Physics used to be much simpler.
When my parents were at school in the 1930s, they were taught that there is nothing smaller than an atom. When I was at school in the 1960s and studying Physics ‘A’ Level, we were taught that there were three sub-atomic particles: the neutron, the proton and the electron. In fact, scientists already knew that there were more than three but our teacher clearly did not want to confuse us.
Now the Standard Model of particle physics – sometimes known as the theory of almost everything – involves many dozens of sub-atomic particles and today we have the news of the discovery of yet another: the chi_b(3P). How exciting is that?