Galileo's Thermometer

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Equipment: A Galileo's thermometer (a sealed liquid filled glass cylinder containing sealed glass floats labeled 18, 19, 20, 21, 22, 24 and 26 degrees C), a 4 liter beaker, ice water and paper towels.

What it does: The floats are adjusted in density so they sink at different temperatures. Each float carries a tag indicating the temperature at which it sinks. Temperature is indicated by the float with the lowest marked temperature which is floating.

Concepts Demonstrated: The temperature dependence of fluid density as a thermometric property.

Classroom assembly:

  1. Read the temperature of the room on the thermometer.
  2. Place the thermometer in a 4 liter beaker (height = approximately 24cm) of cold water.
  3. Read the temperature of the cold water.


Cautions: The thermometer is fragile. Handle with care.

Setup Time: Short.

Difficulty: Straightforward.

Visibility: The temperature tags are small. A video camera is required for this demonstration.

Related demonstrations:

References: PIRA 4A10.20
George Nickas, "A thermometer based on Archimedes' principle", AJP 57, 845-6, (1989)
Ronald Geballe, "Note on 'A thermometer based on Archimedes' principle' by George Nickas [Am J Phys 57, 845-846 (1989)]", AJP 59(1), 90, (1991)

Original Construction: Purchased. There seem to be several manufacturers of these things. A google search for "Galileo's thermometer" should turn up a retailer.

Disclaimer: All demonstrations are posted for the convenience and benefit of faculty and staff in the Department of Physics at Simon Fraser University and are not intended for outside use. The author(s) assume no responsibility or liability for the use of information contained on this site. Warnings and precautionary measures listed on this site assume normal operation of equipment and are not inclusive. Demonstrations may pose a significant hazard and can, in some instances, result in death; reasonable safety precautions must be taken. Demonstrations should be performed by qualified individuals only.

Prepared by Jeff Rudd, 1999
Revised by Laura Schmidt, 2007

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