Origins and use of the Kelvin Temperature Scale

Origins and Use of the Kelvin Temperature Scale

Humankind is constantly seeking to improve its understanding of the fundamental properties of nature. As a result of this curiosity, mankind has devised numerous methods of taking quantitative measurements. As the years passed, we abandoned many of these systems, and only the most fundamental and true remain. Of all of the ways we can measure temperature, the Kelvin scale is the most natural. To understand why, we must look at some history.

Before the Kelvin scale, scientific measurements were taken using the Celsius scale, which is centered around the boiling-point of water. The Celsius scale worked well, and is still used in many scientific reports. However, the boiling point of water is arbitrary, and William Thompson desired a scale that was based upon something much more definite. As temperature is the measure of thermal energy, zero should delineate a thermal-energy free system. This led William Thompson to devise his scale.

By far, the most difficult step in designing the Kelvin scale was to find the temperature of something with no energy. The solution turned out to be gasses. As gasses decrease in temperature, they decrease in volume by a certain amount. An extrapolation of the graphs of differing gasses shows that the linear functions of temperature vs. volume converge at a point. This point, at -273.16C is absolute zero, or 0K.

Before the invention of the Kelvin temperature scale, the following question would be difficult if not impossible to answer:

How many times more thermal energy does mercury have at 70C than at -10C?

As the Celsius scale does not begin at absolute zero, it is difficult to use to answer this question. However, if the temperatures are converted into Kelvin, the question is much simpler:

How many times more thermal energy does mercury have at 343.16K than at 263.16K?

As zero on the Kelvin scale is an absence of thermal energy, the two temperatures can simply be divided to yield the result:

343.16K / 263.16K = 1.3040

The mercury at 343.16K has 1.3040 times more thermal energy than the mercury at 263.16K.

This is the reason that the Kelvin temperature scale is useful to scientists. Because of the properties of the Kelvin scale, it is the only scale that can be used with the ideal gas law. Many scientific equations require temperatures to be input in Kelvin form. This natural scale of measurement is a brilliant invention, and has led the way to the development of modern science.