If you’ve ever looked at a Galileo Thermometer, with all those colorful floating baubles and dangling numbered medallions, and thought, “I have absolutely no idea what that means,” you’re not alone. 34.7% of all people who own a Galileo Thermometer admit that they have no idea how to read it and they just thought it looked cool (Source: none, we just made that up).

The fact is, Galileo Thermometers are actually pretty easy to read. And you’ll definitely leave a lasting impression when your friend wonders how hot it is and, instead of just checking your phone (boring), you whip out a 15″ glass cylinder with floating spheres and read the temperature. They probably won’t forget that for a while.

How do I read this Galileo Thermometer thing?

Right, so, you’ve got your thermometer. This liquid filled cylinder with floating spheres. Each of the spheres has its own tag that represents a different temperature.

how to read a galileo thermometer

You wanna read the temperature, all you do is look at the lowest floating sphere in the upper part of the cylinder.

Yep, that’s it. It’s that easy.

But… why does it work? What’s happening?

Well, remember that as the temperature of water changes it changes density, either expanding or contracting. It decreases as temperature increases, so warm water weighs less than cool water.

Now, each of the spheres is calibrated to have a certain density. If it has a higher density than water at a certain temperature, say 70 degrees, it sinks. If it has a density that is lower than water at 70 degrees, it floats. And the sphere calibrated to represent 70 degrees, the same temperature as the water, will float in the middle or at the bottom of the highest floating baubles.


So, now that you know how to read a Galileo Thermometer, feel free to impress your friends and coworkers by reading them the temperature all the time. Like, constantly, whenever it changes. Even if they ask you to stop or tell you it’s getting kind of annoying, keep telling them. They’re probably just jealous that they can’t read Galileo Thermometers like you can.