Pauli Exclusion Principle
This rule is named for Wolfgang Pauli (1900 - 1958) and is a cornerstone of the Models It states that two identical Fermions cannot occupy the same quantum state. Three scientific models are used to describe the observed behavior of stars and galaxies. The oldest, Newtonian Mechanics, effectively describes large scale motion of stars and galaxies but fails to accurately predict object motions and clock behavior at velocities nearing the speed of light. Einstein's Special Relativity and General Relativity models do accurately predict these behaviors. The scientific principle of Superposition requires new models, with broader applications, to yield the same results as older successful models under restricted conditions. Einstein's relativity models conform to this principle. Application or conditional restrictions imposed on a model are called boundary conditions. Quantum Mechanics, accurately predicts phenomena under boundary conditions outside of both Newtonian and Relativistic Mechanics but attempts to apply it to newtonian and relativistic conditions have proven to be very difficult. Quantum mechanics strong point is that it works where the other two do not even apply.
The Standard Model is an ongoing attempt to unify Relativity and Quantum Mechanics into a Theory of Everything or ToE. String Theory is a conjectured model which attempts to describe subatomic particles as vibrating 2-dimensional strings rather than 1-dimensional points which are an assumption in Quantum Mechanics. Classical Thermodynamics models pressure, volume and temperature relationships under normal stellar conditions, like the Sun's outer layers, but this model fails to describe exotic objects like white dwarf stars and neutron stars. Quantum Thermodynamics reduces to the classical version under normal conditions but also models exotic objects like white dwarf stars and neutron stars. Quantum Chromodynamics is an extension of the original Standard Model which resolves a problem with Composite Particles particles and the Pauli Exclusion Principle. Quantum Degereracy is an exotic state of matter included under the boundary conditions of Quantum Thermodynamics but it is outside of the boundary conditions under Classical Thermodynamics.