QUESTION #178

# What experiments are there to prove Absolute Zero? Who discovered it and how?

The first, and simplest, demonstration of the existence of an 'absolute zero' temperature was found in the behavior of gas pressure vs. temperature. If you plot the pressure of an enclosed gas on a vertical axis against its temperature on the horizontal scale, you get a straight line slanting upward to the right. That just means that increasing the temperature results in increased pressure.

Now, if you merely extrapolate the line backward to the left (toward lower temperatures) it crosses the horizontal axis at about -273 degrees centigrade, regardless of the gas being measured. That is recognized as the coldest possible temperature, when all motion stops.

As to who gets credit for this discovery, that depends on your source. It might have been Guillame Amontons in 1702, or Joseph Lambert in 1779, or someone else. The man most often associated with this concept, however, is Lord Kelvin in the 19th century. It is the Kelvin temperature scale that defines its zero point as absolute zero, and is calculated by adding 273 degrees to the Centigrade temperature.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor