The two “Hubble diagrams” for BAO experiments. The four falling curves give the angular size of the acoustic horizon (left scale) and the four rising curves give the redshift interval of the acoustic horizon (right scale). The solid lines are for (Ω_M,Ω_Λ,w) = (0.27,0.73, −1), the dashed for (1,0, −1) the dotted for (0.27,0, −1), and the dash-dotted for (0.27,0.73, −0.9), The error bars on the solid curve correspond to the four-month run (packed array) of Table 7.