A Blog by our Maths and Physics departments.
If you’ve passed through the upper floor of the QKB recently, you may have spotted something a little different – a striking new exhibit created by the Maths and Physics departments: our giant Galileo thermometer.
Although named after Galileo, the thermometer wasn’t actually invented by him. It was developed around the year 1600 by a group of academics, including at least one of his students. The device demonstrates a key scientific principle – how the density of a liquid changes with temperature.
Many purchasable versions are filled with ethanol, as its density changes significantly with temperature, making them easier to calibrate. For obvious safety reasons, ours does not use ethanol and instead contains about 85 litres of water. However, water’s density changes very little with temperature, which made the calibration process much more challenging. A difference of just 0.2 grams in the mass of one of our 2-litre floating balls would shift its floating point by 1°C.
Each ball has a different density (mass divided by volume) and as the water warms up and its density decreases (fewer molecules per cubic unit), balls whose fixed density becomes greater than that of the surrounding water begin to sink. The thermometer covers a range of approximately 18°C to 24°C.
The project has been a couple of years in the planning and making. What started as a simple-sounding idea became a more complex and demanding task with a few false starts along the way. Our original idea to use 3D printed balls looked promising but we couldn’t achieve the required precision in density. A second approach using large acrylic Christmas baubles proved more successful. After several iterations, we believe we’ve found a set of stable pigments to colour the balls – ones that should retain their vibrancy over time and withstand exposure to daylight.
We are very grateful to the Kimbolton Parents’ Association (KPSA) for funding this project. Their support has helped bring to life a unique and visually engaging display that illustrates fundamental scientific principles in a creative and memorable way.
