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Galileo Thermometer
Item #:
750-GALILEO
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Galileo thermometer or Galilean thermometer is a thermometer made of a sealed glass cylinder containing a clear liquid. Suspended in the liquid are a number of weights. Commonly those weights are themselves sealed glass containers with colored liquid for an attractive effect.
As the liquid changes temperature it changes density and the suspended weights rise and fall to stay at the position where their density is equal to that of the surrounding liquid. If the weights differ by a very small amount and are ordered such that the least dense is at the top and most dense at the bottom, they can form a temperature scale.
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The temperature is typically read from an engraved metal disc on each weight. The lowest weight of the top set of weights indicates the ambient temperature. To achieve this requires manufacturing the weights to a tolerance of less than 1/1000 of a gram
The Galileo thermometer works due to the principle of buoyancy. Buoyancy determines whether objects float or sink in a liquid, and is responsible for the fact that even boats made of steel can float (of course, a solid bar of steel by itself will sink).
The only factor that determines whether an object will float or sink in a particular liquid relates the object's mass to the mass of the liquid displaced by the object when submerged. If the object's mass is greater than the mass of liquid displaced, the object will sink. If the object's mass is less than the mass of liquid displaced, the object will float..
In the Galileo thermometer, the small glass bulbs are partly filled with a different (colored) liquid. Each is filled with a slightly different amount, ranging from lightest at the uppermost bulb to heaviest at the lowermost bulb. The clear liquid in which the bulbs are submerged is not water, but some inert hydrocarbon (chosen because its density varies with temperature more than water does).
Large Galileo thermometer is 11" Tall. Steel Base is 4.5" wide.