Published online by Cambridge University Press: 07 February 2017
Investigations of small scale angular fluctuations and the spectrum of the microwave background radiation is one of the main methods of studying the large scale structure of the Universe. Figure 1 shows the principal stages of the evolution of the Universe. Today we can directly observe galaxies, clusters of galaxies and quasars in the redshift range z ≤ 3.5 by optical, radio and X-ray astronomy. These observations show that significant density perturbations δρ/ρ > 1 are present on mass scales M < 1016 M⊙. the Universe is essentially uniform δρ/ρ < 1 on large scales M ≫ 1016 M⊙.