Twistors in Geometric Algebra

Twistors are re-interpreted in terms of geometric algebra as 4-d spinors with a position dependence. This allows us to construct their properties as observables of a quantum system. The Robinson congruence is derived and extended to non-Euclidean spaces where it is represented in terms of d-lines. Different conformal spaces are constructed through the infinity twistors for Friedmann-Robertson-Walker spaces. Finally, we give a 6-d spinor representation of a twistor, which allows us to define the geometrical properties of the twistors as observables of this higher dimensional space.