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What is a Galileo thermometer?
A Galileo thermometer is a sealed glass cylinder of clear liquid holding several glass bubbles, each weighted to a slightly different density and tagged with a temperature. As the room warms, the liquid expands and becomes less dense, so the heavier bubbles sink; as it cools, they rise. The lowest floating bubble shows the current temperature. Named after Galileo, who discovered the principle, it was built by his students in Florence in the 1600s.
11 modelsFrom £36.9920 to 50 cm, 4 to 10 bubblesReads in 2 degree stepsFree UK delivery over £45
Who is this collection for?
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For a living room or a study
A Galileo thermometer reads the temperature with coloured floating glass bubbles. The most beautiful instrument on the shelf.
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For a retirement, a birthday or a housewarming
Parents, colleagues and friends looking for a classic gift with a scientific story.
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For anyone who likes to see physics happen
Density, buoyancy and temperature in a glass column, exactly as Galileo's students built it.
How to choose a Galileo thermometer
Height decides both the look and the precision: taller thermometers hold more bubbles, so they read in finer steps. Colour of the bubbles and the frame are the rest.
| Type | Best for | Height and bubbles | Price |
|---|---|---|---|
| Small desktop Galileo | Desks, bedside, first one | 20 to 28 cm, 4 to 5 bubbles | £37 to £50 |
| Classic 30 to 40 cm models | Living rooms, mantelpieces | 30 to 40 cm, 5 to 7 bubbles | £50 to £80 |
| Black, wooden or framed models | Studies, offices, gifts | 30 to 45 cm | £60 to £100 |
| Large Galileo thermometers | Statement pieces, hallways | 45 cm and over, 8 to 10 bubbles | £100 to £147 |
Read the tag on the lowest floating bubble. Keep it indoors and out of direct sun, which warms the liquid unevenly. It responds slowly, over ten minutes or so, which is part of its charm.
The science in two lines
The liquid's density changes with temperature; each bubble's density does not. A bubble floats when the liquid is denser than it and sinks when the liquid is lighter, so the set of bubbles sorts itself by temperature. The tags are simply the temperature at which each bubble has neutral buoyancy.
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Galileo Thermometer: your questions, answered
How do I read a Galileo thermometer?
Read the tag on the lowest floating bubble. If bubbles are split between top and bottom, the temperature is between the lowest floating and the highest sunk.
How accurate is it?
Within about 1 to 2 degrees, in steps of 2 degrees on most models. It responds slowly, over ten minutes or so, which is part of its charm.
Why do the bubbles float or sink?
The liquid changes density with temperature. Each bubble is weighted to float at a specific density, so the lowest floater marks the current temperature.
Can it go outside?
No. Keep it indoors, out of direct sunlight, which warms the liquid unevenly.
What size should I choose?
From 20 cm desktop models to 45 cm statement pieces. Height and the number of bubbles are on each product page.
Free UK delivery over £45 and 30 days to return it. For a forecast rather than a reading, the storm glasses sit well beside it.