How a modern day decoration is based off weather instruments from the 1600s


Last week, I received a birthday present from my older brother. Usually, we just give each other gift cards or something of that nature and call it a day. This time, it was a special gift - a Galileo Thermometer.

A lot of you responded to a Facebook post of mine, saying that you had one! I never realized how popular this item was until after it landed on my doorstep.

This piece of modern day decor is actually based off of a weather instrument from the early 1600s, called the thermoscope. This was typically designed to show a liquid rising or falling with the temperature.

The Galileo Thermometer takes this principle, but instead has weights that rise or fall in a glass cylinder full of water. So, how do these weights rise and fall? It has to do with the 'Ideal Gas Law.'

Mathematically, this can be written as P= ρRT; where P is pressure, ρ is density, R is a constant and T is temperature.

What we can take out of this is that temperature and density are inversely proportional to each other. As temperature rises, density falls and vice versa.

As the temperature changes, the density of the water in the cylinder does too. So, let's say you go from a room that is 68°F to one that is 76°F. The weights that represent 68°F and 72°F will fall to the bottom of the cylinder, because they're denser/heavier than the now less dense and warmer water. Meanwhile the lighter 76°F and 80°F weights will remain suspended in the liquid.

If you have one of these contraptions in your home, take a look at it. Maybe now that you understand the science behind them, you'll appreciate them a little more! I know I certainly do...