Their distinctive ornamental (but functional) thermometers utilise 17th-century astronomer Galileo Galilei's discovery that the density of liquids varies with temperature. Carefully weighted glass globes are suspended in a liquid-filled tube, where they sedately sink or float as the surrounding air gets hotter or colder. Temperature is indicated by the engraved brass tag on the lowest floating globe. 5-Globes Galileo thermometers are 34 cm tall. Temperature is shown in Celsius.