Commonly stated as the common sense
notion that two things can not be in exactly the same place at exactly the same time. In physics it is given the specific meaning that no two identical fermion
s can have the same quantum number
s at any given time. This accounts for the fact that electron
s in atom
s stack up in progressively higher energy level
s, which in turn accounts for the fact that chemistry
If two identical particles are forced to try to have the same quantum numbers they will respond with a force called the degeneracy pressure, or the Pauli Repulsion. There is a type of star, called a degenerate white dwarf, that is held up entirely by this force.