How does redshift show that a quasar is far from Earth?

Redshift indicates that a quasar is far from Earth because of the expansion of the universe. As the universe expands, space itself stretches, causing light from distant objects to be displaced toward longer, redder wavelengths—a phenomenon known as cosmological redshift.1

According to Hubble’s law, the recessional velocity of a distant object is proportional to its distance from Earth; therefore, the greater the distance of the object, the larger its recessional velocity and the greater the redshift observed. When astronomers like Maarten Schmidt analyzed the emission lines in the spectra of quasars, they found these lines were shifted toward redder wavelengths compared to laboratory measurements. By applying Hubble’s law to this measured redshift, astronomers can calculate the immense distance of the quasar from Earth.213