A Galileo Thermometer is a sealed glass column containing multiple liquid filled orbs. As the temperature changes, these orbs rise and fall to indicate the current ambient temperature (within the range of the temperature tags). Under normal conditions, the orbs will settle into two groupings toward the top and bottom of the glass column. To read the Galileo Thermometer, observe the metal tags hanging from each orb. The tag on the lowest orb in the top grouping displays the current ambient temperature. If all the orbs float to the top, the temperature is below the lowest temperature tag. If all the orbs sink to the bottom, the temperature is higher than the highest temperature tag.
Inspired by the finding of Galileo Galilei, these high quality glass thermometers demonstrate how temperature effects density and buoyancy. Each glass orb is partially filled with liquid to achieve a precise weight. A metal counterweight for each temperature is hung from the bottom of the orbs. As the temperature changes, the density of the liquid inside each orb changes, causing it to rise or fall within the column. Each thermometer is individually calibrated to achieve an accuracy of 2°F.