So the world didn’t come to an end! On this past March 30th, particle physicists at CERN started colliding beams of particles in an underground circular collider, outside of Geneva. And we didn’t observe the formation of black holes nor the world collapsing into one of them. We were not even close to the end of the world. True, we are exploring the behavior of particles at energies that have never been reached before, but this is only true at the level of a particle. This latest experiment is just another step in the endless quest of mankind to understand nature better. In 2004 Fermilab in Chicago had already explored energies ten times larger than everything that had been studied before. This time we are again gaining a factor of ten in our quest. However, in our macroscopic world these energies are ridiculous, equivalent to the energy of fourteen mosquitoes in flight! Why worry about the end of times then? Or we should also worry every time Roger Federer serves on a tennis court? The potential appearance of mini black-holes is first suggested by an extremely speculative theory, with no experimental basis. Second, this announcement is misleading as, with the energy of fourteen mosquitoes, these black holes would have nothing to do with the gigantic black holes that galaxies contain often in their center.
What could we learn from this gigantic experiment smashing protons (the nuclei of hydrogen atoms) against each other, at the speed of light? On the website of CERN, they announced the exploration of anti-matter. These anti-particles react with the particles we know by annihilating while producing energy. These ideas were exploited in the recent novel “Angels and Demons” by Dan Brown, where this released energy was used as a bomb to destroy the Catholic Church. Remembering the fourteen mosquitoes in flight, we know now that expecting the annihilation of the Vatican from whatever is created in Geneva requires a good amount of imagination. Nature likes symmetries, and indeed, every time a particle is created the same amount of its anti-partner should be created for the reaction to be permitted. A little bit like in chemistry, the presence of a hydrogen atom before the reaction requires its presence at the end in one form or another, for the reaction to be possible. If we apply this symmetry to the letter, when the matter of our universe was created, an anti-universe, made of anti-matter, should also have been created. And this universe could react with ours and make us disappear! Thankfully, by a mechanism yet to be fully understood, at some point during the early history of the universe, the perfect symmetry between matter and anti-matter was broken. This means that slightly more matter than anti-matter was created. Yet that small remaining fraction is all that survived until today, while the rest annihilated. And our entire universe is made of that tiny fraction! CERN is recreating the conditions of temperature and density of the early universe and should shed some light on this broken symmetry.
In the corridor of a particle physics laboratory in Brussels, I recall the title of an article written about another secret that physicists at CERN hope to unveil. It announced a hunt for the “God particle”. This title made me think that scientists and journalists should use comparisons wisely, to avoid disillusion among the population kindly funding these experiments. This now famous Higgs particle was already the reason for building the two previous generations of colliders, the LEP and Fermilab. Although this hunt will not reveal anything about God, the discovery of the Higgs boson would be a major step in the history of our understanding of nature. Our most advanced model of particles was proposed more than 40 years ago by three Nobel Prize winners, one of them (Steven Weinberg) living in Austin. This beautiful model proposed a list of particles with very specific properties, forming a perfectly symmetric ensemble. Since then, every single particle has been discovered, and their properties have been confirmed with an impressive precision, putting together all the pieces of a perfect and symmetrical puzzle. Every single piece, except the Higgs boson. Ironically, this particle plays the most central role possible as it gives a mass to all other particles. The symmetries of nature prevent physicists from postulating a mass for all of them. The only possibility is to assume that this extra-particle would induce their mass. We should then hope that this particle will stop hiding from us or the last 40 years of success will have been nothing more than a mirage.