How does a thermos keep hot drinks hot and cold drinks cold?
Thermos Fortress
How does a thermos keep hot drinks hot and cold drinks cold?
Pour hot cocoa into a thermos in the morning, and at lunch it's still steaming. Pour iced lemonade in, and hours later it's still clinking with cold. One bottle, two opposite jobs. How does it pull off this little magic trick?
Here's the secret: a thermos doesn't actually make anything hot or cold. It just refuses to let heat move. Because heat is sneaky — it's always trying to travel, like a crowd shuffling out of a packed room. Heat slips from warm things into cooler things until everything matches. A thermos is built to block every exit.
