Kelvin degrees are used to measure absolute zero temperature instead of Celsius degrees because the Kelvin scale is an absolute temperature scale, while the Celsius scale is a relative temperature scale.
The Kelvin scale, also known as the Kelvin absolute temperature scale, is based on the properties of ideal gases. It starts at absolute zero, which is the lowest possible temperature that can be reached. Absolute zero is defined as 0 Kelvin (0 K) and is equivalent to -273.15 degrees Celsius. The Kelvin scale uses the same size unit as the Celsius scale (one degree), but it does not use the Celsius degree symbol (°C).
In contrast, the Celsius scale is based on the properties of water. It defines the freezing point of water at 0 degrees Celsius and the boiling point of water at 100 degrees Celsius, both at standard atmospheric pressure. The Celsius scale is relative because it is defined based on the properties of a specific substance (water) and its phase changes under normal atmospheric conditions.
By using the Kelvin scale, scientists and engineers can work with an absolute temperature scale that does not have negative values. This is particularly important in scientific calculations and thermodynamics, where temperature differentials and ratios are significant. Absolute zero, at 0 Kelvin, represents the complete absence of thermal energy, making it a fundamental reference point for many scientific studies.
In summary, Kelvin degrees are used to measure absolute zero temperature because the Kelvin scale is an absolute temperature scale that starts at absolute zero, while the Celsius scale is a relative temperature scale based on the properties of water.