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ACS News Service Weekly PressPac: Wed Sep 05 16:42:03 EDT 2012

Galileo didn't invent thermometer that bears his name

Galilean Thermometer Not So Galilean
Journal of Chemical Education

The great Italian scientist Galileo may have been the first person to use a telescope to observe the heavens, helping spark the scientific revolution of the 16th century, but Galileo definitely did not invent the famous thermometer and captivating curiosity that bears his name. That’s the message of an article in ACS’ Journal of Chemical Education.

Peter Loyson explains that a number of companies sell so-called “Galilean thermometers,” sealed tubes of liquid in which glass spheres float and sink with changes in ambient temperature. Modern versions have morphed into elegant curiosity pieces with multi-colored spheres and gold-plated temperature tags. The instruments rely on a liquid, like water or alcohol, whose density increases as temperature falls. The glass spheres each are made to a precise density that matches that of the suspension liquid at a specific temperature. When a sphere floats midway up the tube, it represents the temperature of the room.

Although Galileo may have originated the idea in a 1638 book, the Accademia del Cimento, an early scientific society founded in Florence in 1657 by Galileo’s students, actually deserves the credit, Loyson says. The Accademia del Cimento — “the Academy of Experiment” — developed other instruments, as well. Loyson suggests “Florentine thermometer” as a more appropriate name for these colorful marvels.

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