Fields

1. The Players.
2. Euler-Lagrange equation:
   • Principle of least action.
   • Derivation.
   • Apply to GEM Lagrange density.
3. Classical fields.
4. Classical fields in detail.
5. Classical field equations:
   • Gauss' law and Newton's [relativistic] gravitational field.
   • Ampere's law and mass current.
   • Vector identities.