Top panel: fraction of the area (shaded region) and of the total Hα flux (blue curve) encompassed by the 3′′ SDSS fiber as a function of z (or, equivalently, lookback time in Gyr; upper label). Bottom panel: radius projected within the SDSS fiber as a function of z for a Friedmann-Robertson-Walker cosmology with H₀ = 70 km s^-1 Mpc^-1, Ω_m = 0.3 and Ω_Λ = 0.7 (black curve) and, for the sake of comparison, a flat, matter-dominated Universe (Ω_m = 1; magenta curve). The radius of the inside-out forming galaxy is drawn in red and the dashed line marks the z = 0.95 below which the area subtended by the SDSS fiber becomes smaller than the galaxy.