October 6th 2015 will be a day that forever lives in infamy in the minds of physics-buffs like myself. Because on that day, perhaps one of the most important discoveries in particle physics was announced by The Royal Swedish Academy of Sciences. That discovery is physical proof that neutrinos have mass, and it won Takaaki Kajita from the University of Tokyo, and Arthur B. McDonald of Queen’s University the 2015 Nobel Prize in physics.
Neutrinos? Particle Physics? Yeah. It sounds, and is, quite confusing. In the most basic terms particle physics is a branch of physics that studies the most fundamental inner workings of matter, and strives to discover new relationships between particles like electrons, leptons, and quarks. Neutrinos, also in the most basic terms are very very tiny parts of matter (so small that they weren’t discovered until 1956) that are the “byproducts” of basically every energetic “explosion” in the universe. They are also harmless, and nearly impossible to detect. In fact if you hold your hand to the sun, billions of neutrinos will bombard it every second, making it one of the most populous particles in the universe. However, neutrinos hardly interact with matter, and can pass through miles of rock without changing course. The only way for scientists to get accurate data on these sneaky particles is to trap them in massive underground lagoons called, surprisingly enough, “neutrino detectors.”
Ok, now that we have the background covered, lets talk about the really exciting, and slightly more confusing, part of this discovery. Ever since neutrinos were first discovered back in 1956, they were believed to have no mass, like that of a photon, the elementary particle of light. However, some physicists woking at neutrino detectors all over the world were noticing something very strange. When these physicists compared their theoretical calculations that predicted the number of neutrinos that should be bombarding earth, and the actual number of those that were detected, they found that over two thirds were unaccounted for. This is the puzzle that Takaaki Kajita and Arthur B. McDonald solved. They discovered, through actual physical evidence (something that had never been done before) that these neutrinos were not “missing in action” but had simply taken a new form or identity. Then, based on this unprecedented evidence and through a whole lot of complicated science and math, they came to the revolutionary conclusion that neutrinos, the supposed massless particle, must have some mass, however small.
This seemingly small discovery took the physics world by storm for a number of reasons, but none more important than its debunking of the infamous standard model of particle physics. The standard model was, before this discovery, the most trusted model that predicted and organized the mysterious workings of the particle world. It predicted the higgs boson, and stood up excellently to years of relentless and fierce scrutiny and survived all experimental challenges. However, it required neutrinos to be massless in order for it to work. That is where the trouble begins, as this new discovery clearly shows that the long standing standard model can no longer be considered a complete and accurate descriptor of the particle world. It shows, in the words of Takaaki Kajita, that “there must be a new kind of physics beyond the so-called Standard Model of fundamental particles.”
This is a truly beautiful discovery because it opens a new page in modern physics, proves to us that there is something out there that we are yet to understand, and in the words of the academy, “has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.” That is the essence, and beauty of science: the perpetual quest for a deeper understanding of the forces that govern our universe. Scientists around the world are busy at the moment sweeping up the dust of their standard model, but thanks to Takaaki Kajita and Arthur B. McDonald, they will soon enough begin work to better understand the implications of this groundbreaking discovery, and who knows what kind of advancements that may bring in the future.