Furthermore, because the Universe is expanding, the absorption lines of all these gas clouds are redshifted by different amounts, leading to a plentiful forest of absorption lines (between a wavelengt...Furthermore, because the Universe is expanding, the absorption lines of all these gas clouds are redshifted by different amounts, leading to a plentiful forest of absorption lines (between a wavelength of 3500−4800 in the example shown in Figure E); the absorption lines in this figure are almost entirely due to hydrogen atoms that are along the line-of-sight to the quasar.
