So let us listen to the light—what music do we hear? For one thing, we can elicit from each chemical element its own, unique chord. You may sometimes have noticed that a bright yellow flash is produced if ordinary table salt is sprinkled on a flame…a first bare hint of the subject of flame spectra… The fact that different elements emit light with different color characteristics is exploited by the makers of fireworks.
Quite undeservedly, the ether has acquired a bad name.
A common habit of thought… is the idea that space is [a] simple receptacle in which bodies move around, with no two bodies present at the same point. …In modern quantum physics generally, and in the standard model of fundamental physics in particular, physical space appears as a far more flexible framework. Many kinds of particles can be present at the same point in space at the same time. Indeed, the primary ingredients of the standard model are not particles at all, but an abundance of quantum fields, each a complex object in itself, and all omnipresent.
There is a simple rule for composite objects, such as nuclei or atoms. The rule is that if such an object contains an odd number of fermions, the composite object is a fermion. Otherwise, it is a boson. …this simple rule doesn't care at all about the number of bosons in the composite object.