(a) Animation 5a corresponds to Fig. 2a of Friedman+2013 for the case in which the event redshifts are fixed to z_A=5 and z_B=3.65, while the angular separation α as seen from Earth is allowed to vary from 0 to 360 degrees (or, without loss of generality, 0 < α < 180 degrees by symmetry about the x-axis). As in Animation 4, the green circles show the projection of the past lightcones on the hypersurface τ=τ_AB when the lightcones first intersect; these are also shown as black circles projected onto the τ=0 plane. For these redshifts, events A and B have a shared causal past for angles below some critical value (α <= α) but do not for angles greater than that value (α > α), where α is found from Eq.~31 of Friedman+2013. The movie represents a point in the z_A - z_B plane which lies in the white box in the upper right region of Fig 3b of Friedman+2013, where event pairs do not have a shared causal past with each other as long as the angular separation α exceeds some critical angle α. Since z_A > 3.65 for any angle α, event A also does not have a shared causal past with our worldline along the τ-axis from the origin. Since z_B=3.65, event B just barely has a shared past with our worldline for all angles α.

(b) Animation 5b for the same case as in Animation 5a, as viewed in the τ=0plane at the big bang.