Temperature

The bottom section of our Galileo thermometer. It’s a sealed glass tube containing little sealed glass bulbs partially filled with different coloured liquids, floating in a clear liquid.

The principle on which it works - which is that the density of water, and other liquids, changes with temperature - was established by Galileo Galilei. The thermometer itself was invented sometime in the mid 17th century - although its operation was extremely slow, so it didn’t particularly catch on. That changed in the 1990’s when the Natural History Museum in London started selling them. I guess most people bought them as curious and attractive decorative objects. We certainly did.

When I took this image the 18°c, 20°c and 22°c bulbs were sitting at the bottom, and the 24°c and 26°c bulbs were floating at the top. So I think room temperature was 23°c.

Thanks to Mary Eliza R for hosting the TT challenge