Galileo's Thermometer
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Searching for a way to accurately measure temperature, Galileo discovered that he could place a number of precisely weighted balls of slightly varying densities in a cylinder filled with a special liquid. The balls would then go up or down one at a time according to the existing temperature. By this method Galileo was finally able to determine the correct temperature. |
The Science Involved
| A solid body with a fixed weight and size has a fixed density. In liquid, a solid body with a fixed density tends to go down as the temperature rises. On the other hand the solid body goes up in the liquid if the temperature falls. This occurs because the liquid containing the various balls expands very slightly at higher temperatures and contracts very slightly at lower temperatures. By precisely calibrating the density (weight) of the various glass balls, they can be made to rise or fall at precise temperature points. In a Galileo thermometer the lowest of the floating balls in the upper part of the cylinder indicates the right temperature. |