Tomorrow I will pop-up at a public event organized by the LuxDoc association to evangelize the masses on stochastic thermodynamics. I will (very briefly) talk about the second law, its several interpretations, and how thermodynamics will save the world. It is a good occasion to present myself on the blog as well. The very nice slides that will accompany my contribution were prepared by my friend ASpectacularMachine on the occasion of the interdisciplinary debate Being Singular Plural in Guimaraes.

*STOCHASTIC THERMODYNAMICS: A (META)PHYSICS FOR THE 21ST CENTURY*

*The word “thermodynamics” evokes mixed feelings. On the one hand, most people have confused and possibly nightmarish memories from high school about thermodynamic transformations, ideal gases, efficiency of machines etc. After this brief encounter, thermodynamics is soon abandoned and forgotten. On the other hand, I often meet curious buddies who have a fascination for the so-called Second Law, and ideas related to irreversibility and disorder. When they find out I am a thermodynamician, they ask me lots of questions, and I’m always a bit uncomfortable. Unfortunately, the laws of thermodynamics, and even the very word “entropy”, afford many different interpretations, and any answer requires a long preamble and appears to be very personal and in contradiction with commonsense. For example, I strongly disagree with **the typical statement that “the entropy of the Universe increases”.*

*There actually is a point in being confused about thermodynamics. Thermodynamics for a long time has been a phenomenological theory that loosely collected general ideas and specific results, and had shaky mathematical foundation. The situation is changing today. My field of research, Stochastic Thermodynamics, is an elegant and complete framework where one can formulate and apply all thermodynamic concepts in a consistent and well-defined way. The noble fathers of this discipline are Boltzmann, Einstein, and many others. As every fundamental physical theory, it is supported by mathematics. Since we are in Luxembourg and many of you might be working in finance, it’s interesting to note that the mathematics behind my discipline is the same as the one that is used for pricing derivative products. And this is not a point in favor.
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*Often, the concept of “entropy” is associated with that of “disorder”. This is true in our framework, but I prefer to talk about “missing information”. If an observer has low entropy, that is, if he disposes of some information about something, he can employ that information to his own benefit. Eventually, we can also build a steam engine that employs some external resource to produce some local work! But this is a long way to go… you have to make a leap of faith. However, the idea of entropy as a measure of disorder seems paradoxical. What is the entropy of my room? To me, since I have information on where things are located, the room is quite OK. To my mother, it’s a complete mess! So, it seems that the laws of physics depend on the observer, and we don’t want that. One of my more speculative contributions has been to show that this paradox can be resolved, but this also leads us astray.
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*What is really fascinating of thermodynamics is that the theory encompasses systems of all sizes, from the molecular to the astronomical scales. For example, I am applying this theory to the metabolism of small cellular systems, which are described by large networks of biochemical reactions. But I could as well apply it to the thermodynamics of information processing in computing devices (which I want to do), to climatology (which I also want to do), and to the thermodynamics of the cosmos (yes, I also want to do this). In fact, it is fair to say that more than being a theory IN physics, thermodynamics is a theory OF physics, that is, a method to approach a certain class of systems by a general set of ideas. In this sense, thermodynamics is a methodology, maybe even a “metaphysics”.*

*The systems that can be approached by thermodynamics are open to the interaction with the environment. Moreover, all of these systems, metabolism, climatology, computation, are nonequilibrium systems, i.e. they are characterized by constant fluxes of matter, heat, charge, information. On another scale, this is the same gross structure of such huge problems like climate change, the drain of resources, macroeconomic energy balances etc. The ultimate scope of thermodynamics is to understand the complexity, efficiency and sustainability of these processes. Therefore I wish thermodynamics will have a seat in the 21st century, along with more specific sciences. But, we shouldn’t think of thermodynamics as an oracle that spells out precise recipes to heal the world and its energetic and material problems. That science can’t really do and any hope in this sense **is misplaced and misleading. Rather I think of thermodynamic as a general method for thinking about problems by reducing their complexity and still keep the important features.
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