  Other post-differential topological geometrical field structures are  similarly restrictive. For example, the microsymmetry group of the  conformal structure, which determines the causal structure of  spacetime, permits 7 degrees of freedom (6 Lorentz transformations  and a dilatation), and permits four more degrees of freedom in second  order. Consequently, the existence of the conformal metrical field  which determines at each point the cones of light propagation would  prevent an arbitrary realignment of light-like fibers, that is, it  would be impossible to realign the earth and the fixed stars such  that both are at rest with the coordinate system of the plasticine. 