An Etymological Dictionary of Astronomy and Astrophysics
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A distance-like quantity derived from → gravitational lensing time delay. It is given by a combination of three angular diameter distances in a strong lens system: D_Δt = (1 + z_L)[D_A(EL)D_A(ES) / D_A(LS)], where z_L is the → redshift of the → gravitational lens, while D_A(EL), D_A(ES), and D_A(LS) are the angular diameter distances from the Earth to the lens, from the Earth to the source, and from the lens to the source, respectively. As each of the distance is proportional to the inverse of H₀, D_Δt is proportional to 1/H₀.

→ time; → delay; → distance.