Photon trajectories (solid curves) drawn from the perspective of an observer in patch C (see Fig. 2). The curve R_γe(t) is the null geodesic for light signals arriving at C at time t_e from any source at proper distance R_src(t) = R_γe(t) (for t < t_e), whereas R_γ0(t) is the corresponding null geodesic for photons arriving at C at time t₀ (>t_e), though from sources at R_src(t) = R_γ0(t) (at any t < t₀). The other curves and symbols are defined in the text.