History of the Thermometer

The first thermoscope was invented in the 2nd Century B.C. This was not a thermometer because it did not have a scale. Philo did experiments putting his thermoscope in the sun and in the shade to show how the gas inside would change with a change in temperature. In 1596, Galileo invented a different version of the thermoscope. Galileo used measurements, like number of fingers, to determine how high the water level inside the thermoscope changed. Shortly after Galileo, Italian scientists Santorio Santorio invented the first thermometer by adding a paper scale to the thermoscope. Now, the exact change in temperature could be measured. In 1654, the Grand Duke of Tuscany, Ferdinando II, invented the sealed liquid in glass thermometer. His thermometer had an alcohol filling, like the one in your classroom, but it was not accurate because there was no standardized scale. Gabriel Fahrenheit was the first person to create a thermometer using the element mercury. Fahrenheit also created a standardized scale, which he named after himself. On the Fahrenheit scale, 32 degrees is the freezing point of water, and 212 degrees is the boiling point. This scale is still used today in the United States. In 1742, a Swedish scientist named Andres Celsius devised a thermometer scale with the freezing point at 0 degrees and the boiling point at 100 degrees. This is the most widely used temperature scale across the world. Today, thermometers are used for many things such as medicine, engineering, and meteorology. Your WeatherSTEM unit has a thermometer that measures air temperature at your school. You can use this information to learn about weather.