Matter and energy generate curvature of spacetime. This is the subject of general relativity. Curvature of spacetime affects electrodynamics. An electromagnetic field having energy and momentum also generates curvature in spacetime. Maxwell's equations in curved spacetime can be obtained by replacing the derivatives in the equations in flat spacetime with covariant derivatives. (Whether this is the appropriate generalization requires separate investigation.) The sourced and source-free equations become (cgs-Gaussian units): 4 π π c j β β = ∂ ∂ α α F α α β β + Γ Γ α α μ μ α α F μ μ β β + Γ Γ β β μ μ α α F α α μ μ = d e f ∇ ∇ α α F α α β β = d e f F α α β β ; α α and 0 = ∂ ∂ γ γ F α α β β + ∂ ∂ β β F γ γ α α + ∂ ∂ α α F β β γ γ = ∇ ∇ γ γ F α α β β + ∇ ∇ β β F γ γ α α + ∇ ∇ α α F β β γ γ .