Why is it interesting?

Layman?

Why not start with quarks? Teachers investigate a learning unit on the subatomic structure of matter with 12-year-olds by Gerfried J. Wiener, Sascha M. Schmeling and Martin Hopf

Student

Researcher

First of all, for a Lorentz-invariant theory the space of single-particle states for a given particle species must be the basis for an irreducible representation of the Lorentz group. Indeed, if the representation were reducible, there would be different states that cannot be brought into one another by any Lorentz transformation. In this case it is natural to talk of different particle species rather than of different states of the same particle. […] Massless particles have no rest-frame—thus there is no reference frame where we can apply our non-relativistic QM knowledge about rotations and spin.

http://phys.columbia.edu/~nicolis/GR_from_LI.pdf

Examples

Example1

Example2:

History