How do thermometers work?

A thermometer is a handy dandy little device that measures temperature. We use them for lots of things, from telling us when we have a fever to making sure our roast chicken is cooked to perfection. But how does a thermometer actually measure how hot or cold something is? We asked physics graduate student Nicolas Dronchi to help us find the answer.Got a question that’s heating up your brain? Send it to us at BrainsOn.org/contact, and we’ll work feverishly to find the answer.