While there are different types of thermometers (mercury, digital, infrared, etc.), they all function on the same principle: measuring the expansion or contraction of a substance (usually mercury or alcohol) in response to temperature changes.
The difference lies in the scale that the thermometer uses:
* Fahrenheit has a freezing point of 32 degrees and a boiling point of 212 degrees.
* Celsius has a freezing point of 0 degrees and a boiling point of 100 degrees.
So, the thermometer itself doesn't change; it's simply calibrated to display the temperature in either Fahrenheit or Celsius.
