This little article marks the first of four on the subject: brief glimpses into the four fundamental axioms that support the entire theory.

Indeed, thermodynamics is a key pillar of physics (and so of human civilisation), and is concerned with the study of the movement of heat. This is perhaps more detailed than it may first seem: understanding heat movement requires an understanding of energy conversion; an understanding of energy conversion is the key to unlocking the entire universe (note that this is not, strictly speaking, an academic article and so mad hyperbole is permitted)!   

One of the particularly nice things about the thermodynamics is that it is a macroscopic theory, which means that it deals only with the collective effects of large numbers of particles, and does not spare a thought on the unpredictable actions of an individual atom.
Such collective effects are familiar to us all, common examples would be: pressure, temperature and volume.

The four foundations of thermodynamics are expressed in four laws, today we will look at…

The Zeroth Law of Thermodynamics

This “Law” is so basic that it does not even deserve to be called ‘First’!

There are a number of ways to express it, a succinct one is:

If two objects are both in thermal equilibrium with a third object then they must also be in thermal equilibrium with each other.

No need to worry about what “thermal equilibrium” means if you don’t want to: what the zeroth law translates to is this:

If Object A is at the same Temperature as Object B,

And if Object B is at the same Temperature as Object C

Then Object C is at the same Temperature as Object A.

Laugh not though, for such seemingly simple rules are the starting points (or ending points, if they are incorrect) of all theories!

What does it mean?

It means that if we want to know whether or not two objects are at the same temperature then we can just measure the temperature of each one and compare… we don’t need to bring the objects into contact with one another and watch what happens!

The zeroth law, as obvious as it may seem, is something we all assume to be true, even if we don’t always think about it.

Next time: The First Law of Thermodynamics!