Milestones in Physics
A trip along the intimate meaning of entropy, information, energy, temperature, partition function, entanglement, relativity, fields, supersymmetry, strings and cosmology

Area 02 – Scienze fisiche

What happens at high energy scale or very short distances is unexpected and out of perception of common people. Uncertainty Principle is the law that governs the behaviour at short scale. It is also the main reason that induces a one-way evolution of systems. Ultimately Second Law of Thermodynamics based on entropy growing and the common notion of time flowing is exactly a consequence of Uncertainty. A completely new set of rules are strongly needed to deal with microscopic world and Quantum Mechanics takes the place of Classical Physics. Even the logic of reasoning changes in an unexpected way. Relativity then requires a further review of the model leading to the concept of field that pervades all space and is a superposition of states of matter and antimatter. The only reasonable way to solve rescaling problems at increasing energy is to admit an exact symmetry between bosons and fermions or Supersymmetry. The price to pay is to enlarge the space-time to anticommuting coordinates as if they were bosonic and fermionic degrees of freedom. Supersymmetry in a curved superspace is then a very promising attempt to merge gravity with the other forces of Standard Model. A much more elegant theory accounting for gravity and all other forces of Nature is String Theory with its supersymmetric extension. Once more a price to pay: the theory is consistent only if the space-time has ten dimensions. But Supersymmetry, Supergravity and Superstrings deal with energies comparable with Planck scale, far from experimental capacity. These efforts are great milestones to understand the origin and evolution of Universe even before the Big Bang. We discover that, what happened in the very beginning, is evident today in the current distribution of matter. So the infinitely large is reminiscent of what happened in the infinitely small and it can be explained with a very large symmetry that brings together all the dimensions of a superspace as quantum fields. But the future will be, for sure, rich of further discoveries.

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