Galileo Thermometer Tell the temperature the old-fashioned way with this wonderfully colourful Galileo Thermometer. This thermometer works by placing it on a flat surface and the lowest temperature ball within the group at the top of the cylinder tells the current temperature. Based on the discovery by Galileo Galilei each of the glass balls is filled with an exact amount of liquid so when the temperature rises the density of each liquid changes and the balls begin to rise. A perfect gift for any keen scientist this Christmas, it also makes a wonderful desk ornament for your home office! This product is not a toy; keep away from children.