Standard Model 7: Pions

This time I’m talking about pions:

Pions were a revolutionary discovery in the 1930s—part of the first wave of the ‘particle zoo’—but I’m explaining them as a way to work toward the math and physics concepts needed for the Standard Model.

As soon as the neutron was discovered in 1932, Heisenberg invented the idea of ‘isospin’, and the idea that the proton and neutron are two different isospin states of a single particle, the ‘nucleon’. This is why I spent 3 videos explaining the math of spin-1/2 particles: in order to talk about isospin.

Three years later, Yukawa came up with the idea that the force holding nuclei together is carried by a new particle. Even better, he predicted the mass of this yet-unseen particle! It’s a fun bit of physics but also a step toward the concept of gauge bosons.

Later, the pion was discovered: in fact, three kinds of pions! I begin to explain how these three pions form a basis of just as the proton and neutron form a basis of

These theories are outdated, but their math gets reused in the Standard Model. We’ll eventually get around to that!