How did scientists first calculate absolute zero?

Probably the first hint was made by a French scientist Guillaume Amontons in 1702. Among many other things, he studied the pressures in gases as a function of temperature - over what he would have called a wide range of temperature (probably ranging from an ice-water bath to boiling water). read more

The first hint that there was an ‘absolute zero’ came from Charles’ Law..see graph. Volume of a gas is directly proportional to it’s temperature. The Volume of a gas could be studied reasonably easily at ‘normal’ temperatures. read more

Here we go. It is the convenient explanation that the Carnot cycle is the base for absolute zero. read more