The Thermometer

A thermometer tells us the temperature. Some thermometers check the weather. Others check if you have a fever. Old ones used a liquid inside a thin glass tube. The liquid would go up when it was hot and down when it was cold. Today, many thermometers are digital.

Early Thermometers

Galileo Galilei made an early thermometer in 1593. It used air and water to show changes in heat. Later, in 1714, Daniel Fahrenheit made a better one using mercury. Another scientist named Anders Celsius made a different scale in 1742. Today we use both the Fahrenheit and Celsius scales.

An old drawing of an early tool for measuring temperature.
An old drawing of an early tool for measuring temperature. (Nysus / Wikimedia Commons)

Kinds of Thermometers

There are many types of thermometers. A medical thermometer checks body temperature. A weather thermometer measures the air outside. A meat thermometer tells you when food is cooked. Some thermometers use infrared light and do not even touch you. They work in just a second or two.

Fun Facts

  • Normal body temperature is about 98.6 degrees Fahrenheit.
  • Old thermometers used mercury, which is a dangerous liquid metal.
  • A thermometer made of wire can measure heat inside an oven.

Did You Know?

Water freezes at 32 degrees Fahrenheit and boils at 212 degrees Fahrenheit.