Seeking a comprehensive theory – delineating all the forces and elements of the cosmos – is arguably the ultimate quest in physics. Even though each of its principal theories operates remarkably effectively, they also conflict with each other – prompting physicists to hunt for a more foundational, underlying theory. Yet, is a comprehensive theory truly essential? And how close are we to realizing one?
They travel at near light-speed. They pass through planets, buildings, and bodies with impunity. They are among the most abundant particles in the cosmos—trillions pass through every square centimeter of your body each second—and yet they leave no mark. Neutrinos, once dismissed as scientific curiosities, are now at the center of a global frontier in particle physics and energy engineering.