Welcome to Christine’s Corner! A place where I, Christine, break down scientific concepts, do fun experiments, or just talk about the latest weather. My corner, my rules. Let’s dive in!

In the video above, I describe what a Galileo Thermometer is and how it works. Here’s a quick recap:

The Galileo Thermometer is a fun way to measure the ambient, or current air temperature of the environment. Some people grew up with it in their home, and perhaps didn’t know exactly what it did. Maybe you’ve seen them in stores, or around other people’s homes. Truth be told, I never had one of these growing up as a kid, but it sure is a fun and colorful looking instrument. So, what is it and how does it work?

This instrument is based on one of the earliest ways scientists were able to measure temperature changes, and it all started with the invention of the thermoscope by Galileo Galilei back in the 17th century. The Galileo Thermometer operates under the same concept as the thermoscope using buoyancy, and is very similar to how the atmosphere works too. A parcel of air heats up and rises as it becomes less dense than the air surrounding it. If this parcel of air becomes cooler than the surrounding air, it sinks because it’s more dense. This thermometer works the same way, except we’re dealing with the density of liquids instead of air.

The components of this unique thermometer include the clear, cylinder case, the clear liquid inside, the small vessels usually containing alcohol and food coloring, and the temperature tags attached to the vessels. Alcohol is typically used inside the vessels since it’s slightly less dense than water.

How it works:

The clear liquid inside the Galileo Thermometer will slowly match the temperature of the air. Once the liquid adjusts to the current air temperature, the various colorful vessels will either float to the top if they’re less dense than the liquid inside, or sink to the bottom if they’re more dense. Each vessel contains a weighted temperature tag that essentially matches the temperature of the outside environment. It’s not the most precise instrument, but it usually gives a good idea!

Here’s how to read the temperature reading the Galileo Thermometer gives:

Check out this video showing one of the vessels sinking as the temperature changes when I brought it from one room to another. *Video is sped up for effect.*

~Meteorologist Christine Gregory