Painted-on salt provides glowing thermometer for tiny things

Enlarge (credit: PHILIPPE HUGUEN/AFP/Getty Images)

Temperature is notoriously difficult to measure, mostly because it’s an average quantity. The temperature of a room is often recorded at a single point, when it’s meant to be a measure of the average energy of the air in the room—a room that will have spatial and temporal fluctuations around that average.

As anyone who has argued over the thermostat will know, measuring the average is difficult enough. But what if I want to measure the actual fluctuations and temperature differences in the room? Then I need a thermometer that provides a temperature image.

You might be thinking “get an IR camera, dummy.” But there is a much cooler option than an infrared camera. It’s a (nearly) normal camera coupled with a laser that measures temperature from the emission of visible light.