Galileo Thermometer

A **Galileo thermometer** is a device that measures temperature by using the density of liquids. It was invented by Galileo Galilei, who observed that the density of a liquid changes with temperature. The thermometer consists of a glass tube filled with a liquid, often ethanol. Inside the tube, there are several glass bulbs filled with other liquids. As the temperature changes, the density of the liquid inside the tube also changes. This causes the glass bulbs to either rise to the surface or sink to the bottom depending on the surrounding liquid's density. To read the temperature, we look at the lowest bulb that is floating. If no bulbs are floating or sinking, the temperature is somewhere between the lowest sunken bulb and the top bulb that has not yet sunk. A Galileo thermometer is not a precise instrument and is mainly used for decorative purposes today.