Last Tuesday, July 5, Constantino Tsallis, Professor/Emeritus Researcher at the Brazilian Center for Physical Research, External Faculty Fellow at Santa Fe Institute and holder of several Doctor Honoris Causa Degrees, gave a Distinguished Lecture titled “Why is it easier to understand what is energy than what is entropy?”. The event took place at Técnico – Alameda campus, and was moderated by the Técnico professors Mário Figueiredo and André Martins (Department of Electrical and Computer Engineering – DEEC).

What is the difference between energy and entropy?

“Energy is linked to the microscopic possibilities of the system” which includes several microscopic states related to “the position, the speed of atoms, electrons, protons, molecules… These are the microscopic possibilities,” explained professor Constantino Tsallis. Entropy relates to the probabilities of these possibilities. “So, entropy is a more sophisticated epistemological concept, because it needs to consider the microscopic possibilities and the probabilities of each of these possibilities”.

The word energy is known and recognized by many people, in different contexts, but the same is not true with the word entropy. Entropy comes from the Greek ‘entropos’. ‘Tropos’ (from the Greek τρόπος) means “a way”. So, the word entropy alludes to the existing microscopic ways or possibilities. Professor Constantino Tsallis explains “entropy is a measure of disorder. It is a measure of the observer’s knowledge of the observed system.”

Additive entropy VS non-additive entropy

In this lecture, professor Constantino Tsallis also addressed the difference between additive and non-additive entropy, to demonstrate the possible generalization of Boltzmann-Gibbs statistics, based on his article “Possible Generalization of Boltzmann-Gibbs Statistics” (1988).

According to professor Constantino Tsallis, additive entropy is not an alternative, but a generalization. It turns out to be more comprehensive and bring other possibilities for analysis, another perspective. But not only that. Additive entropy allows to calculate a priori and more accurately the experiments carried out in the “Large Hadron Collider (LHC), the world’s largest and most powerful particle accelerator, with approximately 27km in circumference and the largest machine ever built by humans”, which pushes protons or ions to near the speed of light, producing massive particles, with a minimal margin for error.