The document discusses different techniques used to measure astronomical distances, from the closest celestial bodies to the farthest reaches of the observable universe. It explains that radar ranging is used to measure distances to planets like Venus and Mars in our solar system, while parallax is used to calculate distances to nearby stars. Farther distances within the Milky Way and to nearby galaxies are obtained via luminosity-temperature relationships and observations of Cepheid variables. Galaxy clusters are measured using their redshifts. The accuracy of early transits of Venus observations were crucial for establishing the astronomical unit and understanding larger cosmological scales.