of The Last Supper exists. It's not...

3d printing human body tissue

How will 3D printing organs work? 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 ๐Ÿ““ The short answer 3D printing organs uses bioinksโ€”materials made from living cells and gel-like substances that act as scaffolds, giving cells a structure to grow on. Simple tissues have already been printed, but printing complex organs like hearts or kidneys is still a work in progress due to...

woman scratching head

Why do we scratch our heads when we think? This question came from a reader submission (thanks Adish!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question ๐Ÿ““ The short answer We scratch our heads when we think because itโ€™s a form of self-soothing, a way to non-verbally show confusion, and possibly a suppressed primal impulse to attack the question-asker when frustrated. ๐Ÿ“š The long answer Search for a stock photo of someone thinking, and...