  Every tetrad uniquely determines the pseudo-Riemannian spacetime metric \(g_{ij}\). However, the converse does not hold since the tetrad has 16 independent components whereas the spacetime metric, \(g_{ij} = g_{ji}\), has only 10 independent components. The extra 6 degrees of freedom of the tetrads that are not determined by the metric may be represented by the elements of a 6-parameter internal Lorentz group. That is, the local tetrads are determined by the spacetime metric up to local Lorentz transformations. The tetrad formalism made it possible, therefore, for Weyl to derive, as a special case of Noether’s second  theorem[101],  the energy-momentum conservation laws for general coordinate transformations and the internal Lorentz transformations of the tetrads. Moreover, Weyl had always emphasized the strong analogy between gravitation and electricity. The tetrad formalism and the conservation laws both made explicit and supported this analogy. 