The Galileo thermometer combines style and function for your home or office. It's sure to be a conversation piece as well as a beautiful accent. The thermometer works on the principle discovered by its namesake Galileo, that liquids change density as temperature changes. The colored glass spheres have been precisely weighted so that they respond to temperature changes by rising or falling in a liquid filled, hand blown glass cylinder. The lowest floating sphere in the top of the tube indicates the current air temperature.