11 Inch Galileo Thermometer It's a must-have for the desk of any science enthusiast. email to friend
print this page

It's a must-have for the desk of any science enthusiast. The Galileo Thermometer is based on a thermoscope invented by Galileo Galilei in the early 1600s. The thermometer consists of a sealed glass tube that is filled with water and a number of floating spheres. The glass spheres are filled with a colored liquid and float up and down according to changes in the temperature. When the temperature rises the spheres will sink and inversely when the temperature falls the spheres will rise due to changes in the specific gravity of liquids. You always read the lowest of the floating temperature tags to determine the correct temperature.

What's included?

1 Galileo Thermometer measuring 11 inches

How does it work?

Galileo thermometers use a specific density principle, first understood by Galileo Galilei (1564 - 1642) the famous Italian inventor, scientist, philosopher, and astronomer. When the temperature rises the spheres will sink and inversely when the temperature falls the spheres will rise due to changes in the specific gravity of liquids. Remember to always read the lowest of the floating temperature tags to determine the correct temperature. Attached to each bubble is a little metal tag that indicates a temperature. A number and degree symbol are engraved in the tag. These metal tags are actually calibrated counterweights. The weight of each tag is slightly different from the others. Since the spheres are all hand-blown glass, no two are exactly the same size and shape. The spheres are calibrated by adding a certain amount of fluid to them so that they have the exact same density. So, after the weighted tags are attached to the bubbles, each differs very slightly in density (the ratio of mass to volume) from the other spheres, and the density of all of them is very close to the density of the surrounding water. As the temperature of the air outside the thermometer changes, so does the temperature of the water surrounding the bubbles. As the temperature of the water changes, it either expands or contracts, thereby changing its density. So, at any given density, some of the bubbles will float and others will sink. The bubble that sinks the most indicates the approximate current temperature.