1964 PRL symmetry breaking papers

In 1964 particle physicists published two important papers about how the smallest pieces of matter in the universe, called particles, interact with each other. These two papers proved that when particles interacted with each other, something called a "symmetry" broke. This "symmetry" means that the particles had an equal amount of strength, and when the symmetry broke, the strength of the particles became unbalanced and the particles would not interact the same way anymore. This was very important to scientists, because understanding how particles interact with each other is important for understanding how matter works in the universe!