The Standard Model: The Constituents (Fermions)

The three generations differ only in mass. In other words, all the properties expect for mass are identical between particles in different generations (for eg., the muon is just a heavy electron).

All the constituents of matter are fermions, i.e. point-like particles with non-integer spin. Fermions obey the Pauli exclusion principle in that two fermions cannot occupy the same state. This property gives rise to all the chemical elements found in nature (and is also the reason why we do not fall through our chairs)!

Quark Confinement

The atomic theory of postulates that matter is made out of discrete objects which cannot be subdivided.

But there is a new twist to the story. Although quarks are constituents of matter, they are permanently confined inside the nucleons - a rather counter-intuitive result.

Furthermore, string theory will show that at the most microscopic level, matter is not made out of discrete objects, but rather of extended objects such as strings, membranes, 3-branes (3-dimensional membranes) all the way to 9-branes (9-dimensional membranes).

Last updated: 13 June, 2005