The reality of the cosmos and of human beings is complex and cannot be fully grasped through a single path of knowledge.
The method of the natural sciences, to which I adhere professionally, uncovers the laws governing matter; these laws describe “how” nature works and, through their application, drive technological progress.
For their part, the humanities – especially philosophy and metaphysics – seek to answer the ultimate “why” of things by means of reasoning, logic, and intuition, stepping in (without contradicting it) where experimental evidence reaches its limit.
My own experience convinces me that only a balanced dialogue between these two approaches allows us to penetrate reality in depth and to face, without inhibitions, the radical questions that existence poses.
These reflections are prompted by the publication in Nature of a striking result from the LHCb experiment at CERN: the first evidence of CP-symmetry violation in the decay of a baryon, the Lambda-b (a heavy cousin of the protons and neutrons that make up ordinary matter). Why is this discovery important?
One of the greatest mysteries of the universe is that, according to the standard hot Big Bang model, the matter created from the thermal energy of the primordial plasma should have been perfectly symmetric: equal amounts of particles and antiparticles. Under those conditions, particles and antiparticles would have collided and annihilated into radiation, leaving no trace of matter behind.
Yet the universe exists as matter (galaxies, stars, planets, you and me) and not as antimatter. Therefore, some mechanism must have broken that primordial symmetry. Calculations show the imbalance was tiny: out of a billion particle–antiparticle pairs, only one particle of matter survived. Why? We still don’t know.
In 1967, the Soviet nuclear physicist Andrei Sakharov (1921–1989) proposed three possible conditions for generating this asymmetry:
- the universe was born already asymmetric (with a thermal imbalance);
- baryon number is not conserved;
- there exist baryonic processes that violate CP symmetry (charge conjugation and parity).
The first option essentially sidesteps the origin of the asymmetry and implicitly hands the question over to metaphysics (and to the preferential option of Creation for matter).
The second condition lacks sufficient experimental support (so far): baryon number appears to be conserved.
The third is precisely the one hinted at by the CERN result, which would imply a difference in decay rates between certain baryons and their antiparticles. CP violation has been known since 1964 in mesons (particles made of a quark–antiquark pair), but never before in baryons (three-quark particles).
Although the evidence remains preliminary, it opens the door to new ideas and perhaps to new laws of nature. Meanwhile, particle physics remains incomplete, and the origin of this “preferential option for matter” continues to be a scientific enigma.
As Emmy Noether taught us, the deepest symmetries of the universe are tied to conservation laws. Breaking a fundamental symmetry means that something (or Someone) allowed the cosmos not to be indifferent between matter and antimatter, between left and right, or between opposite directions of rotation (other mysterious asymmetries that appear in chemistry, DNA, and galaxies).
In the end, the frontier between physics and metaphysics remains alive and fascinating.