As promised yesterday to a friend, I want to talk aboput entropy.

Entropy is wrong for some and bad for others used due to old physic concept joke that says “Mom, you can not fight against entropy” calling entropy to disorder of things.

No, the entropy is not disorder, as many believe, thermodynamic entropy is a measure of the state of affairs.

If we look back and telling a little roll, we know that an atom with one proton and one electron, the latter has several orbits at different distances from the proton (or the nucleus of the atom) depending on the energy you have. Quantumly speaking, the wave equation depends on energy. Thus, more energy, more “distant” of the core is the orbit can go up and down between the different orbits by absorbing or giving off energy in any form.

Then we have an atom can be in different states according to their energy, right. Now, each of these states, when we have to somehow quantify, this is entropy.

Think, too, in atoms as people, where ever we want to do something try to do it the way that costs us less. This is something “natural” in the sense that the universe works like this (I will not enter why…) through the minimum energy. If something must be done, this will use the path of least energy.

Entropy measures the variation from the minimum energy to the energy that has something at that time. In fact measures the variance of the energy (which things).

And because it is one of the foundations of thermodynamics?. It is simple, thermodynamics, despite its prefix “thermo” is not part of physics that studies the temperature (also) but is the part of physics that studies the energy transfer. Fortunately or unfortunately, the temperature is a result of the transfer of a type of energy that has been, always easy to measure. And, as one of the forms of expulsion of energy is heat, it is one of the things that can be measured in the variation of energy of an atom (or atoms) and therefore ultimately entropy is fundamental to the thermodynamics.

What if there is to say, in favor of “order” as some define the entropy, is that this, entropy is the basis of a kind of very important physics, statistical mechanics where the possibility of knowing studying the state in which an atom is and, therefore, its entropy.

This has been the precursor, because statistical mechanics measures the “order” by the amount of information that an atom has has “distorted” the word entropy to the order of things thinking that more entropy more messy (what that is) it was, something that is not true.

In the photo we Rudolf Clausius, considered the creator of thermodynamics, German physicist where, from its equation that relates the temperature of a system with heat curve (all in differential, as it should be) demonstrated the relationship between these states and the state of the atom, mathematically speaking.

That is, the entropy.

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