An essay for Mr. Brian Rohrig’s honors integrated science class.
The Galileo Thermometer is a tall glass cylinder filled with a clear liquid presumed to be water. Inside the thermometer are many small glass bulbs with tags with different temperatures on them. The bulb at the top has a tag with the warmest temperature and the bulb at the bottom has a tag with the coldest temperature. To read the thermometer you read the tag on the lowest floating bulb.
Density is mass divided by volume or how much stuff is in a given space. Water has 1gram in 1mililiter, so it has a density of 1g/ml. Because the glass bubs sometimes sink and sometimes float, their density must be very close to 1g/ml. Waters’ density is one but when it is heated it will be slightly less dense, and when it is chilled it will be slightly more dense.
Because of waters’ variation in density, the glass bulbs will sometimes sink and sometimes float depending on the temperature of the water in the thermometer. When the temperature is colder the water will be more dense. When the water reaches a cretin density one of the different weight tags will sink or float.