Galileo thermometer

Galileo thermometerGalileo thermometer is a special type of thermometer for measuring air temperature. The device got its name from Italian physicist Galileo Galilei. He discovered that liquid density depends on temperature. That means that higher temperature results in lower density.Thermometer design includes a glass cylinder filled with water. Glass spherical vessels filled with colour liquid float in this water. A golden or silver tag with embossed temperature value is attached to each of the vessels.The floating vessels are filled with liquid in such a way that they have different average density. The top vessel has the least density while the bottom one has the biggest density. However, all their values are close to water density and differ from it insignificantly.The operational principle of such thermometer is relatively simple. Changes in the room's air temperature result in changes of water temperature in the vessel. This also changes water density. It is known that bodies with density lower than that of surrounding liquid will float in it.Thus lower temperature in the room increases liquid density in the cylinder. So the balls go up one after another. The opposite process takes place when temperature is increased. The current temperature value is determined in accordance with the lower floating ball. Such effect is achieved through a very high manufacturing accuracy of thermometers. All balls are calibrated according to the floating temperature within the range from 0.4 °С to 4 °С. There may be from 4 to 11 vessels depending on the thermometer size. The device measures temperature within room value range, i.e. from 16 to 28 °С.Nowadays such thermometers are more often used as souvenirs.

[aliandersen]

The temperature is measured according to the gaps that form between the glass bulbs. You can see in the lower image how the temperature level forced two of the bulbs to group in the upper part of the cylinder, while four of the bulbs sank to the lower end. The measuring process basically involves reading the temperatures written on the calibrated weights of the bulbs forming the gap (in the case of the lower image, the bubbles filled with yellow and green fluids), adding them up and dividing the result by two.

The temperature obtained through this process is most likely the closest to the real value. If there are no gaps between the bulbs, then the temperature is read directly off the calibrated weights. When all the glass bulbs move to the lower part of the tube, the one on top will provide the closest value to the real temperature. The opposite is true when all the bulbs group in the upper part of the cylinder.

[dedalus]

Finally someone explain it simply! tks!

[lyu]

Good video, however, I found the sound for English language is not clear in most videos and the volume is small. You can do it better. ^_^