I am a scientist. Specifically, I am a physicist, even more specifically a cosmologist. I consider myself incredibly lucky to have studied science, because I go through life understanding most of what is around me and I wouldn’t want to understand less. When I don’t understand something, I immediately feel the need to learn. And science is not the only way to know. Like we never cease to learn science, we never cease to learn about people either, for example. But this series of posts is there to describe what goes on in my head, as I go about my day.

One of the courses that taught me the most and shaped my thinking the most was the Statistical Physics course given by Prof. Christian Gruber at EPFL in my 3rd year undergraduate. This course was amazing because it taught me to think about systems, not just phenomena. Prof. Gruber started with the two fundamental principles of thermodynamics:

There is a strictly positive quantity,

Energy, that is conserved in a system and in its surroundings.

and

There is a strictly positive quantity,

Entropy, that increases in a system and in its surroundings.

The above are made with the assumption of time moving in only one direction (yup, we need to settle fundamental things like that to make sure we are all on the same page) and until now, there’s nothing to challenge that assumption (sorry, time travel enthusiasts). Also, as far as I can tell, the biggest system of all is the Universe and if we were able to calculate energy in the universe we would find that it is conserved and if we were able to calculate entropy in the universe, we would find that it increases with time. I am not here going to go into hypothetical theories of quantum and general relativistic effects that may challenge the notion of the universe being a closed system because it is not relevant in this context.

From those two principles, Prof. Gruber **deduced** classical mechanics, thermodynamics and electromagnetism, as well as basic chemistry. It was a beautiful and amazing intellectual journey with the rigour of mathematics, the depth of philosophy and it cemented in me a trust in science as more than a method, but as a solid foundation to approach thinking about all the aspects of the world around us. The course helped define systems, equilibrium, near equilibrium (where perturbation theory applies) and intractable aspects of a system out of equilibrium.

I think of these two principles and apply them all the time. Not by plugging numbers into a formula. These are *principles*. More fundamental than formulae.