Galileo Galilei invented the thermometer in the 1590s in Italy to measure temperature. Thermometers use alcohol or mercury in a glass tube, with the liquid expanding when heated and contracting when cooled to indicate the temperature. Different scales measure temperature, with Fahrenheit used mainly in the U.S., Celsius in most other countries, and Kelvin used by scientists. Thermometers allow temperature to be measured for bodies, air, appliances, pools, and other applications.

1. Thermometer By: Alec Sabatini, Connor Floyd, and Carey Sell