The Galileo Thermometer works on the principle of buoyancy and density, discovered by Galileo Galilei. Each glass bulb inside the cylinder is filled to a specific density and tagged with a temperature marker. As the surrounding liquid changes density with temperature fluctuations, the bulbs either sink or float. The bulb that hovers in the middle indicates the current temperature, while gaps between bulbs show a range. This simple yet ingenious design demonstrates how physical properties like density and buoyancy can be used for practical measurement.