Abstract: I introduce Cartan geometry as a generalisation of Riemannian geometry which can be used to understand situations of `spontaneous symmetry breaking' in gravitational theories. For general relativity this leads to a picture of a field of local observers locally breaking Lorentz invariance to a subgroup of rotations. This formalism provides a link between canonical and covariant general relativity, and could have interesting applications to alternative approaches of gravity which do not fundamentally include Lorentz invariance as well as to quantum gravity phenomenology.
