Galileo Thermometer 44cm.
This Galileo Thermometer contains 10 weighted balls. The temperature can be read by observing which bauble is floating in the middle of the column.
A Galileo thermometer (or Galilean thermometer) is a thermometer made of a sealed glass cylinder containing a clear liquid and several glass vessels of varying density.
The individual floats rise or fall in proportion to their respective density and the density of the surrounding liquid as the temperature changes,
It is named after Galileo Galilei because he discovered the principle on which this thermometer is based—that the density of a liquid changes in proportion to its temperature.
In the Galileo thermometer, the small glass bulbs are partly filled with different-coloured liquids. The composition of these liquids is not important for the functioning of the thermometer; they merely function as fixed weights and their colours are only for decoration. Once the bulbs have been sealed, their effective densities are adjusted by means of the metal tags hanging from beneath them. Any expansion due to the temperature change of the coloured liquid and air gap inside the bulbs does not affect the operation of the thermometer, as these materials are sealed inside a glass bulb of fixed size. The clear liquid in which the bulbs are submerged is not water, but some organic compound (such as ethanol) the density of which varies with temperature more than water does. Temperature changes affect the density of the outer clear liquid and this causes the bulbs to rise or sink.